gcc/libgo/go/strings/strings_amd64.go
Ian Lance Taylor e0f69f36ea libgo: change build procedure to use build tags
Previously the libgo Makefile explicitly listed the set of files to
    compile for each package.  For packages that use build tags, this
    required a lot of awkward automake conditionals in the Makefile.
    
    This CL changes the build to look at the build tags in the files.
    The new shell script libgo/match.sh does the matching.  This required
    adjusting a lot of build tags, and removing some files that are never
    used.  I verified that the exact same sets of files are compiled on
    amd64 GNU/Linux.  I also tested the build on i386 Solaris.
    
    Writing match.sh revealed some bugs in the build tag handling that
    already exists, in a slightly different form, in the gotest shell
    script.  This CL fixes those problems as well.
    
    The old code used automake conditionals to handle systems that were
    missing strerror_r and wait4.  Rather than deal with those in Go, those
    functions are now implemented in runtime/go-nosys.c when necessary, so
    the Go code can simply assume that they exist.
    
    The os testsuite looked for dir_unix.go, which was never built for gccgo
    and has now been removed.  I changed the testsuite to look for dir.go
    instead.
    
    Reviewed-on: https://go-review.googlesource.com/25546

From-SVN: r239189
2016-08-06 00:36:33 +00:00

52 lines
1.1 KiB
Go

// Copyright 2015 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.
// +build ignore
package strings
// indexShortStr returns the index of the first instance of c in s, or -1 if c is not present in s.
// indexShortStr requires 2 <= len(c) <= shortStringLen
func indexShortStr(s, c string) int // ../runtime/asm_$GOARCH.s
const shortStringLen = 31
// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
func Index(s, sep string) int {
n := len(sep)
switch {
case n == 0:
return 0
case n == 1:
return IndexByte(s, sep[0])
case n <= shortStringLen:
return indexShortStr(s, sep)
case n == len(s):
if sep == s {
return 0
}
return -1
case n > len(s):
return -1
}
// Rabin-Karp search
hashsep, pow := hashStr(sep)
var h uint32
for i := 0; i < n; i++ {
h = h*primeRK + uint32(s[i])
}
if h == hashsep && s[:n] == sep {
return 0
}
for i := n; i < len(s); {
h *= primeRK
h += uint32(s[i])
h -= pow * uint32(s[i-n])
i++
if h == hashsep && s[i-n:i] == sep {
return i - n
}
}
return -1
}