}
return
}
+
+func StringFind(pattern, text string) int {
+ return makeStringFinder(pattern).next(text)
+}
+
+func DumpTables(pattern string) ([]int, []int) {
+ finder := makeStringFinder(pattern)
+ return finder.badCharSkip[:], finder.goodSuffixSkip
+}
panic("strings.NewReplacer: odd argument count")
}
+ if len(oldnew) == 2 && len(oldnew[0]) > 1 {
+ return &Replacer{r: makeSingleStringReplacer(oldnew[0], oldnew[1])}
+ }
+
allNewBytes := true
for i := 0; i < len(oldnew); i += 2 {
if len(oldnew[i]) != 1 {
return len(s), nil
}
+type stringWriterIface interface {
+ WriteString(string) (int, error)
+}
+
type stringWriter struct {
w io.Writer
}
return w.w.Write([]byte(s))
}
+func getStringWriter(w io.Writer) stringWriterIface {
+ sw, ok := w.(stringWriterIface)
+ if !ok {
+ sw = stringWriter{w}
+ }
+ return sw
+}
+
func (r *genericReplacer) Replace(s string) string {
buf := make(appendSliceWriter, 0, len(s))
r.WriteString(&buf, s)
}
func (r *genericReplacer) WriteString(w io.Writer, s string) (n int, err error) {
- sw, ok := w.(interface {
- WriteString(string) (int, error)
- })
- if !ok {
- sw = stringWriter{w}
- }
-
+ sw := getStringWriter(w)
var last, wn int
var prevMatchEmpty bool
for i := 0; i <= len(s); {
return
}
+// singleStringReplacer is the implementation that's used when there is only
+// one string to replace (and that string has more than one byte).
+type singleStringReplacer struct {
+ finder *stringFinder
+ // value is the new string that replaces that pattern when it's found.
+ value string
+}
+
+func makeSingleStringReplacer(pattern string, value string) *singleStringReplacer {
+ return &singleStringReplacer{finder: makeStringFinder(pattern), value: value}
+}
+
+func (r *singleStringReplacer) Replace(s string) string {
+ var buf []byte
+ i := 0
+ for {
+ match := r.finder.next(s[i:])
+ if match == -1 {
+ break
+ }
+ buf = append(buf, s[i:i+match]...)
+ buf = append(buf, r.value...)
+ i += match + len(r.finder.pattern)
+ }
+ if buf == nil {
+ return s
+ }
+ buf = append(buf, s[i:]...)
+ return string(buf)
+}
+
+func (r *singleStringReplacer) WriteString(w io.Writer, s string) (n int, err error) {
+ sw := getStringWriter(w)
+ var i, wn int
+ for {
+ match := r.finder.next(s[i:])
+ if match == -1 {
+ break
+ }
+ wn, err = sw.WriteString(s[i : i+match])
+ n += wn
+ if err != nil {
+ return
+ }
+ wn, err = sw.WriteString(r.value)
+ n += wn
+ if err != nil {
+ return
+ }
+ i += match + len(r.finder.pattern)
+ }
+ wn, err = sw.WriteString(s[i:])
+ n += wn
+ return
+}
+
// byteReplacer is the implementation that's used when all the "old"
// and "new" values are single ASCII bytes.
type byteReplacer struct {
testCase{blankFoo, "", "X"},
)
+ // single string replacer
+
+ abcMatcher := NewReplacer("abc", "[match]")
+
+ testCases = append(testCases,
+ testCase{abcMatcher, "", ""},
+ testCase{abcMatcher, "ab", "ab"},
+ testCase{abcMatcher, "abcd", "[match]d"},
+ testCase{abcMatcher, "cabcabcdabca", "c[match][match]d[match]a"},
+ )
+
// No-arg test cases.
nop := NewReplacer()
}{
{capitalLetters, "*strings.byteReplacer"},
{htmlEscaper, "*strings.byteStringReplacer"},
- {NewReplacer("12", "123"), "*strings.genericReplacer"},
+ {NewReplacer("12", "123"), "*strings.singleStringReplacer"},
{NewReplacer("1", "12"), "*strings.byteStringReplacer"},
+ {NewReplacer("", "X"), "*strings.genericReplacer"},
{NewReplacer("a", "1", "b", "12", "cde", "123"), "*strings.genericReplacer"},
}
for i, tc := range testCases {
}
}
+func benchmarkSingleString(b *testing.B, pattern, text string) {
+ r := NewReplacer(pattern, "[match]")
+ b.SetBytes(int64(len(text)))
+ b.ResetTimer()
+ for i := 0; i < b.N; i++ {
+ r.Replace(text)
+ }
+}
+
+func BenchmarkSingleMaxSkipping(b *testing.B) {
+ benchmarkSingleString(b, Repeat("b", 25), Repeat("a", 10000))
+}
+
+func BenchmarkSingleLongSuffixFail(b *testing.B) {
+ benchmarkSingleString(b, "b"+Repeat("a", 500), Repeat("a", 1002))
+}
+
+func BenchmarkSingleMatch(b *testing.B) {
+ benchmarkSingleString(b, "abcdef", Repeat("abcdefghijklmno", 1000))
+}
+
func BenchmarkByteByteNoMatch(b *testing.B) {
str := Repeat("A", 100) + Repeat("B", 100)
for i := 0; i < b.N; i++ {
--- /dev/null
+// Copyright 2012 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
+
+// stringFinder efficiently finds strings in a source text. It's implemented
+// using the Boyer-Moore string search algorithm:
+// http://en.wikipedia.org/wiki/Boyer-Moore_string_search_algorithm
+// http://www.cs.utexas.edu/~moore/publications/fstrpos.pdf (note: this aged
+// document uses 1-based indexing)
+type stringFinder struct {
+ // pattern is the string that we are searching for in the text.
+ pattern string
+
+ // badCharSkip[b] contains the distance between the last byte of pattern
+ // and the rightmost occurrence of b in pattern. If b is not in pattern,
+ // badCharSkip[b] is len(pattern).
+ //
+ // Whenever a mismatch is found with byte b in the text, we can safely
+ // shift the matching frame at least badCharSkip[b] until the next time
+ // the matching char could be in alignment.
+ badCharSkip [256]int
+
+ // goodSuffixSkip[i] defines how far we can shift the matching frame given
+ // that the suffix pattern[i+1:] matches, but the byte pattern[i] does
+ // not. There are two cases to consider:
+ //
+ // 1. The matched suffix occurs elsewhere in pattern (with a different
+ // byte preceding it that we might possibly match). In this case, we can
+ // shift the matching frame to align with the next suffix chunk. For
+ // example, the pattern "mississi" has the suffix "issi" next occurring
+ // (in right-to-left order) at index 1, so goodSuffixSkip[3] ==
+ // shift+len(suffix) == 3+4 == 7.
+ //
+ // 2. If the matched suffix does not occur elsewhere in pattern, then the
+ // matching frame may share part of its prefix with the end of the
+ // matching suffix. In this case, goodSuffixSkip[i] will contain how far
+ // to shift the frame to align this portion of the prefix to the
+ // suffix. For example, in the pattern "abcxxxabc", when the first
+ // mismatch from the back is found to be in position 3, the matching
+ // suffix "xxabc" is not found elsewhere in the pattern. However, its
+ // rightmost "abc" (at position 6) is a prefix of the whole pattern, so
+ // goodSuffixSkip[3] == shift+len(suffix) == 6+5 == 11.
+ goodSuffixSkip []int
+}
+
+func makeStringFinder(pattern string) *stringFinder {
+ f := &stringFinder{
+ pattern: pattern,
+ goodSuffixSkip: make([]int, len(pattern)),
+ }
+ // last is the index of the last character in the pattern.
+ last := len(pattern) - 1
+
+ // Build bad character table.
+ // Bytes not in the pattern can skip one pattern's length.
+ for i := range f.badCharSkip {
+ f.badCharSkip[i] = len(pattern)
+ }
+ // The loop condition is < instead of <= so that the last byte does not
+ // have a zero distance to itself. Finding this byte out of place implies
+ // that it is not in the last position.
+ for i := 0; i < last; i++ {
+ f.badCharSkip[pattern[i]] = last - i
+ }
+
+ // Build good suffix table.
+ // First pass: set each value to the next index which starts a prefix of
+ // pattern.
+ lastPrefix := last
+ for i := last; i >= 0; i-- {
+ if HasPrefix(pattern, pattern[i+1:]) {
+ lastPrefix = i + 1
+ }
+ // lastPrefix is the shift, and (last-i) is len(suffix).
+ f.goodSuffixSkip[i] = lastPrefix + last - i
+ }
+ // Second pass: find repeats of pattern's suffix starting from the front.
+ for i := 0; i < last; i++ {
+ lenSuffix := longestCommonSuffix(pattern, pattern[1:i+1])
+ if pattern[i-lenSuffix] != pattern[last-lenSuffix] {
+ // (last-i) is the shift, and lenSuffix is len(suffix).
+ f.goodSuffixSkip[last-lenSuffix] = lenSuffix + last - i
+ }
+ }
+
+ return f
+}
+
+func longestCommonSuffix(a, b string) (i int) {
+ for ; i < len(a) && i < len(b); i++ {
+ if a[len(a)-1-i] != b[len(b)-1-i] {
+ break
+ }
+ }
+ return
+}
+
+// next returns the index in text of the first occurrence of the pattern. If
+// the pattern is not found, it returns -1.
+func (f *stringFinder) next(text string) int {
+ i := len(f.pattern) - 1
+ for i < len(text) {
+ // Compare backwards from the end until the first unmatching character.
+ j := len(f.pattern) - 1
+ for j >= 0 && text[i] == f.pattern[j] {
+ i--
+ j--
+ }
+ if j < 0 {
+ return i + 1 // match
+ }
+ i += max(f.badCharSkip[text[i]], f.goodSuffixSkip[j])
+ }
+ return -1
+}
+
+func max(a, b int) int {
+ if a > b {
+ return a
+ }
+ return b
+}
--- /dev/null
+// Copyright 2012 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_test
+
+import (
+ "reflect"
+ . "strings"
+ "testing"
+)
+
+func TestFinderNext(t *testing.T) {
+ testCases := []struct {
+ pat, text string
+ index int
+ }{
+ {"", "", 0},
+ {"", "abc", 0},
+ {"abc", "", -1},
+ {"abc", "abc", 0},
+ {"d", "abcdefg", 3},
+ {"nan", "banana", 2},
+ {"pan", "anpanman", 2},
+ {"nnaaman", "anpanmanam", -1},
+ {"abcd", "abc", -1},
+ {"abcd", "bcd", -1},
+ {"bcd", "abcd", 1},
+ {"abc", "acca", -1},
+ {"aa", "aaa", 0},
+ {"baa", "aaaaa", -1},
+ {"at that", "which finally halts. at that point", 22},
+ }
+
+ for _, tc := range testCases {
+ got := StringFind(tc.pat, tc.text)
+ want := tc.index
+ if got != want {
+ t.Errorf("stringFind(%q, %q) got %d, want %d\n", tc.pat, tc.text, got, want)
+ }
+ }
+}
+
+func TestFinderCreation(t *testing.T) {
+ testCases := []struct {
+ pattern string
+ bad [256]int
+ suf []int
+ }{
+ {
+ "abc",
+ [256]int{'a': 2, 'b': 1, 'c': 3},
+ []int{5, 4, 1},
+ },
+ {
+ "mississi",
+ [256]int{'i': 3, 'm': 7, 's': 1},
+ []int{15, 14, 13, 7, 11, 10, 7, 1},
+ },
+ // From http://www.cs.utexas.edu/~moore/publications/fstrpos.pdf
+ {
+ "abcxxxabc",
+ [256]int{'a': 2, 'b': 1, 'c': 6, 'x': 3},
+ []int{14, 13, 12, 11, 10, 9, 11, 10, 1},
+ },
+ {
+ "abyxcdeyx",
+ [256]int{'a': 8, 'b': 7, 'c': 4, 'd': 3, 'e': 2, 'y': 1, 'x': 5},
+ []int{17, 16, 15, 14, 13, 12, 7, 10, 1},
+ },
+ }
+
+ for _, tc := range testCases {
+ bad, good := DumpTables(tc.pattern)
+
+ for i, got := range bad {
+ want := tc.bad[i]
+ if want == 0 {
+ want = len(tc.pattern)
+ }
+ if got != want {
+ t.Errorf("boyerMoore(%q) bad['%c']: got %d want %d", tc.pattern, i, got, want)
+ }
+ }
+
+ if !reflect.DeepEqual(good, tc.suf) {
+ t.Errorf("boyerMoore(%q) got %v want %v", tc.pattern, good, tc.suf)
+ }
+ }
+}