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/* ----------------------------------------------------------------------- *
*
* Copyright 2004-2009 H. Peter Anvin - All Rights Reserved
* Copyright 2009 Intel Corporation; author: H. Peter Anvin
*
* Permission is hereby granted, free of charge, to any person
* obtaining a copy of this software and associated documentation
* files (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use,
* copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom
* the Software is furnished to do so, subject to the following
* conditions:
*
* The above copyright notice and this permission notice shall
* be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
* OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
* OTHER DEALINGS IN THE SOFTWARE.
*
* ----------------------------------------------------------------------- */
/*
* read.c
*
* Reading from a file descriptor
*/
#include <errno.h>
#include <string.h>
#include <com32.h>
#include <minmax.h>
#include <klibc/compiler.h>
#include "file.h"
ssize_t read(int fd, void *buf, size_t count)
{
char *datap = buf;
struct file_info *fp = &__file_info[fd];
size_t n0, n1;
if (fd >= NFILES || !fp->iop) {
errno = EBADF;
return -1;
}
if (__unlikely(!count))
return 0;
n0 = min(fp->i.unread_bytes, count);
if (__unlikely(n0)) {
memcpy(datap, unread_data(fp), n0);
fp->i.unread_bytes -= n0;
count -= n0;
datap += n0;
if (!count)
return n0;
}
n1 = fp->iop->read(fp, datap, count);
if (n1 == -1 && n0 > 0)
return n0;
else
return n0 + n1;
}
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