release/src/router/pcre/pcre_scanner.h

   1 // Copyright (c) 2005, Google Inc.
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  29 //
  30 // Author: Sanjay Ghemawat
  31 //
  32 // Regular-expression based scanner for parsing an input stream.
  33 //
  34 // Example 1: parse a sequence of "var = number" entries from input:
  35 //
  36 //      Scanner scanner(input);
  37 //      string var;
  38 //      int number;
  39 //      scanner.SetSkipExpression("\\s+"); // Skip any white space we encounter
  40 //      while (scanner.Consume("(\\w+) = (\\d+)", &var, &number)) {
  41 //        ...;
  42 //      }
  43
  44 #ifndef _PCRE_SCANNER_H
  45 #define _PCRE_SCANNER_H
  46
  47 #include <assert.h>
  48 #include <string>
  49 #include <vector>
  50
  51 #include <pcrecpp.h>
  52 #include <pcre_stringpiece.h>
  53
  54 namespace pcrecpp {
  55
  56 class PCRECPP_EXP_DEFN Scanner {
  57  public:
  58   Scanner();
  59   explicit Scanner(const std::string& input);
  60   ~Scanner();
  61
  62   // Return current line number.  The returned line-number is
  63   // one-based.  I.e. it returns 1 + the number of consumed newlines.
  64   //
  65   // Note: this method may be slow.  It may take time proportional to
  66   // the size of the input.
  67   int LineNumber() const;
  68
  69   // Return the byte-offset that the scanner is looking in the
  70   // input data;
  71   int Offset() const;
  72
  73   // Return true iff the start of the remaining input matches "re"
  74   bool LookingAt(const RE& re) const;
  75
  76   // Return true iff all of the following are true
  77   //    a. the start of the remaining input matches "re",
  78   //    b. if any arguments are supplied, matched sub-patterns can be
  79   //       parsed and stored into the arguments.
  80   // If it returns true, it skips over the matched input and any
  81   // following input that matches the "skip" regular expression.
  82   bool Consume(const RE& re,
  83                const Arg& arg0 = RE::no_arg,
  84                const Arg& arg1 = RE::no_arg,
  85                const Arg& arg2 = RE::no_arg
  86                // TODO: Allow more arguments?
  87                );
  88
  89   // Set the "skip" regular expression.  If after consuming some data,
  90   // a prefix of the input matches this RE, it is automatically
  91   // skipped.  For example, a programming language scanner would use
  92   // a skip RE that matches white space and comments.
  93   //
  94   //    scanner.SetSkipExpression("\\s+|//.*|/[*](.|\n)*?[*]/");
  95   //
  96   // Skipping repeats as long as it succeeds.  We used to let people do
  97   // this by writing "(...)*" in the regular expression, but that added
  98   // up to lots of recursive calls within the pcre library, so now we
  99   // control repetition explicitly via the function call API.
 100   //
 101   // You can pass NULL for "re" if you do not want any data to be skipped.
 102   void Skip(const char* re);   // DEPRECATED; does *not* repeat
 103   void SetSkipExpression(const char* re);
 104
 105   // Temporarily pause "skip"ing. This
 106   //   Skip("Foo"); code ; DisableSkip(); code; EnableSkip()
 107   // is similar to
 108   //   Skip("Foo"); code ; Skip(NULL); code ; Skip("Foo");
 109   // but avoids creating/deleting new RE objects.
 110   void DisableSkip();
 111
 112   // Reenable previously paused skipping.  Any prefix of the input
 113   // that matches the skip pattern is immediately dropped.
 114   void EnableSkip();
 115
 116   /***** Special wrappers around SetSkip() for some common idioms *****/
 117
 118   // Arranges to skip whitespace, C comments, C++ comments.
 119   // The overall RE is a disjunction of the following REs:
 120   //    \\s                     whitespace
 121   //    //.*\n                  C++ comment
 122   //    /[*](.|\n)*?[*]/        C comment (x*? means minimal repetitions of x)
 123   // We get repetition via the semantics of SetSkipExpression, not by using *
 124   void SkipCXXComments() {
 125     SetSkipExpression("\\s|//.*\n|/[*](?:\n|.)*?[*]/");
 126   }
 127
 128   void set_save_comments(bool comments) {
 129     save_comments_ = comments;
 130   }
 131
 132   bool save_comments() {
 133     return save_comments_;
 134   }
 135
 136   // Append to vector ranges the comments found in the
 137   // byte range [start,end] (inclusive) of the input data.
 138   // Only comments that were extracted entirely within that
 139   // range are returned: no range splitting of atomically-extracted
 140   // comments is performed.
 141   void GetComments(int start, int end, std::vector<StringPiece> *ranges);
 142
 143   // Append to vector ranges the comments added
 144   // since the last time this was called. This
 145   // functionality is provided for efficiency when
 146   // interleaving scanning with parsing.
 147   void GetNextComments(std::vector<StringPiece> *ranges);
 148
 149  private:
 150   std::string   data_;          // All the input data
 151   StringPiece   input_;         // Unprocessed input
 152   RE*           skip_;          // If non-NULL, RE for skipping input
 153   bool          should_skip_;   // If true, use skip_
 154   bool          skip_repeat_;   // If true, repeat skip_ as long as it works
 155   bool          save_comments_; // If true, aggregate the skip expression
 156
 157   // the skipped comments
 158   // TODO: later consider requiring that the StringPieces be added
 159   // in order by their start position
 160   std::vector<StringPiece> *comments_;
 161
 162   // the offset into comments_ that has been returned by GetNextComments
 163   int           comments_offset_;
 164
 165   // helper function to consume *skip_ and honour
 166   // save_comments_
 167   void ConsumeSkip();
 168 };
 169
 170 }   // namespace pcrecpp
 171
 172 #endif /* _PCRE_SCANNER_H */