// Copyright 2007 The RE2 Authors. All Rights Reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Compile regular expression to Prog.
//
// Prog and Inst are defined in prog.h.
// This file's external interface is just Regexp::CompileToProg.
// The Compiler class defined in this file is private.
#include "re2/prog.h"
#include "re2/re2.h"
#include "re2/regexp.h"
#include "re2/walker-inl.h"
namespace re2 {
// List of pointers to Inst* that need to be filled in (patched).
// Because the Inst* haven't been filled in yet,
// we can use the Inst* word to hold the list's "next" pointer.
// It's kind of sleazy, but it works well in practice.
// See http://swtch.com/~rsc/regexp/regexp1.html for inspiration.
//
// Because the out and out1 fields in Inst are no longer pointers,
// we can't use pointers directly here either. Instead, p refers
// to inst_[p>>1].out (p&1 == 0) or inst_[p>>1].out1 (p&1 == 1).
// p == 0 represents the NULL list. This is okay because instruction #0
// is always the fail instruction, which never appears on a list.
struct PatchList {
uint32 p;
// Returns patch list containing just p.
static PatchList Mk(uint32 p);
// Patches all the entries on l to have value v.
// Caller must not ever use patch list again.
static void Patch(Prog::Inst *inst0, PatchList l, uint32 v);
// Deref returns the next pointer pointed at by p.
static PatchList Deref(Prog::Inst *inst0, PatchList l);
// Appends two patch lists and returns result.
static PatchList Append(Prog::Inst *inst0, PatchList l1, PatchList l2);
};
static PatchList nullPatchList;
// Returns patch list containing just p.
PatchList PatchList::Mk(uint32 p) {
PatchList l;
l.p = p;
return l;
}
// Returns the next pointer pointed at by l.
PatchList PatchList::Deref(Prog::Inst* inst0, PatchList l) {
Prog::Inst* ip = &inst0[l.p>>1];
if (l.p&1)
l.p = ip->out1();
else
l.p = ip->out();
return l;
}
// Patches all the entries on l to have value v.
void PatchList::Patch(Prog::Inst *inst0, PatchList l, uint32 val) {
while (l.p != 0) {
Prog::Inst* ip = &inst0[l.p>>1];
if (l.p&1) {
l.p = ip->out1();
ip->out1_ = val;
} else {
l.p = ip->out();
ip->set_out(val);
}
}
}
// Appends two patch lists and returns result.
PatchList PatchList::Append(Prog::Inst* inst0, PatchList l1, PatchList l2) {
if (l1.p == 0)
return l2;
if (l2.p == 0)
return l1;
PatchList l = l1;
for (;;) {
PatchList next = PatchList::Deref(inst0, l);
if (next.p == 0)
break;
l = next;
}
Prog::Inst* ip = &inst0[l.p>>1];
if (l.p&1)
ip->out1_ = l2.p;
else
ip->set_out(l2.p);
return l1;
}
// Compiled program fragment.
struct Frag {
uint32 begin;
PatchList end;
explicit Frag(LinkerInitialized) {}
Frag() : begin(0) { end.p = 0; } // needed so Frag can go in vector
Frag(uint32 begin, PatchList end) : begin(begin), end(end) {}
};
static Frag kNullFrag(LINKER_INITIALIZED);
// Input encodings.
enum Encoding {
kEncodingUTF8 = 1, // UTF-8 (0-10FFFF)
kEncodingLatin1, // Latin1 (0-FF)
};
class Compiler : public Regexp::Walker<Frag> {
public:
explicit Compiler();
~Compiler();
// Compiles Regexp to a new Prog.
// Caller is responsible for deleting Prog when finished with it.
// If reversed is true, compiles for walking over the input
// string backward (reverses all concatenations).
static Prog *Compile(Regexp* re, bool reversed, int64 max_mem);
// Compiles alternation of all the re to a new Prog.
// Each re has a match with an id equal to its index in the vector.
static Prog* CompileSet(const RE2::Options& options, RE2::Anchor anchor,
Regexp* re);
// Interface for Regexp::Walker, which helps traverse the Regexp.
// The walk is purely post-recursive: given the machines for the
// children, PostVisit combines them to create the machine for
// the current node. The child_args are Frags.
// The Compiler traverses the Regexp parse tree, visiting
// each node in depth-first order. It invokes PreVisit before
// visiting the node's children and PostVisit after visiting
// the children.
Frag PreVisit(Regexp* re, Frag parent_arg, bool* stop);
Frag PostVisit(Regexp* re, Frag parent_arg, Frag pre_arg, Frag* child_args,
int nchild_args);
Frag ShortVisit(Regexp* re, Frag parent_arg);
Frag Copy(Frag arg);
// Given fragment a, returns a+ or a+?; a* or a*?; a? or a??
Frag Plus(Frag a, bool nongreedy);
Frag Star(Frag a, bool nongreedy);
Frag Quest(Frag a, bool nongreedy);
// Given fragment a, returns (a) capturing as \n.
Frag Capture(Frag a, int n);
// Given fragments a and b, returns ab; a|b
Frag Cat(Frag a, Frag b);
Frag Alt(Frag a, Frag b);
// Returns a fragment that can't match anything.
Frag NoMatch();
// Returns a fragment that matches the empty string.
Frag Match(int32 id);
// Returns a no-op fragment.
Frag Nop();
// Returns a fragment matching the byte range lo-hi.
Frag ByteRange(int lo, int hi, bool foldcase);
// Returns a fragment matching an empty-width special op.
Frag EmptyWidth(EmptyOp op);
// Adds n instructions to the program.
// Returns the index of the first one.
// Returns -1 if no more instructions are available.
int AllocInst(int n);
// Deletes unused instructions.
void Trim();
// Rune range compiler.
// Begins a new alternation.
void BeginRange();
// Adds a fragment matching the rune range lo-hi.
void AddRuneRange(Rune lo, Rune hi, bool foldcase);
void AddRuneRangeLatin1(Rune lo, Rune hi, bool foldcase);
void AddRuneRangeUTF8(Rune lo, Rune hi, bool foldcase);
void Add_80_10ffff();
// New suffix that matches the byte range lo-hi, then goes to next.
int RuneByteSuffix(uint8 lo, uint8 hi, bool foldcase, int next);
int UncachedRuneByteSuffix(uint8 lo, uint8 hi, bool foldcase, int next);
// Adds a suffix to alternation.
void AddSuffix(int id);
// Returns the alternation of all the added suffixes.
Frag EndRange();
// Single rune.
Frag Literal(Rune r, bool foldcase);
void Setup(Regexp::ParseFlags, int64, RE2::Anchor);
Prog* Finish();
// Returns .* where dot = any byte
Frag DotStar();
private:
Prog* prog_; // Program being built.
bool failed_; // Did we give up compiling?
Encoding encoding_; // Input encoding
bool reversed_; // Should program run backward over text?
int max_inst_; // Maximum number of instructions.
Prog::Inst* inst_; // Pointer to first instruction.
int inst_len_; // Number of instructions used.
int inst_cap_; // Number of instructions allocated.
int64 max_mem_; // Total memory budget.
map<uint64, int> rune_cache_;
Frag rune_range_;
RE2::Anchor anchor_; // anchor mode for RE2::Set
DISALLOW_EVIL_CONSTRUCTORS(Compiler);
};
Compiler::Compiler() {
prog_ = new Prog();
failed_ = false;
encoding_ = kEncodingUTF8;
reversed_ = false;
inst_ = NULL;
inst_len_ = 0;
inst_cap_ = 0;
max_inst_ = 1; // make AllocInst for fail instruction okay
max_mem_ = 0;
int fail = AllocInst(1);
inst_[fail].InitFail();
max_inst_ = 0; // Caller must change
}
Compiler::~Compiler() {
delete prog_;
delete[] inst_;
}
int Compiler::AllocInst(int n) {
if (failed_ || inst_len_ + n > max_inst_) {
failed_ = true;
return -1;
}
if (inst_len_ + n > inst_cap_) {
if (inst_cap_ == 0)
inst_cap_ = 8;
while (inst_len_ + n > inst_cap_)
inst_cap_ *= 2;
Prog::Inst* ip = new Prog::Inst[inst_cap_];
memmove(ip, inst_, inst_len_ * sizeof ip[0]);
memset(ip + inst_len_, 0, (inst_cap_ - inst_len_) * sizeof ip[0]);
delete[] inst_;
inst_ = ip;
}
int id = inst_len_;
inst_len_ += n;
return id;
}
void Compiler::Trim() {
if (inst_len_ < inst_cap_) {
Prog::Inst* ip = new Prog::Inst[inst_len_];
memmove(ip, inst_, inst_len_ * sizeof ip[0]);
delete[] inst_;
inst_ = ip;
inst_cap_ = inst_len_;
}
}
// These routines are somewhat hard to visualize in text --
// see http://swtch.com/~rsc/regexp/regexp1.html for
// pictures explaining what is going on here.
// Returns an unmatchable fragment.
Frag Compiler::NoMatch() {
return Frag(0, nullPatchList);
}
// Is a an unmatchable fragment?
static bool IsNoMatch(Frag a) {
return a.begin == 0;
}
// Given fragments a and b, returns fragment for ab.
Frag Compiler::Cat(Frag a, Frag b) {
if (IsNoMatch(a) || IsNoMatch(b))
return NoMatch();
// Elide no-op.
Prog::Inst* begin = &inst_[a.begin];
if (begin->opcode() == kInstNop &&
a.end.p == (a.begin << 1) &&
begin->out() == 0) {
PatchList::Patch(inst_, a.end, b.begin); // in case refs to a somewhere
return b;
}
// To run backward over string, reverse all concatenations.
if (reversed_) {
PatchList::Patch(inst_, b.end, a.begin);
return Frag(b.begin, a.end);
}
PatchList::Patch(inst_, a.end, b.begin);
return Frag(a.begin, b.end);
}
// Given fragments for a and b, returns fragment for a|b.
Frag Compiler::Alt(Frag a, Frag b) {
// Special case for convenience in loops.
if (IsNoMatch(a))
return b;
if (IsNoMatch(b))
return a;
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitAlt(a.begin, b.begin);
return Frag(id, PatchList::Append(inst_, a.end, b.end));
}
// When capturing submatches in like-Perl mode, a kOpAlt Inst
// treats out_ as the first choice, out1_ as the second.
//
// For *, +, and ?, if out_ causes another repetition,
// then the operator is greedy. If out1_ is the repetition
// (and out_ moves forward), then the operator is non-greedy.
// Given a fragment a, returns a fragment for a* or a*? (if nongreedy)
Frag Compiler::Star(Frag a, bool nongreedy) {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitAlt(0, 0);
PatchList::Patch(inst_, a.end, id);
if (nongreedy) {
inst_[id].out1_ = a.begin;
return Frag(id, PatchList::Mk(id << 1));
} else {
inst_[id].set_out(a.begin);
return Frag(id, PatchList::Mk((id << 1) | 1));
}
}
// Given a fragment for a, returns a fragment for a+ or a+? (if nongreedy)
Frag Compiler::Plus(Frag a, bool nongreedy) {
// a+ is just a* with a different entry point.
Frag f = Star(a, nongreedy);
return Frag(a.begin, f.end);
}
// Given a fragment for a, returns a fragment for a? or a?? (if nongreedy)
Frag Compiler::Quest(Frag a, bool nongreedy) {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
PatchList pl;
if (nongreedy) {
inst_[id].InitAlt(0, a.begin);
pl = PatchList::Mk(id << 1);
} else {
inst_[id].InitAlt(a.begin, 0);
pl = PatchList::Mk((id << 1) | 1);
}
return Frag(id, PatchList::Append(inst_, pl, a.end));
}
// Returns a fragment for the byte range lo-hi.
Frag Compiler::ByteRange(int lo, int hi, bool foldcase) {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitByteRange(lo, hi, foldcase, 0);
prog_->byte_inst_count_++;
prog_->MarkByteRange(lo, hi);
if (foldcase && lo <= 'z' && hi >= 'a') {
if (lo < 'a')
lo = 'a';
if (hi > 'z')
hi = 'z';
if (lo <= hi)
prog_->MarkByteRange(lo + 'A' - 'a', hi + 'A' - 'a');
}
return Frag(id, PatchList::Mk(id << 1));
}
// Returns a no-op fragment. Sometimes unavoidable.
Frag Compiler::Nop() {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitNop(0);
return Frag(id, PatchList::Mk(id << 1));
}
// Returns a fragment that signals a match.
Frag Compiler::Match(int32 match_id) {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitMatch(match_id);
return Frag(id, nullPatchList);
}
// Returns a fragment matching a particular empty-width op (like ^ or $)
Frag Compiler::EmptyWidth(EmptyOp empty) {
int id = AllocInst(1);
if (id < 0)
return NoMatch();
inst_[id].InitEmptyWidth(empty, 0);
if (empty & (kEmptyBeginLine|kEmptyEndLine))
prog_->MarkByteRange('\n', '\n');
if (empty & (kEmptyWordBoundary|kEmptyNonWordBoundary)) {
int j;
for (int i = 0; i < 256; i = j) {
for (j = i+1; j < 256 && Prog::IsWordChar(i) == Prog::IsWordChar(j); j++)
;
prog_->MarkByteRange(i, j-1);
}
}
return Frag(id, PatchList::Mk(id << 1));
}
// Given a fragment a, returns a fragment with capturing parens around a.
Frag Compiler::Capture(Frag a, int n) {
int id = AllocInst(2);
if (id < 0)
return NoMatch();
inst_[id].InitCapture(2*n, a.begin);
inst_[id+1].InitCapture(2*n+1, 0);
PatchList::Patch(inst_, a.end, id+1);
return Frag(id, PatchList::Mk((id+1) << 1));
}
// A Rune is a name for a Unicode code point.
// Returns maximum rune encoded by UTF-8 sequence of length len.
static int MaxRune(int len) {
int b; // number of Rune bits in len-byte UTF-8 sequence (len < UTFmax)
if (len == 1)
b = 7;
else
b = 8-(len+1) + 6*(len-1);
return (1<<b) - 1; // maximum Rune for b bits.
}
// The rune range compiler caches common suffix fragments,
// which are very common in UTF-8 (e.g., [80-bf]).
// The fragment suffixes are identified by their start
// instructions. NULL denotes the eventual end match.
// The Frag accumulates in rune_range_. Caching common
// suffixes reduces the UTF-8 "." from 32 to 24 instructions,
// and it reduces the corresponding one-pass NFA from 16 nodes to 8.
void Compiler::BeginRange() {
rune_cache_.clear();
rune_range_.begin = 0;
rune_range_.end = nullPatchList;
}
int Compiler::UncachedRuneByteSuffix(uint8 lo, uint8 hi, bool foldcase,
int next) {
Frag f = ByteRange(lo, hi, foldcase);
if (next != 0) {
PatchList::Patch(inst_, f.end, next);
} else {
rune_range_.end = PatchList::Append(inst_, rune_range_.end, f.end);
}
return f.begin;
}
int Compiler::RuneByteSuffix(uint8 lo, uint8 hi, bool foldcase, int next) {
// In Latin1 mode, there's no point in caching.
// In forward UTF-8 mode, only need to cache continuation bytes.
if (encoding_ == kEncodingLatin1 ||
(encoding_ == kEncodingUTF8 &&
!reversed_ &&
!(0x80 <= lo && hi <= 0xbf))) {
return UncachedRuneByteSuffix(lo, hi, foldcase, next);
}
uint64 key = ((uint64)next << 17) | (lo<<9) | (hi<<1) | foldcase;
map<uint64, int>::iterator it = rune_cache_.find(key);
if (it != rune_cache_.end())
return it->second;
int id = UncachedRuneByteSuffix(lo, hi, foldcase, next);
rune_cache_[key] = id;
return id;
}
void Compiler::AddSuffix(int id) {
if (rune_range_.begin == 0) {
rune_range_.begin = id;
return;
}
int alt = AllocInst(1);
if (alt < 0) {
rune_range_.begin = 0;
return;
}
inst_[alt].InitAlt(rune_range_.begin, id);
rune_range_.begin = alt;
}
Frag Compiler::EndRange() {
return rune_range_;
}
// Converts rune range lo-hi into a fragment that recognizes
// the bytes that would make up those runes in the current
// encoding (Latin 1 or UTF-8).
// This lets the machine work byte-by-byte even when
// using multibyte encodings.
void Compiler::AddRuneRange(Rune lo, Rune hi, bool foldcase) {
switch (encoding_) {
default:
case kEncodingUTF8:
AddRuneRangeUTF8(lo, hi, foldcase);
break;
case kEncodingLatin1:
AddRuneRangeLatin1(lo, hi, foldcase);
break;
}
}
void Compiler::AddRuneRangeLatin1(Rune lo, Rune hi, bool foldcase) {
// Latin1 is easy: runes *are* bytes.
if (lo > hi || lo > 0xFF)
return;
if (hi > 0xFF)
hi = 0xFF;
AddSuffix(RuneByteSuffix(lo, hi, foldcase, 0));
}
// Table describing how to make a UTF-8 matching machine
// for the rune range 80-10FFFF (Runeself-Runemax).
// This range happens frequently enough (for example /./ and /[^a-z]/)
// and the rune_cache_ map is slow enough that this is worth
// special handling. Makes compilation of a small expression
// with a dot in it about 10% faster.
// The * in the comments below mark whole sequences.
static struct ByteRangeProg {
int next;
int lo;
int hi;
} prog_80_10ffff[] = {
// Two-byte
{ -1, 0x80, 0xBF, }, // 0: 80-BF
{ 0, 0xC2, 0xDF, }, // 1: C2-DF 80-BF*
// Three-byte
{ 0, 0xA0, 0xBF, }, // 2: A0-BF 80-BF
{ 2, 0xE0, 0xE0, }, // 3: E0 A0-BF 80-BF*
{ 0, 0x80, 0xBF, }, // 4: 80-BF 80-BF
{ 4, 0xE1, 0xEF, }, // 5: E1-EF 80-BF 80-BF*
// Four-byte
{ 4, 0x90, 0xBF, }, // 6: 90-BF 80-BF 80-BF
{ 6, 0xF0, 0xF0, }, // 7: F0 90-BF 80-BF 80-BF*
{ 4, 0x80, 0xBF, }, // 8: 80-BF 80-BF 80-BF
{ 8, 0xF1, 0xF3, }, // 9: F1-F3 80-BF 80-BF 80-BF*
{ 4, 0x80, 0x8F, }, // 10: 80-8F 80-BF 80-BF
{ 10, 0xF4, 0xF4, }, // 11: F4 80-8F 80-BF 80-BF*
};
void Compiler::Add_80_10ffff() {
int inst[arraysize(prog_80_10ffff)] = { 0 }; // does not need to be initialized; silences gcc warning
for (int i = 0; i < arraysize(prog_80_10ffff); i++) {
const ByteRangeProg& p = prog_80_10ffff[i];
int next = 0;
if (p.next >= 0)
next = inst[p.next];
inst[i] = UncachedRuneByteSuffix(p.lo, p.hi, false, next);
if ((p.lo & 0xC0) != 0x80)
AddSuffix(inst[i]);
}
}
void Compiler::AddRuneRangeUTF8(Rune lo, Rune hi, bool foldcase) {
if (lo > hi)
return;
// Pick off 80-10FFFF as a common special case
// that can bypass the slow rune_cache_.
if (lo == 0x80 && hi == 0x10ffff && !reversed_) {
Add_80_10ffff();
return;
}
// Split range into same-length sized ranges.
for (int i = 1; i < UTFmax; i++) {
Rune max = MaxRune(i);
if (lo <= max && max < hi) {
AddRuneRangeUTF8(lo, max, foldcase);
AddRuneRangeUTF8(max+1, hi, foldcase);
return;
}
}
// ASCII range is always a special case.
if (hi < Runeself) {
AddSuffix(RuneByteSuffix(lo, hi, foldcase, 0));
return;
}
// Split range into sections that agree on leading bytes.
for (int i = 1; i < UTFmax; i++) {
uint m = (1<<(6*i)) - 1; // last i bytes of a UTF-8 sequence
if ((lo & ~m) != (hi & ~m)) {
if ((lo & m) != 0) {
AddRuneRangeUTF8(lo, lo|m, foldcase);
AddRuneRangeUTF8((lo|m)+1, hi, foldcase);
return;
}
if ((hi & m) != m) {
AddRuneRangeUTF8(lo, (hi&~m)-1, foldcase);
AddRuneRangeUTF8(hi&~m, hi, foldcase);
return;
}
}
}
// Finally. Generate byte matching equivalent for lo-hi.
uint8 ulo[UTFmax], uhi[UTFmax];
int n = runetochar(reinterpret_cast<char*>(ulo), &lo);
int m = runetochar(reinterpret_cast<char*>(uhi), &hi);
(void)m; // USED(m)
DCHECK_EQ(n, m);
int id = 0;
if (reversed_) {
for (int i = 0; i < n; i++)
id = RuneByteSuffix(ulo[i], uhi[i], false, id);
} else {
for (int i = n-1; i >= 0; i--)
id = RuneByteSuffix(ulo[i], uhi[i], false, id);
}
AddSuffix(id);
}
// Should not be called.
Frag Compiler::Copy(Frag arg) {
// We're using WalkExponential; there should be no copying.
LOG(DFATAL) << "Compiler::Copy called!";
failed_ = true;
return NoMatch();
}
// Visits a node quickly; called once WalkExponential has
// decided to cut this walk short.
Frag Compiler::ShortVisit(Regexp* re, Frag) {
failed_ = true;
return NoMatch();
}
// Called before traversing a node's children during the walk.
Frag Compiler::PreVisit(Regexp* re, Frag, bool* stop) {
// Cut off walk if we've already failed.
if (failed_)
*stop = true;
return kNullFrag; // not used by caller
}
Frag Compiler::Literal(Rune r, bool foldcase) {
switch (encoding_) {
default:
return kNullFrag;
case kEncodingLatin1:
return ByteRange(r, r, foldcase);
case kEncodingUTF8: {
if (r < Runeself) // Make common case fast.
return ByteRange(r, r, foldcase);
uint8 buf[UTFmax];
int n = runetochar(reinterpret_cast<char*>(buf), &r);
Frag f = ByteRange((uint8)buf[0], buf[0], false);
for (int i = 1; i < n; i++)
f = Cat(f, ByteRange((uint8)buf[i], buf[i], false));
return f;
}
}
}
// Called after traversing the node's children during the walk.
// Given their frags, build and return the frag for this re.
Frag Compiler::PostVisit(Regexp* re, Frag, Frag, Frag* child_frags,
int nchild_frags) {
// If a child failed, don't bother going forward, especially
// since the child_frags might contain Frags with NULLs in them.
if (failed_)
return NoMatch();
// Given the child fragments, return the fragment for this node.
switch (re->op()) {
case kRegexpRepeat:
// Should not see; code at bottom of function will print error
break;
case kRegexpNoMatch:
return NoMatch();
case kRegexpEmptyMatch:
return Nop();
case kRegexpHaveMatch: {
Frag f = Match(re->match_id());
// Remember unanchored match to end of string.
if (anchor_ != RE2::ANCHOR_BOTH)
f = Cat(DotStar(), Cat(EmptyWidth(kEmptyEndText), f));
return f;
}
case kRegexpConcat: {
Frag f = child_frags[0];
for (int i = 1; i < nchild_frags; i++)
f = Cat(f, child_frags[i]);
return f;
}
case kRegexpAlternate: {
Frag f = child_frags[0];
for (int i = 1; i < nchild_frags; i++)
f = Alt(f, child_frags[i]);
return f;
}
case kRegexpStar:
return Star(child_frags[0], re->parse_flags()&Regexp::NonGreedy);
case kRegexpPlus:
return Plus(child_frags[0], re->parse_flags()&Regexp::NonGreedy);
case kRegexpQuest:
return Quest(child_frags[0], re->parse_flags()&Regexp::NonGreedy);
case kRegexpLiteral:
return Literal(re->rune(), re->parse_flags()&Regexp::FoldCase);
case kRegexpLiteralString: {
// Concatenation of literals.
if (re->nrunes() == 0)
return Nop();
Frag f;
for (int i = 0; i < re->nrunes(); i++) {
Frag f1 = Literal(re->runes()[i], re->parse_flags()&Regexp::FoldCase);
if (i == 0)
f = f1;
else
f = Cat(f, f1);
}
return f;
}
case kRegexpAnyChar:
BeginRange();
AddRuneRange(0, Runemax, false);
return EndRange();
case kRegexpAnyByte:
return ByteRange(0x00, 0xFF, false);
case kRegexpCharClass: {
CharClass* cc = re->cc();
if (cc->empty()) {
// This can't happen.
LOG(DFATAL) << "No ranges in char class";
failed_ = true;
return NoMatch();
}
// ASCII case-folding optimization: if the char class
// behaves the same on A-Z as it does on a-z,
// discard any ranges wholly contained in A-Z
// and mark the other ranges as foldascii.
// This reduces the size of a program for
// (?i)abc from 3 insts per letter to 1 per letter.
bool foldascii = cc->FoldsASCII();
// Character class is just a big OR of the different
// character ranges in the class.
BeginRange();
for (CharClass::iterator i = cc->begin(); i != cc->end(); ++i) {
// ASCII case-folding optimization (see above).
if (foldascii && 'A' <= i->lo && i->hi <= 'Z')
continue;
// If this range contains all of A-Za-z or none of it,
// the fold flag is unnecessary; don't bother.
bool fold = foldascii;
if ((i->lo <= 'A' && 'z' <= i->hi) || i->hi < 'A' || 'z' < i->lo)
fold = false;
AddRuneRange(i->lo, i->hi, fold);
}
return EndRange();
}
case kRegexpCapture:
// If this is a non-capturing parenthesis -- (?:foo) --
// just use the inner expression.
if (re->cap() < 0)
return child_frags[0];
return Capture(child_frags[0], re->cap());
case kRegexpBeginLine:
return EmptyWidth(reversed_ ? kEmptyEndLine : kEmptyBeginLine);
case kRegexpEndLine:
return EmptyWidth(reversed_ ? kEmptyBeginLine : kEmptyEndLine);
case kRegexpBeginText:
return EmptyWidth(reversed_ ? kEmptyEndText : kEmptyBeginText);
case kRegexpEndText:
return EmptyWidth(reversed_ ? kEmptyBeginText : kEmptyEndText);
case kRegexpWordBoundary:
return EmptyWidth(kEmptyWordBoundary);
case kRegexpNoWordBoundary:
return EmptyWidth(kEmptyNonWordBoundary);
}
LOG(DFATAL) << "Missing case in Compiler: " << re->op();
failed_ = true;
return NoMatch();
}
// Is this regexp required to start at the beginning of the text?
// Only approximate; can return false for complicated regexps like (\Aa|\Ab),
// but handles (\A(a|b)). Could use the Walker to write a more exact one.
static bool IsAnchorStart(Regexp** pre, int depth) {
Regexp* re = *pre;
Regexp* sub;
// The depth limit makes sure that we don't overflow
// the stack on a deeply nested regexp. As the comment
// above says, IsAnchorStart is conservative, so returning
// a false negative is okay. The exact limit is somewhat arbitrary.
if (re == NULL || depth >= 4)
return false;
switch (re->op()) {
default:
break;
case kRegexpConcat:
if (re->nsub() > 0) {
sub = re->sub()[0]->Incref();
if (IsAnchorStart(&sub, depth+1)) {
Regexp** subcopy = new Regexp*[re->nsub()];
subcopy[0] = sub; // already have reference
for (int i = 1; i < re->nsub(); i++)
subcopy[i] = re->sub()[i]->Incref();
*pre = Regexp::Concat(subcopy, re->nsub(), re->parse_flags());
delete[] subcopy;
re->Decref();
return true;
}
sub->Decref();
}
break;
case kRegexpCapture:
sub = re->sub()[0]->Incref();
if (IsAnchorStart(&sub, depth+1)) {
*pre = Regexp::Capture(sub, re->parse_flags(), re->cap());
re->Decref();
return true;
}
sub->Decref();
break;
case kRegexpBeginText:
*pre = Regexp::LiteralString(NULL, 0, re->parse_flags());
re->Decref();
return true;
}
return false;
}
// Is this regexp required to start at the end of the text?
// Only approximate; can return false for complicated regexps like (a\z|b\z),
// but handles ((a|b)\z). Could use the Walker to write a more exact one.
static bool IsAnchorEnd(Regexp** pre, int depth) {
Regexp* re = *pre;
Regexp* sub;
// The depth limit makes sure that we don't overflow
// the stack on a deeply nested regexp. As the comment
// above says, IsAnchorEnd is conservative, so returning
// a false negative is okay. The exact limit is somewhat arbitrary.
if (re == NULL || depth >= 4)
return false;
switch (re->op()) {
default:
break;
case kRegexpConcat:
if (re->nsub() > 0) {
sub = re->sub()[re->nsub() - 1]->Incref();
if (IsAnchorEnd(&sub, depth+1)) {
Regexp** subcopy = new Regexp*[re->nsub()];
subcopy[re->nsub() - 1] = sub; // already have reference
for (int i = 0; i < re->nsub() - 1; i++)
subcopy[i] = re->sub()[i]->Incref();
*pre = Regexp::Concat(subcopy, re->nsub(), re->parse_flags());
delete[] subcopy;
re->Decref();
return true;
}
sub->Decref();
}
break;
case kRegexpCapture:
sub = re->sub()[0]->Incref();
if (IsAnchorEnd(&sub, depth+1)) {
*pre = Regexp::Capture(sub, re->parse_flags(), re->cap());
re->Decref();
return true;
}
sub->Decref();
break;
case kRegexpEndText:
*pre = Regexp::LiteralString(NULL, 0, re->parse_flags());
re->Decref();
return true;
}
return false;
}
void Compiler::Setup(Regexp::ParseFlags flags, int64 max_mem,
RE2::Anchor anchor) {
prog_->set_flags(flags);
if (flags & Regexp::Latin1)
encoding_ = kEncodingLatin1;
max_mem_ = max_mem;
if (max_mem <= 0) {
max_inst_ = 100000; // more than enough
} else if (max_mem <= sizeof(Prog)) {
// No room for anything.
max_inst_ = 0;
} else {
int64 m = (max_mem - sizeof(Prog)) / sizeof(Prog::Inst);
// Limit instruction count so that inst->id() fits nicely in an int.
// SparseArray also assumes that the indices (inst->id()) are ints.
// The call to WalkExponential uses 2*max_inst_ below,
// and other places in the code use 2 or 3 * prog->size().
// Limiting to 2^24 should avoid overflow in those places.
// (The point of allowing more than 32 bits of memory is to
// have plenty of room for the DFA states, not to use it up
// on the program.)
if (m >= 1<<24)
m = 1<<24;
// Inst imposes its own limit (currently bigger than 2^24 but be safe).
if (m > Prog::Inst::kMaxInst)
m = Prog::Inst::kMaxInst;
max_inst_ = m;
}
anchor_ = anchor;
}
// Compiles re, returning program.
// Caller is responsible for deleting prog_.
// If reversed is true, compiles a program that expects
// to run over the input string backward (reverses all concatenations).
// The reversed flag is also recorded in the returned program.
Prog* Compiler::Compile(Regexp* re, bool reversed, int64 max_mem) {
Compiler c;
c.Setup(re->parse_flags(), max_mem, RE2::ANCHOR_BOTH /* unused */);
c.reversed_ = reversed;
// Simplify to remove things like counted repetitions
// and character classes like \d.
Regexp* sre = re->Simplify();
if (sre == NULL)
return NULL;
// Record whether prog is anchored, removing the anchors.
// (They get in the way of other optimizations.)
bool is_anchor_start = IsAnchorStart(&sre, 0);
bool is_anchor_end = IsAnchorEnd(&sre, 0);
// Generate fragment for entire regexp.
Frag f = c.WalkExponential(sre, kNullFrag, 2*c.max_inst_);
sre->Decref();
if (c.failed_)
return NULL;
// Success! Finish by putting Match node at end, and record start.
// Turn off c.reversed_ (if it is set) to force the remaining concatenations
// to behave normally.
c.reversed_ = false;
Frag all = c.Cat(f, c.Match(0));
c.prog_->set_start(all.begin);
if (reversed) {
c.prog_->set_anchor_start(is_anchor_end);
c.prog_->set_anchor_end(is_anchor_start);
} else {
c.prog_->set_anchor_start(is_anchor_start);
c.prog_->set_anchor_end(is_anchor_end);
}
// Also create unanchored version, which starts with a .*? loop.
if (c.prog_->anchor_start()) {
c.prog_->set_start_unanchored(c.prog_->start());
} else {
Frag unanchored = c.Cat(c.DotStar(), all);
c.prog_->set_start_unanchored(unanchored.begin);
}
c.prog_->set_reversed(reversed);
// Hand ownership of prog_ to caller.
return c.Finish();
}
Prog* Compiler::Finish() {
if (failed_)
return NULL;
if (prog_->start() == 0 && prog_->start_unanchored() == 0) {
// No possible matches; keep Fail instruction only.
inst_len_ = 1;
}
// Trim instruction to minimum array and transfer to Prog.
Trim();
prog_->inst_ = inst_;
prog_->size_ = inst_len_;
inst_ = NULL;
// Compute byte map.
prog_->ComputeByteMap();
prog_->Optimize();
// Record remaining memory for DFA.
if (max_mem_ <= 0) {
prog_->set_dfa_mem(1<<20);
} else {
int64 m = max_mem_ - sizeof(Prog) - inst_len_*sizeof(Prog::Inst);
if (m < 0)
m = 0;
prog_->set_dfa_mem(m);
}
Prog* p = prog_;
prog_ = NULL;
return p;
}
// Converts Regexp to Prog.
Prog* Regexp::CompileToProg(int64 max_mem) {
return Compiler::Compile(this, false, max_mem);
}
Prog* Regexp::CompileToReverseProg(int64 max_mem) {
return Compiler::Compile(this, true, max_mem);
}
Frag Compiler::DotStar() {
return Star(ByteRange(0x00, 0xff, false), true);
}
// Compiles RE set to Prog.
Prog* Compiler::CompileSet(const RE2::Options& options, RE2::Anchor anchor,
Regexp* re) {
Compiler c;
Regexp::ParseFlags pf = static_cast<Regexp::ParseFlags>(options.ParseFlags());
c.Setup(pf, options.max_mem(), anchor);
// Compile alternation of fragments.
Frag all = c.WalkExponential(re, kNullFrag, 2*c.max_inst_);
re->Decref();
if (c.failed_)
return NULL;
if (anchor == RE2::UNANCHORED) {
// The trailing .* was added while handling kRegexpHaveMatch.
// We just have to add the leading one.
all = c.Cat(c.DotStar(), all);
}
c.prog_->set_start(all.begin);
c.prog_->set_start_unanchored(all.begin);
c.prog_->set_anchor_start(true);
c.prog_->set_anchor_end(true);
Prog* prog = c.Finish();
if (prog == NULL)
return NULL;
// Make sure DFA has enough memory to operate,
// since we're not going to fall back to the NFA.
bool failed;
StringPiece sp = "hello, world";
prog->SearchDFA(sp, sp, Prog::kAnchored, Prog::kManyMatch,
NULL, &failed, NULL);
if (failed) {
delete prog;
return NULL;
}
return prog;
}
Prog* Prog::CompileSet(const RE2::Options& options, RE2::Anchor anchor,
Regexp* re) {
return Compiler::CompileSet(options, anchor, re);
}
} // namespace re2