pcrecpp/include/pcre_scanner.h

// Copyright (c) 2005, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Author: Sanjay Ghemawat
//
// Regular-expression based scanner for parsing an input stream.
//
// Example 1: parse a sequence of "var = number" entries from input:
//
//      Scanner scanner(input);
//      string var;
//      int number;
//      scanner.SetSkipExpression("\\s+"); // Skip any white space we encounter
//      while (scanner.Consume("(\\w+) = (\\d+)", &var, &number)) {
//        ...;
//      }

#ifndef _PCRE_SCANNER_H
#define _PCRE_SCANNER_H

#include <assert.h>
#include <string>
#include <vector>

#include <pcrecpp.h>
#include <pcre_stringpiece.h>

namespace pcrecpp {

class Scanner {
 public:
  Scanner();
  explicit Scanner(const std::string& input);
  ~Scanner();

  // Return current line number.  The returned line-number is
  // one-based.  I.e. it returns 1 + the number of consumed newlines.
  //
  // Note: this method may be slow.  It may take time proportional to
  // the size of the input.
  int LineNumber() const;

  // Return the byte-offset that the scanner is looking in the
  // input data;
  int Offset() const;

  // Return true iff the start of the remaining input matches "re"
  bool LookingAt(const RE& re) const;

  // Return true iff all of the following are true
  //    a. the start of the remaining input matches "re",
  //    b. if any arguments are supplied, matched sub-patterns can be
  //       parsed and stored into the arguments.
  // If it returns true, it skips over the matched input and any
  // following input that matches the "skip" regular expression.
  template<typename ... ARGS>
  bool Consume(const RE& re, ARGS && ... args) {
    const bool result = re.Consume(&input_, args...);
    if (result && should_skip_)
      ConsumeSkip();
    return result;
  }

  // Set the "skip" regular expression.  If after consuming some data,
  // a prefix of the input matches this RE, it is automatically
  // skipped.  For example, a programming language scanner would use
  // a skip RE that matches white space and comments.
  //
  //    scanner.SetSkipExpression("\\s+|//.*|/[*](.|\n)*?[*]/");
  //
  // Skipping repeats as long as it succeeds.  We used to let people do
  // this by writing "(...)*" in the regular expression, but that added
  // up to lots of recursive calls within the pcre library, so now we
  // control repetition explicitly via the function call API.
  //
  // You can pass NULL for "re" if you do not want any data to be skipped.
  void Skip(const char* re);   // DEPRECATED; does *not* repeat
  void SetSkipExpression(const char* re);

  // Temporarily pause "skip"ing. This
  //   Skip("Foo"); code ; DisableSkip(); code; EnableSkip()
  // is similar to
  //   Skip("Foo"); code ; Skip(NULL); code ; Skip("Foo");
  // but avoids creating/deleting new RE objects.
  void DisableSkip();

  // Reenable previously paused skipping.  Any prefix of the input
  // that matches the skip pattern is immediately dropped.
  void EnableSkip();

  /***** Special wrappers around SetSkip() for some common idioms *****/

  // Arranges to skip whitespace, C comments, C++ comments.
  // The overall RE is a disjunction of the following REs:
  //    \\s                     whitespace
  //    //.*\n                  C++ comment
  //    /[*](.|\n)*?[*]/        C comment (x*? means minimal repetitions of x)
  // We get repetition via the semantics of SetSkipExpression, not by using *
  void SkipCXXComments() {
    SetSkipExpression("\\s|//.*\n|/[*](?:\n|.)*?[*]/");
  }

  void set_save_comments(bool comments) {
    save_comments_ = comments;
  }

  bool save_comments() {
    return save_comments_;
  }

  // Append to vector ranges the comments found in the
  // byte range [start,end] (inclusive) of the input data.
  // Only comments that were extracted entirely within that
  // range are returned: no range splitting of atomically-extracted
  // comments is performed.
  void GetComments(int start, int end, std::vector<StringPiece> *ranges);

  // Append to vector ranges the comments added
  // since the last time this was called. This
  // functionality is provided for efficiency when
  // interleaving scanning with parsing.
  void GetNextComments(std::vector<StringPiece> *ranges);

 private:
  std::string   data_;          // All the input data
  StringPiece   input_;         // Unprocessed input
  RE*           skip_;          // If non-NULL, RE for skipping input
  bool          should_skip_;   // If true, use skip_
  bool          skip_repeat_;   // If true, repeat skip_ as long as it works
  bool          save_comments_; // If true, aggregate the skip expression

  // the skipped comments
  // TODO: later consider requiring that the StringPieces be added
  // in order by their start position
  std::vector<StringPiece> *comments_;

  // the offset into comments_ that has been returned by GetNextComments
  int           comments_offset_;

  // helper function to consume *skip_ and honour
  // save_comments_
  void ConsumeSkip();
};

}   // namespace pcrecpp

#endif /* _PCRE_SCANNER_H */