qemu/roms/openbios/fs/iso9660/iso9660_read.c

   1 /*
   2  *
   3  * (c) 2005-2009 Laurent Vivier <Laurent@vivier.eu>
   4  *
   5  * This file has been copied from EMILE, http://emile.sf.net
   6  *
   7  */
   8
   9 #include "libiso9660.h"
  10 #include "libopenbios/bindings.h"
  11 #include "libc/diskio.h"
  12
  13 size_t iso9660_read(iso9660_FILE *_file, char *buf, size_t count)
  14 {
  15         iso9660_FILE *file = (iso9660_FILE*)_file;
  16         size_t read = 0;
  17
  18         if ( count > (file->size  - file->offset) )
  19                 count = file->size  - file->offset;
  20
  21         while (count > 0)
  22         {
  23                 size_t part;
  24                 int offset_extent;
  25                 int offset_index;
  26
  27                 offset_extent = file->base +
  28                                     (file->offset / ISOFS_BLOCK_SIZE);
  29                 offset_index = file->offset % ISOFS_BLOCK_SIZE;
  30
  31                 if (file->current != offset_extent)
  32                 {
  33                         if ( (offset_index == 0) &&
  34                              (count >= ISOFS_BLOCK_SIZE) )
  35                         {
  36                                 /* direct i/o */
  37
  38                                 int extents_nb;
  39
  40                                 extents_nb = count / ISOFS_BLOCK_SIZE;
  41
  42                                 part = extents_nb * ISOFS_BLOCK_SIZE;
  43
  44                                 seek_io(file->volume->fd,
  45                                         offset_extent * ISOFS_BLOCK_SIZE);
  46                                 read_io(file->volume->fd, buf + read, part);
  47
  48                                 file->offset += part;
  49                                 count -= part;
  50                                 read += part;
  51
  52                                 continue;
  53                         }
  54
  55                         file->current = offset_extent;
  56                         seek_io(file->volume->fd,
  57                                 offset_extent * ISOFS_BLOCK_SIZE);
  58                         read_io(file->volume->fd, file->buffer,
  59                                 ISOFS_BLOCK_SIZE);
  60                 }
  61
  62                 part = ISOFS_BLOCK_SIZE - offset_index;
  63                 if (count < part)
  64                         part = count;
  65
  66                 memcpy(buf + read, file->buffer + offset_index, part);
  67
  68                 file->offset += part;
  69                 count -= part;
  70                 read += part;
  71         }
  72
  73         return read;
  74 }