c70ff9f9be
The gc compiler has started permitting go:linkname comments with a
single argument to mean that a function should be externally visible
outside the package. Implement this in the Go frontend.
Change the libgo runtime package to use it, rather than repeating the
name just to export a function.
Remove a couple of unnecessary go:linkname comments on declarations.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/192197
From-SVN: r275239
139 lines
3.5 KiB
Go
139 lines
3.5 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package runtime
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import _ "unsafe" // For go:linkname.
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// For gccgo, use go:linkname to export compiler-called functions.
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//
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//go:linkname decoderune
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// Numbers fundamental to the encoding.
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const (
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runeError = '\uFFFD' // the "error" Rune or "Unicode replacement character"
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runeSelf = 0x80 // characters below Runeself are represented as themselves in a single byte.
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maxRune = '\U0010FFFF' // Maximum valid Unicode code point.
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)
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// Code points in the surrogate range are not valid for UTF-8.
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const (
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surrogateMin = 0xD800
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surrogateMax = 0xDFFF
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)
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const (
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t1 = 0x00 // 0000 0000
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tx = 0x80 // 1000 0000
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t2 = 0xC0 // 1100 0000
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t3 = 0xE0 // 1110 0000
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t4 = 0xF0 // 1111 0000
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t5 = 0xF8 // 1111 1000
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maskx = 0x3F // 0011 1111
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mask2 = 0x1F // 0001 1111
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mask3 = 0x0F // 0000 1111
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mask4 = 0x07 // 0000 0111
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rune1Max = 1<<7 - 1
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rune2Max = 1<<11 - 1
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rune3Max = 1<<16 - 1
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// The default lowest and highest continuation byte.
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locb = 0x80 // 1000 0000
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hicb = 0xBF // 1011 1111
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)
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// countrunes returns the number of runes in s.
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func countrunes(s string) int {
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n := 0
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for range s {
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n++
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}
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return n
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}
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// decoderune returns the non-ASCII rune at the start of
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// s[k:] and the index after the rune in s.
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//
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// decoderune assumes that caller has checked that
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// the to be decoded rune is a non-ASCII rune.
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//
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// If the string appears to be incomplete or decoding problems
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// are encountered (runeerror, k + 1) is returned to ensure
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// progress when decoderune is used to iterate over a string.
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func decoderune(s string, k int) (r rune, pos int) {
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pos = k
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if k >= len(s) {
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return runeError, k + 1
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}
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s = s[k:]
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switch {
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case t2 <= s[0] && s[0] < t3:
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// 0080-07FF two byte sequence
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if len(s) > 1 && (locb <= s[1] && s[1] <= hicb) {
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r = rune(s[0]&mask2)<<6 | rune(s[1]&maskx)
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pos += 2
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if rune1Max < r {
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return
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}
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}
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case t3 <= s[0] && s[0] < t4:
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// 0800-FFFF three byte sequence
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if len(s) > 2 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) {
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r = rune(s[0]&mask3)<<12 | rune(s[1]&maskx)<<6 | rune(s[2]&maskx)
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pos += 3
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if rune2Max < r && !(surrogateMin <= r && r <= surrogateMax) {
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return
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}
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}
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case t4 <= s[0] && s[0] < t5:
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// 10000-1FFFFF four byte sequence
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if len(s) > 3 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) && (locb <= s[3] && s[3] <= hicb) {
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r = rune(s[0]&mask4)<<18 | rune(s[1]&maskx)<<12 | rune(s[2]&maskx)<<6 | rune(s[3]&maskx)
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pos += 4
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if rune3Max < r && r <= maxRune {
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return
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}
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}
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}
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return runeError, k + 1
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}
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// encoderune writes into p (which must be large enough) the UTF-8 encoding of the rune.
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// It returns the number of bytes written.
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func encoderune(p []byte, r rune) int {
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// Negative values are erroneous. Making it unsigned addresses the problem.
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switch i := uint32(r); {
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case i <= rune1Max:
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p[0] = byte(r)
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return 1
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case i <= rune2Max:
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_ = p[1] // eliminate bounds checks
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p[0] = t2 | byte(r>>6)
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p[1] = tx | byte(r)&maskx
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return 2
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case i > maxRune, surrogateMin <= i && i <= surrogateMax:
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r = runeError
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fallthrough
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case i <= rune3Max:
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_ = p[2] // eliminate bounds checks
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p[0] = t3 | byte(r>>12)
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p[1] = tx | byte(r>>6)&maskx
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p[2] = tx | byte(r)&maskx
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return 3
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default:
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_ = p[3] // eliminate bounds checks
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p[0] = t4 | byte(r>>18)
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p[1] = tx | byte(r>>12)&maskx
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p[2] = tx | byte(r>>6)&maskx
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p[3] = tx | byte(r)&maskx
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return 4
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}
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}
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