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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gen
import (
"bytes"
"encoding/gob"
"fmt"
"hash"
"hash/fnv"
"io"
"log"
"os"
"reflect"
"strings"
"unicode"
"unicode/utf8"
)
// This file contains utilities for generating code.
// TODO: other write methods like:
// - slices, maps, types, etc.
// CodeWriter is a utility for writing structured code. It computes the content
// hash and size of written content. It ensures there are newlines between
// written code blocks.
type CodeWriter struct {
buf bytes.Buffer
Size int
Hash hash.Hash32 // content hash
gob *gob.Encoder
// For comments we skip the usual one-line separator if they are followed by
// a code block.
skipSep bool
}
func (w *CodeWriter) Write(p []byte) (n int, err error) {
return w.buf.Write(p)
}
// NewCodeWriter returns a new CodeWriter.
func NewCodeWriter() *CodeWriter {
h := fnv.New32()
return &CodeWriter{Hash: h, gob: gob.NewEncoder(h)}
}
// WriteGoFile appends the buffer with the total size of all created structures
// and writes it as a Go file to the the given file with the given package name.
func (w *CodeWriter) WriteGoFile(filename, pkg string) {
f, err := os.Create(filename)
if err != nil {
log.Fatalf("Could not create file %s: %v", filename, err)
}
defer f.Close()
if _, err = w.WriteGo(f, pkg, ""); err != nil {
log.Fatalf("Error writing file %s: %v", filename, err)
}
}
// WriteVersionedGoFile appends the buffer with the total size of all created
// structures and writes it as a Go file to the the given file with the given
// package name and build tags for the current Unicode version,
func (w *CodeWriter) WriteVersionedGoFile(filename, pkg string) {
tags := buildTags()
if tags != "" {
filename = insertVersion(filename, UnicodeVersion())
}
f, err := os.Create(filename)
if err != nil {
log.Fatalf("Could not create file %s: %v", filename, err)
}
defer f.Close()
if _, err = w.WriteGo(f, pkg, tags); err != nil {
log.Fatalf("Error writing file %s: %v", filename, err)
}
}
// WriteGo appends the buffer with the total size of all created structures and
// writes it as a Go file to the the given writer with the given package name.
func (w *CodeWriter) WriteGo(out io.Writer, pkg, tags string) (n int, err error) {
sz := w.Size
w.WriteComment("Total table size %d bytes (%dKiB); checksum: %X\n", sz, sz/1024, w.Hash.Sum32())
defer w.buf.Reset()
return WriteGo(out, pkg, tags, w.buf.Bytes())
}
func (w *CodeWriter) printf(f string, x ...interface{}) {
fmt.Fprintf(w, f, x...)
}
func (w *CodeWriter) insertSep() {
if w.skipSep {
w.skipSep = false
return
}
// Use at least two newlines to ensure a blank space between the previous
// block. WriteGoFile will remove extraneous newlines.
w.printf("\n\n")
}
// WriteComment writes a comment block. All line starts are prefixed with "//".
// Initial empty lines are gobbled. The indentation for the first line is
// stripped from consecutive lines.
func (w *CodeWriter) WriteComment(comment string, args ...interface{}) {
s := fmt.Sprintf(comment, args...)
s = strings.Trim(s, "\n")
// Use at least two newlines to ensure a blank space between the previous
// block. WriteGoFile will remove extraneous newlines.
w.printf("\n\n// ")
w.skipSep = true
// strip first indent level.
sep := "\n"
for ; len(s) > 0 && (s[0] == '\t' || s[0] == ' '); s = s[1:] {
sep += s[:1]
}
strings.NewReplacer(sep, "\n// ", "\n", "\n// ").WriteString(w, s)
w.printf("\n")
}
func (w *CodeWriter) writeSizeInfo(size int) {
w.printf("// Size: %d bytes\n", size)
}
// WriteConst writes a constant of the given name and value.
func (w *CodeWriter) WriteConst(name string, x interface{}) {
w.insertSep()
v := reflect.ValueOf(x)
switch v.Type().Kind() {
case reflect.String:
w.printf("const %s %s = ", name, typeName(x))
w.WriteString(v.String())
w.printf("\n")
default:
w.printf("const %s = %#v\n", name, x)
}
}
// WriteVar writes a variable of the given name and value.
func (w *CodeWriter) WriteVar(name string, x interface{}) {
w.insertSep()
v := reflect.ValueOf(x)
oldSize := w.Size
sz := int(v.Type().Size())
w.Size += sz
switch v.Type().Kind() {
case reflect.String:
w.printf("var %s %s = ", name, typeName(x))
w.WriteString(v.String())
case reflect.Struct:
w.gob.Encode(x)
fallthrough
case reflect.Slice, reflect.Array:
w.printf("var %s = ", name)
w.writeValue(v)
w.writeSizeInfo(w.Size - oldSize)
default:
w.printf("var %s %s = ", name, typeName(x))
w.gob.Encode(x)
w.writeValue(v)
w.writeSizeInfo(w.Size - oldSize)
}
w.printf("\n")
}
func (w *CodeWriter) writeValue(v reflect.Value) {
x := v.Interface()
switch v.Kind() {
case reflect.String:
w.WriteString(v.String())
case reflect.Array:
// Don't double count: callers of WriteArray count on the size being
// added, so we need to discount it here.
w.Size -= int(v.Type().Size())
w.writeSlice(x, true)
case reflect.Slice:
w.writeSlice(x, false)
case reflect.Struct:
w.printf("%s{\n", typeName(v.Interface()))
t := v.Type()
for i := 0; i < v.NumField(); i++ {
w.printf("%s: ", t.Field(i).Name)
w.writeValue(v.Field(i))
w.printf(",\n")
}
w.printf("}")
default:
w.printf("%#v", x)
}
}
// WriteString writes a string literal.
func (w *CodeWriter) WriteString(s string) {
s = strings.Replace(s, `\`, `\\`, -1)
io.WriteString(w.Hash, s) // content hash
w.Size += len(s)
const maxInline = 40
if len(s) <= maxInline {
w.printf("%q", s)
return
}
// We will render the string as a multi-line string.
const maxWidth = 80 - 4 - len(`"`) - len(`" +`)
// When starting on its own line, go fmt indents line 2+ an extra level.
n, max := maxWidth, maxWidth-4
// As per https://golang.org/issue/18078, the compiler has trouble
// compiling the concatenation of many strings, s0 + s1 + s2 + ... + sN,
// for large N. We insert redundant, explicit parentheses to work around
// that, lowering the N at any given step: (s0 + s1 + ... + s63) + (s64 +
// ... + s127) + etc + (etc + ... + sN).
explicitParens, extraComment := len(s) > 128*1024, ""
if explicitParens {
w.printf(`(`)
extraComment = "; the redundant, explicit parens are for https://golang.org/issue/18078"
}
// Print "" +\n, if a string does not start on its own line.
b := w.buf.Bytes()
if p := len(bytes.TrimRight(b, " \t")); p > 0 && b[p-1] != '\n' {
w.printf("\"\" + // Size: %d bytes%s\n", len(s), extraComment)
n, max = maxWidth, maxWidth
}
w.printf(`"`)
for sz, p, nLines := 0, 0, 0; p < len(s); {
var r rune
r, sz = utf8.DecodeRuneInString(s[p:])
out := s[p : p+sz]
chars := 1
if !unicode.IsPrint(r) || r == utf8.RuneError || r == '"' {
switch sz {
case 1:
out = fmt.Sprintf("\\x%02x", s[p])
case 2, 3:
out = fmt.Sprintf("\\u%04x", r)
case 4:
out = fmt.Sprintf("\\U%08x", r)
}
chars = len(out)
}
if n -= chars; n < 0 {
nLines++
if explicitParens && nLines&63 == 63 {
w.printf("\") + (\"")
}
w.printf("\" +\n\"")
n = max - len(out)
}
w.printf("%s", out)
p += sz
}
w.printf(`"`)
if explicitParens {
w.printf(`)`)
}
}
// WriteSlice writes a slice value.
func (w *CodeWriter) WriteSlice(x interface{}) {
w.writeSlice(x, false)
}
// WriteArray writes an array value.
func (w *CodeWriter) WriteArray(x interface{}) {
w.writeSlice(x, true)
}
func (w *CodeWriter) writeSlice(x interface{}, isArray bool) {
v := reflect.ValueOf(x)
w.gob.Encode(v.Len())
w.Size += v.Len() * int(v.Type().Elem().Size())
name := typeName(x)
if isArray {
name = fmt.Sprintf("[%d]%s", v.Len(), name[strings.Index(name, "]")+1:])
}
if isArray {
w.printf("%s{\n", name)
} else {
w.printf("%s{ // %d elements\n", name, v.Len())
}
switch kind := v.Type().Elem().Kind(); kind {
case reflect.String:
for _, s := range x.([]string) {
w.WriteString(s)
w.printf(",\n")
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
// nLine and nBlock are the number of elements per line and block.
nLine, nBlock, format := 8, 64, "%d,"
switch kind {
case reflect.Uint8:
format = "%#02x,"
case reflect.Uint16:
format = "%#04x,"
case reflect.Uint32:
nLine, nBlock, format = 4, 32, "%#08x,"
case reflect.Uint, reflect.Uint64:
nLine, nBlock, format = 4, 32, "%#016x,"
case reflect.Int8:
nLine = 16
}
n := nLine
for i := 0; i < v.Len(); i++ {
if i%nBlock == 0 && v.Len() > nBlock {
w.printf("// Entry %X - %X\n", i, i+nBlock-1)
}
x := v.Index(i).Interface()
w.gob.Encode(x)
w.printf(format, x)
if n--; n == 0 {
n = nLine
w.printf("\n")
}
}
w.printf("\n")
case reflect.Struct:
zero := reflect.Zero(v.Type().Elem()).Interface()
for i := 0; i < v.Len(); i++ {
x := v.Index(i).Interface()
w.gob.EncodeValue(v)
if !reflect.DeepEqual(zero, x) {
line := fmt.Sprintf("%#v,\n", x)
line = line[strings.IndexByte(line, '{'):]
w.printf("%d: ", i)
w.printf(line)
}
}
case reflect.Array:
for i := 0; i < v.Len(); i++ {
w.printf("%d: %#v,\n", i, v.Index(i).Interface())
}
default:
panic("gen: slice elem type not supported")
}
w.printf("}")
}
// WriteType writes a definition of the type of the given value and returns the
// type name.
func (w *CodeWriter) WriteType(x interface{}) string {
t := reflect.TypeOf(x)
w.printf("type %s struct {\n", t.Name())
for i := 0; i < t.NumField(); i++ {
w.printf("\t%s %s\n", t.Field(i).Name, t.Field(i).Type)
}
w.printf("}\n")
return t.Name()
}
// typeName returns the name of the go type of x.
func typeName(x interface{}) string {
t := reflect.ValueOf(x).Type()
return strings.Replace(fmt.Sprint(t), "main.", "", 1)
}