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/* read for MMIXware.
Copyright (C) 2001 Hans-Peter Nilsson.
Permission to use, copy, modify, and distribute this software is freely
granted, provided that this notice is preserved with no changes.
THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE. */
#include <_ansi.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "sys/syscall.h"
#include <errno.h>
int
_read (int file,
char *ptr,
size_t len)
{
long ret;
if ((unsigned int) file >= 32 || _MMIX_allocated_filehandle[file] == 0)
{
errno = EBADF;
return -1;
}
ret = TRAP3f (SYS_Fread, file, ptr, len);
/* Map the return codes:
-1-len: an error. We return -1.
0: success. We return len.
n-len: end-of-file after n chars read. We return n. */
if (ret == 0)
return len;
if (ret == -1 - (long) len)
{
/* We don't know the nature of the failure, so this is an
approximation. */
errno = EIO;
return -1;
}
return ret + len;
}
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