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match.go
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match.go
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// Copyright 2011 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 regexp
import (
"bytes"
"encoding/binary"
"flag"
"fmt"
"io"
"os"
"regexp/syntax"
"sort"
"code.google.com/p/codesearch/sparse"
)
// A matcher holds the state for running regular expression search.
type matcher struct {
prog *syntax.Prog // compiled program
dstate map[string]*dstate // dstate cache
start *dstate // start state
startLine *dstate // start state for beginning of line
z1, z2 nstate // two temporary nstates
}
// An nstate corresponds to an NFA state.
type nstate struct {
q sparse.Set // queue of program instructions
partial rune // partially decoded rune (TODO)
flag flags // flags (TODO)
}
// The flags record state about a position between bytes in the text.
type flags uint32
const (
flagBOL flags = 1 << iota // beginning of line
flagEOL // end of line
flagBOT // beginning of text
flagEOT // end of text
flagWord // last byte was word byte
)
// A dstate corresponds to a DFA state.
type dstate struct {
next [256]*dstate // next state, per byte
enc string // encoded nstate
matchNL bool // match when next byte is \n
matchEOT bool // match in this state at end of text
}
func (z *nstate) String() string {
return fmt.Sprintf("%v/%#x+%#x", z.q.Dense(), z.flag, z.partial)
}
// enc encodes z as a string.
func (z *nstate) enc() string {
var buf []byte
var v [10]byte
last := ^uint32(0)
n := binary.PutUvarint(v[:], uint64(z.partial))
buf = append(buf, v[:n]...)
n = binary.PutUvarint(v[:], uint64(z.flag))
buf = append(buf, v[:n]...)
dense := z.q.Dense()
ids := make([]int, 0, len(dense))
for _, id := range z.q.Dense() {
ids = append(ids, int(id))
}
sort.Ints(ids)
for _, id := range ids {
n := binary.PutUvarint(v[:], uint64(uint32(id)-last))
buf = append(buf, v[:n]...)
last = uint32(id)
}
return string(buf)
}
// dec decodes the encoding s into z.
func (z *nstate) dec(s string) {
b := []byte(s)
i, n := binary.Uvarint(b)
if n <= 0 {
bug()
}
b = b[n:]
z.partial = rune(i)
i, n = binary.Uvarint(b)
if n <= 0 {
bug()
}
b = b[n:]
z.flag = flags(i)
z.q.Reset()
last := ^uint32(0)
for len(b) > 0 {
i, n = binary.Uvarint(b)
if n <= 0 {
bug()
}
b = b[n:]
last += uint32(i)
z.q.Add(last)
}
}
// dmatch is the state we're in when we've seen a match and are just
// waiting for the end of the line.
var dmatch = dstate{
matchNL: true,
matchEOT: true,
}
func init() {
var z nstate
dmatch.enc = z.enc()
for i := range dmatch.next {
if i != '\n' {
dmatch.next[i] = &dmatch
}
}
}
// init initializes the matcher.
func (m *matcher) init(prog *syntax.Prog) error {
m.prog = prog
m.dstate = make(map[string]*dstate)
m.z1.q.Init(uint32(len(prog.Inst)))
m.z2.q.Init(uint32(len(prog.Inst)))
m.addq(&m.z1.q, uint32(prog.Start), syntax.EmptyBeginLine|syntax.EmptyBeginText)
m.z1.flag = flagBOL | flagBOT
m.start = m.cache(&m.z1)
m.z1.q.Reset()
m.addq(&m.z1.q, uint32(prog.Start), syntax.EmptyBeginLine)
m.z1.flag = flagBOL
m.startLine = m.cache(&m.z1)
return nil
}
// stepEmpty steps runq to nextq expanding according to flag.
func (m *matcher) stepEmpty(runq, nextq *sparse.Set, flag syntax.EmptyOp) {
nextq.Reset()
for _, id := range runq.Dense() {
m.addq(nextq, id, flag)
}
}
// stepByte steps runq to nextq consuming c and then expanding according to flag.
// It returns true if a match ends immediately before c.
// c is either an input byte or endText.
func (m *matcher) stepByte(runq, nextq *sparse.Set, c int, flag syntax.EmptyOp) (match bool) {
nextq.Reset()
m.addq(nextq, uint32(m.prog.Start), flag)
for _, id := range runq.Dense() {
i := &m.prog.Inst[id]
switch i.Op {
default:
continue
case syntax.InstMatch:
match = true
continue
case instByteRange:
if c == endText {
break
}
lo := int((i.Arg >> 8) & 0xFF)
hi := int(i.Arg & 0xFF)
ch := c
if i.Arg&argFold != 0 && 'a' <= ch && ch <= 'z' {
ch += 'A' - 'a'
}
if lo <= ch && ch <= hi {
m.addq(nextq, i.Out, flag)
}
}
}
return
}
// addq adds id to the queue, expanding according to flag.
func (m *matcher) addq(q *sparse.Set, id uint32, flag syntax.EmptyOp) {
if q.Has(id) {
return
}
q.Add(id)
i := &m.prog.Inst[id]
switch i.Op {
case syntax.InstCapture, syntax.InstNop:
m.addq(q, i.Out, flag)
case syntax.InstAlt, syntax.InstAltMatch:
m.addq(q, i.Out, flag)
m.addq(q, i.Arg, flag)
case syntax.InstEmptyWidth:
if syntax.EmptyOp(i.Arg)&^flag == 0 {
m.addq(q, i.Out, flag)
}
}
}
const endText = -1
// computeNext computes the next DFA state if we're in d reading c (an input byte or endText).
func (m *matcher) computeNext(d *dstate, c int) *dstate {
this, next := &m.z1, &m.z2
this.dec(d.enc)
// compute flags in effect before c
flag := syntax.EmptyOp(0)
if this.flag&flagBOL != 0 {
flag |= syntax.EmptyBeginLine
}
if this.flag&flagBOT != 0 {
flag |= syntax.EmptyBeginText
}
if this.flag&flagWord != 0 {
if !isWordByte(c) {
flag |= syntax.EmptyWordBoundary
} else {
flag |= syntax.EmptyNoWordBoundary
}
} else {
if isWordByte(c) {
flag |= syntax.EmptyWordBoundary
} else {
flag |= syntax.EmptyNoWordBoundary
}
}
if c == '\n' {
flag |= syntax.EmptyEndLine
}
if c == endText {
flag |= syntax.EmptyEndLine | syntax.EmptyEndText
}
// re-expand queue using new flags.
// TODO: only do this when it matters
// (something is gating on word boundaries).
m.stepEmpty(&this.q, &next.q, flag)
this, next = next, this
// now compute flags after c.
flag = 0
next.flag = 0
if c == '\n' {
flag |= syntax.EmptyBeginLine
next.flag |= flagBOL
}
if isWordByte(c) {
next.flag |= flagWord
}
// re-add start, process rune + expand according to flags.
if m.stepByte(&this.q, &next.q, c, flag) {
return &dmatch
}
return m.cache(next)
}
func (m *matcher) cache(z *nstate) *dstate {
enc := z.enc()
d := m.dstate[enc]
if d != nil {
return d
}
d = &dstate{enc: enc}
m.dstate[enc] = d
d.matchNL = m.computeNext(d, '\n') == &dmatch
d.matchEOT = m.computeNext(d, endText) == &dmatch
return d
}
func (m *matcher) match(b []byte, beginText, endText bool) (end int) {
// fmt.Printf("%v\n", m.prog)
d := m.startLine
if beginText {
d = m.start
}
// m.z1.dec(d.enc)
// fmt.Printf("%v (%v)\n", &m.z1, d==&dmatch)
for i, c := range b {
d1 := d.next[c]
if d1 == nil {
if c == '\n' {
if d.matchNL {
return i
}
d1 = m.startLine
} else {
d1 = m.computeNext(d, int(c))
}
d.next[c] = d1
}
d = d1
// m.z1.dec(d.enc)
// fmt.Printf("%#U: %v (%v, %v, %v)\n", c, &m.z1, d==&dmatch, d.matchNL, d.matchEOT)
}
if d.matchNL || endText && d.matchEOT {
return len(b)
}
return -1
}
func (m *matcher) matchString(b string, beginText, endText bool) (end int) {
d := m.startLine
if beginText {
d = m.start
}
for i := 0; i < len(b); i++ {
c := b[i]
d1 := d.next[c]
if d1 == nil {
if c == '\n' {
if d.matchNL {
return i
}
d1 = m.startLine
} else {
d1 = m.computeNext(d, int(c))
}
d.next[c] = d1
}
d = d1
}
if d.matchNL || endText && d.matchEOT {
return len(b)
}
return -1
}
// isWordByte reports whether the byte c is a word character: ASCII only.
// This is used to implement \b and \B. This is not right for Unicode, but:
// - it's hard to get right in a byte-at-a-time matching world
// (the DFA has only one-byte lookahead)
// - this crude approximation is the same one PCRE uses
func isWordByte(c int) bool {
return 'A' <= c && c <= 'Z' ||
'a' <= c && c <= 'z' ||
'0' <= c && c <= '9' ||
c == '_'
}
// TODO:
type Grep struct {
Regexp *Regexp // regexp to search for
Stdout io.Writer // output target
Stderr io.Writer // error target
L bool // L flag - print file names only
C bool // C flag - print count of matches
N bool // N flag - print line numbers
H bool // H flag - do not print file names
Match bool
buf []byte
}
func (g *Grep) AddFlags() {
flag.BoolVar(&g.L, "l", false, "list matching files only")
flag.BoolVar(&g.C, "c", false, "print match counts only")
flag.BoolVar(&g.N, "n", false, "show line numbers")
flag.BoolVar(&g.H, "h", false, "omit file names")
}
func (g *Grep) File(name string) {
f, err := os.Open(name)
if err != nil {
fmt.Fprintf(g.Stderr, "%s\n", err)
return
}
defer f.Close()
g.Reader(f, name)
}
var nl = []byte{'\n'}
func countNL(b []byte) int {
n := 0
for {
i := bytes.IndexByte(b, '\n')
if i < 0 {
break
}
n++
b = b[i+1:]
}
return n
}
func (g *Grep) Reader(r io.Reader, name string) {
if g.buf == nil {
g.buf = make([]byte, 1<<20)
}
var (
buf = g.buf[:0]
needLineno = g.N
lineno = 1
count = 0
prefix = ""
beginText = true
endText = false
)
if !g.H {
prefix = name + ":"
}
for {
n, err := io.ReadFull(r, buf[len(buf):cap(buf)])
buf = buf[:len(buf)+n]
end := len(buf)
if err == nil {
end = bytes.LastIndex(buf, nl) + 1
} else {
endText = true
}
chunkStart := 0
for chunkStart < end {
m1 := g.Regexp.Match(buf[chunkStart:end], beginText, endText) + chunkStart
beginText = false
if m1 < chunkStart {
break
}
g.Match = true
if g.L {
fmt.Fprintf(g.Stdout, "%s\n", name)
return
}
lineStart := bytes.LastIndex(buf[chunkStart:m1], nl) + 1 + chunkStart
lineEnd := m1 + 1
if lineEnd > end {
lineEnd = end
}
if needLineno {
lineno += countNL(buf[chunkStart:lineStart])
}
line := buf[lineStart:lineEnd]
switch {
case g.C:
count++
case g.N:
fmt.Fprintf(g.Stdout, "%s%d:%s", prefix, lineno, line)
default:
fmt.Fprintf(g.Stdout, "%s%s", prefix, line)
}
if needLineno {
lineno++
}
chunkStart = lineEnd
}
if needLineno && err == nil {
lineno += countNL(buf[chunkStart:end])
}
n = copy(buf, buf[end:])
buf = buf[:n]
if len(buf) == 0 && err != nil {
if err != io.EOF && err != io.ErrUnexpectedEOF {
fmt.Fprintf(g.Stderr, "%s: %v\n", name, err)
}
break
}
}
if g.C && count > 0 {
fmt.Fprintf(g.Stdout, "%s: %d\n", name, count)
}
}