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package syntax
import (
"bytes"
"fmt"
"strconv"
"unicode"
"unicode/utf8"
)
type Prefix struct {
PrefixStr []rune
PrefixSet CharSet
CaseInsensitive bool
}
// It takes a RegexTree and computes the set of chars that can start it.
func getFirstCharsPrefix(tree *RegexTree) *Prefix {
s := regexFcd{
fcStack: make([]regexFc, 32),
intStack: make([]int, 32),
}
fc := s.regexFCFromRegexTree(tree)
if fc == nil || fc.nullable || fc.cc.IsEmpty() {
return nil
}
fcSet := fc.getFirstChars()
return &Prefix{PrefixSet: fcSet, CaseInsensitive: fc.caseInsensitive}
}
type regexFcd struct {
intStack []int
intDepth int
fcStack []regexFc
fcDepth int
skipAllChildren bool // don't process any more children at the current level
skipchild bool // don't process the current child.
failed bool
}
/*
* The main FC computation. It does a shortcutted depth-first walk
* through the tree and calls CalculateFC to emits code before
* and after each child of an interior node, and at each leaf.
*/
func (s *regexFcd) regexFCFromRegexTree(tree *RegexTree) *regexFc {
curNode := tree.root
curChild := 0
for {
if len(curNode.children) == 0 {
// This is a leaf node
s.calculateFC(curNode.t, curNode, 0)
} else if curChild < len(curNode.children) && !s.skipAllChildren {
// This is an interior node, and we have more children to analyze
s.calculateFC(curNode.t|beforeChild, curNode, curChild)
if !s.skipchild {
curNode = curNode.children[curChild]
// this stack is how we get a depth first walk of the tree.
s.pushInt(curChild)
curChild = 0
} else {
curChild++
s.skipchild = false
}
continue
}
// This is an interior node where we've finished analyzing all the children, or
// the end of a leaf node.
s.skipAllChildren = false
if s.intIsEmpty() {
break
}
curChild = s.popInt()
curNode = curNode.next
s.calculateFC(curNode.t|afterChild, curNode, curChild)
if s.failed {
return nil
}
curChild++
}
if s.fcIsEmpty() {
return nil
}
return s.popFC()
}
// To avoid recursion, we use a simple integer stack.
// This is the push.
func (s *regexFcd) pushInt(I int) {
if s.intDepth >= len(s.intStack) {
expanded := make([]int, s.intDepth*2)
copy(expanded, s.intStack)
s.intStack = expanded
}
s.intStack[s.intDepth] = I
s.intDepth++
}
// True if the stack is empty.
func (s *regexFcd) intIsEmpty() bool {
return s.intDepth == 0
}
// This is the pop.
func (s *regexFcd) popInt() int {
s.intDepth--
return s.intStack[s.intDepth]
}
// We also use a stack of RegexFC objects.
// This is the push.
func (s *regexFcd) pushFC(fc regexFc) {
if s.fcDepth >= len(s.fcStack) {
expanded := make([]regexFc, s.fcDepth*2)
copy(expanded, s.fcStack)
s.fcStack = expanded
}
s.fcStack[s.fcDepth] = fc
s.fcDepth++
}
// True if the stack is empty.
func (s *regexFcd) fcIsEmpty() bool {
return s.fcDepth == 0
}
// This is the pop.
func (s *regexFcd) popFC() *regexFc {
s.fcDepth--
return &s.fcStack[s.fcDepth]
}
// This is the top.
func (s *regexFcd) topFC() *regexFc {
return &s.fcStack[s.fcDepth-1]
}
// Called in Beforechild to prevent further processing of the current child
func (s *regexFcd) skipChild() {
s.skipchild = true
}
// FC computation and shortcut cases for each node type
func (s *regexFcd) calculateFC(nt nodeType, node *regexNode, CurIndex int) {
//fmt.Printf("NodeType: %v, CurIndex: %v, Desc: %v\n", nt, CurIndex, node.description())
ci := false
rtl := false
if nt <= ntRef {
if (node.options & IgnoreCase) != 0 {
ci = true
}
if (node.options & RightToLeft) != 0 {
rtl = true
}
}
switch nt {
case ntConcatenate | beforeChild, ntAlternate | beforeChild, ntTestref | beforeChild, ntLoop | beforeChild, ntLazyloop | beforeChild:
break
case ntTestgroup | beforeChild:
if CurIndex == 0 {
s.skipChild()
}
break
case ntEmpty:
s.pushFC(regexFc{nullable: true})
break
case ntConcatenate | afterChild:
if CurIndex != 0 {
child := s.popFC()
cumul := s.topFC()
s.failed = !cumul.addFC(*child, true)
}
fc := s.topFC()
if !fc.nullable {
s.skipAllChildren = true
}
break
case ntTestgroup | afterChild:
if CurIndex > 1 {
child := s.popFC()
cumul := s.topFC()
s.failed = !cumul.addFC(*child, false)
}
break
case ntAlternate | afterChild, ntTestref | afterChild:
if CurIndex != 0 {
child := s.popFC()
cumul := s.topFC()
s.failed = !cumul.addFC(*child, false)
}
break
case ntLoop | afterChild, ntLazyloop | afterChild:
if node.m == 0 {
fc := s.topFC()
fc.nullable = true
}
break
case ntGroup | beforeChild, ntGroup | afterChild, ntCapture | beforeChild, ntCapture | afterChild, ntGreedy | beforeChild, ntGreedy | afterChild:
break
case ntRequire | beforeChild, ntPrevent | beforeChild:
s.skipChild()
s.pushFC(regexFc{nullable: true})
break
case ntRequire | afterChild, ntPrevent | afterChild:
break
case ntOne, ntNotone:
s.pushFC(newRegexFc(node.ch, nt == ntNotone, false, ci))
break
case ntOneloop, ntOnelazy:
s.pushFC(newRegexFc(node.ch, false, node.m == 0, ci))
break
case ntNotoneloop, ntNotonelazy:
s.pushFC(newRegexFc(node.ch, true, node.m == 0, ci))
break
case ntMulti:
if len(node.str) == 0 {
s.pushFC(regexFc{nullable: true})
} else if !rtl {
s.pushFC(newRegexFc(node.str[0], false, false, ci))
} else {
s.pushFC(newRegexFc(node.str[len(node.str)-1], false, false, ci))
}
break
case ntSet:
s.pushFC(regexFc{cc: node.set.Copy(), nullable: false, caseInsensitive: ci})
break
case ntSetloop, ntSetlazy:
s.pushFC(regexFc{cc: node.set.Copy(), nullable: node.m == 0, caseInsensitive: ci})
break
case ntRef:
s.pushFC(regexFc{cc: *AnyClass(), nullable: true, caseInsensitive: false})
break
case ntNothing, ntBol, ntEol, ntBoundary, ntNonboundary, ntECMABoundary, ntNonECMABoundary, ntBeginning, ntStart, ntEndZ, ntEnd:
s.pushFC(regexFc{nullable: true})
break
default:
panic(fmt.Sprintf("unexpected op code: %v", nt))
}
}
type regexFc struct {
cc CharSet
nullable bool
caseInsensitive bool
}
func newRegexFc(ch rune, not, nullable, caseInsensitive bool) regexFc {
r := regexFc{
caseInsensitive: caseInsensitive,
nullable: nullable,
}
if not {
if ch > 0 {
r.cc.addRange('\x00', ch-1)
}
if ch < 0xFFFF {
r.cc.addRange(ch+1, utf8.MaxRune)
}
} else {
r.cc.addRange(ch, ch)
}
return r
}
func (r *regexFc) getFirstChars() CharSet {
if r.caseInsensitive {
r.cc.addLowercase()
}
return r.cc
}
func (r *regexFc) addFC(fc regexFc, concatenate bool) bool {
if !r.cc.IsMergeable() || !fc.cc.IsMergeable() {
return false
}
if concatenate {
if !r.nullable {
return true
}
if !fc.nullable {
r.nullable = false
}
} else {
if fc.nullable {
r.nullable = true
}
}
r.caseInsensitive = r.caseInsensitive || fc.caseInsensitive
r.cc.addSet(fc.cc)
return true
}
// This is a related computation: it takes a RegexTree and computes the
// leading substring if it sees one. It's quite trivial and gives up easily.
func getPrefix(tree *RegexTree) *Prefix {
var concatNode *regexNode
nextChild := 0
curNode := tree.root
for {
switch curNode.t {
case ntConcatenate:
if len(curNode.children) > 0 {
concatNode = curNode
nextChild = 0
}
case ntGreedy, ntCapture:
curNode = curNode.children[0]
concatNode = nil
continue
case ntOneloop, ntOnelazy:
if curNode.m > 0 {
return &Prefix{
PrefixStr: repeat(curNode.ch, curNode.m),
CaseInsensitive: (curNode.options & IgnoreCase) != 0,
}
}
return nil
case ntOne:
return &Prefix{
PrefixStr: []rune{curNode.ch},
CaseInsensitive: (curNode.options & IgnoreCase) != 0,
}
case ntMulti:
return &Prefix{
PrefixStr: curNode.str,
CaseInsensitive: (curNode.options & IgnoreCase) != 0,
}
case ntBol, ntEol, ntBoundary, ntECMABoundary, ntBeginning, ntStart,
ntEndZ, ntEnd, ntEmpty, ntRequire, ntPrevent:
default:
return nil
}
if concatNode == nil || nextChild >= len(concatNode.children) {
return nil
}
curNode = concatNode.children[nextChild]
nextChild++
}
}
// repeat the rune r, c times... up to the max of MaxPrefixSize
func repeat(r rune, c int) []rune {
if c > MaxPrefixSize {
c = MaxPrefixSize
}
ret := make([]rune, c)
// binary growth using copy for speed
ret[0] = r
bp := 1
for bp < len(ret) {
copy(ret[bp:], ret[:bp])
bp *= 2
}
return ret
}
// BmPrefix precomputes the Boyer-Moore
// tables for fast string scanning. These tables allow
// you to scan for the first occurrence of a string within
// a large body of text without examining every character.
// The performance of the heuristic depends on the actual
// string and the text being searched, but usually, the longer
// the string that is being searched for, the fewer characters
// need to be examined.
type BmPrefix struct {
positive []int
negativeASCII []int
negativeUnicode [][]int
pattern []rune
lowASCII rune
highASCII rune
rightToLeft bool
caseInsensitive bool
}
func newBmPrefix(pattern []rune, caseInsensitive, rightToLeft bool) *BmPrefix {
b := &BmPrefix{
rightToLeft: rightToLeft,
caseInsensitive: caseInsensitive,
pattern: pattern,
}
if caseInsensitive {
for i := 0; i < len(b.pattern); i++ {
// We do the ToLower character by character for consistency. With surrogate chars, doing
// a ToLower on the entire string could actually change the surrogate pair. This is more correct
// linguistically, but since Regex doesn't support surrogates, it's more important to be
// consistent.
b.pattern[i] = unicode.ToLower(b.pattern[i])
}
}
var beforefirst, last, bump int
var scan, match int
if !rightToLeft {
beforefirst = -1
last = len(b.pattern) - 1
bump = 1
} else {
beforefirst = len(b.pattern)
last = 0
bump = -1
}
// PART I - the good-suffix shift table
//
// compute the positive requirement:
// if char "i" is the first one from the right that doesn't match,
// then we know the matcher can advance by _positive[i].
//
// This algorithm is a simplified variant of the standard
// Boyer-Moore good suffix calculation.
b.positive = make([]int, len(b.pattern))
examine := last
ch := b.pattern[examine]
b.positive[examine] = bump
examine -= bump
Outerloop:
for {
// find an internal char (examine) that matches the tail
for {
if examine == beforefirst {
break Outerloop
}
if b.pattern[examine] == ch {
break
}
examine -= bump
}
match = last
scan = examine
// find the length of the match
for {
if scan == beforefirst || b.pattern[match] != b.pattern[scan] {
// at the end of the match, note the difference in _positive
// this is not the length of the match, but the distance from the internal match
// to the tail suffix.
if b.positive[match] == 0 {
b.positive[match] = match - scan
}
// System.Diagnostics.Debug.WriteLine("Set positive[" + match + "] to " + (match - scan));
break
}
scan -= bump
match -= bump
}
examine -= bump
}
match = last - bump
// scan for the chars for which there are no shifts that yield a different candidate
// The inside of the if statement used to say
// "_positive[match] = last - beforefirst;"
// This is slightly less aggressive in how much we skip, but at worst it
// should mean a little more work rather than skipping a potential match.
for match != beforefirst {
if b.positive[match] == 0 {
b.positive[match] = bump
}
match -= bump
}
// PART II - the bad-character shift table
//
// compute the negative requirement:
// if char "ch" is the reject character when testing position "i",
// we can slide up by _negative[ch];
// (_negative[ch] = str.Length - 1 - str.LastIndexOf(ch))
//
// the lookup table is divided into ASCII and Unicode portions;
// only those parts of the Unicode 16-bit code set that actually
// appear in the string are in the table. (Maximum size with
// Unicode is 65K; ASCII only case is 512 bytes.)
b.negativeASCII = make([]int, 128)
for i := 0; i < len(b.negativeASCII); i++ {
b.negativeASCII[i] = last - beforefirst
}
b.lowASCII = 127
b.highASCII = 0
for examine = last; examine != beforefirst; examine -= bump {
ch = b.pattern[examine]
switch {
case ch < 128:
if b.lowASCII > ch {
b.lowASCII = ch
}
if b.highASCII < ch {
b.highASCII = ch
}
if b.negativeASCII[ch] == last-beforefirst {
b.negativeASCII[ch] = last - examine
}
case ch <= 0xffff:
i, j := ch>>8, ch&0xFF
if b.negativeUnicode == nil {
b.negativeUnicode = make([][]int, 256)
}
if b.negativeUnicode[i] == nil {
newarray := make([]int, 256)
for k := 0; k < len(newarray); k++ {
newarray[k] = last - beforefirst
}
if i == 0 {
copy(newarray, b.negativeASCII)
//TODO: this line needed?
b.negativeASCII = newarray
}
b.negativeUnicode[i] = newarray
}
if b.negativeUnicode[i][j] == last-beforefirst {
b.negativeUnicode[i][j] = last - examine
}
default:
// we can't do the filter because this algo doesn't support
// unicode chars >0xffff
return nil
}
}
return b
}
func (b *BmPrefix) String() string {
return string(b.pattern)
}
// Dump returns the contents of the filter as a human readable string
func (b *BmPrefix) Dump(indent string) string {
buf := &bytes.Buffer{}
fmt.Fprintf(buf, "%sBM Pattern: %s\n%sPositive: ", indent, string(b.pattern), indent)
for i := 0; i < len(b.positive); i++ {
buf.WriteString(strconv.Itoa(b.positive[i]))
buf.WriteRune(' ')
}
buf.WriteRune('\n')
if b.negativeASCII != nil {
buf.WriteString(indent)
buf.WriteString("Negative table\n")
for i := 0; i < len(b.negativeASCII); i++ {
if b.negativeASCII[i] != len(b.pattern) {
fmt.Fprintf(buf, "%s %s %s\n", indent, Escape(string(rune(i))), strconv.Itoa(b.negativeASCII[i]))
}
}
}
return buf.String()
}
// Scan uses the Boyer-Moore algorithm to find the first occurrence
// of the specified string within text, beginning at index, and
// constrained within beglimit and endlimit.
//
// The direction and case-sensitivity of the match is determined
// by the arguments to the RegexBoyerMoore constructor.
func (b *BmPrefix) Scan(text []rune, index, beglimit, endlimit int) int {
var (
defadv, test, test2 int
match, startmatch, endmatch int
bump, advance int
chTest rune
unicodeLookup []int
)
if !b.rightToLeft {
defadv = len(b.pattern)
startmatch = len(b.pattern) - 1
endmatch = 0
test = index + defadv - 1
bump = 1
} else {
defadv = -len(b.pattern)
startmatch = 0
endmatch = -defadv - 1
test = index + defadv
bump = -1
}
chMatch := b.pattern[startmatch]
for {
if test >= endlimit || test < beglimit {
return -1
}
chTest = text[test]
if b.caseInsensitive {
chTest = unicode.ToLower(chTest)
}
if chTest != chMatch {
if chTest < 128 {
advance = b.negativeASCII[chTest]
} else if chTest < 0xffff && len(b.negativeUnicode) > 0 {
unicodeLookup = b.negativeUnicode[chTest>>8]
if len(unicodeLookup) > 0 {
advance = unicodeLookup[chTest&0xFF]
} else {
advance = defadv
}
} else {
advance = defadv
}
test += advance
} else { // if (chTest == chMatch)
test2 = test
match = startmatch
for {
if match == endmatch {
if b.rightToLeft {
return test2 + 1
} else {
return test2
}
}
match -= bump
test2 -= bump
chTest = text[test2]
if b.caseInsensitive {
chTest = unicode.ToLower(chTest)
}
if chTest != b.pattern[match] {
advance = b.positive[match]
if chTest < 128 {
test2 = (match - startmatch) + b.negativeASCII[chTest]
} else if chTest < 0xffff && len(b.negativeUnicode) > 0 {
unicodeLookup = b.negativeUnicode[chTest>>8]
if len(unicodeLookup) > 0 {
test2 = (match - startmatch) + unicodeLookup[chTest&0xFF]
} else {
test += advance
break
}
} else {
test += advance
break
}
if b.rightToLeft {
if test2 < advance {
advance = test2
}
} else if test2 > advance {
advance = test2
}
test += advance
break
}
}
}
}
}
// When a regex is anchored, we can do a quick IsMatch test instead of a Scan
func (b *BmPrefix) IsMatch(text []rune, index, beglimit, endlimit int) bool {
if !b.rightToLeft {
if index < beglimit || endlimit-index < len(b.pattern) {
return false
}
return b.matchPattern(text, index)
} else {
if index > endlimit || index-beglimit < len(b.pattern) {
return false
}
return b.matchPattern(text, index-len(b.pattern))
}
}
func (b *BmPrefix) matchPattern(text []rune, index int) bool {
if len(text)-index < len(b.pattern) {
return false
}
if b.caseInsensitive {
for i := 0; i < len(b.pattern); i++ {
//Debug.Assert(textinfo.ToLower(_pattern[i]) == _pattern[i], "pattern should be converted to lower case in constructor!");
if unicode.ToLower(text[index+i]) != b.pattern[i] {
return false
}
}
return true
} else {
for i := 0; i < len(b.pattern); i++ {
if text[index+i] != b.pattern[i] {
return false
}
}
return true
}
}
type AnchorLoc int16
// where the regex can be pegged
const (
AnchorBeginning AnchorLoc = 0x0001
AnchorBol = 0x0002
AnchorStart = 0x0004
AnchorEol = 0x0008
AnchorEndZ = 0x0010
AnchorEnd = 0x0020
AnchorBoundary = 0x0040
AnchorECMABoundary = 0x0080
)
func getAnchors(tree *RegexTree) AnchorLoc {
var concatNode *regexNode
nextChild, result := 0, AnchorLoc(0)
curNode := tree.root
for {
switch curNode.t {
case ntConcatenate:
if len(curNode.children) > 0 {
concatNode = curNode
nextChild = 0
}
case ntGreedy, ntCapture:
curNode = curNode.children[0]
concatNode = nil
continue
case ntBol, ntEol, ntBoundary, ntECMABoundary, ntBeginning,
ntStart, ntEndZ, ntEnd:
return result | anchorFromType(curNode.t)
case ntEmpty, ntRequire, ntPrevent:
default:
return result
}
if concatNode == nil || nextChild >= len(concatNode.children) {
return result
}
curNode = concatNode.children[nextChild]
nextChild++
}
}
func anchorFromType(t nodeType) AnchorLoc {
switch t {
case ntBol:
return AnchorBol
case ntEol:
return AnchorEol
case ntBoundary:
return AnchorBoundary
case ntECMABoundary:
return AnchorECMABoundary
case ntBeginning:
return AnchorBeginning
case ntStart:
return AnchorStart
case ntEndZ:
return AnchorEndZ
case ntEnd:
return AnchorEnd
default:
return 0
}
}
// anchorDescription returns a human-readable description of the anchors
func (anchors AnchorLoc) String() string {
buf := &bytes.Buffer{}
if 0 != (anchors & AnchorBeginning) {
buf.WriteString(", Beginning")
}
if 0 != (anchors & AnchorStart) {
buf.WriteString(", Start")
}
if 0 != (anchors & AnchorBol) {
buf.WriteString(", Bol")
}
if 0 != (anchors & AnchorBoundary) {
buf.WriteString(", Boundary")
}
if 0 != (anchors & AnchorECMABoundary) {
buf.WriteString(", ECMABoundary")
}
if 0 != (anchors & AnchorEol) {
buf.WriteString(", Eol")
}
if 0 != (anchors & AnchorEnd) {
buf.WriteString(", End")
}
if 0 != (anchors & AnchorEndZ) {
buf.WriteString(", EndZ")
}
// trim off comma
if buf.Len() >= 2 {
return buf.String()[2:]
}
return "None"
}
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