1 files changed, 588 insertions, 0 deletions
diff --git a/src/runtime/string.go b/src/runtime/string.go
new file mode 100644
index 0000000..e01b7fc
--- /dev/null
+++ b/src/runtime/string.go
@@ -0,0 +1,588 @@
+// 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/abi"
+	"internal/bytealg"
+	"internal/goarch"
+	"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, a0, a1 string) string {
+	return concatstrings(buf, []string{a0, a1})
+}
+
+func concatstring3(buf *tmpBuf, a0, a1, a2 string) string {
+	return concatstrings(buf, []string{a0, a1, a2})
+}
+
+func concatstring4(buf *tmpBuf, a0, a1, a2, a3 string) string {
+	return concatstrings(buf, []string{a0, a1, a2, a3})
+}
+
+func concatstring5(buf *tmpBuf, a0, a1, a2, a3, a4 string) string {
+	return concatstrings(buf, []string{a0, a1, a2, a3, a4})
+}
+
+// slicebytetostring converts a byte slice to a string.
+// It is inserted by the compiler into generated code.
+// ptr is a pointer to the first element of the slice;
+// n is the length of the slice.
+// Buf is a fixed-size buffer for the result,
+// it is not nil if the result does not escape.
+func slicebytetostring(buf *tmpBuf, ptr *byte, n int) string {
+	if n == 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(ptr),
+			uintptr(n),
+			getcallerpc(),
+			abi.FuncPCABIInternal(slicebytetostring))
+	}
+	if msanenabled {
+		msanread(unsafe.Pointer(ptr), uintptr(n))
+	}
+	if asanenabled {
+		asanread(unsafe.Pointer(ptr), uintptr(n))
+	}
+	if n == 1 {
+		p := unsafe.Pointer(&staticuint64s[*ptr])
+		if goarch.BigEndian {
+			p = add(p, 7)
+		}
+		return unsafe.String((*byte)(p), 1)
+	}
+
+	var p unsafe.Pointer
+	if buf != nil && n <= len(buf) {
+		p = unsafe.Pointer(buf)
+	} else {
+		p = mallocgc(uintptr(n), nil, false)
+	}
+	memmove(p, unsafe.Pointer(ptr), uintptr(n))
+	return unsafe.String((*byte)(p), n)
+}
+
+// stringDataOnStack reports whether the string's data is
+// stored on the current goroutine's stack.
+func stringDataOnStack(s string) bool {
+	ptr := uintptr(unsafe.Pointer(unsafe.StringData(s)))
+	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[0], len(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(ptr *byte, n int) string {
+	if raceenabled && n > 0 {
+		racereadrangepc(unsafe.Pointer(ptr),
+			uintptr(n),
+			getcallerpc(),
+			abi.FuncPCABIInternal(slicebytetostringtmp))
+	}
+	if msanenabled && n > 0 {
+		msanread(unsafe.Pointer(ptr), uintptr(n))
+	}
+	if asanenabled && n > 0 {
+		asanread(unsafe.Pointer(ptr), uintptr(n))
+	}
+	return unsafe.String(ptr, n)
+}
+
+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(),
+			abi.FuncPCABIInternal(slicerunetostring))
+	}
+	if msanenabled && len(a) > 0 {
+		msanread(unsafe.Pointer(&a[0]), uintptr(len(a))*unsafe.Sizeof(a[0]))
+	}
+	if asanenabled && len(a) > 0 {
+		asanread(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) {
+	var b []byte
+	if buf != nil {
+		b = buf[:]
+		s = slicebytetostringtmp(&b[0], len(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)
+	return unsafe.String((*byte)(p), size), unsafe.Slice((*byte)(p), size)
+}
+
+// rawbyteslice allocates a new byte slice. The byte slice is not zeroed.
+func rawbyteslice(size int) (b []byte) {
+	cap := roundupsize(uintptr(size), true)
+	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, true)
+	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
+}
+
+// This is exported via linkname to assembly in syscall (for Plan9).
+//
+//go:linkname gostring
+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
+}
+
+// internal_syscall_gostring is a version of gostring for internal/syscall/unix.
+//
+//go:linkname internal_syscall_gostring internal/syscall/unix.gostring
+func internal_syscall_gostring(p *byte) string {
+	return gostring(p)
+}
+
+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 hasPrefix(s, prefix string) bool {
+	return len(s) >= len(prefix) && s[:len(prefix)] == prefix
+}
+
+func hasSuffix(s, suffix string) bool {
+	return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
+}
+
+const (
+	maxUint64 = ^uint64(0)
+	maxInt64  = int64(maxUint64 >> 1)
+)
+
+// atoi64 parses an int64 from a string s.
+// The bool result reports whether s is a number
+// representable by a value of type int64.
+func atoi64(s string) (int64, bool) {
+	if s == "" {
+		return 0, false
+	}
+
+	neg := false
+	if s[0] == '-' {
+		neg = true
+		s = s[1:]
+	}
+
+	un := uint64(0)
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c < '0' || c > '9' {
+			return 0, false
+		}
+		if un > maxUint64/10 {
+			// overflow
+			return 0, false
+		}
+		un *= 10
+		un1 := un + uint64(c) - '0'
+		if un1 < un {
+			// overflow
+			return 0, false
+		}
+		un = un1
+	}
+
+	if !neg && un > uint64(maxInt64) {
+		return 0, false
+	}
+	if neg && un > uint64(maxInt64)+1 {
+		return 0, false
+	}
+
+	n := int64(un)
+	if neg {
+		n = -n
+	}
+
+	return n, true
+}
+
+// atoi is like atoi64 but for integers
+// that fit into an int.
+func atoi(s string) (int, bool) {
+	if n, ok := atoi64(s); n == int64(int(n)) {
+		return int(n), ok
+	}
+	return 0, false
+}
+
+// atoi32 is like atoi but for integers
+// that fit into an int32.
+func atoi32(s string) (int32, bool) {
+	if n, ok := atoi64(s); n == int64(int32(n)) {
+		return int32(n), ok
+	}
+	return 0, false
+}
+
+// parseByteCount parses a string that represents a count of bytes.
+//
+// s must match the following regular expression:
+//
+//	^[0-9]+(([KMGT]i)?B)?$
+//
+// In other words, an integer byte count with an optional unit
+// suffix. Acceptable suffixes include one of
+// - KiB, MiB, GiB, TiB which represent binary IEC/ISO 80000 units, or
+// - B, which just represents bytes.
+//
+// Returns an int64 because that's what its callers want and receive,
+// but the result is always non-negative.
+func parseByteCount(s string) (int64, bool) {
+	// The empty string is not valid.
+	if s == "" {
+		return 0, false
+	}
+	// Handle the easy non-suffix case.
+	last := s[len(s)-1]
+	if last >= '0' && last <= '9' {
+		n, ok := atoi64(s)
+		if !ok || n < 0 {
+			return 0, false
+		}
+		return n, ok
+	}
+	// Failing a trailing digit, this must always end in 'B'.
+	// Also at this point there must be at least one digit before
+	// that B.
+	if last != 'B' || len(s) < 2 {
+		return 0, false
+	}
+	// The one before that must always be a digit or 'i'.
+	if c := s[len(s)-2]; c >= '0' && c <= '9' {
+		// Trivial 'B' suffix.
+		n, ok := atoi64(s[:len(s)-1])
+		if !ok || n < 0 {
+			return 0, false
+		}
+		return n, ok
+	} else if c != 'i' {
+		return 0, false
+	}
+	// Finally, we need at least 4 characters now, for the unit
+	// prefix and at least one digit.
+	if len(s) < 4 {
+		return 0, false
+	}
+	power := 0
+	switch s[len(s)-3] {
+	case 'K':
+		power = 1
+	case 'M':
+		power = 2
+	case 'G':
+		power = 3
+	case 'T':
+		power = 4
+	default:
+		// Invalid suffix.
+		return 0, false
+	}
+	m := uint64(1)
+	for i := 0; i < power; i++ {
+		m *= 1024
+	}
+	n, ok := atoi64(s[:len(s)-3])
+	if !ok || n < 0 {
+		return 0, false
+	}
+	un := uint64(n)
+	if un > maxUint64/m {
+		// Overflow.
+		return 0, false
+	}
+	un *= m
+	if un > uint64(maxInt64) {
+		// Overflow.
+		return 0, false
+	}
+	return int64(un), true
+}
+
+//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]
+}