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342 lines
8.1 KiB
C++
342 lines
8.1 KiB
C++
// Copyright 2006 The RE2 Authors. All Rights Reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Format a regular expression structure as a string.
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// Tested by parse_test.cc
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#include "util/util.h"
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#include "re2/regexp.h"
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#include "re2/walker-inl.h"
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namespace re2 {
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enum {
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PrecAtom,
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PrecUnary,
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PrecConcat,
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PrecAlternate,
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PrecEmpty,
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PrecParen,
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PrecToplevel,
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};
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// Helper function. See description below.
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static void AppendCCRange(string* t, Rune lo, Rune hi);
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// Walker to generate string in s_.
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// The arg pointers are actually integers giving the
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// context precedence.
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// The child_args are always NULL.
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class ToStringWalker : public Regexp::Walker<int> {
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public:
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explicit ToStringWalker(string* t) : t_(t) {}
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virtual int PreVisit(Regexp* re, int parent_arg, bool* stop);
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virtual int PostVisit(Regexp* re, int parent_arg, int pre_arg,
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int* child_args, int nchild_args);
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virtual int ShortVisit(Regexp* re, int parent_arg) {
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return 0;
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}
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private:
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string* t_; // The string the walker appends to.
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DISALLOW_EVIL_CONSTRUCTORS(ToStringWalker);
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};
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string Regexp::ToString() {
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string t;
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ToStringWalker w(&t);
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w.WalkExponential(this, PrecToplevel, 100000);
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if (w.stopped_early())
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t += " [truncated]";
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return t;
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}
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#define ToString DontCallToString // Avoid accidental recursion.
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// Visits re before children are processed.
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// Appends ( if needed and passes new precedence to children.
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int ToStringWalker::PreVisit(Regexp* re, int parent_arg, bool* stop) {
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int prec = parent_arg;
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int nprec = PrecAtom;
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switch (re->op()) {
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case kRegexpNoMatch:
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case kRegexpEmptyMatch:
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case kRegexpLiteral:
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case kRegexpAnyChar:
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case kRegexpAnyByte:
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case kRegexpBeginLine:
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case kRegexpEndLine:
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case kRegexpBeginText:
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case kRegexpEndText:
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case kRegexpWordBoundary:
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case kRegexpNoWordBoundary:
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case kRegexpCharClass:
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case kRegexpHaveMatch:
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nprec = PrecAtom;
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break;
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case kRegexpConcat:
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case kRegexpLiteralString:
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if (prec < PrecConcat)
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t_->append("(?:");
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nprec = PrecConcat;
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break;
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case kRegexpAlternate:
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if (prec < PrecAlternate)
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t_->append("(?:");
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nprec = PrecAlternate;
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break;
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case kRegexpCapture:
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t_->append("(");
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if (re->name()) {
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t_->append("?P<");
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t_->append(*re->name());
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t_->append(">");
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}
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nprec = PrecParen;
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break;
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case kRegexpStar:
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case kRegexpPlus:
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case kRegexpQuest:
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case kRegexpRepeat:
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if (prec < PrecUnary)
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t_->append("(?:");
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// The subprecedence here is PrecAtom instead of PrecUnary
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// because PCRE treats two unary ops in a row as a parse error.
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nprec = PrecAtom;
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break;
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}
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return nprec;
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}
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static void AppendLiteral(string *t, Rune r, bool foldcase) {
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if (r != 0 && r < 0x80 && strchr("(){}[]*+?|.^$\\", r)) {
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t->append(1, '\\');
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t->append(1, r);
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} else if (foldcase && 'a' <= r && r <= 'z') {
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if ('a' <= r && r <= 'z')
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r += 'A' - 'a';
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t->append(1, '[');
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t->append(1, r);
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t->append(1, r + 'a' - 'A');
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t->append(1, ']');
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} else {
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AppendCCRange(t, r, r);
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}
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}
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// Visits re after children are processed.
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// For childless regexps, all the work is done here.
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// For regexps with children, append any unary suffixes or ).
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int ToStringWalker::PostVisit(Regexp* re, int parent_arg, int pre_arg,
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int* child_args, int nchild_args) {
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int prec = parent_arg;
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switch (re->op()) {
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case kRegexpNoMatch:
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// There's no simple symbol for "no match", but
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// [^0-Runemax] excludes everything.
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t_->append("[^\\x00-\\x{10ffff}]");
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break;
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case kRegexpEmptyMatch:
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// Append (?:) to make empty string visible,
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// unless this is already being parenthesized.
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if (prec < PrecEmpty)
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t_->append("(?:)");
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break;
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case kRegexpLiteral:
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AppendLiteral(t_, re->rune(), re->parse_flags() & Regexp::FoldCase);
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break;
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case kRegexpLiteralString:
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for (int i = 0; i < re->nrunes(); i++)
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AppendLiteral(t_, re->runes()[i], re->parse_flags() & Regexp::FoldCase);
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if (prec < PrecConcat)
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t_->append(")");
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break;
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case kRegexpConcat:
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if (prec < PrecConcat)
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t_->append(")");
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break;
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case kRegexpAlternate:
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// Clumsy but workable: the children all appended |
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// at the end of their strings, so just remove the last one.
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if ((*t_)[t_->size()-1] == '|')
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t_->erase(t_->size()-1);
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else
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LOG(DFATAL) << "Bad final char: " << t_;
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if (prec < PrecAlternate)
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t_->append(")");
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break;
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case kRegexpStar:
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t_->append("*");
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if (re->parse_flags() & Regexp::NonGreedy)
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t_->append("?");
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if (prec < PrecUnary)
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t_->append(")");
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break;
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case kRegexpPlus:
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t_->append("+");
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if (re->parse_flags() & Regexp::NonGreedy)
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t_->append("?");
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if (prec < PrecUnary)
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t_->append(")");
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break;
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case kRegexpQuest:
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t_->append("?");
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if (re->parse_flags() & Regexp::NonGreedy)
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t_->append("?");
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if (prec < PrecUnary)
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t_->append(")");
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break;
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case kRegexpRepeat:
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if (re->max() == -1)
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t_->append(StringPrintf("{%d,}", re->min()));
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else if (re->min() == re->max())
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t_->append(StringPrintf("{%d}", re->min()));
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else
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t_->append(StringPrintf("{%d,%d}", re->min(), re->max()));
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if (re->parse_flags() & Regexp::NonGreedy)
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t_->append("?");
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if (prec < PrecUnary)
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t_->append(")");
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break;
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case kRegexpAnyChar:
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t_->append(".");
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break;
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case kRegexpAnyByte:
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t_->append("\\C");
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break;
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case kRegexpBeginLine:
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t_->append("^");
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break;
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case kRegexpEndLine:
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t_->append("$");
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break;
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case kRegexpBeginText:
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t_->append("(?-m:^)");
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break;
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case kRegexpEndText:
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if (re->parse_flags() & Regexp::WasDollar)
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t_->append("(?-m:$)");
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else
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t_->append("\\z");
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break;
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case kRegexpWordBoundary:
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t_->append("\\b");
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break;
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case kRegexpNoWordBoundary:
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t_->append("\\B");
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break;
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case kRegexpCharClass: {
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if (re->cc()->size() == 0) {
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t_->append("[^\\x00-\\x{10ffff}]");
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break;
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}
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t_->append("[");
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// Heuristic: show class as negated if it contains the
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// non-character 0xFFFE.
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CharClass* cc = re->cc();
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if (cc->Contains(0xFFFE)) {
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cc = cc->Negate();
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t_->append("^");
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}
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for (CharClass::iterator i = cc->begin(); i != cc->end(); ++i)
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AppendCCRange(t_, i->lo, i->hi);
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if (cc != re->cc())
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cc->Delete();
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t_->append("]");
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break;
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}
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case kRegexpCapture:
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t_->append(")");
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break;
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case kRegexpHaveMatch:
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// There's no syntax accepted by the parser to generate
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// this node (it is generated by RE2::Set) so make something
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// up that is readable but won't compile.
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t_->append("(?HaveMatch:%d)", re->match_id());
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break;
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}
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// If the parent is an alternation, append the | for it.
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if (prec == PrecAlternate)
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t_->append("|");
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return 0;
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}
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// Appends a rune for use in a character class to the string t.
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static void AppendCCChar(string* t, Rune r) {
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if (0x20 <= r && r <= 0x7E) {
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if (strchr("[]^-\\", r))
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t->append("\\");
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t->append(1, r);
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return;
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}
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switch (r) {
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default:
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break;
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case '\r':
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t->append("\\r");
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return;
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case '\t':
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t->append("\\t");
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return;
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case '\n':
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t->append("\\n");
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return;
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case '\f':
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t->append("\\f");
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return;
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}
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if (r < 0x100) {
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StringAppendF(t, "\\x%02x", static_cast<int>(r));
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return;
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}
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StringAppendF(t, "\\x{%x}", static_cast<int>(r));
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}
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static void AppendCCRange(string* t, Rune lo, Rune hi) {
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if (lo > hi)
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return;
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AppendCCChar(t, lo);
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if (lo < hi) {
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t->append("-");
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AppendCCChar(t, hi);
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}
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}
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} // namespace re2
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