[dev.cc] runtime: convert basic library routines from C to Go
float.c held bit patterns for special float64 values,
hiding from the real uses. Rewrite Go code not to
refer to those values directly.
Convert library routines in runtime.c and string.c.
LGTM=r
R=r, dave
CC=austin, dvyukov, golang-codereviews, iant, khr
https://golang.org/cl/170330043
diff --git a/src/runtime/string1.go b/src/runtime/string1.go
new file mode 100644
index 0000000..35cde43
--- /dev/null
+++ b/src/runtime/string1.go
@@ -0,0 +1,108 @@
+// Copyright 2009 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"
+
+//go:nosplit
+func findnull(s *byte) int {
+ if s == nil {
+ return 0
+ }
+ p := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s))
+ l := 0
+ for p[l] != 0 {
+ l++
+ }
+ return l
+}
+
+func findnullw(s *uint16) int {
+ if s == nil {
+ return 0
+ }
+ p := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(s))
+ l := 0
+ for p[l] != 0 {
+ l++
+ }
+ return l
+}
+
+var maxstring uintptr = 256 // a hint for print
+
+//go:nosplit
+func gostringnocopy(str *byte) string {
+ var s string
+ sp := (*stringStruct)(unsafe.Pointer(&s))
+ sp.str = unsafe.Pointer(str)
+ sp.len = findnull(str)
+ for {
+ ms := maxstring
+ if uintptr(len(s)) <= ms || casuintptr(&maxstring, ms, uintptr(len(s))) {
+ break
+ }
+ }
+ return s
+}
+
+func gostringw(strw *uint16) string {
+ var buf [8]byte
+ str := (*[_MaxMem/2/2 - 1]uint16)(unsafe.Pointer(strw))
+ n1 := 0
+ for i := 0; str[i] != 0; i++ {
+ n1 += runetochar(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 += runetochar(b[n2:], rune(str[i]))
+ }
+ b[n2] = 0 // for luck
+ return s[:n2]
+}
+
+func strcmp(s1, s2 *byte) int32 {
+ p1 := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s1))
+ p2 := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s2))
+
+ for i := uintptr(0); ; i++ {
+ c1 := p1[i]
+ c2 := p2[i]
+ if c1 < c2 {
+ return -1
+ }
+ if c1 > c2 {
+ return +1
+ }
+ if c1 == 0 {
+ return 0
+ }
+ }
+}
+
+func strncmp(s1, s2 *byte, n uintptr) int32 {
+ p1 := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s1))
+ p2 := (*[_MaxMem/2 - 1]byte)(unsafe.Pointer(s2))
+
+ for i := uintptr(0); i < n; i++ {
+ c1 := p1[i]
+ c2 := p2[i]
+ if c1 < c2 {
+ return -1
+ }
+ if c1 > c2 {
+ return +1
+ }
+ if c1 == 0 {
+ break
+ }
+ }
+ return 0
+}
