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+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.
+// http://code.google.com/p/protobuf/
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// Class for parsing tokenized text from a ZeroCopyInputStream.
+
+#ifndef GOOGLE_PROTOBUF_IO_TOKENIZER_H__
+#define GOOGLE_PROTOBUF_IO_TOKENIZER_H__
+
+#include <string>
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+
+class ZeroCopyInputStream;     // zero_copy_stream.h
+
+// Defined in this file.
+class ErrorCollector;
+class Tokenizer;
+
+// Abstract interface for an object which collects the errors that occur
+// during parsing.  A typical implementation might simply print the errors
+// to stdout.
+class LIBPROTOBUF_EXPORT ErrorCollector {
+ public:
+  inline ErrorCollector() {}
+  virtual ~ErrorCollector();
+
+  // Indicates that there was an error in the input at the given line and
+  // column numbers.  The numbers are zero-based, so you may want to add
+  // 1 to each before printing them.
+  virtual void AddError(int line, int column, const string& message) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ErrorCollector);
+};
+
+// This class converts a stream of raw text into a stream of tokens for
+// the protocol definition parser to parse.  The tokens recognized are
+// similar to those that make up the C language; see the TokenType enum for
+// precise descriptions.  Whitespace and comments are skipped.  By default,
+// C- and C++-style comments are recognized, but other styles can be used by
+// calling set_comment_style().
+class LIBPROTOBUF_EXPORT Tokenizer {
+ public:
+  // Construct a Tokenizer that reads and tokenizes text from the given
+  // input stream and writes errors to the given error_collector.
+  // The caller keeps ownership of input and error_collector.
+  Tokenizer(ZeroCopyInputStream* input, ErrorCollector* error_collector);
+  ~Tokenizer();
+
+  enum TokenType {
+    TYPE_START,       // Next() has not yet been called.
+    TYPE_END,         // End of input reached.  "text" is empty.
+
+    TYPE_IDENTIFIER,  // A sequence of letters, digits, and underscores, not
+                      // starting with a digit.  It is an error for a number
+                      // to be followed by an identifier with no space in
+                      // between.
+    TYPE_INTEGER,     // A sequence of digits representing an integer.  Normally
+                      // the digits are decimal, but a prefix of "0x" indicates
+                      // a hex number and a leading zero indicates octal, just
+                      // like with C numeric literals.  A leading negative sign
+                      // is NOT included in the token; it's up to the parser to
+                      // interpret the unary minus operator on its own.
+    TYPE_FLOAT,       // A floating point literal, with a fractional part and/or
+                      // an exponent.  Always in decimal.  Again, never
+                      // negative.
+    TYPE_STRING,      // A quoted sequence of escaped characters.  Either single
+                      // or double quotes can be used, but they must match.
+                      // A string literal cannot cross a line break.
+    TYPE_SYMBOL,      // Any other printable character, like '!' or '+'.
+                      // Symbols are always a single character, so "!+$%" is
+                      // four tokens.
+  };
+
+  // Structure representing a token read from the token stream.
+  struct Token {
+    TokenType type;
+    string text;       // The exact text of the token as it appeared in
+                       // the input.  e.g. tokens of TYPE_STRING will still
+                       // be escaped and in quotes.
+
+    // "line" and "column" specify the position of the first character of
+    // the token within the input stream.  They are zero-based.
+    int line;
+    int column;
+  };
+
+  // Get the current token.  This is updated when Next() is called.  Before
+  // the first call to Next(), current() has type TYPE_START and no contents.
+  const Token& current();
+
+  // Advance to the next token.  Returns false if the end of the input is
+  // reached.
+  bool Next();
+
+  // Parse helpers ---------------------------------------------------
+
+  // Parses a TYPE_FLOAT token.  This never fails, so long as the text actually
+  // comes from a TYPE_FLOAT token parsed by Tokenizer.  If it doesn't, the
+  // result is undefined (possibly an assert failure).
+  static double ParseFloat(const string& text);
+
+  // Parses a TYPE_STRING token.  This never fails, so long as the text actually
+  // comes from a TYPE_STRING token parsed by Tokenizer.  If it doesn't, the
+  // result is undefined (possibly an assert failure).
+  static void ParseString(const string& text, string* output);
+
+  // Parses a TYPE_INTEGER token.  Returns false if the result would be
+  // greater than max_value.  Otherwise, returns true and sets *output to the
+  // result.  If the text is not from a Token of type TYPE_INTEGER originally
+  // parsed by a Tokenizer, the result is undefined (possibly an assert
+  // failure).
+  static bool ParseInteger(const string& text, uint64 max_value,
+                           uint64* output);
+
+  // Options ---------------------------------------------------------
+
+  // Set true to allow floats to be suffixed with the letter 'f'.  Tokens
+  // which would otherwise be integers but which have the 'f' suffix will be
+  // forced to be interpreted as floats.  For all other purposes, the 'f' is
+  // ignored.
+  void set_allow_f_after_float(bool value) { allow_f_after_float_ = value; }
+
+  // Valid values for set_comment_style().
+  enum CommentStyle {
+    // Line comments begin with "//", block comments are delimited by "/*" and
+    // "*/".
+    CPP_COMMENT_STYLE,
+    // Line comments begin with "#".  No way to write block comments.
+    SH_COMMENT_STYLE
+  };
+
+  // Sets the comment style.
+  void set_comment_style(CommentStyle style) { comment_style_ = style; }
+
+  // -----------------------------------------------------------------
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Tokenizer);
+
+  Token current_;           // Returned by current().
+
+  ZeroCopyInputStream* input_;
+  ErrorCollector* error_collector_;
+
+  char current_char_;       // == buffer_[buffer_pos_], updated by NextChar().
+  const char* buffer_;      // Current buffer returned from input_.
+  int buffer_size_;         // Size of buffer_.
+  int buffer_pos_;          // Current position within the buffer.
+  bool read_error_;         // Did we previously encounter a read error?
+
+  // Line and column number of current_char_ within the whole input stream.
+  int line_;
+  int column_;
+
+  // Position in buffer_ where StartToken() was called.  If the token
+  // started in the previous buffer, this is zero, and current_.text already
+  // contains the part of the token from the previous buffer.  If not
+  // currently parsing a token, this is -1.
+  int token_start_;
+
+  // Options.
+  bool allow_f_after_float_;
+  CommentStyle comment_style_;
+
+  // Since we count columns we need to interpret tabs somehow.  We'll take
+  // the standard 8-character definition for lack of any way to do better.
+  static const int kTabWidth = 8;
+
+  // -----------------------------------------------------------------
+  // Helper methods.
+
+  // Consume this character and advance to the next one.
+  void NextChar();
+
+  // Read a new buffer from the input.
+  void Refresh();
+
+  // Called when the current character is the first character of a new
+  // token (not including whitespace or comments).
+  inline void StartToken();
+  // Called when the current character is the first character after the
+  // end of the last token.  After this returns, current_.text will
+  // contain all text consumed since StartToken() was called.
+  inline void EndToken();
+
+  // Convenience method to add an error at the current line and column.
+  void AddError(const string& message) {
+    error_collector_->AddError(line_, column_, message);
+  }
+
+  // -----------------------------------------------------------------
+  // The following four methods are used to consume tokens of specific
+  // types.  They are actually used to consume all characters *after*
+  // the first, since the calling function consumes the first character
+  // in order to decide what kind of token is being read.
+
+  // Read and consume a string, ending when the given delimiter is
+  // consumed.
+  void ConsumeString(char delimiter);
+
+  // Read and consume a number, returning TYPE_FLOAT or TYPE_INTEGER
+  // depending on what was read.  This needs to know if the first
+  // character was a zero in order to correctly recognize hex and octal
+  // numbers.
+  // It also needs to know if the first characted was a . to parse floating
+  // point correctly.
+  TokenType ConsumeNumber(bool started_with_zero, bool started_with_dot);
+
+  // Consume the rest of a line.
+  void ConsumeLineComment();
+  // Consume until "*/".
+  void ConsumeBlockComment();
+
+  // -----------------------------------------------------------------
+  // These helper methods make the parsing code more readable.  The
+  // "character classes" refered to are defined at the top of the .cc file.
+  // Basically it is a C++ class with one method:
+  //   static bool InClass(char c);
+  // The method returns true if c is a member of this "class", like "Letter"
+  // or "Digit".
+
+  // Returns true if the current character is of the given character
+  // class, but does not consume anything.
+  template<typename CharacterClass>
+  inline bool LookingAt();
+
+  // If the current character is in the given class, consume it and return
+  // true.  Otherwise return false.
+  // e.g. TryConsumeOne<Letter>()
+  template<typename CharacterClass>
+  inline bool TryConsumeOne();
+
+  // Like above, but try to consume the specific character indicated.
+  inline bool TryConsume(char c);
+
+  // Consume zero or more of the given character class.
+  template<typename CharacterClass>
+  inline void ConsumeZeroOrMore();
+
+  // Consume one or more of the given character class or log the given
+  // error message.
+  // e.g. ConsumeOneOrMore<Digit>("Expected digits.");
+  template<typename CharacterClass>
+  inline void ConsumeOneOrMore(const char* error);
+};
+
+// inline methods ====================================================
+inline const Tokenizer::Token& Tokenizer::current() {
+  return current_;
+}
+
+}  // namespace io
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_IO_TOKENIZER_H__