ssa: string range; string convert bytes/rune; op eql/less

internal/runtime/utf8.go

@@ -0,0 +1,132 @@
+// Copyright 2016 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
+
+// Numbers fundamental to the encoding.
+const (
+	runeError = '\uFFFD'     // the "error" Rune or "Unicode replacement character"
+	runeSelf  = 0x80         // characters below runeSelf are represented as themselves in a single byte.
+	maxRune   = '\U0010FFFF' // Maximum valid Unicode code point.
+)
+
+// Code points in the surrogate range are not valid for UTF-8.
+const (
+	surrogateMin = 0xD800
+	surrogateMax = 0xDFFF
+)
+
+const (
+	t1 = 0x00 // 0000 0000
+	tx = 0x80 // 1000 0000
+	t2 = 0xC0 // 1100 0000
+	t3 = 0xE0 // 1110 0000
+	t4 = 0xF0 // 1111 0000
+	t5 = 0xF8 // 1111 1000
+
+	maskx = 0x3F // 0011 1111
+	mask2 = 0x1F // 0001 1111
+	mask3 = 0x0F // 0000 1111
+	mask4 = 0x07 // 0000 0111
+
+	rune1Max = 1<<7 - 1
+	rune2Max = 1<<11 - 1
+	rune3Max = 1<<16 - 1
+
+	// The default lowest and highest continuation byte.
+	locb = 0x80 // 1000 0000
+	hicb = 0xBF // 1011 1111
+)
+
+// countrunes returns the number of runes in s.
+// func countrunes(s string) int {
+// 	n := 0
+// 	for range s {
+// 		n++
+// 	}
+// 	return n
+// }
+
+// decoderune returns the non-ASCII rune at the start of
+// s[k:] and the index after the rune in s.
+//
+// decoderune assumes that caller has checked that
+// the to be decoded rune is a non-ASCII rune.
+//
+// If the string appears to be incomplete or decoding problems
+// are encountered (runeerror, k + 1) is returned to ensure
+// progress when decoderune is used to iterate over a string.
+func decoderune(s string, k int) (r rune, pos int) {
+	pos = k
+
+	if k >= len(s) {
+		return runeError, k + 1
+	}
+
+	s = s[k:]
+
+	switch {
+	case t2 <= s[0] && s[0] < t3:
+		// 0080-07FF two byte sequence
+		if len(s) > 1 && (locb <= s[1] && s[1] <= hicb) {
+			r = rune(s[0]&mask2)<<6 | rune(s[1]&maskx)
+			pos += 2
+			if rune1Max < r {
+				return
+			}
+		}
+	case t3 <= s[0] && s[0] < t4:
+		// 0800-FFFF three byte sequence
+		if len(s) > 2 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) {
+			r = rune(s[0]&mask3)<<12 | rune(s[1]&maskx)<<6 | rune(s[2]&maskx)
+			pos += 3
+			if rune2Max < r && !(surrogateMin <= r && r <= surrogateMax) {
+				return
+			}
+		}
+	case t4 <= s[0] && s[0] < t5:
+		// 10000-1FFFFF four byte sequence
+		if len(s) > 3 && (locb <= s[1] && s[1] <= hicb) && (locb <= s[2] && s[2] <= hicb) && (locb <= s[3] && s[3] <= hicb) {
+			r = rune(s[0]&mask4)<<18 | rune(s[1]&maskx)<<12 | rune(s[2]&maskx)<<6 | rune(s[3]&maskx)
+			pos += 4
+			if rune3Max < r && r <= maxRune {
+				return
+			}
+		}
+	}
+
+	return runeError, k + 1
+}
+
+// encoderune writes into p (which must be large enough) the UTF-8 encoding of the rune.
+// It returns the number of bytes written.
+func encoderune(p []byte, r rune) int {
+	// Negative values are erroneous. Making it unsigned addresses the problem.
+	switch i := uint32(r); {
+	case i <= rune1Max:
+		p[0] = byte(r)
+		return 1
+	case i <= rune2Max:
+		_ = p[1] // eliminate bounds checks
+		p[0] = t2 | byte(r>>6)
+		p[1] = tx | byte(r)&maskx
+		return 2
+	case i > maxRune, surrogateMin <= i && i <= surrogateMax:
+		r = runeError
+		fallthrough
+	case i <= rune3Max:
+		_ = p[2] // eliminate bounds checks
+		p[0] = t3 | byte(r>>12)
+		p[1] = tx | byte(r>>6)&maskx
+		p[2] = tx | byte(r)&maskx
+		return 3
+	default:
+		_ = p[3] // eliminate bounds checks
+		p[0] = t4 | byte(r>>18)
+		p[1] = tx | byte(r>>12)&maskx
+		p[2] = tx | byte(r>>6)&maskx
+		p[3] = tx | byte(r)&maskx
+		return 4
+	}
+}

internal/runtime/z_string.go

@@ -70,4 +70,119 @@ func NewStringSlice(base String, i, j int) String {
 	return String{nil, 0}
 }
 
+type StringIter struct {
+	s   string
+	pos int
+}
+
+func NewStringIter(s string) *StringIter {
+	return &StringIter{s, 0}
+}
+
+func StringIterNext(it *StringIter) (ok bool, k int, v rune) {
+	if it.pos >= len(it.s) {
+		return false, 0, 0
+	}
+	k = it.pos
+	if c := it.s[it.pos]; c < runeSelf {
+		it.pos++
+		v = rune(c)
+	} else {
+		v, it.pos = decoderune(it.s, it.pos)
+	}
+	ok = true
+	return
+}
+
+func StringToBytes(s String) []byte {
+	if s.len == 0 {
+		return nil
+	}
+	data := make([]byte, s.len)
+	c.Memcpy(unsafe.Pointer(&data[0]), s.data, uintptr(s.len))
+	return data
+}
+
+func StringToRunes(s string) []rune {
+	if len(s) == 0 {
+		return nil
+	}
+	data := make([]rune, len(s))
+	var index uint
+	for i := 0; i < len(s); {
+		if c := s[i]; c < runeSelf {
+			data[index] = rune(c)
+			i++
+		} else {
+			data[index], i = decoderune(s, i)
+		}
+		index++
+	}
+	return data[:index:index]
+}
+
+func StringFromBytes(b Slice) (s String) {
+	if b.len == 0 {
+		return
+	}
+	s.len = b.len
+	s.data = AllocU(uintptr(s.len))
+	c.Memcpy(s.data, b.data, uintptr(b.len))
+	return
+}
+
+func StringFromRunes(rs []rune) (s String) {
+	if len(rs) == 0 {
+		return
+	}
+	data := make([]byte, len(rs)*4)
+	var index int
+	for _, r := range rs {
+		n := encoderune(data[index:], r)
+		index += n
+	}
+	s.len = index
+	s.data = unsafe.Pointer(&data[0])
+	return
+}
+
+func StringFromRune(r rune) (s String) {
+	var buf [4]byte
+	n := encoderune(buf[:], r)
+	s.len = n
+	s.data = unsafe.Pointer(&buf[0])
+	return
+}
+
+func StringEqual(x, y String) bool {
+	if x.len != y.len {
+		return false
+	}
+	if x.data != y.data {
+		for i := 0; i < x.len; i++ {
+			if *(*byte)(c.Advance(x.data, i)) != *(*byte)(c.Advance(y.data, i)) {
+				return false
+			}
+		}
+	}
+	return true
+}
+
+func StringLess(x, y String) bool {
+	n := x.len
+	if n > y.len {
+		n = y.len
+	}
+	for i := 0; i < n; i++ {
+		ix := *(*byte)(c.Advance(x.data, i))
+		iy := *(*byte)(c.Advance(y.data, i))
+		if ix < iy {
+			return true
+		} else if ix > iy {
+			return false
+		}
+	}
+	return x.len < y.len
+}
+
 // -----------------------------------------------------------------------------