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builder.go
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builder.go
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package pattern
import (
"errors"
"fmt"
)
const maxPatternSize = 10000
type patternBuilder struct {
items []patternItem
ciMax uint64
cStack []uint64
ptn string
i int
anchorLeft, anchorRight bool
}
func (pb *patternBuilder) getPattern() (*Pattern, error) {
// var anchorLeft, anchorRight bool
// if len(pb.ptn) > 0 && pb.ptn[0] == '^' {
// anchorLeft = true
// pb.ptn = pb.ptn[1:]
// }
// if last := len(pb.ptn) - 1; last >= 0 && pb.ptn[last] == '$' {
// anchorRight = true
// pb.ptn = pb.ptn[:last]
// }
sz := 0
for pb.i < len(pb.ptn) {
err := pb.getPatternItem()
if err != nil {
return nil, err
}
sz++
if sz > maxPatternSize {
return nil, errPatternTooComplex
}
}
if len(pb.cStack) != 0 {
return nil, errUnfinishedCapture
}
return &Pattern{
items: pb.items,
captureCount: int(pb.ciMax),
startAnchor: pb.anchorLeft,
endAnchor: pb.anchorRight,
}, nil
}
func (pb *patternBuilder) next() (byte, error) {
if pb.i >= len(pb.ptn) {
return 0, errInvalidPattern
}
b := pb.ptn[pb.i]
pb.i++
return b, nil
}
func (pb *patternBuilder) back() {
pb.i--
}
func (pb *patternBuilder) emit(item patternItem) {
pb.items = append(pb.items, item)
}
func (pb *patternBuilder) getPatternItem() error {
b, err := pb.next()
if err != nil {
return err
}
var s byteSet
switch b {
case '^':
if pb.i == 1 {
pb.anchorLeft = true
return nil
}
pb.back()
s, err = pb.getCharClass()
case '$':
if pb.i == len(pb.ptn) {
pb.anchorRight = true
return nil
}
pb.back()
s, err = pb.getCharClass()
case '(':
pb.ciMax++
if pb.ciMax >= 10 {
return errInvalidPattern
}
b, err = pb.next()
if err != nil {
return err
}
if b != ')' {
// Special case: empty capture will generate a position. So we only
// emit a ptnStartCapture and skip the ptnEndCapture. The pattern
// matcher will then create a capture whose end is -1.
pb.back()
pb.cStack = append(pb.cStack, pb.ciMax)
}
pb.emit(patternItem{byteSet{pb.ciMax}, ptnStartCapture})
return nil
case ')':
i := len(pb.cStack) - 1
if i < 0 {
return errInvalidPatternCapture
}
pb.emit(patternItem{byteSet{pb.cStack[i]}, ptnEndCapture})
pb.cStack = pb.cStack[:i]
return nil
case '%':
c, err := pb.next()
if err != nil {
return err
}
switch {
case c == 'f':
s, err := pb.getCharClass()
if err == nil {
pb.emit(patternItem{s, ptnFrontier})
}
return err
case c == 'b':
op, err := pb.next()
if err != nil {
return err
}
cl, err := pb.next()
if err != nil {
return err
}
// The doc says op and cl must be different, but the 5.3.4
// implementation allows them to be equal.
// if op == cl {
// return errInvalidPattern
// }
pb.emit(patternItem{[4]uint64{uint64(op), uint64(cl)}, ptnBalanced})
return nil
case c >= '1' && c <= '9':
ci := uint64(c - '0')
if !pb.checkCapture(ci) {
return ErrInvalidCaptureIdx(int(ci))
}
pb.emit(patternItem{[4]uint64{ci}, ptnCapture})
return nil
default:
s, err = getCharRange(c)
if err != nil {
return err
}
}
default:
pb.back()
s, err = pb.getCharClass()
}
if err != nil {
return err
}
b, err = pb.next()
ptnType := ptnOnce
if err == nil {
switch b {
case '*':
ptnType = ptnGreedyRepeat
case '+':
ptnType = ptnGreedyRepeatOnce
case '-':
ptnType = ptnRepeat
case '?':
ptnType = ptnOptional
default:
pb.back()
}
}
pb.emit(patternItem{s, ptnType})
return nil
}
func (pb *patternBuilder) checkCapture(ci uint64) bool {
if ci > pb.ciMax {
return false
}
for _, sci := range pb.cStack {
if sci == ci {
return false
}
}
return true
}
func (pb *patternBuilder) getCharClass() (byteSet, error) {
b, err := pb.next()
if err != nil {
return byteSet{}, err
}
switch b {
case '.':
return fullSet, nil
case '%':
b, err := pb.next()
if err != nil {
return byteSet{}, err
}
return getCharRange(b)
case '[':
return pb.getUnion()
default:
s := byteSet{}
s.add(b)
return s, nil
}
}
func (pb *patternBuilder) getUnion() (s byteSet, err error) {
var b byte
b, err = pb.next()
neg := false
// Note: no need to check err if b is not 0
if b == '^' {
neg = true
b, err = pb.next()
}
if b == ']' {
s.add(b)
b, err = pb.next()
}
var r byteSet
Loop:
for err == nil {
switch {
case b == ']':
if neg {
s.complement()
}
return
case b == '%':
b, err = pb.next()
if err != nil {
return
}
r, err = getCharRange(b)
if err != nil {
return
}
s.merge(r)
default:
c := b
b, err = pb.next()
if err != nil {
return
}
if b == '-' {
b, err = pb.next()
if err != nil {
return
}
if b == ']' {
s.add(c)
s.add('-')
continue Loop
}
s.merge(byteRange(c, b))
} else {
s.add(c)
continue Loop
}
}
b, err = pb.next()
}
return
}
func getCharRange(c byte) (byteSet, error) {
s, ok := namedByteSet[c]
if !ok {
switch {
case c == '0':
return s, ErrInvalidCaptureIdx(0)
case (c >= '1' && c <= '9') || (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z'):
return s, ErrInvalidPct
default:
s.add(c)
}
}
return s, nil
}
var ErrInvalidPct = errors.New("invalid use of '%'")
func ErrInvalidCaptureIdx(i int) error {
return fmt.Errorf("invalid capture index %%%d", i)
}