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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 (
"internal/bytealg"
"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)
for _, x := range a {
copy(b, x)
b = b[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) (str 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 {
racereadrangepc(unsafe.Pointer(&b[0]),
uintptr(l),
getcallerpc(),
funcPC(slicebytetostring))
}
if msanenabled {
msanread(unsafe.Pointer(&b[0]), uintptr(l))
}
if l == 1 {
stringStructOf(&str).str = unsafe.Pointer(&staticbytes[b[0]])
stringStructOf(&str).len = 1
return
}
var p unsafe.Pointer
if buf != nil && len(b) <= len(buf) {
p = unsafe.Pointer(buf)
} else {
p = mallocgc(uintptr(len(b)), nil, false)
}
stringStructOf(&str).str = p
stringStructOf(&str).len = len(b)
memmove(p, (*(*slice)(unsafe.Pointer(&b))).array, uintptr(len(b)))
return
}
// stringDataOnStack reports whether the string's data is
// stored on the current goroutine's stack.
func stringDataOnStack(s string) bool {
ptr := uintptr(stringStructOf(&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
}
// slicebytetostringtmp returns a "string" referring to the actual []byte bytes.
//
// Callers need to ensure that the returned string will not be used after
// the calling goroutine modifies the original slice or synchronizes with
// another goroutine.
//
// The function is only called when instrumenting
// and otherwise intrinsified by the compiler.
//
// Some internal compiler optimizations use this function.
// - Used for m[T1{... Tn{..., string(k), ...} ...}] and m[string(k)]
// where k is []byte, T1 to Tn is a nesting of struct and array literals.
// - Used for "<"+string(b)+">" concatenation where b is []byte.
// - Used for string(b)=="foo" comparison where b is []byte.
func slicebytetostringtmp(b []byte) string {
if raceenabled && len(b) > 0 {
racereadrangepc(unsafe.Pointer(&b[0]),
uintptr(len(b)),
getcallerpc(),
funcPC(slicebytetostringtmp))
}
if msanenabled && len(b) > 0 {
msanread(unsafe.Pointer(&b[0]), uintptr(len(b)))
}
return *(*string)(unsafe.Pointer(&b))
}
func stringtoslicebyte(buf *tmpBuf, s string) []byte {
var b []byte
if buf != nil && len(s) <= len(buf) {
*buf = tmpBuf{}
b = buf[:len(s)]
} else {
b = rawbyteslice(len(s))
}
copy(b, s)
return b
}
func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
// two passes.
// unlike slicerunetostring, no race because strings are immutable.
n := 0
for range s {
n++
}
var a []rune
if buf != nil && n <= len(buf) {
*buf = [tmpStringBufSize]rune{}
a = buf[:n]
} else {
a = rawruneslice(n)
}
n = 0
for _, r := range s {
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(),
funcPC(slicerunetostring))
}
if msanenabled && len(a) > 0 {
msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]))
}
var dum [4]byte
size1 := 0
for _, r := range a {
size1 += encoderune(dum[:], r)
}
s, b := rawstringtmp(buf, size1+3)
size2 := 0
for _, r := range a {
// check for race
if size2 >= size1 {
break
}
size2 += encoderune(b[size2:], r)
}
return s[:size2]
}
type stringStruct struct {
str unsafe.Pointer
len int
}
// Variant with *byte pointer type for DWARF debugging.
type stringStructDWARF struct {
str *byte
len int
}
func stringStructOf(sp *string) *stringStruct {
return (*stringStruct)(unsafe.Pointer(sp))
}
func intstring(buf *[4]byte, v int64) (s string) {
if v >= 0 && v < runeSelf {
stringStructOf(&s).str = unsafe.Pointer(&staticbytes[v])
stringStructOf(&s).len = 1
return
}
var b []byte
if buf != nil {
b = buf[:]
s = slicebytetostringtmp(b)
} else {
s, b = rawstring(4)
}
if int64(rune(v)) != v {
v = runeError
}
n := encoderune(b, rune(v))
return s[:n]
}
// 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, false)
stringStructOf(&s).str = p
stringStructOf(&s).len = size
*(*slice)(unsafe.Pointer(&b)) = slice{p, size, 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, false)
if cap != uintptr(size) {
memclrNoHeapPointers(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) > maxAlloc/4 {
throw("out of memory")
}
mem := roundupsize(uintptr(size) * 4)
p := mallocgc(mem, nil, false)
if mem != uintptr(size)*4 {
memclrNoHeapPointers(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) (b []byte) {
if n == 0 {
return make([]byte, 0)
}
if n < 0 || uintptr(n) > maxAlloc {
panic(errorString("gobytes: length out of range"))
}
bp := mallocgc(uintptr(n), nil, false)
memmove(bp, unsafe.Pointer(p), uintptr(n))
*(*slice)(unsafe.Pointer(&b)) = slice{bp, n, n}
return
}
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, prefix string) bool {
return len(s) >= len(prefix) && s[:len(prefix)] == prefix
}
const (
maxUint = ^uint(0)
maxInt = int(maxUint >> 1)
)
// atoi parses an int from a string s.
// The bool result reports whether s is a number
// representable by a value of type int.
func atoi(s string) (int, bool) {
if s == "" {
return 0, false
}
neg := false
if s[0] == '-' {
neg = true
s = s[1:]
}
un := uint(0)
for i := 0; i < len(s); i++ {
c := s[i]
if c < '0' || c > '9' {
return 0, false
}
if un > maxUint/10 {
// overflow
return 0, false
}
un *= 10
un1 := un + uint(c) - '0'
if un1 < un {
// overflow
return 0, false
}
un = un1
}
if !neg && un > uint(maxInt) {
return 0, false
}
if neg && un > uint(maxInt)+1 {
return 0, false
}
n := int(un)
if neg {
n = -n
}
return n, true
}
// atoi32 is like atoi but for integers
// that fit into an int32.
func atoi32(s string) (int32, bool) {
if n, ok := atoi(s); n == int(int32(n)) {
return int32(n), ok
}
return 0, false
}
//go:nosplit
func findnull(s *byte) int {
if s == nil {
return 0
}
// Avoid IndexByteString on Plan 9 because it uses SSE instructions
// on x86 machines, and those are classified as floating point instructions,
// which are illegal in a note handler.
if GOOS == "plan9" {
p := (*[maxAlloc/2 - 1]byte)(unsafe.Pointer(s))
l := 0
for p[l] != 0 {
l++
}
return l
}
// pageSize is the unit we scan at a time looking for NULL.
// It must be the minimum page size for any architecture Go
// runs on. It's okay (just a minor performance loss) if the
// actual system page size is larger than this value.
const pageSize = 4096
offset := 0
ptr := unsafe.Pointer(s)
// IndexByteString uses wide reads, so we need to be careful
// with page boundaries. Call IndexByteString on
// [ptr, endOfPage) interval.
safeLen := int(pageSize - uintptr(ptr)%pageSize)
for {
t := *(*string)(unsafe.Pointer(&stringStruct{ptr, safeLen}))
// Check one page at a time.
if i := bytealg.IndexByteString(t, 0); i != -1 {
return offset + i
}
// Move to next page
ptr = unsafe.Pointer(uintptr(ptr) + uintptr(safeLen))
offset += safeLen
safeLen = pageSize
}
}
func findnullw(s *uint16) int {
if s == nil {
return 0
}
p := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(s))
l := 0
for p[l] != 0 {
l++
}
return l
}
//go:nosplit
func gostringnocopy(str *byte) string {
ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
s := *(*string)(unsafe.Pointer(&ss))
return s
}
func gostringw(strw *uint16) string {
var buf [8]byte
str := (*[maxAlloc/2/2 - 1]uint16)(unsafe.Pointer(strw))
n1 := 0
for i := 0; str[i] != 0; i++ {
n1 += encoderune(buf[:], rune(str[i]))
}
s, b := rawstring(n1 + 4)
n2 := 0
for i := 0; str[i] != 0; i++ {
// check for race
if n2 >= n1 {
break
}
n2 += encoderune(b[n2:], rune(str[i]))
}
b[n2] = 0 // for luck
return s[:n2]
}