1 files changed, 298 insertions, 0 deletions
diff --git a/src/runtime/string.go b/src/runtime/string.go
new file mode 100644
index 000000000..0809f89bc
--- /dev/null
+++ b/src/runtime/string.go
@@ -0,0 +1,298 @@
+// 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"
+)
+
+func concatstrings(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 {
+			gothrow("string concatenation too long")
+		}
+		l += n
+		count++
+		idx = i
+	}
+	if count == 0 {
+		return ""
+	}
+	if count == 1 {
+		return a[idx]
+	}
+	s, b := rawstring(l)
+	l = 0
+	for _, x := range a {
+		copy(b[l:], x)
+		l += len(x)
+	}
+	return s
+}
+
+//go:nosplit
+func concatstring2(a [2]string) string {
+	return concatstrings(a[:])
+}
+
+//go:nosplit
+func concatstring3(a [3]string) string {
+	return concatstrings(a[:])
+}
+
+//go:nosplit
+func concatstring4(a [4]string) string {
+	return concatstrings(a[:])
+}
+
+//go:nosplit
+func concatstring5(a [5]string) string {
+	return concatstrings(a[:])
+}
+
+func slicebytetostring(b []byte) string {
+	if raceenabled && len(b) > 0 {
+		racereadrangepc(unsafe.Pointer(&b[0]),
+			uintptr(len(b)),
+			getcallerpc(unsafe.Pointer(&b)),
+			funcPC(slicebytetostring))
+	}
+	s, c := rawstring(len(b))
+	copy(c, b)
+	return s
+}
+
+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.
+	// Today, the only such case is a m[string(k)] lookup where
+	// m is a string-keyed map and k is a []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(s string) []byte {
+	b := rawbyteslice(len(s))
+	copy(b, s)
+	return b
+}
+
+func stringtoslicerune(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++
+	}
+	a := rawruneslice(n)
+	n = 0
+	for len(t) > 0 {
+		r, k := charntorune(t)
+		t = t[k:]
+		a[n] = r
+		n++
+	}
+	return a
+}
+
+func slicerunetostring(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 := rawstring(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(v int64) string {
+	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)).array = (*uint8)(p)
+	(*slice)(unsafe.Pointer(&b)).len = uint(size)
+	(*slice)(unsafe.Pointer(&b)).cap = uint(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 := goroundupsize(uintptr(size))
+	p := mallocgc(cap, nil, flagNoScan|flagNoZero)
+	if cap != uintptr(size) {
+		memclr(add(p, uintptr(size)), cap-uintptr(size))
+	}
+
+	(*slice)(unsafe.Pointer(&b)).array = (*uint8)(p)
+	(*slice)(unsafe.Pointer(&b)).len = uint(size)
+	(*slice)(unsafe.Pointer(&b)).cap = uint(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 {
+		gothrow("out of memory")
+	}
+	mem := goroundupsize(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)).array = (*uint8)(p)
+	(*slice)(unsafe.Pointer(&b)).len = uint(size)
+	(*slice)(unsafe.Pointer(&b)).cap = uint(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 gostringsize(n int) string {
+	s, _ := rawstring(n)
+	return s
+}
+
+//go:noescape
+func findnull(*byte) int
+
+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
+}