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// Copyright 2014 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 runtime
import (
"unsafe"
)
// The constant is known to the compiler.
// There is no fundamental theory behind this number.
const tmpStringBufSize = 32
type tmpBuf [tmpStringBufSize]byte
// concatstrings implements a Go string concatenation x+y+z+...
// The operands are passed in the slice a.
// If buf != nil, the compiler has determined that the result does not
// escape the calling function, so the string data can be stored in buf
// if small enough.
func concatstrings(buf *tmpBuf, a []string) string {
idx := 0
l := 0
count := 0
for i, x := range a {
n := len(x)
if n == 0 {
continue
}
if l+n < l {
throw("string concatenation too long")
}
l += n
count++
idx = i
}
if count == 0 {
return ""
}
// If there is just one string and either it is not on the stack
// or our result does not escape the calling frame (buf != nil),
// then we can return that string directly.
if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) {
return a[idx]
}
s, b := rawstringtmp(buf, l)
l = 0
for _, x := range a {
copy(b[l:], x)
l += len(x)
}
return s
}
func concatstring2(buf *tmpBuf, a [2]string) string {
return concatstrings(buf, a[:])
}
func concatstring3(buf *tmpBuf, a [3]string) string {
return concatstrings(buf, a[:])
}
func concatstring4(buf *tmpBuf, a [4]string) string {
return concatstrings(buf, a[:])
}
func concatstring5(buf *tmpBuf, a [5]string) string {
return concatstrings(buf, a[:])
}
// Buf is a fixed-size buffer for the result,
// it is not nil if the result does not escape.
func slicebytetostring(buf *tmpBuf, b []byte) string {
l := len(b)
if l == 0 {
// Turns out to be a relatively common case.
// Consider that you want to parse out data between parens in "foo()bar",
// you find the indices and convert the subslice to string.
return ""
}
if raceenabled && l > 0 {
racereadrangepc(unsafe.Pointer(&b[0]),
uintptr(l),
getcallerpc(unsafe.Pointer(&b)),
funcPC(slicebytetostring))
}
s, c := rawstringtmp(buf, l)
copy(c, b)
return s
}
// stringDataOnStack reports whether the string's data is
// stored on the current goroutine's stack.
func stringDataOnStack(s string) bool {
ptr := uintptr((*stringStruct)(unsafe.Pointer(&s)).str)
stk := getg().stack
return stk.lo <= ptr && ptr < stk.hi
}
func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) {
if buf != nil && l <= len(buf) {
b = buf[:l]
s = slicebytetostringtmp(b)
} else {
s, b = rawstring(l)
}
return
}
func slicebytetostringtmp(b []byte) string {
// Return a "string" referring to the actual []byte bytes.
// This is only for use by internal compiler optimizations
// that know that the string form will be discarded before
// the calling goroutine could possibly modify the original
// slice or synchronize with another goroutine.
// First such case is a m[string(k)] lookup where
// m is a string-keyed map and k is a []byte.
// Second such case is "<"+string(b)+">" concatenation where b is []byte.
// Third such case is string(b)=="foo" comparison where b is []byte.
if raceenabled && len(b) > 0 {
racereadrangepc(unsafe.Pointer(&b[0]),
uintptr(len(b)),
getcallerpc(unsafe.Pointer(&b)),
funcPC(slicebytetostringtmp))
}
return *(*string)(unsafe.Pointer(&b))
}
func stringtoslicebyte(buf *tmpBuf, s string) []byte {
var b []byte
if buf != nil && len(s) <= len(buf) {
b = buf[:len(s)]
} else {
b = rawbyteslice(len(s))
}
copy(b, s)
return b
}
func stringtoslicebytetmp(s string) []byte {
// Return a slice referring to the actual string bytes.
// This is only for use by internal compiler optimizations
// that know that the slice won't be mutated.
// The only such case today is:
// for i, c := range []byte(str)
str := (*stringStruct)(unsafe.Pointer(&s))
ret := slice{array: unsafe.Pointer(str.str), len: str.len, cap: str.len}
return *(*[]byte)(unsafe.Pointer(&ret))
}
func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
// two passes.
// unlike slicerunetostring, no race because strings are immutable.
n := 0
t := s
for len(s) > 0 {
_, k := charntorune(s)
s = s[k:]
n++
}
var a []rune
if buf != nil && n <= len(buf) {
a = buf[:n]
} else {
a = rawruneslice(n)
}
n = 0
for len(t) > 0 {
r, k := charntorune(t)
t = t[k:]
a[n] = r
n++
}
return a
}
func slicerunetostring(buf *tmpBuf, a []rune) string {
if raceenabled && len(a) > 0 {
racereadrangepc(unsafe.Pointer(&a[0]),
uintptr(len(a))*unsafe.Sizeof(a[0]),
getcallerpc(unsafe.Pointer(&a)),
funcPC(slicerunetostring))
}
var dum [4]byte
size1 := 0
for _, r := range a {
size1 += runetochar(dum[:], r)
}
s, b := rawstringtmp(buf, size1+3)
size2 := 0
for _, r := range a {
// check for race
if size2 >= size1 {
break
}
size2 += runetochar(b[size2:], r)
}
return s[:size2]
}
type stringStruct struct {
str unsafe.Pointer
len int
}
func intstring(buf *[4]byte, v int64) string {
var s string
var b []byte
if buf != nil {
b = buf[:]
s = slicebytetostringtmp(b)
} else {
s, b = rawstring(4)
}
n := runetochar(b, rune(v))
return s[:n]
}
// stringiter returns the index of the next
// rune after the rune that starts at s[k].
func stringiter(s string, k int) int {
if k >= len(s) {
// 0 is end of iteration
return 0
}
c := s[k]
if c < runeself {
return k + 1
}
// multi-char rune
_, n := charntorune(s[k:])
return k + n
}
// stringiter2 returns the rune that starts at s[k]
// and the index where the next rune starts.
func stringiter2(s string, k int) (int, rune) {
if k >= len(s) {
// 0 is end of iteration
return 0, 0
}
c := s[k]
if c < runeself {
return k + 1, rune(c)
}
// multi-char rune
r, n := charntorune(s[k:])
return k + n, r
}
// rawstring allocates storage for a new string. The returned
// string and byte slice both refer to the same storage.
// The storage is not zeroed. Callers should use
// b to set the string contents and then drop b.
func rawstring(size int) (s string, b []byte) {
p := mallocgc(uintptr(size), nil, flagNoScan|flagNoZero)
(*stringStruct)(unsafe.Pointer(&s)).str = p
(*stringStruct)(unsafe.Pointer(&s)).len = size
*(*slice)(unsafe.Pointer(&b)) = slice{p, size, size}
for {
ms := maxstring
if uintptr(size) <= uintptr(ms) || casuintptr((*uintptr)(unsafe.Pointer(&maxstring)), uintptr(ms), uintptr(size)) {
return
}
}
}
// rawbyteslice allocates a new byte slice. The byte slice is not zeroed.
func rawbyteslice(size int) (b []byte) {
cap := roundupsize(uintptr(size))
p := mallocgc(cap, nil, flagNoScan|flagNoZero)
if cap != uintptr(size) {
memclr(add(p, uintptr(size)), cap-uintptr(size))
}
*(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)}
return
}
// rawruneslice allocates a new rune slice. The rune slice is not zeroed.
func rawruneslice(size int) (b []rune) {
if uintptr(size) > _MaxMem/4 {
throw("out of memory")
}
mem := roundupsize(uintptr(size) * 4)
p := mallocgc(mem, nil, flagNoScan|flagNoZero)
if mem != uintptr(size)*4 {
memclr(add(p, uintptr(size)*4), mem-uintptr(size)*4)
}
*(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)}
return
}
// used by cmd/cgo
func gobytes(p *byte, n int) []byte {
if n == 0 {
return make([]byte, 0)
}
x := make([]byte, n)
memmove(unsafe.Pointer(&x[0]), unsafe.Pointer(p), uintptr(n))
return x
}
func gostring(p *byte) string {
l := findnull(p)
if l == 0 {
return ""
}
s, b := rawstring(l)
memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
return s
}
func gostringn(p *byte, l int) string {
if l == 0 {
return ""
}
s, b := rawstring(l)
memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
return s
}
func index(s, t string) int {
if len(t) == 0 {
return 0
}
for i := 0; i < len(s); i++ {
if s[i] == t[0] && hasprefix(s[i:], t) {
return i
}
}
return -1
}
func contains(s, t string) bool {
return index(s, t) >= 0
}
func hasprefix(s, t string) bool {
return len(s) >= len(t) && s[:len(t)] == t
}
func atoi(s string) int {
n := 0
for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
n = n*10 + int(s[0]) - '0'
s = s[1:]
}
return n
}