103 lines
2.9 KiB
C
103 lines
2.9 KiB
C
/* Copyright (C) 1991, 1992, 1996, 1997, 2002 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <limits.h>
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#include <stdbool.h>
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#include <sys/param.h>
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#include <sys/uio.h>
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/* Read data from file descriptor FD, and put the result in the
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buffers described by VECTOR, which is a vector of COUNT `struct iovec's.
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The buffers are filled in the order specified.
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Operates just like `read' (see <unistd.h>) except that data are
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put in VECTOR instead of a contiguous buffer. */
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ssize_t
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__readv (fd, vector, count)
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int fd;
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const struct iovec *vector;
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int count;
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{
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char *buffer;
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char *buffer_start;
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size_t bytes;
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ssize_t bytes_read;
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int i;
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bool use_malloc = false;
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/* Find the total number of bytes to be read. */
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bytes = 0;
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for (i = 0; i < count; ++i)
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{
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/* Check for ssize_t overflow. */
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if (SSIZE_MAX - bytes < vector[i].iov_len)
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{
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errno = EINVAL;
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return -1;
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}
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bytes += vector[i].iov_len;
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}
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/* Allocate a temporary buffer to hold the data. We should normally
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use alloca since it's faster and does not require synchronization
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with other threads. But we cannot if the amount of memory
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required is too large. Use 512k as the limit. */
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if (bytes < 512 * 1024)
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buffer = (char *) __alloca (bytes);
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else
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{
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buffer = (char *) malloc (bytes);
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if (buffer == NULL)
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/* XXX I don't know whether it is acceptable to try reading
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the data in chunks. Probably not so we just fail here. */
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return -1;
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use_malloc = true;
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}
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/* Read the data. */
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bytes_read = __read (fd, buffer, bytes);
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if (bytes_read <= 0)
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return -1;
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/* Copy the data from BUFFER into the memory specified by VECTOR. */
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bytes = bytes_read;
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buffer_start = buffer;
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for (i = 0; i < count; ++i)
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{
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size_t copy = MIN (vector[i].iov_len, bytes);
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(void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy);
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buffer += copy;
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bytes -= copy;
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if (bytes == 0)
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break;
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}
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if (use_malloc)
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free (buffer_start);
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return bytes_read;
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}
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#ifndef __readv
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weak_alias (__readv, readv)
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#endif
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