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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 *
SkipCXXComments()124   void SkipCXXComments() {
125     SetSkipExpression("\\s|//.*\n|/[*](?:\n|.)*?[*]/");
126   }
127 
set_save_comments(bool comments)128   void set_save_comments(bool comments) {
129     save_comments_ = comments;
130   }
131 
save_comments()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 */
173