fastpastebin/vendor/github.com/dlclark/regexp2/syntax/writer.go

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package syntax
import (
"bytes"
"fmt"
"math"
"os"
)
func Write(tree *RegexTree) (*Code, error) {
w := writer{
intStack: make([]int, 0, 32),
emitted: make([]int, 2),
stringhash: make(map[string]int),
sethash: make(map[string]int),
}
code, err := w.codeFromTree(tree)
if tree.options&Debug > 0 && code != nil {
os.Stdout.WriteString(code.Dump())
os.Stdout.WriteString("\n")
}
return code, err
}
type writer struct {
emitted []int
intStack []int
curpos int
stringhash map[string]int
stringtable [][]rune
sethash map[string]int
settable []*CharSet
counting bool
count int
trackcount int
caps map[int]int
}
const (
beforeChild nodeType = 64
afterChild = 128
//MaxPrefixSize is the largest number of runes we'll use for a BoyerMoyer prefix
MaxPrefixSize = 50
)
// The top level RegexCode generator. It does a depth-first walk
// through the tree and calls EmitFragment to emits code before
// and after each child of an interior node, and at each leaf.
//
// It runs two passes, first to count the size of the generated
// code, and second to generate the code.
//
// We should time it against the alternative, which is
// to just generate the code and grow the array as we go.
func (w *writer) codeFromTree(tree *RegexTree) (*Code, error) {
var (
curNode *regexNode
curChild int
capsize int
)
// construct sparse capnum mapping if some numbers are unused
if tree.capnumlist == nil || tree.captop == len(tree.capnumlist) {
capsize = tree.captop
w.caps = nil
} else {
capsize = len(tree.capnumlist)
w.caps = tree.caps
for i := 0; i < len(tree.capnumlist); i++ {
w.caps[tree.capnumlist[i]] = i
}
}
w.counting = true
for {
if !w.counting {
w.emitted = make([]int, w.count)
}
curNode = tree.root
curChild = 0
w.emit1(Lazybranch, 0)
for {
if len(curNode.children) == 0 {
w.emitFragment(curNode.t, curNode, 0)
} else if curChild < len(curNode.children) {
w.emitFragment(curNode.t|beforeChild, curNode, curChild)
curNode = curNode.children[curChild]
w.pushInt(curChild)
curChild = 0
continue
}
if w.emptyStack() {
break
}
curChild = w.popInt()
curNode = curNode.next
w.emitFragment(curNode.t|afterChild, curNode, curChild)
curChild++
}
w.patchJump(0, w.curPos())
w.emit(Stop)
if !w.counting {
break
}
w.counting = false
}
fcPrefix := getFirstCharsPrefix(tree)
prefix := getPrefix(tree)
rtl := (tree.options & RightToLeft) != 0
var bmPrefix *BmPrefix
//TODO: benchmark string prefixes
if prefix != nil && len(prefix.PrefixStr) > 0 && MaxPrefixSize > 0 {
if len(prefix.PrefixStr) > MaxPrefixSize {
// limit prefix changes to 10k
prefix.PrefixStr = prefix.PrefixStr[:MaxPrefixSize]
}
bmPrefix = newBmPrefix(prefix.PrefixStr, prefix.CaseInsensitive, rtl)
} else {
bmPrefix = nil
}
return &Code{
Codes: w.emitted,
Strings: w.stringtable,
Sets: w.settable,
TrackCount: w.trackcount,
Caps: w.caps,
Capsize: capsize,
FcPrefix: fcPrefix,
BmPrefix: bmPrefix,
Anchors: getAnchors(tree),
RightToLeft: rtl,
}, nil
}
// The main RegexCode generator. It does a depth-first walk
// through the tree and calls EmitFragment to emits code before
// and after each child of an interior node, and at each leaf.
func (w *writer) emitFragment(nodetype nodeType, node *regexNode, curIndex int) error {
bits := InstOp(0)
if nodetype <= ntRef {
if (node.options & RightToLeft) != 0 {
bits |= Rtl
}
if (node.options & IgnoreCase) != 0 {
bits |= Ci
}
}
ntBits := nodeType(bits)
switch nodetype {
case ntConcatenate | beforeChild, ntConcatenate | afterChild, ntEmpty:
break
case ntAlternate | beforeChild:
if curIndex < len(node.children)-1 {
w.pushInt(w.curPos())
w.emit1(Lazybranch, 0)
}
case ntAlternate | afterChild:
if curIndex < len(node.children)-1 {
lbPos := w.popInt()
w.pushInt(w.curPos())
w.emit1(Goto, 0)
w.patchJump(lbPos, w.curPos())
} else {
for i := 0; i < curIndex; i++ {
w.patchJump(w.popInt(), w.curPos())
}
}
break
case ntTestref | beforeChild:
if curIndex == 0 {
w.emit(Setjump)
w.pushInt(w.curPos())
w.emit1(Lazybranch, 0)
w.emit1(Testref, w.mapCapnum(node.m))
w.emit(Forejump)
}
case ntTestref | afterChild:
if curIndex == 0 {
branchpos := w.popInt()
w.pushInt(w.curPos())
w.emit1(Goto, 0)
w.patchJump(branchpos, w.curPos())
w.emit(Forejump)
if len(node.children) <= 1 {
w.patchJump(w.popInt(), w.curPos())
}
} else if curIndex == 1 {
w.patchJump(w.popInt(), w.curPos())
}
case ntTestgroup | beforeChild:
if curIndex == 0 {
w.emit(Setjump)
w.emit(Setmark)
w.pushInt(w.curPos())
w.emit1(Lazybranch, 0)
}
case ntTestgroup | afterChild:
if curIndex == 0 {
w.emit(Getmark)
w.emit(Forejump)
} else if curIndex == 1 {
Branchpos := w.popInt()
w.pushInt(w.curPos())
w.emit1(Goto, 0)
w.patchJump(Branchpos, w.curPos())
w.emit(Getmark)
w.emit(Forejump)
if len(node.children) <= 2 {
w.patchJump(w.popInt(), w.curPos())
}
} else if curIndex == 2 {
w.patchJump(w.popInt(), w.curPos())
}
case ntLoop | beforeChild, ntLazyloop | beforeChild:
if node.n < math.MaxInt32 || node.m > 1 {
if node.m == 0 {
w.emit1(Nullcount, 0)
} else {
w.emit1(Setcount, 1-node.m)
}
} else if node.m == 0 {
w.emit(Nullmark)
} else {
w.emit(Setmark)
}
if node.m == 0 {
w.pushInt(w.curPos())
w.emit1(Goto, 0)
}
w.pushInt(w.curPos())
case ntLoop | afterChild, ntLazyloop | afterChild:
startJumpPos := w.curPos()
lazy := (nodetype - (ntLoop | afterChild))
if node.n < math.MaxInt32 || node.m > 1 {
if node.n == math.MaxInt32 {
w.emit2(InstOp(Branchcount+lazy), w.popInt(), math.MaxInt32)
} else {
w.emit2(InstOp(Branchcount+lazy), w.popInt(), node.n-node.m)
}
} else {
w.emit1(InstOp(Branchmark+lazy), w.popInt())
}
if node.m == 0 {
w.patchJump(w.popInt(), startJumpPos)
}
case ntGroup | beforeChild, ntGroup | afterChild:
case ntCapture | beforeChild:
w.emit(Setmark)
case ntCapture | afterChild:
w.emit2(Capturemark, w.mapCapnum(node.m), w.mapCapnum(node.n))
case ntRequire | beforeChild:
// NOTE: the following line causes lookahead/lookbehind to be
// NON-BACKTRACKING. It can be commented out with (*)
w.emit(Setjump)
w.emit(Setmark)
case ntRequire | afterChild:
w.emit(Getmark)
// NOTE: the following line causes lookahead/lookbehind to be
// NON-BACKTRACKING. It can be commented out with (*)
w.emit(Forejump)
case ntPrevent | beforeChild:
w.emit(Setjump)
w.pushInt(w.curPos())
w.emit1(Lazybranch, 0)
case ntPrevent | afterChild:
w.emit(Backjump)
w.patchJump(w.popInt(), w.curPos())
w.emit(Forejump)
case ntGreedy | beforeChild:
w.emit(Setjump)
case ntGreedy | afterChild:
w.emit(Forejump)
case ntOne, ntNotone:
w.emit1(InstOp(node.t|ntBits), int(node.ch))
case ntNotoneloop, ntNotonelazy, ntOneloop, ntOnelazy:
if node.m > 0 {
if node.t == ntOneloop || node.t == ntOnelazy {
w.emit2(Onerep|bits, int(node.ch), node.m)
} else {
w.emit2(Notonerep|bits, int(node.ch), node.m)
}
}
if node.n > node.m {
if node.n == math.MaxInt32 {
w.emit2(InstOp(node.t|ntBits), int(node.ch), math.MaxInt32)
} else {
w.emit2(InstOp(node.t|ntBits), int(node.ch), node.n-node.m)
}
}
case ntSetloop, ntSetlazy:
if node.m > 0 {
w.emit2(Setrep|bits, w.setCode(node.set), node.m)
}
if node.n > node.m {
if node.n == math.MaxInt32 {
w.emit2(InstOp(node.t|ntBits), w.setCode(node.set), math.MaxInt32)
} else {
w.emit2(InstOp(node.t|ntBits), w.setCode(node.set), node.n-node.m)
}
}
case ntMulti:
w.emit1(InstOp(node.t|ntBits), w.stringCode(node.str))
case ntSet:
w.emit1(InstOp(node.t|ntBits), w.setCode(node.set))
case ntRef:
w.emit1(InstOp(node.t|ntBits), w.mapCapnum(node.m))
case ntNothing, ntBol, ntEol, ntBoundary, ntNonboundary, ntECMABoundary, ntNonECMABoundary, ntBeginning, ntStart, ntEndZ, ntEnd:
w.emit(InstOp(node.t))
default:
return fmt.Errorf("unexpected opcode in regular expression generation: %v", nodetype)
}
return nil
}
// To avoid recursion, we use a simple integer stack.
// This is the push.
func (w *writer) pushInt(i int) {
w.intStack = append(w.intStack, i)
}
// Returns true if the stack is empty.
func (w *writer) emptyStack() bool {
return len(w.intStack) == 0
}
// This is the pop.
func (w *writer) popInt() int {
//get our item
idx := len(w.intStack) - 1
i := w.intStack[idx]
//trim our slice
w.intStack = w.intStack[:idx]
return i
}
// Returns the current position in the emitted code.
func (w *writer) curPos() int {
return w.curpos
}
// Fixes up a jump instruction at the specified offset
// so that it jumps to the specified jumpDest.
func (w *writer) patchJump(offset, jumpDest int) {
w.emitted[offset+1] = jumpDest
}
// Returns an index in the set table for a charset
// uses a map to eliminate duplicates.
func (w *writer) setCode(set *CharSet) int {
if w.counting {
return 0
}
buf := &bytes.Buffer{}
set.mapHashFill(buf)
hash := buf.String()
i, ok := w.sethash[hash]
if !ok {
i = len(w.sethash)
w.sethash[hash] = i
w.settable = append(w.settable, set)
}
return i
}
// Returns an index in the string table for a string.
// uses a map to eliminate duplicates.
func (w *writer) stringCode(str []rune) int {
if w.counting {
return 0
}
hash := string(str)
i, ok := w.stringhash[hash]
if !ok {
i = len(w.stringhash)
w.stringhash[hash] = i
w.stringtable = append(w.stringtable, str)
}
return i
}
// When generating code on a regex that uses a sparse set
// of capture slots, we hash them to a dense set of indices
// for an array of capture slots. Instead of doing the hash
// at match time, it's done at compile time, here.
func (w *writer) mapCapnum(capnum int) int {
if capnum == -1 {
return -1
}
if w.caps != nil {
return w.caps[capnum]
}
return capnum
}
// Emits a zero-argument operation. Note that the emit
// functions all run in two modes: they can emit code, or
// they can just count the size of the code.
func (w *writer) emit(op InstOp) {
if w.counting {
w.count++
if opcodeBacktracks(op) {
w.trackcount++
}
return
}
w.emitted[w.curpos] = int(op)
w.curpos++
}
// Emits a one-argument operation.
func (w *writer) emit1(op InstOp, opd1 int) {
if w.counting {
w.count += 2
if opcodeBacktracks(op) {
w.trackcount++
}
return
}
w.emitted[w.curpos] = int(op)
w.curpos++
w.emitted[w.curpos] = opd1
w.curpos++
}
// Emits a two-argument operation.
func (w *writer) emit2(op InstOp, opd1, opd2 int) {
if w.counting {
w.count += 3
if opcodeBacktracks(op) {
w.trackcount++
}
return
}
w.emitted[w.curpos] = int(op)
w.curpos++
w.emitted[w.curpos] = opd1
w.curpos++
w.emitted[w.curpos] = opd2
w.curpos++
}