lib-src/automata/iolexerbuf.cc

   1 //////////////////////////////////////////////////////////////////////////////
   2 // NOTICE:
   3 //
   4 // ADLib, Prop and their related set of tools and documentation are in the
   5 // public domain.   The author(s) of this software reserve no copyrights on
   6 // the source code and any code generated using the tools.  You are encouraged
   7 // to use ADLib and Prop to develop software, in both academic and commercial
   8 // settings, and are welcomed to incorporate any part of ADLib and Prop into
   9 // your programs.
  10 //
  11 // Although you are under no obligation to do so, we strongly recommend that
  12 // you give away all software developed using our tools.
  13 //
  14 // We also ask that credit be given to us when ADLib and/or Prop are used in
  15 // your programs, and that this notice be preserved intact in all the source
  16 // code.
  17 //
  18 // This software is still under development and we welcome(read crave for)
  19 // any suggestions and help from the users.
  20 //
  21 // Allen Leung (leunga@cs.nyu.edu)
  22 // 1994-1995
  23 //////////////////////////////////////////////////////////////////////////////
  24
  25 #include <iostream.h>
  26 #include <string.h>
  27 #include <AD/automata/iolexerbuf.h>
  28
  29 //////////////////////////////////////////////////////////////////////////////
  30 //  Constructor and destructor
  31 //////////////////////////////////////////////////////////////////////////////
  32 IOLexerBuffer:: IOLexerBuffer() : input(&cin)
  33    { allocate_buffer(4096); }
  34 IOLexerBuffer:: IOLexerBuffer(istream& in) : input(&in)
  35    { allocate_buffer(4096); }
  36 IOLexerBuffer::~IOLexerBuffer() {}
  37
  38 //////////////////////////////////////////////////////////////////////////////
  39 //  Allocate the space for a buffer
  40 //////////////////////////////////////////////////////////////////////////////
  41 void IOLexerBuffer::allocate_buffer(size_t n)
  42 {  buffer = buffer_limit = cursor = cursor_limit = new char [n+1];
  43    buffer_size = n; more_input = true;
  44    pinned = false; // buffer is not pinned, can be deleted
  45 }
  46
  47 //////////////////////////////////////////////////////////////////////////////
  48 //  Method to get new input from the istream
  49 //////////////////////////////////////////////////////////////////////////////
  50 size_t IOLexerBuffer::read_buffer(char * buf, size_t n)
  51 {  // Input one line at a time for interactive use.
  52    size_t len = input->get(buf, n - 1).gcount();
  53    if (input->peek() == '\n') { buf[len++] = input->get(); }
  54    buf[len] = '\0';
  55    return len;
  56 }
  57
  58 //////////////////////////////////////////////////////////////////////////////
  59 //  Method to fill the input buffer
  60 //////////////////////////////////////////////////////////////////////////////
  61 size_t IOLexerBuffer::fill_buffer()
  62 {  //  Shift the remaining contents to the begining of the buffer.
  63    size_t left_over = buffer_limit - cursor_limit;
  64    memcpy(buffer, cursor_limit, left_over);
  65    int count = read_buffer(buffer + left_over,buffer_size - left_over);
  66    more_input = count > 0;
  67    buffer_limit = buffer + left_over + count;
  68    cursor = cursor_limit = buffer;
  69    return count;
  70 }
  71
  72 //////////////////////////////////////////////////////////////////////////////
  73 //  Set/reset the input buffer
  74 //////////////////////////////////////////////////////////////////////////////
  75 void IOLexerBuffer::set_stream(istream& in)
  76 {  // Yank back the saved character
  77    if (buffer && saved_char >= 0) *cursor_limit = saved_char;
  78    saved_char = -1;
  79    // Reset the buffer
  80    cursor = cursor_limit = buffer;
  81    input = &in;
  82 }