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| <div id="heading"><a href="/">The Go Programming Language</a></div> | |
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| <h1>Go 1 Release Notes</h1> | |
| <div id="nav"></div> | |
| <h2 id="introduction">Introduction to Go 1</h2> | |
| <p> | |
| Go version 1, Go 1 for short, defines a language and a set of core libraries | |
| that provide a stable foundation for creating reliable products, projects, and | |
| publications. | |
| </p> | |
| <p> | |
| The driving motivation for Go 1 is stability for its users. People should be able to | |
| write Go programs and expect that they will continue to compile and run without | |
| change, on a time scale of years, including in production environments such as | |
| Google App Engine. Similarly, people should be able to write books about Go, be | |
| able to say which version of Go the book is describing, and have that version | |
| number still be meaningful much later. | |
| </p> | |
| <p> | |
| Code that compiles in Go 1 should, with few exceptions, continue to compile and | |
| run throughout the lifetime of that version, even as we issue updates and bug | |
| fixes such as Go version 1.1, 1.2, and so on. Other than critical fixes, changes | |
| made to the language and library for subsequent releases of Go 1 may | |
| add functionality but will not break existing Go 1 programs. | |
| <a href="go1compat.html">The Go 1 compatibility document</a> | |
| explains the compatibility guidelines in more detail. | |
| </p> | |
| <p> | |
| Go 1 is a representation of Go as it used today, not a wholesale rethinking of | |
| the language. We avoided designing new features and instead focused on cleaning | |
| up problems and inconsistencies and improving portability. There are a number | |
| changes to the Go language and packages that we had considered for some time and | |
| prototyped but not released primarily because they are significant and | |
| backwards-incompatible. Go 1 was an opportunity to get them out, which is | |
| helpful for the long term, but also means that Go 1 introduces incompatibilities | |
| for old programs. Fortunately, the <code>go</code> <code>fix</code> tool can | |
| automate much of the work needed to bring programs up to the Go 1 standard. | |
| </p> | |
| <p> | |
| This document outlines the major changes in Go 1 that will affect programmers | |
| updating existing code; its reference point is the prior release, r60 (tagged as | |
| r60.3). It also explains how to update code from r60 to run under Go 1. | |
| </p> | |
| <h2 id="language">Changes to the language</h2> | |
| <h3 id="append">Append</h3> | |
| <p> | |
| The <code>append</code> predeclared variadic function makes it easy to grow a slice | |
| by adding elements to the end. | |
| A common use is to add bytes to the end of a byte slice when generating output. | |
| However, <code>append</code> did not provide a way to append a string to a <code>[]byte</code>, | |
| which is another common case. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/greeting := ..byte/` `/append.*hello/`}} | |
| --> greeting := []byte{} | |
| greeting = append(greeting, []byte("hello ")...)</pre> | |
| <p> | |
| By analogy with the similar property of <code>copy</code>, Go 1 | |
| permits a string to be appended (byte-wise) directly to a byte | |
| slice, reducing the friction between strings and byte slices. | |
| The conversion is no longer necessary: | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/append.*world/`}} | |
| --> greeting = append(greeting, "world"...)</pre> | |
| <p> | |
| <em>Updating</em>: | |
| This is a new feature, so existing code needs no changes. | |
| </p> | |
| <h3 id="close">Close</h3> | |
| <p> | |
| The <code>close</code> predeclared function provides a mechanism | |
| for a sender to signal that no more values will be sent. | |
| It is important to the implementation of <code>for</code> <code>range</code> | |
| loops over channels and is helpful in other situations. | |
| Partly by design and partly because of race conditions that can occur otherwise, | |
| it is intended for use only by the goroutine sending on the channel, | |
| not by the goroutine receiving data. | |
| However, before Go 1 there was no compile-time checking that <code>close</code> | |
| was being used correctly. | |
| </p> | |
| <p> | |
| To close this gap, at least in part, Go 1 disallows <code>close</code> on receive-only channels. | |
| Attempting to close such a channel is a compile-time error. | |
| </p> | |
| <pre> | |
| var c chan int | |
| var csend chan<- int = c | |
| var crecv <-chan int = c | |
| close(c) // legal | |
| close(csend) // legal | |
| close(crecv) // illegal | |
| </pre> | |
| <p> | |
| <em>Updating</em>: | |
| Existing code that attempts to close a receive-only channel was | |
| erroneous even before Go 1 and should be fixed. The compiler will | |
| now reject such code. | |
| </p> | |
| <h3 id="literals">Composite literals</h3> | |
| <p> | |
| In Go 1, a composite literal of array, slice, or map type can elide the | |
| type specification for the elements' initializers if they are of pointer type. | |
| All four of the initializations in this example are legal; the last one was illegal before Go 1. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/type Date struct/` `/STOP/`}} | |
| --> type Date struct { | |
| month string | |
| day int | |
| } | |
| <span class="comment">// Struct values, fully qualified; always legal.</span> | |
| holiday1 := []Date{ | |
| Date{"Feb", 14}, | |
| Date{"Nov", 11}, | |
| Date{"Dec", 25}, | |
| } | |
| <span class="comment">// Struct values, type name elided; always legal.</span> | |
| holiday2 := []Date{ | |
| {"Feb", 14}, | |
| {"Nov", 11}, | |
| {"Dec", 25}, | |
| } | |
| <span class="comment">// Pointers, fully qualified, always legal.</span> | |
| holiday3 := []*Date{ | |
| &Date{"Feb", 14}, | |
| &Date{"Nov", 11}, | |
| &Date{"Dec", 25}, | |
| } | |
| <span class="comment">// Pointers, type name elided; legal in Go 1.</span> | |
| holiday4 := []*Date{ | |
| {"Feb", 14}, | |
| {"Nov", 11}, | |
| {"Dec", 25}, | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| This change has no effect on existing code, but the command | |
| <code>gofmt</code> <code>-s</code> applied to existing source | |
| will, among other things, elide explicit element types wherever permitted. | |
| </p> | |
| <h3 id="init">Goroutines during init</h3> | |
| <p> | |
| The old language defined that <code>go</code> statements executed during initialization created goroutines but that they did not begin to run until initialization of the entire program was complete. | |
| This introduced clumsiness in many places and, in effect, limited the utility | |
| of the <code>init</code> construct: | |
| if it was possible for another package to use the library during initialization, the library | |
| was forced to avoid goroutines. | |
| This design was done for reasons of simplicity and safety but, | |
| as our confidence in the language grew, it seemed unnecessary. | |
| Running goroutines during initialization is no more complex or unsafe than running them during normal execution. | |
| </p> | |
| <p> | |
| In Go 1, code that uses goroutines can be called from | |
| <code>init</code> routines and global initialization expressions | |
| without introducing a deadlock. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/PackageGlobal/` `/^}/`}} | |
| -->var PackageGlobal int | |
| func init() { | |
| c := make(chan int) | |
| go initializationFunction(c) | |
| PackageGlobal = <-c | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| This is a new feature, so existing code needs no changes, | |
| although it's possible that code that depends on goroutines not starting before <code>main</code> will break. | |
| There was no such code in the standard repository. | |
| </p> | |
| <h3 id="rune">The rune type</h3> | |
| <p> | |
| The language spec allows the <code>int</code> type to be 32 or 64 bits wide, but current implementations set <code>int</code> to 32 bits even on 64-bit platforms. | |
| It would be preferable to have <code>int</code> be 64 bits on 64-bit platforms. | |
| (There are important consequences for indexing large slices.) | |
| However, this change would waste space when processing Unicode characters with | |
| the old language because the <code>int</code> type was also used to hold Unicode code points: each code point would waste an extra 32 bits of storage if <code>int</code> grew from 32 bits to 64. | |
| </p> | |
| <p> | |
| To make changing to 64-bit <code>int</code> feasible, | |
| Go 1 introduces a new basic type, <code>rune</code>, to represent | |
| individual Unicode code points. | |
| It is an alias for <code>int32</code>, analogous to <code>byte</code> | |
| as an alias for <code>uint8</code>. | |
| </p> | |
| <p> | |
| Character literals such as <code>'a'</code>, <code>'語'</code>, and <code>'\u0345'</code> | |
| now have default type <code>rune</code>, | |
| analogous to <code>1.0</code> having default type <code>float64</code>. | |
| A variable initialized to a character constant will therefore | |
| have type <code>rune</code> unless otherwise specified. | |
| </p> | |
| <p> | |
| Libraries have been updated to use <code>rune</code> rather than <code>int</code> | |
| when appropriate. For instance, the functions <code>unicode.ToLower</code> and | |
| relatives now take and return a <code>rune</code>. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/STARTRUNE/` `/ENDRUNE/`}} | |
| --> delta := 'δ' <span class="comment">// delta has type rune.</span> | |
| var DELTA rune | |
| DELTA = unicode.ToUpper(delta) | |
| epsilon := unicode.ToLower(DELTA + 1) | |
| if epsilon != 'δ'+1 { | |
| log.Fatal("inconsistent casing for Greek") | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| Most source code will be unaffected by this because the type inference from | |
| <code>:=</code> initializers introduces the new type silently, and it propagates | |
| from there. | |
| Some code may get type errors that a trivial conversion will resolve. | |
| </p> | |
| <h3 id="error">The error type</h3> | |
| <p> | |
| Go 1 introduces a new built-in type, <code>error</code>, which has the following definition: | |
| </p> | |
| <pre> | |
| type error interface { | |
| Error() string | |
| } | |
| </pre> | |
| <p> | |
| Since the consequences of this type are all in the package library, | |
| it is discussed <a href="#errors">below</a>. | |
| </p> | |
| <h3 id="delete">Deleting from maps</h3> | |
| <p> | |
| In the old language, to delete the entry with key <code>k</code> from map <code>m</code>, one wrote the statement, | |
| </p> | |
| <pre> | |
| m[k] = value, false | |
| </pre> | |
| <p> | |
| This syntax was a peculiar special case, the only two-to-one assignment. | |
| It required passing a value (usually ignored) that is evaluated but discarded, | |
| plus a boolean that was nearly always the constant <code>false</code>. | |
| It did the job but was odd and a point of contention. | |
| </p> | |
| <p> | |
| In Go 1, that syntax has gone; instead there is a new built-in | |
| function, <code>delete</code>. The call | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/delete\(m, k\)/`}} | |
| --> delete(m, k)</pre> | |
| <p> | |
| will delete the map entry retrieved by the expression <code>m[k]</code>. | |
| There is no return value. Deleting a non-existent entry is a no-op. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will convert expressions of the form <code>m[k] = value, | |
| false</code> into <code>delete(m, k)</code> when it is clear that | |
| the ignored value can be safely discarded from the program and | |
| <code>false</code> refers to the predefined boolean constant. | |
| The fix tool | |
| will flag other uses of the syntax for inspection by the programmer. | |
| </p> | |
| <h3 id="iteration">Iterating in maps</h3> | |
| <p> | |
| The old language specification did not define the order of iteration for maps, | |
| and in practice it differed across hardware platforms. | |
| This caused tests that iterated over maps to be fragile and non-portable, with the | |
| unpleasant property that a test might always pass on one machine but break on another. | |
| </p> | |
| <p> | |
| In Go 1, the order in which elements are visited when iterating | |
| over a map using a <code>for</code> <code>range</code> statement | |
| is defined to be unpredictable, even if the same loop is run multiple | |
| times with the same map. | |
| Code should not assume that the elements are visited in any particular order. | |
| </p> | |
| <p> | |
| This change means that code that depends on iteration order is very likely to break early and be fixed long before it becomes a problem. | |
| Just as important, it allows the map implementation to ensure better map balancing even when programs are using range loops to select an element from a map. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/Sunday/` `/^ }/`}} | |
| --> m := map[string]int{"Sunday": 0, "Monday": 1} | |
| for name, value := range m { | |
| <span class="comment">// This loop should not assume Sunday will be visited first.</span> | |
| f(name, value) | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| This is one change where tools cannot help. Most existing code | |
| will be unaffected, but some programs may break or misbehave; we | |
| recommend manual checking of all range statements over maps to | |
| verify they do not depend on iteration order. There were a few such | |
| examples in the standard repository; they have been fixed. | |
| Note that it was already incorrect to depend on the iteration order, which | |
| was unspecified. This change codifies the unpredictability. | |
| </p> | |
| <h3 id="multiple_assignment">Multiple assignment</h3> | |
| <p> | |
| The language specification has long guaranteed that in assignments | |
| the right-hand-side expressions are all evaluated before any left-hand-side expressions are assigned. | |
| To guarantee predictable behavior, | |
| Go 1 refines the specification further. | |
| </p> | |
| <p> | |
| If the left-hand side of the assignment | |
| statement contains expressions that require evaluation, such as | |
| function calls or array indexing operations, these will all be done | |
| using the usual left-to-right rule before any variables are assigned | |
| their value. Once everything is evaluated, the actual assignments | |
| proceed in left-to-right order. | |
| </p> | |
| <p> | |
| These examples illustrate the behavior. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/sa :=/` `/then sc.0. = 2/`}} | |
| --> sa := []int{1, 2, 3} | |
| i := 0 | |
| i, sa[i] = 1, 2 <span class="comment">// sets i = 1, sa[0] = 2</span> | |
| sb := []int{1, 2, 3} | |
| j := 0 | |
| sb[j], j = 2, 1 <span class="comment">// sets sb[0] = 2, j = 1</span> | |
| sc := []int{1, 2, 3} | |
| sc[0], sc[0] = 1, 2 <span class="comment">// sets sc[0] = 1, then sc[0] = 2 (so sc[0] = 2 at end)</span></pre> | |
| <p> | |
| <em>Updating</em>: | |
| This is one change where tools cannot help, but breakage is unlikely. | |
| No code in the standard repository was broken by this change, and code | |
| that depended on the previous unspecified behavior was already incorrect. | |
| </p> | |
| <h3 id="shadowing">Returns and shadowed variables</h3> | |
| <p> | |
| A common mistake is to use <code>return</code> (without arguments) after an assignment to a variable that has the same name as a result variable but is not the same variable. | |
| This situation is called <em>shadowing</em>: the result variable has been shadowed by another variable with the same name declared in an inner scope. | |
| </p> | |
| <p> | |
| In functions with named return values, | |
| the Go 1 compilers disallow return statements without arguments if any of the named return values is shadowed at the point of the return statement. | |
| (It isn't part of the specification, because this is one area we are still exploring; | |
| the situation is analogous to the compilers rejecting functions that do not end with an explicit return statement.) | |
| </p> | |
| <p> | |
| This function implicitly returns a shadowed return value and will be rejected by the compiler: | |
| </p> | |
| <pre> | |
| func Bug() (i, j, k int) { | |
| for i = 0; i < 5; i++ { | |
| for j := 0; j < 5; j++ { // Redeclares j. | |
| k += i*j | |
| if k > 100 { | |
| return // Rejected: j is shadowed here. | |
| } | |
| } | |
| } | |
| return // OK: j is not shadowed here. | |
| } | |
| </pre> | |
| <p> | |
| <em>Updating</em>: | |
| Code that shadows return values in this way will be rejected by the compiler and will need to be fixed by hand. | |
| The few cases that arose in the standard repository were mostly bugs. | |
| </p> | |
| <h3 id="unexported">Copying structs with unexported fields</h3> | |
| <p> | |
| The old language did not allow a package to make a copy of a struct value containing unexported fields belonging to a different package. | |
| There was, however, a required exception for a method receiver; | |
| also, the implementations of <code>copy</code> and <code>append</code> have never honored the restriction. | |
| </p> | |
| <p> | |
| Go 1 will allow packages to copy struct values containing unexported fields from other packages. | |
| Besides resolving the inconsistency, | |
| this change admits a new kind of API: a package can return an opaque value without resorting to a pointer or interface. | |
| The new implementations of <code>time.Time</code> and | |
| <code>reflect.Value</code> are examples of types taking advantage of this new property. | |
| </p> | |
| <p> | |
| As an example, if package <code>p</code> includes the definitions, | |
| </p> | |
| <pre> | |
| type Struct struct { | |
| Public int | |
| secret int | |
| } | |
| func NewStruct(a int) Struct { // Note: not a pointer. | |
| return Struct{a, f(a)} | |
| } | |
| func (s Struct) String() string { | |
| return fmt.Sprintf("{%d (secret %d)}", s.Public, s.secret) | |
| } | |
| </pre> | |
| <p> | |
| a package that imports <code>p</code> can assign and copy values of type | |
| <code>p.Struct</code> at will. | |
| Behind the scenes the unexported fields will be assigned and copied just | |
| as if they were exported, | |
| but the client code will never be aware of them. The code | |
| </p> | |
| <pre> | |
| import "p" | |
| myStruct := p.NewStruct(23) | |
| copyOfMyStruct := myStruct | |
| fmt.Println(myStruct, copyOfMyStruct) | |
| </pre> | |
| <p> | |
| will show that the secret field of the struct has been copied to the new value. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| This is a new feature, so existing code needs no changes. | |
| </p> | |
| <h3 id="equality">Equality</h3> | |
| <p> | |
| Before Go 1, the language did not define equality on struct and array values. | |
| This meant, | |
| among other things, that structs and arrays could not be used as map keys. | |
| On the other hand, Go did define equality on function and map values. | |
| Function equality was problematic in the presence of closures | |
| (when are two closures equal?) | |
| while map equality compared pointers, not the maps' content, which was usually | |
| not what the user would want. | |
| </p> | |
| <p> | |
| Go 1 addressed these issues. | |
| First, structs and arrays can be compared for equality and inequality | |
| (<code>==</code> and <code>!=</code>), | |
| and therefore be used as map keys, | |
| provided they are composed from elements for which equality is also defined, | |
| using element-wise comparison. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/type Day struct/` `/Printf/`}} | |
| --> type Day struct { | |
| long string | |
| short string | |
| } | |
| Christmas := Day{"Christmas", "XMas"} | |
| Thanksgiving := Day{"Thanksgiving", "Turkey"} | |
| holiday := map[Day]bool{ | |
| Christmas: true, | |
| Thanksgiving: true, | |
| } | |
| fmt.Printf("Christmas is a holiday: %t\n", holiday[Christmas])</pre> | |
| <p> | |
| Second, Go 1 removes the definition of equality for function values, | |
| except for comparison with <code>nil</code>. | |
| Finally, map equality is gone too, also except for comparison with <code>nil</code>. | |
| </p> | |
| <p> | |
| Note that equality is still undefined for slices, for which the | |
| calculation is in general infeasible. Also note that the ordered | |
| comparison operators (<code><</code> <code><=</code> | |
| <code>></code> <code>>=</code>) are still undefined for | |
| structs and arrays. | |
| <p> | |
| <em>Updating</em>: | |
| Struct and array equality is a new feature, so existing code needs no changes. | |
| Existing code that depends on function or map equality will be | |
| rejected by the compiler and will need to be fixed by hand. | |
| Few programs will be affected, but the fix may require some | |
| redesign. | |
| </p> | |
| <h2 id="packages">The package hierarchy</h2> | |
| <p> | |
| Go 1 addresses many deficiencies in the old standard library and | |
| cleans up a number of packages, making them more internally consistent | |
| and portable. | |
| </p> | |
| <p> | |
| This section describes how the packages have been rearranged in Go 1. | |
| Some have moved, some have been renamed, some have been deleted. | |
| New packages are described in later sections. | |
| </p> | |
| <h3 id="hierarchy">The package hierarchy</h3> | |
| <p> | |
| Go 1 has a rearranged package hierarchy that groups related items | |
| into subdirectories. For instance, <code>utf8</code> and | |
| <code>utf16</code> now occupy subdirectories of <code>unicode</code>. | |
| Also, <a href="#subrepo">some packages</a> have moved into | |
| subrepositories of | |
| <a href="http://code.google.com/p/go"><code>code.google.com/p/go</code></a> | |
| while <a href="#deleted">others</a> have been deleted outright. | |
| </p> | |
| <table class="codetable" frame="border" summary="Moved packages"> | |
| <colgroup align="left" width="60%"></colgroup> | |
| <colgroup align="left" width="40%"></colgroup> | |
| <tr> | |
| <th align="left">Old path</th> | |
| <th align="left">New path</th> | |
| </tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>asn1</td> <td>encoding/asn1</td></tr> | |
| <tr><td>csv</td> <td>encoding/csv</td></tr> | |
| <tr><td>gob</td> <td>encoding/gob</td></tr> | |
| <tr><td>json</td> <td>encoding/json</td></tr> | |
| <tr><td>xml</td> <td>encoding/xml</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>exp/template/html</td> <td>html/template</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>big</td> <td>math/big</td></tr> | |
| <tr><td>cmath</td> <td>math/cmplx</td></tr> | |
| <tr><td>rand</td> <td>math/rand</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>http</td> <td>net/http</td></tr> | |
| <tr><td>http/cgi</td> <td>net/http/cgi</td></tr> | |
| <tr><td>http/fcgi</td> <td>net/http/fcgi</td></tr> | |
| <tr><td>http/httptest</td> <td>net/http/httptest</td></tr> | |
| <tr><td>http/pprof</td> <td>net/http/pprof</td></tr> | |
| <tr><td>mail</td> <td>net/mail</td></tr> | |
| <tr><td>rpc</td> <td>net/rpc</td></tr> | |
| <tr><td>rpc/jsonrpc</td> <td>net/rpc/jsonrpc</td></tr> | |
| <tr><td>smtp</td> <td>net/smtp</td></tr> | |
| <tr><td>url</td> <td>net/url</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>exec</td> <td>os/exec</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>scanner</td> <td>text/scanner</td></tr> | |
| <tr><td>tabwriter</td> <td>text/tabwriter</td></tr> | |
| <tr><td>template</td> <td>text/template</td></tr> | |
| <tr><td>template/parse</td> <td>text/template/parse</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>utf8</td> <td>unicode/utf8</td></tr> | |
| <tr><td>utf16</td> <td>unicode/utf16</td></tr> | |
| </table> | |
| <p> | |
| Note that the package names for the old <code>cmath</code> and | |
| <code>exp/template/html</code> packages have changed to <code>cmplx</code> | |
| and <code>template</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update all imports and package renames for packages that | |
| remain inside the standard repository. Programs that import packages | |
| that are no longer in the standard repository will need to be edited | |
| by hand. | |
| </p> | |
| <h3 id="exp">The package tree exp</h3> | |
| <p> | |
| Because they are not standardized, the packages under the <code>exp</code> directory will not be available in the | |
| standard Go 1 release distributions, although they will be available in source code form | |
| in <a href="http://code.google.com/p/go/">the repository</a> for | |
| developers who wish to use them. | |
| </p> | |
| <p> | |
| Several packages have moved under <code>exp</code> at the time of Go 1's release: | |
| </p> | |
| <ul> | |
| <li><code>ebnf</code></li> | |
| <li><code>html</code><sup>†</sup></li> | |
| <li><code>go/types</code></li> | |
| </ul> | |
| <p> | |
| (<sup>†</sup>The <code>EscapeString</code> and <code>UnescapeString</code> types remain | |
| in package <code>html</code>.) | |
| </p> | |
| <p> | |
| All these packages are available under the same names, with the prefix <code>exp/</code>: <code>exp/ebnf</code> etc. | |
| </p> | |
| <p> | |
| Also, the <code>utf8.String</code> type has been moved to its own package, <code>exp/utf8string</code>. | |
| </p> | |
| <p> | |
| Finally, the <code>gotype</code> command now resides in <code>exp/gotype</code>, while | |
| <code>ebnflint</code> is now in <code>exp/ebnflint</code>. | |
| If they are installed, they now reside in <code>$GOROOT/bin/tool</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses packages in <code>exp</code> will need to be updated by hand, | |
| or else compiled from an installation that has <code>exp</code> available. | |
| The <code>go</code> <code>fix</code> tool or the compiler will complain about such uses. | |
| </p> | |
| <h3 id="old">The package tree old</h3> | |
| <p> | |
| Because they are deprecated, the packages under the <code>old</code> directory will not be available in the | |
| standard Go 1 release distributions, although they will be available in source code form for | |
| developers who wish to use them. | |
| </p> | |
| <p> | |
| The packages in their new locations are: | |
| </p> | |
| <ul> | |
| <li><code>old/netchan</code></li> | |
| <li><code>old/regexp</code></li> | |
| <li><code>old/template</code></li> | |
| </ul> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses packages now in <code>old</code> will need to be updated by hand, | |
| or else compiled from an installation that has <code>old</code> available. | |
| The <code>go</code> <code>fix</code> tool will warn about such uses. | |
| </p> | |
| <h3 id="deleted">Deleted packages</h3> | |
| <p> | |
| Go 1 deletes several packages outright: | |
| </p> | |
| <ul> | |
| <li><code>container/vector</code></li> | |
| <li><code>exp/datafmt</code></li> | |
| <li><code>go/typechecker</code></li> | |
| <li><code>try</code></li> | |
| </ul> | |
| <p> | |
| and also the command <code>gotry</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses <code>container/vector</code> should be updated to use | |
| slices directly. See | |
| <a href="http://code.google.com/p/go-wiki/wiki/SliceTricks">the Go | |
| Language Community Wiki</a> for some suggestions. | |
| Code that uses the other packages (there should be almost zero) will need to be rethought. | |
| </p> | |
| <h3 id="subrepo">Packages moving to subrepositories</h3> | |
| <p> | |
| Go 1 has moved a number of packages into other repositories, usually sub-repositories of | |
| <a href="http://code.google.com/p/go/">the main Go repository</a>. | |
| This table lists the old and new import paths: | |
| <table class="codetable" frame="border" summary="Sub-repositories"> | |
| <colgroup align="left" width="40%"></colgroup> | |
| <colgroup align="left" width="60%"></colgroup> | |
| <tr> | |
| <th align="left">Old</th> | |
| <th align="left">New</th> | |
| </tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>crypto/bcrypt</td> <td>code.google.com/p/go.crypto/bcrypt</tr> | |
| <tr><td>crypto/blowfish</td> <td>code.google.com/p/go.crypto/blowfish</tr> | |
| <tr><td>crypto/cast5</td> <td>code.google.com/p/go.crypto/cast5</tr> | |
| <tr><td>crypto/md4</td> <td>code.google.com/p/go.crypto/md4</tr> | |
| <tr><td>crypto/ocsp</td> <td>code.google.com/p/go.crypto/ocsp</tr> | |
| <tr><td>crypto/openpgp</td> <td>code.google.com/p/go.crypto/openpgp</tr> | |
| <tr><td>crypto/openpgp/armor</td> <td>code.google.com/p/go.crypto/openpgp/armor</tr> | |
| <tr><td>crypto/openpgp/elgamal</td> <td>code.google.com/p/go.crypto/openpgp/elgamal</tr> | |
| <tr><td>crypto/openpgp/errors</td> <td>code.google.com/p/go.crypto/openpgp/errors</tr> | |
| <tr><td>crypto/openpgp/packet</td> <td>code.google.com/p/go.crypto/openpgp/packet</tr> | |
| <tr><td>crypto/openpgp/s2k</td> <td>code.google.com/p/go.crypto/openpgp/s2k</tr> | |
| <tr><td>crypto/ripemd160</td> <td>code.google.com/p/go.crypto/ripemd160</tr> | |
| <tr><td>crypto/twofish</td> <td>code.google.com/p/go.crypto/twofish</tr> | |
| <tr><td>crypto/xtea</td> <td>code.google.com/p/go.crypto/xtea</tr> | |
| <tr><td>exp/ssh</td> <td>code.google.com/p/go.crypto/ssh</tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>image/bmp</td> <td>code.google.com/p/go.image/bmp</tr> | |
| <tr><td>image/tiff</td> <td>code.google.com/p/go.image/tiff</tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>net/dict</td> <td>code.google.com/p/go.net/dict</tr> | |
| <tr><td>net/websocket</td> <td>code.google.com/p/go.net/websocket</tr> | |
| <tr><td>exp/spdy</td> <td>code.google.com/p/go.net/spdy</tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>encoding/git85</td> <td>code.google.com/p/go.codereview/git85</tr> | |
| <tr><td>patch</td> <td>code.google.com/p/go.codereview/patch</tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>exp/wingui</td> <td>code.google.com/p/gowingui</tr> | |
| </table> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update imports of these packages to use the new import paths. | |
| Installations that depend on these packages will need to install them using | |
| a <code>go get</code> command. | |
| </p> | |
| <h2 id="major">Major changes to the library</h2> | |
| <p> | |
| This section describes significant changes to the core libraries, the ones that | |
| affect the most programs. | |
| </p> | |
| <h3 id="errors">The error type and errors package</h3> | |
| <p> | |
| The placement of <code>os.Error</code> in package <code>os</code> is mostly historical: errors first came up when implementing package <code>os</code>, and they seemed system-related at the time. | |
| Since then it has become clear that errors are more fundamental than the operating system. For example, it would be nice to use <code>Errors</code> in packages that <code>os</code> depends on, like <code>syscall</code>. | |
| Also, having <code>Error</code> in <code>os</code> introduces many dependencies on <code>os</code> that would otherwise not exist. | |
| </p> | |
| <p> | |
| Go 1 solves these problems by introducing a built-in <code>error</code> interface type and a separate <code>errors</code> package (analogous to <code>bytes</code> and <code>strings</code>) that contains utility functions. | |
| It replaces <code>os.NewError</code> with | |
| <a href="/pkg/errors/#New"><code>errors.New</code></a>, | |
| giving errors a more central place in the environment. | |
| </p> | |
| <p> | |
| So the widely-used <code>String</code> method does not cause accidental satisfaction | |
| of the <code>error</code> interface, the <code>error</code> interface uses instead | |
| the name <code>Error</code> for that method: | |
| </p> | |
| <pre> | |
| type error interface { | |
| Error() string | |
| } | |
| </pre> | |
| <p> | |
| The <code>fmt</code> library automatically invokes <code>Error</code>, as it already | |
| does for <code>String</code>, for easy printing of error values. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/START ERROR EXAMPLE/` `/END ERROR EXAMPLE/`}} | |
| -->type SyntaxError struct { | |
| File string | |
| Line int | |
| Message string | |
| } | |
| func (se *SyntaxError) Error() string { | |
| return fmt.Sprintf("%s:%d: %s", se.File, se.Line, se.Message) | |
| }</pre> | |
| <p> | |
| All standard packages have been updated to use the new interface; the old <code>os.Error</code> is gone. | |
| </p> | |
| <p> | |
| A new package, <a href="/pkg/errors/"><code>errors</code></a>, contains the function | |
| </p> | |
| <pre> | |
| func New(text string) error | |
| </pre> | |
| <p> | |
| to turn a string into an error. It replaces the old <code>os.NewError</code>. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/ErrSyntax/`}} | |
| --> var ErrSyntax = errors.New("syntax error")</pre> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update almost all code affected by the change. | |
| Code that defines error types with a <code>String</code> method will need to be updated | |
| by hand to rename the methods to <code>Error</code>. | |
| </p> | |
| <h3 id="errno">System call errors</h3> | |
| <p> | |
| The old <code>syscall</code> package, which predated <code>os.Error</code> | |
| (and just about everything else), | |
| returned errors as <code>int</code> values. | |
| In turn, the <code>os</code> package forwarded many of these errors, such | |
| as <code>EINVAL</code>, but using a different set of errors on each platform. | |
| This behavior was unpleasant and unportable. | |
| </p> | |
| <p> | |
| In Go 1, the | |
| <a href="/pkg/syscall/"><code>syscall</code></a> | |
| package instead returns an <code>error</code> for system call errors. | |
| On Unix, the implementation is done by a | |
| <a href="/pkg/syscall/#Errno"><code>syscall.Errno</code></a> type | |
| that satisfies <code>error</code> and replaces the old <code>os.Errno</code>. | |
| </p> | |
| <p> | |
| The changes affecting <code>os.EINVAL</code> and relatives are | |
| described <a href="#os">elsewhere</a>. | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update almost all code affected by the change. | |
| Regardless, most code should use the <code>os</code> package | |
| rather than <code>syscall</code> and so will be unaffected. | |
| </p> | |
| <h3 id="time">Time</h3> | |
| <p> | |
| Time is always a challenge to support well in a programming language. | |
| The old Go <code>time</code> package had <code>int64</code> units, no | |
| real type safety, | |
| and no distinction between absolute times and durations. | |
| </p> | |
| <p> | |
| One of the most sweeping changes in the Go 1 library is therefore a | |
| complete redesign of the | |
| <a href="/pkg/time/"><code>time</code></a> package. | |
| Instead of an integer number of nanoseconds as an <code>int64</code>, | |
| and a separate <code>*time.Time</code> type to deal with human | |
| units such as hours and years, | |
| there are now two fundamental types: | |
| <a href="/pkg/time/#Time"><code>time.Time</code></a> | |
| (a value, so the <code>*</code> is gone), which represents a moment in time; | |
| and <a href="/pkg/time/#Duration"><code>time.Duration</code></a>, | |
| which represents an interval. | |
| Both have nanosecond resolution. | |
| A <code>Time</code> can represent any time into the ancient | |
| past and remote future, while a <code>Duration</code> can | |
| span plus or minus only about 290 years. | |
| There are methods on these types, plus a number of helpful | |
| predefined constant durations such as <code>time.Second</code>. | |
| </p> | |
| <p> | |
| Among the new methods are things like | |
| <a href="/pkg/time/#Time.Add"><code>Time.Add</code></a>, | |
| which adds a <code>Duration</code> to a <code>Time</code>, and | |
| <a href="/pkg/time/#Time.Sub"><code>Time.Sub</code></a>, | |
| which subtracts two <code>Times</code> to yield a <code>Duration</code>. | |
| </p> | |
| <p> | |
| The most important semantic change is that the Unix epoch (Jan 1, 1970) is now | |
| relevant only for those functions and methods that mention Unix: | |
| <a href="/pkg/time/#Unix"><code>time.Unix</code></a> | |
| and the <a href="/pkg/time/#Time.Unix"><code>Unix</code></a> | |
| and <a href="/pkg/time/#Time.UnixNano"><code>UnixNano</code></a> methods | |
| of the <code>Time</code> type. | |
| In particular, | |
| <a href="/pkg/time/#Now"><code>time.Now</code></a> | |
| returns a <code>time.Time</code> value rather than, in the old | |
| API, an integer nanosecond count since the Unix epoch. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/sleepUntil/` `/^}/`}} | |
| --><span class="comment">// sleepUntil sleeps until the specified time. It returns immediately if it's too late.</span> | |
| func sleepUntil(wakeup time.Time) { | |
| now := time.Now() <span class="comment">// A Time.</span> | |
| if !wakeup.After(now) { | |
| return | |
| } | |
| delta := wakeup.Sub(now) <span class="comment">// A Duration.</span> | |
| fmt.Printf("Sleeping for %.3fs\n", delta.Seconds()) | |
| time.Sleep(delta) | |
| }</pre> | |
| <p> | |
| The new types, methods, and constants have been propagated through | |
| all the standard packages that use time, such as <code>os</code> and | |
| its representation of file time stamps. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| The <code>go</code> <code>fix</code> tool will update many uses of the old <code>time</code> package to use the new | |
| types and methods, although it does not replace values such as <code>1e9</code> | |
| representing nanoseconds per second. | |
| Also, because of type changes in some of the values that arise, | |
| some of the expressions rewritten by the fix tool may require | |
| further hand editing; in such cases the rewrite will include | |
| the correct function or method for the old functionality, but | |
| may have the wrong type or require further analysis. | |
| </p> | |
| <h2 id="minor">Minor changes to the library</h2> | |
| <p> | |
| This section describes smaller changes, such as those to less commonly | |
| used packages or that affect | |
| few programs beyond the need to run <code>go</code> <code>fix</code>. | |
| This category includes packages that are new in Go 1. | |
| Collectively they improve portability, regularize behavior, and | |
| make the interfaces more modern and Go-like. | |
| </p> | |
| <h3 id="archive_zip">The archive/zip package</h3> | |
| <p> | |
| In Go 1, <a href="/pkg/archive/zip/#Writer"><code>*zip.Writer</code></a> no | |
| longer has a <code>Write</code> method. Its presence was a mistake. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| What little code is affected will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="bufio">The bufio package</h3> | |
| <p> | |
| In Go 1, <a href="/pkg/bufio/#NewReaderSize"><code>bufio.NewReaderSize</code></a> | |
| and | |
| <a href="/pkg/bufio/#NewWriterSize"><code>bufio.NewWriterSize</code></a> | |
| functions no longer return an error for invalid sizes. | |
| If the argument size is too small or invalid, it is adjusted. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update calls that assign the error to _. | |
| Calls that aren't fixed will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="compress">The compress/flate, compress/gzip and compress/zlib packages</h3> | |
| <p> | |
| In Go 1, the <code>NewWriterXxx</code> functions in | |
| <a href="/pkg/compress/flate"><code>compress/flate</code></a>, | |
| <a href="/pkg/compress/gzip"><code>compress/gzip</code></a> and | |
| <a href="/pkg/compress/zlib"><code>compress/zlib</code></a> | |
| all return <code>(*Writer, error)</code> if they take a compression level, | |
| and <code>*Writer</code> otherwise. Package <code>gzip</code>'s | |
| <code>Compressor</code> and <code>Decompressor</code> types have been renamed | |
| to <code>Writer</code> and <code>Reader</code>. Package <code>flate</code>'s | |
| <code>WrongValueError</code> type has been removed. | |
| </p> | |
| <p> | |
| <em>Updating</em> | |
| Running <code>go</code> <code>fix</code> will update old names and calls that assign the error to _. | |
| Calls that aren't fixed will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="crypto_aes_des">The crypto/aes and crypto/des packages</h3> | |
| <p> | |
| In Go 1, the <code>Reset</code> method has been removed. Go does not guarantee | |
| that memory is not copied and therefore this method was misleading. | |
| </p> | |
| <p> | |
| The cipher-specific types <code>*aes.Cipher</code>, <code>*des.Cipher</code>, | |
| and <code>*des.TripleDESCipher</code> have been removed in favor of | |
| <code>cipher.Block</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Remove the calls to Reset. Replace uses of the specific cipher types with | |
| cipher.Block. | |
| </p> | |
| <h3 id="crypto_elliptic">The crypto/elliptic package</h3> | |
| <p> | |
| In Go 1, <a href="/pkg/crypto/elliptic/#Curve"><code>elliptic.Curve</code></a> | |
| has been made an interface to permit alternative implementations. The curve | |
| parameters have been moved to the | |
| <a href="/pkg/crypto/elliptic/#CurveParams"><code>elliptic.CurveParams</code></a> | |
| structure. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Existing users of <code>*elliptic.Curve</code> will need to change to | |
| simply <code>elliptic.Curve</code>. Calls to <code>Marshal</code>, | |
| <code>Unmarshal</code> and <code>GenerateKey</code> are now functions | |
| in <code>crypto/elliptic</code> that take an <code>elliptic.Curve</code> | |
| as their first argument. | |
| </p> | |
| <h3 id="crypto_hmac">The crypto/hmac package</h3> | |
| <p> | |
| In Go 1, the hash-specific functions, such as <code>hmac.NewMD5</code>, have | |
| been removed from <code>crypto/hmac</code>. Instead, <code>hmac.New</code> takes | |
| a function that returns a <code>hash.Hash</code>, such as <code>md5.New</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will perform the needed changes. | |
| </p> | |
| <h3 id="crypto_x509">The crypto/x509 package</h3> | |
| <p> | |
| In Go 1, the | |
| <a href="/pkg/crypto/x509/#CreateCertificate"><code>CreateCertificate</code></a> | |
| and | |
| <a href="/pkg/crypto/x509/#CreateCRL"><code>CreateCRL</code></a> | |
| functions in <code>crypto/x509</code> have been altered to take an | |
| <code>interface{}</code> where they previously took a <code>*rsa.PublicKey</code> | |
| or <code>*rsa.PrivateKey</code>. This will allow other public key algorithms | |
| to be implemented in the future. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| No changes will be needed. | |
| </p> | |
| <h3 id="encoding_binary">The encoding/binary package</h3> | |
| <p> | |
| In Go 1, the <code>binary.TotalSize</code> function has been replaced by | |
| <a href="/pkg/encoding/binary/#Size"><code>Size</code></a>, | |
| which takes an <code>interface{}</code> argument rather than | |
| a <code>reflect.Value</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| What little code is affected will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="encoding_xml">The encoding/xml package</h3> | |
| <p> | |
| In Go 1, the <a href="/pkg/encoding/xml/"><code>xml</code></a> package | |
| has been brought closer in design to the other marshaling packages such | |
| as <a href="/pkg/encoding/gob/"><code>encoding/gob</code></a>. | |
| </p> | |
| <p> | |
| The old <code>Parser</code> type is renamed | |
| <a href="/pkg/encoding/xml/#Decoder"><code>Decoder</code></a> and has a new | |
| <a href="/pkg/encoding/xml/#Decoder.Decode"><code>Decode</code></a> method. An | |
| <a href="/pkg/encoding/xml/#Encoder"><code>Encoder</code></a> type was also introduced. | |
| </p> | |
| <p> | |
| The functions <a href="/pkg/encoding/xml/#Marshal"><code>Marshal</code></a> | |
| and <a href="/pkg/encoding/xml/#Unmarshal"><code>Unmarshal</code></a> | |
| work with <code>[]byte</code> values now. To work with streams, | |
| use the new <a href="/pkg/encoding/xml/#Encoder"><code>Encoder</code></a> | |
| and <a href="/pkg/encoding/xml/#Decoder"><code>Decoder</code></a> types. | |
| </p> | |
| <p> | |
| When marshaling or unmarshaling values, the format of supported flags in | |
| field tags has changed to be closer to the | |
| <a href="/pkg/encoding/json"><code>json</code></a> package | |
| (<code>`xml:"name,flag"`</code>). The matching done between field tags, field | |
| names, and the XML attribute and element names is now case-sensitive. | |
| The <code>XMLName</code> field tag, if present, must also match the name | |
| of the XML element being marshaled. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update most uses of the package except for some calls to | |
| <code>Unmarshal</code>. Special care must be taken with field tags, | |
| since the fix tool will not update them and if not fixed by hand they will | |
| misbehave silently in some cases. For example, the old | |
| <code>"attr"</code> is now written <code>",attr"</code> while plain | |
| <code>"attr"</code> remains valid but with a different meaning. | |
| </p> | |
| <h3 id="expvar">The expvar package</h3> | |
| <p> | |
| In Go 1, the <code>RemoveAll</code> function has been removed. | |
| The <code>Iter</code> function and Iter method on <code>*Map</code> have | |
| been replaced by | |
| <a href="/pkg/expvar/#Do"><code>Do</code></a> | |
| and | |
| <a href="/pkg/expvar/#Map.Do"><code>(*Map).Do</code></a>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Most code using <code>expvar</code> will not need changing. The rare code that used | |
| <code>Iter</code> can be updated to pass a closure to <code>Do</code> to achieve the same effect. | |
| </p> | |
| <h3 id="flag">The flag package</h3> | |
| <p> | |
| In Go 1, the interface <a href="/pkg/flag/#Value"><code>flag.Value</code></a> has changed slightly. | |
| The <code>Set</code> method now returns an <code>error</code> instead of | |
| a <code>bool</code> to indicate success or failure. | |
| </p> | |
| <p> | |
| There is also a new kind of flag, <code>Duration</code>, to support argument | |
| values specifying time intervals. | |
| Values for such flags must be given units, just as <code>time.Duration</code> | |
| formats them: <code>10s</code>, <code>1h30m</code>, etc. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/timeout/`}} | |
| -->var timeout = flag.Duration("timeout", 30*time.Second, "how long to wait for completion")</pre> | |
| <p> | |
| <em>Updating</em>: | |
| Programs that implement their own flags will need minor manual fixes to update their | |
| <code>Set</code> methods. | |
| The <code>Duration</code> flag is new and affects no existing code. | |
| </p> | |
| <h3 id="go">The go/* packages</h3> | |
| <p> | |
| Several packages under <code>go</code> have slightly revised APIs. | |
| </p> | |
| <p> | |
| A concrete <code>Mode</code> type was introduced for configuration mode flags | |
| in the packages | |
| <a href="/pkg/go/scanner/"><code>go/scanner</code></a>, | |
| <a href="/pkg/go/parser/"><code>go/parser</code></a>, | |
| <a href="/pkg/go/printer/"><code>go/printer</code></a>, and | |
| <a href="/pkg/go/doc/"><code>go/doc</code></a>. | |
| </p> | |
| <p> | |
| The modes <code>AllowIllegalChars</code> and <code>InsertSemis</code> have been removed | |
| from the <a href="/pkg/go/scanner/"><code>go/scanner</code></a> package. They were mostly | |
| useful for scanning text other then Go source files. Instead, the | |
| <a href="/pkg/text/scanner/"><code>text/scanner</code></a> package should be used | |
| for that purpose. | |
| </p> | |
| <p> | |
| The <a href="/pkg/go/scanner/#ErrorHandler"><code>ErrorHandler</code></a> provided | |
| to the scanner's <a href="/pkg/go/scanner/#Scanner.Init"><code>Init</code></a> method is | |
| now simply a function rather than an interface. The <code>ErrorVector</code> type has | |
| been removed in favor of the (existing) <a href="/pkg/go/scanner/#ErrorList"><code>ErrorList</code></a> | |
| type, and the <code>ErrorVector</code> methods have been migrated. Instead of embedding | |
| an <code>ErrorVector</code> in a client of the scanner, now a client should maintain | |
| an <code>ErrorList</code>. | |
| </p> | |
| <p> | |
| The set of parse functions provided by the <a href="/pkg/go/parser/"><code>go/parser</code></a> | |
| package has been reduced to the primary parse function | |
| <a href="/pkg/go/parser/#ParseFile"><code>ParseFile</code></a>, and a couple of | |
| convenience functions <a href="/pkg/go/parser/#ParseDir"><code>ParseDir</code></a> | |
| and <a href="/pkg/go/parser/#ParseExpr"><code>ParseExpr</code></a>. | |
| </p> | |
| <p> | |
| The <a href="/pkg/go/printer/"><code>go/printer</code></a> package supports an additional | |
| configuration mode <a href="/pkg/go/printer/#Mode"><code>SourcePos</code></a>; | |
| if set, the printer will emit <code>//line</code> comments such that the generated | |
| output contains the original source code position information. The new type | |
| <a href="/pkg/go/printer/#CommentedNode"><code>CommentedNode</code></a> can be | |
| used to provide comments associated with an arbitrary | |
| <a href="/pkg/go/ast/#Node"><code>ast.Node</code></a> (until now only | |
| <a href="/pkg/go/ast/#File"><code>ast.File</code></a> carried comment information). | |
| </p> | |
| <p> | |
| The type names of the <a href="/pkg/go/doc/"><code>go/doc</code></a> package have been | |
| streamlined by removing the <code>Doc</code> suffix: <code>PackageDoc</code> | |
| is now <code>Package</code>, <code>ValueDoc</code> is <code>Value</code>, etc. | |
| Also, all types now consistently have a <code>Name</code> field (or <code>Names</code>, | |
| in the case of type <code>Value</code>) and <code>Type.Factories</code> has become | |
| <code>Type.Funcs</code>. | |
| Instead of calling <code>doc.NewPackageDoc(pkg, importpath)</code>, | |
| documentation for a package is created with: | |
| </p> | |
| <pre> | |
| doc.New(pkg, importpath, mode) | |
| </pre> | |
| <p> | |
| where the new <code>mode</code> parameter specifies the operation mode: | |
| if set to <a href="/pkg/go/doc/#AllDecls"><code>AllDecls</code></a>, all declarations | |
| (not just exported ones) are considered. | |
| The function <code>NewFileDoc</code> was removed, and the function | |
| <code>CommentText</code> has become the method | |
| <a href="/pkg/go/ast/#Text"><code>Text</code></a> of | |
| <a href="/pkg/go/ast/#CommentGroup"><code>ast.CommentGroup</code></a>. | |
| </p> | |
| <p> | |
| In package <a href="/pkg/go/token/"><code>go/token</code></a>, the | |
| <a href="/pkg/go/token/#FileSet"><code>token.FileSet</code></a> method <code>Files</code> | |
| (which originally returned a channel of <code>*token.File</code>s) has been replaced | |
| with the iterator <a href="/pkg/go/token/#FileSet.Iterate"><code>Iterate</code></a> that | |
| accepts a function argument instead. | |
| </p> | |
| <p> | |
| In package <a href="/pkg/go/build/"><code>go/build</code></a>, the API | |
| has been nearly completely replaced. | |
| The package still computes Go package information | |
| but it does not run the build: the <code>Cmd</code> and <code>Script</code> | |
| types are gone. | |
| (To build code, use the new | |
| <a href="/cmd/go/"><code>go</code></a> command instead.) | |
| The <code>DirInfo</code> type is now named | |
| <a href="/pkg/go/build/#Package"><code>Package</code></a>. | |
| <code>FindTree</code> and <code>ScanDir</code> are replaced by | |
| <a href="/pkg/go/build/#Import"><code>Import</code></a> | |
| and | |
| <a href="/pkg/go/build/#ImportDir"><code>ImportDir</code></a>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses packages in <code>go</code> will have to be updated by hand; the | |
| compiler will reject incorrect uses. Templates used in conjunction with any of the | |
| <code>go/doc</code> types may need manual fixes; the renamed fields will lead | |
| to run-time errors. | |
| </p> | |
| <h3 id="hash">The hash package</h3> | |
| <p> | |
| In Go 1, the definition of <a href="/pkg/hash/#Hash"><code>hash.Hash</code></a> includes | |
| a new method, <code>BlockSize</code>. This new method is used primarily in the | |
| cryptographic libraries. | |
| </p> | |
| <p> | |
| The <code>Sum</code> method of the | |
| <a href="/pkg/hash/#Hash"><code>hash.Hash</code></a> interface now takes a | |
| <code>[]byte</code> argument, to which the hash value will be appended. | |
| The previous behavior can be recreated by adding a <code>nil</code> argument to the call. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Existing implementations of <code>hash.Hash</code> will need to add a | |
| <code>BlockSize</code> method. Hashes that process the input one byte at | |
| a time can implement <code>BlockSize</code> to return 1. | |
| Running <code>go</code> <code>fix</code> will update calls to the <code>Sum</code> methods of the various | |
| implementations of <code>hash.Hash</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Since the package's functionality is new, no updating is necessary. | |
| </p> | |
| <h3 id="http">The http package</h3> | |
| <p> | |
| In Go 1 the <a href="/pkg/net/http/"><code>http</code></a> package is refactored, | |
| putting some of the utilities into a | |
| <a href="/pkg/net/http/httputil/"><code>httputil</code></a> subdirectory. | |
| These pieces are only rarely needed by HTTP clients. | |
| The affected items are: | |
| </p> | |
| <ul> | |
| <li>ClientConn</li> | |
| <li>DumpRequest</li> | |
| <li>DumpRequestOut</li> | |
| <li>DumpResponse</li> | |
| <li>NewChunkedReader</li> | |
| <li>NewChunkedWriter</li> | |
| <li>NewClientConn</li> | |
| <li>NewProxyClientConn</li> | |
| <li>NewServerConn</li> | |
| <li>NewSingleHostReverseProxy</li> | |
| <li>ReverseProxy</li> | |
| <li>ServerConn</li> | |
| </ul> | |
| <p> | |
| The <code>Request.RawURL</code> field has been removed; it was a | |
| historical artifact. | |
| </p> | |
| <p> | |
| The <code>Handle</code> and <code>HandleFunc</code> | |
| functions, and the similarly-named methods of <code>ServeMux</code>, | |
| now panic if an attempt is made to register the same pattern twice. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update the few programs that are affected except for | |
| uses of <code>RawURL</code>, which must be fixed by hand. | |
| </p> | |
| <h3 id="image">The image package</h3> | |
| <p> | |
| The <a href="/pkg/image/"><code>image</code></a> package has had a number of | |
| minor changes, rearrangements and renamings. | |
| </p> | |
| <p> | |
| Most of the color handling code has been moved into its own package, | |
| <a href="/pkg/image/color/"><code>image/color</code></a>. | |
| For the elements that moved, a symmetry arises; for instance, | |
| each pixel of an | |
| <a href="/pkg/image/#RGBA"><code>image.RGBA</code></a> | |
| is a | |
| <a href="/pkg/image/color/#RGBA"><code>color.RGBA</code></a>. | |
| </p> | |
| <p> | |
| The old <code>image/ycbcr</code> package has been folded, with some | |
| renamings, into the | |
| <a href="/pkg/image/"><code>image</code></a> | |
| and | |
| <a href="/pkg/image/color/"><code>image/color</code></a> | |
| packages. | |
| </p> | |
| <p> | |
| The old <code>image.ColorImage</code> type is still in the <code>image</code> | |
| package but has been renamed | |
| <a href="/pkg/image/#Uniform"><code>image.Uniform</code></a>, | |
| while <code>image.Tiled</code> has been removed. | |
| </p> | |
| <p> | |
| This table lists the renamings. | |
| </p> | |
| <table class="codetable" frame="border" summary="image renames"> | |
| <colgroup align="left" width="50%"></colgroup> | |
| <colgroup align="left" width="50%"></colgroup> | |
| <tr> | |
| <th align="left">Old</th> | |
| <th align="left">New</th> | |
| </tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>image.Color</td> <td>color.Color</td></tr> | |
| <tr><td>image.ColorModel</td> <td>color.Model</td></tr> | |
| <tr><td>image.ColorModelFunc</td> <td>color.ModelFunc</td></tr> | |
| <tr><td>image.PalettedColorModel</td> <td>color.Palette</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>image.RGBAColor</td> <td>color.RGBA</td></tr> | |
| <tr><td>image.RGBA64Color</td> <td>color.RGBA64</td></tr> | |
| <tr><td>image.NRGBAColor</td> <td>color.NRGBA</td></tr> | |
| <tr><td>image.NRGBA64Color</td> <td>color.NRGBA64</td></tr> | |
| <tr><td>image.AlphaColor</td> <td>color.Alpha</td></tr> | |
| <tr><td>image.Alpha16Color</td> <td>color.Alpha16</td></tr> | |
| <tr><td>image.GrayColor</td> <td>color.Gray</td></tr> | |
| <tr><td>image.Gray16Color</td> <td>color.Gray16</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>image.RGBAColorModel</td> <td>color.RGBAModel</td></tr> | |
| <tr><td>image.RGBA64ColorModel</td> <td>color.RGBA64Model</td></tr> | |
| <tr><td>image.NRGBAColorModel</td> <td>color.NRGBAModel</td></tr> | |
| <tr><td>image.NRGBA64ColorModel</td> <td>color.NRGBA64Model</td></tr> | |
| <tr><td>image.AlphaColorModel</td> <td>color.AlphaModel</td></tr> | |
| <tr><td>image.Alpha16ColorModel</td> <td>color.Alpha16Model</td></tr> | |
| <tr><td>image.GrayColorModel</td> <td>color.GrayModel</td></tr> | |
| <tr><td>image.Gray16ColorModel</td> <td>color.Gray16Model</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>ycbcr.RGBToYCbCr</td> <td>color.RGBToYCbCr</td></tr> | |
| <tr><td>ycbcr.YCbCrToRGB</td> <td>color.YCbCrToRGB</td></tr> | |
| <tr><td>ycbcr.YCbCrColorModel</td> <td>color.YCbCrModel</td></tr> | |
| <tr><td>ycbcr.YCbCrColor</td> <td>color.YCbCr</td></tr> | |
| <tr><td>ycbcr.YCbCr</td> <td>image.YCbCr</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>ycbcr.SubsampleRatio444</td> <td>image.YCbCrSubsampleRatio444</td></tr> | |
| <tr><td>ycbcr.SubsampleRatio422</td> <td>image.YCbCrSubsampleRatio422</td></tr> | |
| <tr><td>ycbcr.SubsampleRatio420</td> <td>image.YCbCrSubsampleRatio420</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>image.ColorImage</td> <td>image.Uniform</td></tr> | |
| </table> | |
| <p> | |
| The image package's <code>New</code> functions | |
| (<a href="/pkg/image/#NewRGBA"><code>NewRGBA</code></a>, | |
| <a href="/pkg/image/#NewRGBA64"><code>NewRGBA64</code></a>, etc.) | |
| take an <a href="/pkg/image/#Rectangle"><code>image.Rectangle</code></a> as an argument | |
| instead of four integers. | |
| </p> | |
| <p> | |
| Finally, there are new predefined <code>color.Color</code> variables | |
| <a href="/pkg/image/color/#Black"><code>color.Black</code></a>, | |
| <a href="/pkg/image/color/#White"><code>color.White</code></a>, | |
| <a href="/pkg/image/color/#Opaque"><code>color.Opaque</code></a> | |
| and | |
| <a href="/pkg/image/color/#Transparent"><code>color.Transparent</code></a>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update almost all code affected by the change. | |
| </p> | |
| <h3 id="log_syslog">The log/syslog package</h3> | |
| <p> | |
| In Go 1, the <a href="/pkg/log/syslog/#NewLogger"><code>syslog.NewLogger</code></a> | |
| function returns an error as well as a <code>log.Logger</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| What little code is affected will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="mime">The mime package</h3> | |
| <p> | |
| In Go 1, the <a href="/pkg/mime/#FormatMediaType"><code>FormatMediaType</code></a> function | |
| of the <code>mime</code> package has been simplified to make it | |
| consistent with | |
| <a href="/pkg/mime/#ParseMediaType"><code>ParseMediaType</code></a>. | |
| It now takes <code>"text/html"</code> rather than <code>"text"</code> and <code>"html"</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| What little code is affected will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h3 id="net">The net package</h3> | |
| <p> | |
| In Go 1, the various <code>SetTimeout</code>, | |
| <code>SetReadTimeout</code>, and <code>SetWriteTimeout</code> methods | |
| have been replaced with | |
| <a href="/pkg/net/#IPConn.SetDeadline"><code>SetDeadline</code></a>, | |
| <a href="/pkg/net/#IPConn.SetReadDeadline"><code>SetReadDeadline</code></a>, and | |
| <a href="/pkg/net/#IPConn.SetWriteDeadline"><code>SetWriteDeadline</code></a>, | |
| respectively. Rather than taking a timeout value in nanoseconds that | |
| apply to any activity on the connection, the new methods set an | |
| absolute deadline (as a <code>time.Time</code> value) after which | |
| reads and writes will time out and no longer block. | |
| </p> | |
| <p> | |
| There are also new functions | |
| <a href="/pkg/net/#DialTimeout"><code>net.DialTimeout</code></a> | |
| to simplify timing out dialing a network address and | |
| <a href="/pkg/net/#ListenMulticastUDP"><code>net.ListenMulticastUDP</code></a> | |
| to allow multicast UDP to listen concurrently across multiple listeners. | |
| The <code>net.ListenMulticastUDP</code> function replaces the old | |
| <code>JoinGroup</code> and <code>LeaveGroup</code> methods. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses the old methods will fail to compile and must be updated by hand. | |
| The semantic change makes it difficult for the fix tool to update automatically. | |
| </p> | |
| <h3 id="os">The os package</h3> | |
| <p> | |
| The <code>Time</code> function has been removed; callers should use | |
| the <a href="/pkg/time/#Time"><code>Time</code></a> type from the | |
| <code>time</code> package. | |
| </p> | |
| <p> | |
| The <code>Exec</code> function has been removed; callers should use | |
| <code>Exec</code> from the <code>syscall</code> package, where available. | |
| </p> | |
| <p> | |
| The <code>ShellExpand</code> function has been renamed to <a | |
| href="/pkg/os/#ExpandEnv"><code>ExpandEnv</code></a>. | |
| </p> | |
| <p> | |
| The <a href="/pkg/os/#NewFile"><code>NewFile</code></a> function | |
| now takes a <code>uintptr</code> fd, instead of an <code>int</code>. | |
| The <a href="/pkg/os/#File.Fd"><code>Fd</code></a> method on files now | |
| also returns a <code>uintptr</code>. | |
| </p> | |
| <p> | |
| There are no longer error constants such as <code>EINVAL</code> | |
| in the <code>os</code> package, since the set of values varied with | |
| the underlying operating system. There are new portable functions like | |
| <a href="/pkg/os/#IsPermission"><code>IsPermission</code></a> | |
| to test common error properties, plus a few new error values | |
| with more Go-like names, such as | |
| <a href="/pkg/os/#ErrPermission"><code>ErrPermission</code></a> | |
| and | |
| <a href="/pkg/os/#ErrNoEnv"><code>ErrNoEnv</code></a>. | |
| </p> | |
| <p> | |
| The <code>Getenverror</code> function has been removed. To distinguish | |
| between a non-existent environment variable and an empty string, | |
| use <a href="/pkg/os/#Environ"><code>os.Environ</code></a> or | |
| <a href="/pkg/syscall/#Getenv"><code>syscall.Getenv</code></a>. | |
| </p> | |
| <p> | |
| The <a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> method has | |
| dropped its option argument and the associated constants are gone | |
| from the package. | |
| Also, the function <code>Wait</code> is gone; only the method of | |
| the <code>Process</code> type persists. | |
| </p> | |
| <p> | |
| The <code>Waitmsg</code> type returned by | |
| <a href="/pkg/os/#Process.Wait"><code>Process.Wait</code></a> | |
| has been replaced with a more portable | |
| <a href="/pkg/os/#ProcessState"><code>ProcessState</code></a> | |
| type with accessor methods to recover information about the | |
| process. | |
| Because of changes to <code>Wait</code>, the <code>ProcessState</code> | |
| value always describes an exited process. | |
| Portability concerns simplified the interface in other ways, but the values returned by the | |
| <a href="/pkg/os/#ProcessState.Sys"><code>ProcessState.Sys</code></a> and | |
| <a href="/pkg/os/#ProcessState.SysUsage"><code>ProcessState.SysUsage</code></a> | |
| methods can be type-asserted to underlying system-specific data structures such as | |
| <a href="/pkg/syscall/#WaitStatus"><code>syscall.WaitStatus</code></a> and | |
| <a href="/pkg/syscall/#Rusage"><code>syscall.Rusage</code></a> on Unix. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will drop a zero argument to <code>Process.Wait</code>. | |
| All other changes will be caught by the compiler and must be updated by hand. | |
| </p> | |
| <h4 id="os_fileinfo">The os.FileInfo type</h4> | |
| <p> | |
| Go 1 redefines the <a href="/pkg/os/#FileInfo"><code>os.FileInfo</code></a> type, | |
| changing it from a struct to an interface: | |
| </p> | |
| <pre> | |
| type FileInfo interface { | |
| Name() string // base name of the file | |
| Size() int64 // length in bytes | |
| Mode() FileMode // file mode bits | |
| ModTime() time.Time // modification time | |
| IsDir() bool // abbreviation for Mode().IsDir() | |
| Sys() interface{} // underlying data source (can return nil) | |
| } | |
| </pre> | |
| <p> | |
| The file mode information has been moved into a subtype called | |
| <a href="/pkg/os/#FileMode"><code>os.FileMode</code></a>, | |
| a simple integer type with <code>IsDir</code>, <code>Perm</code>, and <code>String</code> | |
| methods. | |
| </p> | |
| <p> | |
| The system-specific details of file modes and properties such as (on Unix) | |
| i-number have been removed from <code>FileInfo</code> altogether. | |
| Instead, each operating system's <code>os</code> package provides an | |
| implementation of the <code>FileInfo</code> interface, which | |
| has a <code>Sys</code> method that returns the | |
| system-specific representation of file metadata. | |
| For instance, to discover the i-number of a file on a Unix system, unpack | |
| the <code>FileInfo</code> like this: | |
| </p> | |
| <pre> | |
| fi, err := os.Stat("hello.go") | |
| if err != nil { | |
| log.Fatal(err) | |
| } | |
| // Check that it's a Unix file. | |
| unixStat, ok := fi.Sys().(*syscall.Stat_t) | |
| if !ok { | |
| log.Fatal("hello.go: not a Unix file") | |
| } | |
| fmt.Printf("file i-number: %d\n", unixStat.Ino) | |
| </pre> | |
| <p> | |
| Assuming (which is unwise) that <code>"hello.go"</code> is a Unix file, | |
| the i-number expression could be contracted to | |
| </p> | |
| <pre> | |
| fi.Sys().(*syscall.Stat_t).Ino | |
| </pre> | |
| <p> | |
| The vast majority of uses of <code>FileInfo</code> need only the methods | |
| of the standard interface. | |
| </p> | |
| <p> | |
| The <code>os</code> package no longer contains wrappers for the POSIX errors | |
| such as <code>ENOENT</code>. | |
| For the few programs that need to verify particular error conditions, there are | |
| now the boolean functions | |
| <a href="/pkg/os/#IsExist"><code>IsExist</code></a>, | |
| <a href="/pkg/os/#IsNotExist"><code>IsNotExist</code></a> | |
| and | |
| <a href="/pkg/os/#IsPermission"><code>IsPermission</code></a>. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/os\.Open/` `/}/`}} | |
| --> f, err := os.OpenFile(name, os.O_RDWR|os.O_CREATE|os.O_EXCL, 0600) | |
| if os.IsExist(err) { | |
| log.Printf("%s already exists", name) | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update code that uses the old equivalent of the current <code>os.FileInfo</code> | |
| and <code>os.FileMode</code> API. | |
| Code that needs system-specific file details will need to be updated by hand. | |
| Code that uses the old POSIX error values from the <code>os</code> package | |
| will fail to compile and will also need to be updated by hand. | |
| </p> | |
| <h3 id="os_signal">The os/signal package</h3> | |
| <p> | |
| The <code>os/signal</code> package in Go 1 replaces the | |
| <code>Incoming</code> function, which returned a channel | |
| that received all incoming signals, | |
| with the selective <code>Notify</code> function, which asks | |
| for delivery of specific signals on an existing channel. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code must be updated by hand. | |
| A literal translation of | |
| </p> | |
| <pre> | |
| c := signal.Incoming() | |
| </pre> | |
| <p> | |
| is | |
| </p> | |
| <pre> | |
| c := make(chan os.Signal) | |
| signal.Notify(c) // ask for all signals | |
| </pre> | |
| <p> | |
| but most code should list the specific signals it wants to handle instead: | |
| </p> | |
| <pre> | |
| c := make(chan os.Signal) | |
| signal.Notify(c, syscall.SIGHUP, syscall.SIGQUIT) | |
| </pre> | |
| <h3 id="path_filepath">The path/filepath package</h3> | |
| <p> | |
| In Go 1, the <a href="/pkg/path/filepath/#Walk"><code>Walk</code></a> function of the | |
| <code>path/filepath</code> package | |
| has been changed to take a function value of type | |
| <a href="/pkg/path/filepath/#WalkFunc"><code>WalkFunc</code></a> | |
| instead of a <code>Visitor</code> interface value. | |
| <code>WalkFunc</code> unifies the handling of both files and directories. | |
| </p> | |
| <pre> | |
| type WalkFunc func(path string, info os.FileInfo, err error) error | |
| </pre> | |
| <p> | |
| The <code>WalkFunc</code> function will be called even for files or directories that could not be opened; | |
| in such cases the error argument will describe the failure. | |
| If a directory's contents are to be skipped, | |
| the function should return the value <a href="/pkg/path/filepath/#variables"><code>filepath.SkipDir</code></a> | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/STARTWALK/` `/ENDWALK/`}} | |
| --> markFn := func(path string, info os.FileInfo, err error) error { | |
| if path == "pictures" { <span class="comment">// Will skip walking of directory pictures and its contents.</span> | |
| return filepath.SkipDir | |
| } | |
| if err != nil { | |
| return err | |
| } | |
| log.Println(path) | |
| return nil | |
| } | |
| err := filepath.Walk(".", markFn) | |
| if err != nil { | |
| log.Fatal(err) | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| The change simplifies most code but has subtle consequences, so affected programs | |
| will need to be updated by hand. | |
| The compiler will catch code using the old interface. | |
| </p> | |
| <h3 id="regexp">The regexp package</h3> | |
| <p> | |
| The <a href="/pkg/regexp/"><code>regexp</code></a> package has been rewritten. | |
| It has the same interface but the specification of the regular expressions | |
| it supports has changed from the old "egrep" form to that of | |
| <a href="http://code.google.com/p/re2/">RE2</a>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses the package should have its regular expressions checked by hand. | |
| </p> | |
| <h3 id="runtime">The runtime package</h3> | |
| <p> | |
| In Go 1, much of the API exported by package | |
| <code>runtime</code> has been removed in favor of | |
| functionality provided by other packages. | |
| Code using the <code>runtime.Type</code> interface | |
| or its specific concrete type implementations should | |
| now use package <a href="/pkg/reflect/"><code>reflect</code></a>. | |
| Code using <code>runtime.Semacquire</code> or <code>runtime.Semrelease</code> | |
| should use channels or the abstractions in package <a href="/pkg/sync/"><code>sync</code></a>. | |
| The <code>runtime.Alloc</code>, <code>runtime.Free</code>, | |
| and <code>runtime.Lookup</code> functions, an unsafe API created for | |
| debugging the memory allocator, have no replacement. | |
| </p> | |
| <p> | |
| Before, <code>runtime.MemStats</code> was a global variable holding | |
| statistics about memory allocation, and calls to <code>runtime.UpdateMemStats</code> | |
| ensured that it was up to date. | |
| In Go 1, <code>runtime.MemStats</code> is a struct type, and code should use | |
| <a href="/pkg/runtime/#ReadMemStats"><code>runtime.ReadMemStats</code></a> | |
| to obtain the current statistics. | |
| </p> | |
| <p> | |
| The package adds a new function, | |
| <a href="/pkg/runtime/#NumCPU"><code>runtime.NumCPU</code></a>, that returns the number of CPUs available | |
| for parallel execution, as reported by the operating system kernel. | |
| Its value can inform the setting of <code>GOMAXPROCS</code>. | |
| The <code>runtime.Cgocalls</code> and <code>runtime.Goroutines</code> functions | |
| have been renamed to <code>runtime.NumCgoCall</code> and <code>runtime.NumGoroutine</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update code for the function renamings. | |
| Other code will need to be updated by hand. | |
| </p> | |
| <h3 id="strconv">The strconv package</h3> | |
| <p> | |
| In Go 1, the | |
| <a href="/pkg/strconv/"><code>strconv</code></a> | |
| package has been significantly reworked to make it more Go-like and less C-like, | |
| although <code>Atoi</code> lives on (it's similar to | |
| <code>int(ParseInt(x, 10, 0))</code>, as does | |
| <code>Itoa(x)</code> (<code>FormatInt(int64(x), 10)</code>). | |
| There are also new variants of some of the functions that append to byte slices rather than | |
| return strings, to allow control over allocation. | |
| </p> | |
| <p> | |
| This table summarizes the renamings; see the | |
| <a href="/pkg/strconv/">package documentation</a> | |
| for full details. | |
| </p> | |
| <table class="codetable" frame="border" summary="strconv renames"> | |
| <colgroup align="left" width="50%"></colgroup> | |
| <colgroup align="left" width="50%"></colgroup> | |
| <tr> | |
| <th align="left">Old call</th> | |
| <th align="left">New call</th> | |
| </tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Atob(x)</td> <td>ParseBool(x)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Atof32(x)</td> <td>ParseFloat(x, 32)§</td></tr> | |
| <tr><td>Atof64(x)</td> <td>ParseFloat(x, 64)</td></tr> | |
| <tr><td>AtofN(x, n)</td> <td>ParseFloat(x, n)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Atoi(x)</td> <td>Atoi(x)</td></tr> | |
| <tr><td>Atoi(x)</td> <td>ParseInt(x, 10, 0)§</td></tr> | |
| <tr><td>Atoi64(x)</td> <td>ParseInt(x, 10, 64)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Atoui(x)</td> <td>ParseUint(x, 10, 0)§</td></tr> | |
| <tr><td>Atoui64(x)</td> <td>ParseUint(x, 10, 64)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Btoi64(x, b)</td> <td>ParseInt(x, b, 64)</td></tr> | |
| <tr><td>Btoui64(x, b)</td> <td>ParseUint(x, b, 64)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Btoa(x)</td> <td>FormatBool(x)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Ftoa32(x, f, p)</td> <td>FormatFloat(float64(x), f, p, 32)</td></tr> | |
| <tr><td>Ftoa64(x, f, p)</td> <td>FormatFloat(x, f, p, 64)</td></tr> | |
| <tr><td>FtoaN(x, f, p, n)</td> <td>FormatFloat(x, f, p, n)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Itoa(x)</td> <td>Itoa(x)</td></tr> | |
| <tr><td>Itoa(x)</td> <td>FormatInt(int64(x), 10)</td></tr> | |
| <tr><td>Itoa64(x)</td> <td>FormatInt(x, 10)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Itob(x, b)</td> <td>FormatInt(int64(x), b)</td></tr> | |
| <tr><td>Itob64(x, b)</td> <td>FormatInt(x, b)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Uitoa(x)</td> <td>FormatUint(uint64(x), 10)</td></tr> | |
| <tr><td>Uitoa64(x)</td> <td>FormatUint(x, 10)</td></tr> | |
| <tr> | |
| <td colspan="2"><hr></td> | |
| </tr> | |
| <tr><td>Uitob(x, b)</td> <td>FormatUint(uint64(x), b)</td></tr> | |
| <tr><td>Uitob64(x, b)</td> <td>FormatUint(x, b)</td></tr> | |
| </table> | |
| <p> | |
| <em>Updating</em>: | |
| Running <code>go</code> <code>fix</code> will update almost all code affected by the change. | |
| <br> | |
| § <code>Atoi</code> persists but <code>Atoui</code> and <code>Atof32</code> do not, so | |
| they may require | |
| a cast that must be added by hand; the <code>go</code> <code>fix</code> tool will warn about it. | |
| </p> | |
| <h3 id="templates">The template packages</h3> | |
| <p> | |
| The <code>template</code> and <code>exp/template/html</code> packages have moved to | |
| <a href="/pkg/text/template/"><code>text/template</code></a> and | |
| <a href="/pkg/html/template/"><code>html/template</code></a>. | |
| More significant, the interface to these packages has been simplified. | |
| The template language is the same, but the concept of "template set" is gone | |
| and the functions and methods of the packages have changed accordingly, | |
| often by elimination. | |
| </p> | |
| <p> | |
| Instead of sets, a <code>Template</code> object | |
| may contain multiple named template definitions, | |
| in effect constructing | |
| name spaces for template invocation. | |
| A template can invoke any other template associated with it, but only those | |
| templates associated with it. | |
| The simplest way to associate templates is to parse them together, something | |
| made easier with the new structure of the packages. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| The imports will be updated by fix tool. | |
| Single-template uses will be otherwise be largely unaffected. | |
| Code that uses multiple templates in concert will need to be updated by hand. | |
| The <a href="/pkg/text/template/#examples">examples</a> in | |
| the documentation for <code>text/template</code> can provide guidance. | |
| </p> | |
| <h3 id="testing">The testing package</h3> | |
| <p> | |
| The testing package has a type, <code>B</code>, passed as an argument to benchmark functions. | |
| In Go 1, <code>B</code> has new methods, analogous to those of <code>T</code>, enabling | |
| logging and failure reporting. | |
| </p> | |
| <pre><!--{{code "/doc/progs/go1.go" `/func.*Benchmark/` `/^}/`}} | |
| -->func BenchmarkSprintf(b *testing.B) { | |
| <span class="comment">// Verify correctness before running benchmark.</span> | |
| b.StopTimer() | |
| got := fmt.Sprintf("%x", 23) | |
| const expect = "17" | |
| if expect != got { | |
| b.Fatalf("expected %q; got %q", expect, got) | |
| } | |
| b.StartTimer() | |
| for i := 0; i < b.N; i++ { | |
| fmt.Sprintf("%x", 23) | |
| } | |
| }</pre> | |
| <p> | |
| <em>Updating</em>: | |
| Existing code is unaffected, although benchmarks that use <code>println</code> | |
| or <code>panic</code> should be updated to use the new methods. | |
| </p> | |
| <h3 id="testing_script">The testing/script package</h3> | |
| <p> | |
| The testing/script package has been deleted. It was a dreg. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| No code is likely to be affected. | |
| </p> | |
| <h3 id="unsafe">The unsafe package</h3> | |
| <p> | |
| In Go 1, the functions | |
| <code>unsafe.Typeof</code>, <code>unsafe.Reflect</code>, | |
| <code>unsafe.Unreflect</code>, <code>unsafe.New</code>, and | |
| <code>unsafe.NewArray</code> have been removed; | |
| they duplicated safer functionality provided by | |
| package <a href="/pkg/reflect/"><code>reflect</code></a>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code using these functions must be rewritten to use | |
| package <a href="/pkg/reflect/"><code>reflect</code></a>. | |
| The changes to <a href="http://code.google.com/p/go/source/detail?r=2646dc956207">encoding/gob</a> and the <a href="http://code.google.com/p/goprotobuf/source/detail?r=5340ad310031">protocol buffer library</a> | |
| may be helpful as examples. | |
| </p> | |
| <h3 id="url">The url package</h3> | |
| <p> | |
| In Go 1 several fields from the <a href="/pkg/net/url/#URL"><code>url.URL</code></a> type | |
| were removed or replaced. | |
| </p> | |
| <p> | |
| The <a href="/pkg/net/url/#URL.String"><code>String</code></a> method now | |
| predictably rebuilds an encoded URL string using all of <code>URL</code>'s | |
| fields as necessary. The resulting string will also no longer have | |
| passwords escaped. | |
| </p> | |
| <p> | |
| The <code>Raw</code> field has been removed. In most cases the <code>String</code> | |
| method may be used in its place. | |
| </p> | |
| <p> | |
| The old <code>RawUserinfo</code> field is replaced by the <code>User</code> | |
| field, of type <a href="/pkg/net/url/#Userinfo"><code>*net.Userinfo</code></a>. | |
| Values of this type may be created using the new <a href="/pkg/net/url/#User"><code>net.User</code></a> | |
| and <a href="/pkg/net/url/#UserPassword"><code>net.UserPassword</code></a> | |
| functions. The <code>EscapeUserinfo</code> and <code>UnescapeUserinfo</code> | |
| functions are also gone. | |
| </p> | |
| <p> | |
| The <code>RawAuthority</code> field has been removed. The same information is | |
| available in the <code>Host</code> and <code>User</code> fields. | |
| </p> | |
| <p> | |
| The <code>RawPath</code> field and the <code>EncodedPath</code> method have | |
| been removed. The path information in rooted URLs (with a slash following the | |
| schema) is now available only in decoded form in the <code>Path</code> field. | |
| Occasionally, the encoded data may be required to obtain information that | |
| was lost in the decoding process. These cases must be handled by accessing | |
| the data the URL was built from. | |
| </p> | |
| <p> | |
| URLs with non-rooted paths, such as <code>"mailto:dev@golang.org?subject=Hi"</code>, | |
| are also handled differently. The <code>OpaquePath</code> boolean field has been | |
| removed and a new <code>Opaque</code> string field introduced to hold the encoded | |
| path for such URLs. In Go 1, the cited URL parses as: | |
| </p> | |
| <pre> | |
| URL{ | |
| Scheme: "mailto", | |
| Opaque: "dev@golang.org", | |
| RawQuery: "subject=Hi", | |
| } | |
| </pre> | |
| <p> | |
| A new <a href="/pkg/net/url/#URL.RequestURI"><code>RequestURI</code></a> method was | |
| added to <code>URL</code>. | |
| </p> | |
| <p> | |
| The <code>ParseWithReference</code> function has been renamed to <code>ParseWithFragment</code>. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Code that uses the old fields will fail to compile and must be updated by hand. | |
| The semantic changes make it difficult for the fix tool to update automatically. | |
| </p> | |
| <h2 id="cmd_go">The go command</h2> | |
| <p> | |
| Go 1 introduces the <a href="/cmd/go/">go command</a>, a tool for fetching, | |
| building, and installing Go packages and commands. The <code>go</code> command | |
| does away with makefiles, instead using Go source code to find dependencies and | |
| determine build conditions. Most existing Go programs will no longer require | |
| makefiles to be built. | |
| </p> | |
| <p> | |
| See <a href="/doc/code.html">How to Write Go Code</a> for a primer on the | |
| <code>go</code> command and the <a href="/cmd/go/">go command documentation</a> | |
| for the full details. | |
| </p> | |
| <p> | |
| <em>Updating</em>: | |
| Projects that depend on the Go project's old makefile-based build | |
| infrastructure (<code>Make.pkg</code>, <code>Make.cmd</code>, and so on) should | |
| switch to using the <code>go</code> command for building Go code and, if | |
| necessary, rewrite their makefiles to perform any auxiliary build tasks. | |
| </p> | |
| <h2 id="cmd_cgo">The cgo command</h2> | |
| <p> | |
| In Go 1, the <a href="/cmd/cgo">cgo command</a> | |
| uses a different <code>_cgo_export.h</code> | |
| file, which is generated for packages containing <code>//export</code> lines. | |
| The <code>_cgo_export.h</code> file now begins with the C preamble comment, | |
| so that exported function definitions can use types defined there. | |
| This has the effect of compiling the preamble multiple times, so a | |
| package using <code>//export</code> must not put function definitions | |
| or variable initializations in the C preamble. | |
| </p> | |
| <h2 id="releases">Packaged releases</h2> | |
| <p> | |
| One of the most significant changes associated with Go 1 is the availability | |
| of prepackaged, downloadable distributions. | |
| They are available for many combinations of architecture and operating system | |
| (including Windows) and the list will grow. | |
| Installation details are described on the | |
| <a href="/doc/install">Getting Started</a> page, while | |
| the distributions themselves are listed on the | |
| <a href="http://code.google.com/p/go/downloads/list">downloads page</a>. | |
| </div> | |
| <div id="footer"> | |
| Build version go1.0.1.<br> | |
| A link <a href="http://code.google.com/policies.html#restrictions">noted</a>, | |
| and then, coming up on the very next line, we will | |
| find yet another link, link 3.0 if you will, | |
| after a few more words <a href="/LINK">link text</a>.<br> | |
| <a href="/doc/tos.html">Terms of Service</a> | | |
| <a href="http://www.google.com/intl/en/privacy/privacy-policy.html">Privacy Policy</a> | |
| </div> | |
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