io_stream_memory.h

   1 /*
   2  * Copyright (c) 2001, Robert Collins.
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     A copy of the GNU General Public License can be found at
  10  *     http://www.gnu.org/
  11  *
  12  * Written by Robert Collins  <rbtcollins@hotmail.com>
  13  *
  14  */
  15
  16 #ifndef SETUP_IO_STREAM_MEMORY_H
  17 #define SETUP_IO_STREAM_MEMORY_H
  18
  19 /* needed to parse */
  20 #include <errno.h>
  21
  22 /* this is a stream class that simply abstracts the issue of maintaining
  23  * amemory buffer.
  24  * It's not as efficient as if can be, but that can be fixed without affecting
  25  * the API.
  26  */
  27
  28 class memblock
  29 {
  30 public:
  31   memblock ():next (0), len (0), data (0)
  32   {}
  33   memblock (size_t size):next (0), len (size)
  34   {
  35     data = new unsigned char[size];
  36     if (!data)
  37       len = 0;
  38   }
  39   ~memblock ();
  40   memblock *next;
  41   size_t len;
  42   unsigned char *data;
  43 };
  44
  45 class io_stream_memory:public io_stream
  46 {
  47 public:
  48   io_stream_memory (): lasterr (0), mtime (0), length (0), head (),
  49     tail (&head), pos_block (head.next), pos_block_offset (0), pos (0)
  50   {}
  51   /* set the modification time of a file - returns 1 on failure
  52    * may distrupt internal state - use after all important io is complete
  53    */
  54   virtual int set_mtime (time_t newmtime)
  55   {
  56     mtime = newmtime;
  57     return 0;
  58   }
  59   /* get the mtime for a file TODO make this a stat(0 style call */
  60   virtual time_t get_mtime () { return mtime; }
  61   virtual mode_t get_mode () { return 0; }
  62   /* returns the _current_ size. */
  63   virtual size_t get_size () { return length; }
  64   /* read data (duh!) */
  65   virtual ssize_t read (void *buffer, size_t len);
  66   /* provide data to (double duh!) */
  67   virtual ssize_t write (const void *buffer, size_t len);
  68   /* read data without removing it from the class's internal buffer */
  69   virtual ssize_t peek (void *buffer, size_t len);
  70   /* ever read the f* functions from libc ? */
  71   virtual off_t tell ()
  72   {
  73     return pos;
  74   }
  75   virtual off_t seek (off_t where, io_stream_seek_t whence)
  76   {
  77     if (whence != IO_SEEK_SET)
  78       {
  79         lasterr = EINVAL;
  80         return -1;
  81       }
  82     ssize_t count = 0;
  83     pos = 0;
  84     pos_block = head.next;
  85     pos_block_offset = 0;
  86     while (count < where && pos < (off_t) length)
  87       {
  88         pos_block_offset++;
  89         if (pos_block_offset == pos_block->len)
  90           {
  91             pos_block = pos_block->next;
  92             pos_block_offset = 0;
  93           }
  94         pos++;
  95         count++;
  96       }
  97     return 0;
  98   }
  99
 100   /* try guessing this one */
 101   virtual int error ();
 102 //  virtual const char* next_file_name() = NULL;
 103   /* if you are still needing these hints... give up now! */
 104   virtual ~io_stream_memory ();
 105 private:
 106   int lasterr;
 107   time_t mtime;
 108   size_t length;
 109   memblock head;
 110   memblock *tail;
 111   memblock *pos_block;
 112   size_t pos_block_offset;
 113   off_t pos;
 114 };
 115
 116 #endif /* SETUP_IO_STREAM_MEMORY_H */