rudimentary string utilities.

R=r
DELTA=314  (306 added, 8 deleted, 0 changed)
OCL=15074
CL=15263

src/lib/strings.go

@@ -0,0 +1,198 @@
+// 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 strings
+
+// Count UTF-8 sequences in s.
+// Assumes s is well-formed.
+export func utflen(s string) int {
+	n := 0;
+	for i := 0; i < len(s); i++ {
+		if s[i]&0xC0 != 0x80 {
+			n++
+		}
+	}
+	return n
+}
+
+// Split string into array of UTF-8 sequences (still strings)
+export func explode(s string) *[]string {
+	a := new([]string, utflen(s));
+	j := 0;
+	for i := 0; i < len(a); i++ {
+		ej := j;
+		ej++;
+		for ej < len(s) && (s[ej]&0xC0) == 0x80 {
+			ej++
+		}
+		a[i] = s[j:ej];
+		j = ej
+	}
+	return a
+}
+
+// Count non-overlapping instances of sep in s.
+export func count(s, sep string) int {
+	if sep == "" {
+		return utflen(s)+1
+	}
+	c := sep[0];
+	n := 0;
+	for i := 0; i+len(sep) <= len(s); i++ {
+		if s[i] == c && (len(sep) == 1 || s[i:i+len(sep)] == sep) {
+			n++;
+			i += len(sep)-1
+		}
+	}
+	return n
+}
+
+// Return index of first instance of sep in s.
+export func index(s, sep string) int {
+	if sep == "" {
+		return 0
+	}
+	c := sep[0];
+	for i := 0; i+len(sep) <= len(s); i++ {
+		if s[i] == c && (len(sep) == 1 || s[i:i+len(sep)] == sep) {
+			return i
+		}
+	}
+	return -1
+}
+
+// Split string into list of strings at separators
+export func split(s, sep string) *[]string {
+	if sep == "" {
+		return explode(s)
+	}
+	c := sep[0];
+	start := 0;
+	n := count(s, sep)+1;
+	a := new([]string, n);
+	na := 0;
+	for i := 0; i+len(sep) <= len(s); i++ {
+		if s[i] == c && (len(sep) == 1 || s[i:i+len(sep)] == sep) {
+			a[na] = s[start:i];
+			na++;
+			start = i+len(sep);
+			i += len(sep)-1
+		}
+	}
+	a[na] = s[start:len(s)];
+	return a
+}
+	
+// Join list of strings with separators between them.
+export func join(a *[]string, sep string) string {
+	if len(a) == 0 {
+		return 0
+	}
+	if len(a) == 1 {
+		return a[0]
+	}
+	n := len(sep) * (len(a)-1);
+	for i := 0; i < len(a); i++ {
+		n += len(a[i])
+	}
+
+	b := new([]byte, n);
+	bp := 0;
+	for i := 0; i < len(a); i++ {
+		s := a[i];
+		for j := 0; j < len(s); j++ {
+			b[bp] = s[j];
+			bp++
+		}
+		if i + 1 < len(a) {
+			s = sep;
+			for j := 0; j < len(s); j++ {
+				b[bp] = s[j];
+				bp++
+			}
+		}
+	}
+	return string(b)
+}
+
+// Convert decimal string to integer.
+// TODO: Doesn't check for overflow.
+export func atoi(s string) (i int, ok bool) {
+	// empty string bad
+	if len(s) == 0 { 
+		return 0, false
+	}
+	
+	// pick off leading sign
+	neg := false;
+	if s[0] == '+' {
+		s = s[1:len(s)]
+	} else if s[0] == '-' {
+		neg = true;
+		s = s[1:len(s)]
+	}
+	
+	// empty string bad
+	if len(s) == 0 { 
+		return 0, false
+	}
+
+	// pick off zero
+	if s == "0" {
+		return 0, true
+	}
+	
+	// otherwise, leading zero bad
+	if s[0] == '0' {
+		return 0, false
+	}
+
+	// parse number
+	n := 0;
+	for i := 0; i < len(s); i++ {
+		if s[i] < '0' || s[i] > '9' {
+			return 0, false
+		}
+		n = n*10 + int(s[i] - '0')
+	}
+	if neg {
+		n = -n
+	}
+	return n, true
+}
+
+export func itoa(i int) string {
+	if i == 0 {
+		return "0"
+	}
+	
+	neg := false;	// negative
+	bigneg := false;	// largest negative number
+	if i < 0 {
+		neg = true;
+		i = -i;
+		if i < 0 {
+			bigneg = true;	// is largest negative int
+			i--	// now positive
+		}
+	}
+
+	// Assemble decimal in reverse order.
+	var b [32]byte;
+	bp := len(b);
+	for ; i > 0; i /= 10 {
+		bp--;
+		b[bp] = byte(i%10) + '0'
+	}
+	if neg {	// add sign
+		bp--;
+		b[bp] = '-'
+	}
+	if bigneg {	// account for i-- above
+		b[len(b)-1]++
+	}
+	
+	// BUG return string(b[bp:len(b)])
+	return string((&b)[bp:len(b)])
+}