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 _IO_STREAM_MEMORY_H_
  17 #define _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   memblock (size_t size) : next (0), len (size) {data = new unsigned char[size]; if (!data) len = 0;};
  33   ~memblock ();
  34   memblock *next;
  35   size_t len;
  36   unsigned char *data;
  37 };
  38
  39 class io_stream_memory :public io_stream
  40 {
  41 public:
  42   io_stream_memory () : lasterr (0), mtime(0),length (0), head(), tail (&head), pos_block (head.next), pos_block_offset (0), pos (0) {};
  43   /* set the modification time of a file - returns 1 on failure
  44    * may distrupt internal state - use after all important io is complete
  45    */
  46   virtual int set_mtime (int newmtime) {mtime = newmtime;return 0;};
  47   /* get the mtime for a file TODO make this a stat(0 style call */
  48   virtual int get_mtime () {return mtime;};
  49   /* returns the _current_ size. */
  50   virtual size_t get_size () {return length;};
  51   /* read data (duh!) */
  52   virtual ssize_t read (void *buffer, size_t len);
  53   /* provide data to (double duh!) */
  54   virtual ssize_t write (const void *buffer, size_t len);
  55   /* read data without removing it from the class's internal buffer */
  56   virtual ssize_t peek (void *buffer, size_t len);
  57   /* ever read the f* functions from libc ? */
  58   virtual long tell () {return pos;};
  59   virtual int seek (long where, io_stream_seek_t whence) { if (whence != IO_SEEK_SET) { lasterr = EINVAL; return -1;} ssize_t count=0; pos = 0; pos_block = head.next; pos_block_offset = 0; while (count < where && pos < length) {pos_block_offset++; if (pos_block_offset == pos_block->len) {pos_block = pos_block->next; pos_block_offset = 0;}pos++;count++;}return 0;};
  60
  61   /* try guessing this one */
  62   virtual int error ();
  63 //  virtual const char* next_file_name() = NULL;
  64   /* if you are still needing these hints... give up now! */
  65   virtual ~ io_stream_memory ();
  66 private:
  67   int lasterr;
  68   int mtime;
  69   size_t length;
  70   memblock head;
  71   memblock *tail;
  72   memblock *pos_block;
  73   size_t pos_block_offset;
  74   size_t pos;
  75 };
  76
  77 #endif /* _IO_STREAM_MEMORY_H_ */