com32/lib/sys/fileread.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2004 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   Permission is hereby granted, free of charge, to any person
   6  *   obtaining a copy of this software and associated documentation
   7  *   files (the "Software"), to deal in the Software without
   8  *   restriction, including without limitation the rights to use,
   9  *   copy, modify, merge, publish, distribute, sublicense, and/or
  10  *   sell copies of the Software, and to permit persons to whom
  11  *   the Software is furnished to do so, subject to the following
  12  *   conditions:
  13  *
  14  *   The above copyright notice and this permission notice shall
  15  *   be included in all copies or substantial portions of the Software.
  16  *
  17  *   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  18  *   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
  19  *   OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  20  *   NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
  21  *   HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
  22  *   WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  23  *   FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  24  *   OTHER DEALINGS IN THE SOFTWARE.
  25  *
  26  * ----------------------------------------------------------------------- */
  27
  28 /*
  29  * read.c
  30  *
  31  * Reading from a file
  32  */
  33
  34 #include <errno.h>
  35 #include <string.h>
  36 #include <com32.h>
  37 #include <minmax.h>
  38 #include "file.h"
  39
  40 ssize_t __file_read(struct file_info *fp, void *buf, size_t count)
  41 {
  42   com32sys_t ireg, oreg;
  43   char *bufp = buf;
  44   size_t n = 0;
  45   size_t ncopy;
  46
  47   memset(&ireg, 0, sizeof ireg);
  48   ireg.eax.w[0] = 0x0007;       /* Read file */
  49   ireg.ebx.w[0] = OFFS(__com32.cs_bounce);
  50   ireg.es = SEG(__com32.cs_bounce);
  51
  52   while ( count ) {
  53     if ( fp->i.nbytes == 0 ) {
  54       if ( fp->i.offset >= fp->i.length || !fp->i.filedes )
  55         return n;               /* As good as it gets... */
  56
  57       ireg.esi.w[0] = fp->i.filedes;
  58       ireg.ecx.w[0] = MAXBLOCK >> fp->i.blocklg2;
  59
  60       __intcall(0x22, &ireg, &oreg);
  61
  62       if ( oreg.eflags.l & EFLAGS_CF ) {
  63         errno = EIO;
  64         return -1;
  65       }
  66
  67       fp->i.filedes = oreg.esi.w[0];
  68       fp->i.nbytes = min(fp->i.length-fp->i.offset, (unsigned)MAXBLOCK);
  69       fp->i.datap = fp->i.buf;
  70       memcpy(fp->i.buf, __com32.cs_bounce, fp->i.nbytes);
  71     }
  72
  73     ncopy = min(count, fp->i.nbytes);
  74     memcpy(bufp, fp->i.datap, ncopy);
  75
  76     n += ncopy;
  77     bufp += ncopy;
  78     count -= ncopy;
  79     fp->i.datap += ncopy;
  80     fp->i.offset += ncopy;
  81     fp->i.nbytes -= ncopy;
  82   }
  83
  84   return n;
  85 }