2009-06-04 15:41:31 -06:00
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// Copyright 2009 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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// A package of simple functions to manipulate arrays of bytes.
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// Analagous to the facilities of the strings package.
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package bytes
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import "utf8"
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// Compare returns an integer comparing the two byte arrays lexicographically.
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// The result will be 0 if a==b, -1 if a < b, and +1 if a > b
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func Compare(a, b []byte) int {
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for i := 0; i < len(a) && i < len(b); i++ {
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switch {
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case a[i] > b[i]:
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return 1
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case a[i] < b[i]:
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return -1
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}
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}
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switch {
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case len(a) < len(b):
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return -1
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case len(a) > len(b):
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return 1
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}
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return 0
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}
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// Equal returns a boolean reporting whether a == b.
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func Equal(a, b []byte) bool {
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if len(a) != len(b) {
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return false
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}
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for i := 0; i < len(a); i++ {
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if a[i] != b[i] {
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return false
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}
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}
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return true
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}
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2009-06-24 16:35:35 -06:00
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// Copy copies bytes from src to dst,
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// stopping when either all of src has been copied
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// or all of dst has been filled.
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// It returns the number of bytes copied.
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2009-06-04 16:28:09 -06:00
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func Copy(dst, src []byte) int {
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2009-06-24 16:35:35 -06:00
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if len(src) > len(dst) {
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src = src[0:len(dst)];
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}
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2009-06-04 16:00:15 -06:00
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for i, x := range src {
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dst[i] = x
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}
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2009-06-04 16:28:09 -06:00
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return len(src)
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2009-06-04 16:00:15 -06:00
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}
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2009-06-24 20:02:29 -06:00
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// explode splits s into an array of UTF-8 sequences, one per Unicode character (still arrays of bytes),
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// up to a maximum of n byte arrays. Invalid UTF-8 sequences are chopped into individual bytes.
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func explode(s []byte, n int) [][]byte {
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if n <= 0 {
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n = len(s);
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}
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a := make([][]byte, n);
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2009-06-04 15:41:31 -06:00
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var size, rune int;
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2009-06-24 20:02:29 -06:00
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na := 0;
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2009-06-04 15:41:31 -06:00
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for len(s) > 0 {
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2009-06-24 20:02:29 -06:00
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if na+1 >= n {
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a[na] = s;
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na++;
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break
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}
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2009-06-04 15:41:31 -06:00
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rune, size = utf8.DecodeRune(s);
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2009-06-24 20:02:29 -06:00
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a[na] = s[0:size];
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2009-06-04 15:41:31 -06:00
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s = s[size:len(s)];
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2009-06-24 20:02:29 -06:00
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na++;
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2009-06-04 15:41:31 -06:00
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}
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2009-06-24 20:02:29 -06:00
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return a[0:na]
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2009-06-04 15:41:31 -06:00
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}
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// Count counts the number of non-overlapping instances of sep in s.
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func Count(s, sep []byte) int {
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if len(sep) == 0 {
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return utf8.RuneCount(s)+1
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}
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c := sep[0];
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n := 0;
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for i := 0; i+len(sep) <= len(s); i++ {
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if s[i] == c && (len(sep) == 1 || Equal(s[i:i+len(sep)], sep)) {
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n++;
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i += len(sep)-1
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}
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}
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return n
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}
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// Index returns the index of the first instance of sep in s, or -1 if sep is not present in s.
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func Index(s, sep []byte) int {
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n := len(sep);
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if n == 0 {
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return 0
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}
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c := sep[0];
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for i := 0; i+n <= len(s); i++ {
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if s[i] == c && (n == 1 || Equal(s[i:i+n], sep)) {
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return i
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}
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}
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return -1
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}
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2009-06-24 20:02:29 -06:00
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// Split splits the array s around each instance of sep, returning an array of subarrays of s.
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// If sep is empty, Split splits s after each UTF-8 sequence.
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// If n > 0, split Splits s into at most n subarrays; the last subarray will contain an unsplit remainder.
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func Split(s, sep []byte, n int) [][]byte {
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if len(sep) == 0 {
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2009-06-24 20:02:29 -06:00
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return explode(s, n)
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}
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if n <= 0 {
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n = Count(s, sep) + 1;
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}
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c := sep[0];
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start := 0;
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a := make([][]byte, n);
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na := 0;
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2009-06-24 20:02:29 -06:00
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for i := 0; i+len(sep) <= len(s) && na+1 < n; i++ {
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2009-06-04 15:41:31 -06:00
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if s[i] == c && (len(sep) == 1 || Equal(s[i:i+len(sep)], sep)) {
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a[na] = s[start:i];
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na++;
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start = i+len(sep);
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2009-06-24 20:02:29 -06:00
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i += len(sep)-1;
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2009-06-04 15:41:31 -06:00
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}
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}
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a[na] = s[start:len(s)];
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2009-06-24 20:02:29 -06:00
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return a[0:na+1]
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2009-06-04 15:41:31 -06:00
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}
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// Join concatenates the elements of a to create a single byte array. The separator
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// sep is placed between elements in the resulting array.
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func Join(a [][]byte, sep []byte) []byte {
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if len(a) == 0 {
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return []byte{}
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}
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if len(a) == 1 {
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return a[0]
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}
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n := len(sep) * (len(a)-1);
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for i := 0; i < len(a); i++ {
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n += len(a[i])
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}
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b := make([]byte, n);
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bp := 0;
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for i := 0; i < len(a); i++ {
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s := a[i];
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for j := 0; j < len(s); j++ {
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b[bp] = s[j];
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bp++
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}
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if i + 1 < len(a) {
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s = sep;
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for j := 0; j < len(s); j++ {
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b[bp] = s[j];
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bp++
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}
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}
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}
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return b
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}
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// HasPrefix tests whether the byte array s begins with prefix.
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func HasPrefix(s, prefix []byte) bool {
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return len(s) >= len(prefix) && Equal(s[0:len(prefix)], prefix)
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}
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// HasSuffix tests whether the byte array s ends with suffix.
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func HasSuffix(s, suffix []byte) bool {
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return len(s) >= len(suffix) && Equal(s[len(s)-len(suffix):len(s)], suffix)
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}
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