1 // Copyright 2014 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
9 // The constant is known to the compiler.
10 // There is no fundamental theory behind this number.
11 const tmpStringBufSize = 32
13 type tmpBuf [tmpStringBufSize]byte
15 // concatstrings implements a Go string concatenation x+y+z+...
16 // The operands are passed in the slice a.
17 // If buf != nil, the compiler has determined that the result does not
18 // escape the calling function, so the string data can be stored in buf
20 func concatstrings(buf *tmpBuf, a []string) string {
30 throw("string concatenation too long")
40 // If there is just one string and either it is not on the stack
41 // or our result does not escape the calling frame (buf != nil),
42 // then we can return that string directly.
43 if count == 1 && (buf != nil || !stringDataOnStack(a[idx])) {
46 s, b := rawstringtmp(buf, l)
54 func concatstring2(buf *tmpBuf, a [2]string) string {
55 return concatstrings(buf, a[:])
58 func concatstring3(buf *tmpBuf, a [3]string) string {
59 return concatstrings(buf, a[:])
62 func concatstring4(buf *tmpBuf, a [4]string) string {
63 return concatstrings(buf, a[:])
66 func concatstring5(buf *tmpBuf, a [5]string) string {
67 return concatstrings(buf, a[:])
70 // Buf is a fixed-size buffer for the result,
71 // it is not nil if the result does not escape.
72 func slicebytetostring(buf *tmpBuf, b []byte) string {
75 // Turns out to be a relatively common case.
76 // Consider that you want to parse out data between parens in "foo()bar",
77 // you find the indices and convert the subslice to string.
80 if raceenabled && l > 0 {
81 racereadrangepc(unsafe.Pointer(&b[0]),
83 getcallerpc(unsafe.Pointer(&buf)),
84 funcPC(slicebytetostring))
86 if msanenabled && l > 0 {
87 msanread(unsafe.Pointer(&b[0]), uintptr(l))
89 s, c := rawstringtmp(buf, l)
94 // stringDataOnStack reports whether the string's data is
95 // stored on the current goroutine's stack.
96 func stringDataOnStack(s string) bool {
97 ptr := uintptr(stringStructOf(&s).str)
99 return stk.lo <= ptr && ptr < stk.hi
102 func rawstringtmp(buf *tmpBuf, l int) (s string, b []byte) {
103 if buf != nil && l <= len(buf) {
105 s = slicebytetostringtmp(b)
112 func slicebytetostringtmp(b []byte) string {
113 // Return a "string" referring to the actual []byte bytes.
114 // This is only for use by internal compiler optimizations
115 // that know that the string form will be discarded before
116 // the calling goroutine could possibly modify the original
117 // slice or synchronize with another goroutine.
118 // First such case is a m[string(k)] lookup where
119 // m is a string-keyed map and k is a []byte.
120 // Second such case is "<"+string(b)+">" concatenation where b is []byte.
121 // Third such case is string(b)=="foo" comparison where b is []byte.
123 if raceenabled && len(b) > 0 {
124 racereadrangepc(unsafe.Pointer(&b[0]),
126 getcallerpc(unsafe.Pointer(&b)),
127 funcPC(slicebytetostringtmp))
129 if msanenabled && len(b) > 0 {
130 msanread(unsafe.Pointer(&b[0]), uintptr(len(b)))
132 return *(*string)(unsafe.Pointer(&b))
135 func stringtoslicebyte(buf *tmpBuf, s string) []byte {
137 if buf != nil && len(s) <= len(buf) {
141 b = rawbyteslice(len(s))
147 func stringtoslicebytetmp(s string) []byte {
148 // Return a slice referring to the actual string bytes.
149 // This is only for use by internal compiler optimizations
150 // that know that the slice won't be mutated.
151 // The only such case today is:
152 // for i, c := range []byte(str)
154 str := stringStructOf(&s)
155 ret := slice{array: str.str, len: str.len, cap: str.len}
156 return *(*[]byte)(unsafe.Pointer(&ret))
159 func stringtoslicerune(buf *[tmpStringBufSize]rune, s string) []rune {
161 // unlike slicerunetostring, no race because strings are immutable.
168 if buf != nil && n <= len(buf) {
169 *buf = [tmpStringBufSize]rune{}
176 for _, r := range s {
183 func slicerunetostring(buf *tmpBuf, a []rune) string {
184 if raceenabled && len(a) > 0 {
185 racereadrangepc(unsafe.Pointer(&a[0]),
186 uintptr(len(a))*unsafe.Sizeof(a[0]),
187 getcallerpc(unsafe.Pointer(&buf)),
188 funcPC(slicerunetostring))
190 if msanenabled && len(a) > 0 {
191 msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]))
195 for _, r := range a {
196 size1 += runetochar(dum[:], r)
198 s, b := rawstringtmp(buf, size1+3)
200 for _, r := range a {
205 size2 += runetochar(b[size2:], r)
210 type stringStruct struct {
215 // Variant with *byte pointer type for DWARF debugging.
216 type stringStructDWARF struct {
221 func stringStructOf(sp *string) *stringStruct {
222 return (*stringStruct)(unsafe.Pointer(sp))
225 func intstring(buf *[4]byte, v int64) string {
230 s = slicebytetostringtmp(b)
234 if int64(rune(v)) != v {
237 n := runetochar(b, rune(v))
241 // rawstring allocates storage for a new string. The returned
242 // string and byte slice both refer to the same storage.
243 // The storage is not zeroed. Callers should use
244 // b to set the string contents and then drop b.
245 func rawstring(size int) (s string, b []byte) {
246 p := mallocgc(uintptr(size), nil, false)
248 stringStructOf(&s).str = p
249 stringStructOf(&s).len = size
251 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, size}
256 // rawbyteslice allocates a new byte slice. The byte slice is not zeroed.
257 func rawbyteslice(size int) (b []byte) {
258 cap := roundupsize(uintptr(size))
259 p := mallocgc(cap, nil, false)
260 if cap != uintptr(size) {
261 memclr(add(p, uintptr(size)), cap-uintptr(size))
264 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(cap)}
268 // rawruneslice allocates a new rune slice. The rune slice is not zeroed.
269 func rawruneslice(size int) (b []rune) {
270 if uintptr(size) > _MaxMem/4 {
271 throw("out of memory")
273 mem := roundupsize(uintptr(size) * 4)
274 p := mallocgc(mem, nil, false)
275 if mem != uintptr(size)*4 {
276 memclr(add(p, uintptr(size)*4), mem-uintptr(size)*4)
279 *(*slice)(unsafe.Pointer(&b)) = slice{p, size, int(mem / 4)}
284 func gobytes(p *byte, n int) []byte {
286 return make([]byte, 0)
289 memmove(unsafe.Pointer(&x[0]), unsafe.Pointer(p), uintptr(n))
293 func gostring(p *byte) string {
299 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
303 func gostringn(p *byte, l int) string {
308 memmove(unsafe.Pointer(&b[0]), unsafe.Pointer(p), uintptr(l))
312 func index(s, t string) int {
316 for i := 0; i < len(s); i++ {
317 if s[i] == t[0] && hasprefix(s[i:], t) {
324 func contains(s, t string) bool {
325 return index(s, t) >= 0
328 func hasprefix(s, t string) bool {
329 return len(s) >= len(t) && s[:len(t)] == t
332 func atoi(s string) int {
334 for len(s) > 0 && '0' <= s[0] && s[0] <= '9' {
335 n = n*10 + int(s[0]) - '0'
342 func findnull(s *byte) int {
346 p := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s))
354 func findnullw(s *uint16) int {
358 p := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(s))
367 func gostringnocopy(str *byte) string {
368 ss := stringStruct{str: unsafe.Pointer(str), len: findnull(str)}
369 s := *(*string)(unsafe.Pointer(&ss))
373 func gostringw(strw *uint16) string {
375 str := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(strw))
377 for i := 0; str[i] != 0; i++ {
378 n1 += runetochar(buf[:], rune(str[i]))
380 s, b := rawstring(n1 + 4)
382 for i := 0; str[i] != 0; i++ {
387 n2 += runetochar(b[n2:], rune(str[i]))
389 b[n2] = 0 // for luck