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