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annotate buffer_const.c @ 261:6795f8427fed

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buffer: allow buffer truncation This is a similar idea to the POSIX truncate() function. It sets the used buffer size to a certain value. If the new size is larger than the old size, the newly visible bytes are zeroed out. If the new size is smaller than the old size, the bytes at the end are "lost" but the underlying buffer allocation remains unchanged. Signed-off-by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
author Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
date Tue, 11 Jul 2017 00:39:14 +0300
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1 /*
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2 * Copyright (c) 2017 Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
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3 *
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4 * Permission is hereby granted, free of charge, to any person obtaining a copy
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5 * of this software and associated documentation files (the "Software"), to deal
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6 * in the Software without restriction, including without limitation the rights
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7 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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8 * copies of the Software, and to permit persons to whom the Software is
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9 * furnished to do so, subject to the following conditions:
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10 *
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11 * The above copyright notice and this permission notice shall be included in
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12 * all copies or substantial portions of the Software.
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13 *
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14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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17 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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18 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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19 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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20 * SOFTWARE.
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21 */
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22
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23 #include "buffer_impl.h"
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24
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25 static int const_buffer_check_append(struct buffer *buffer, const void *data,
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26 size_t size)
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27 {
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28 return -EROFS;
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29 }
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30
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31 static int const_buffer_check_truncate(struct buffer *buffer, size_t size)
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32 {
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33 return -EROFS;
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34 }
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36 const struct buffer_ops const_buffer = {
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37 .check_append = const_buffer_check_append,
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38 .check_truncate = const_buffer_check_truncate,
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39
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40 /*
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41 * no need for:
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42 * - realloc since we have a borrowed const buffer
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43 * - free since we have a borrowed const buffer
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44 */
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45
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46 .clear = generic_buffer_clear_panic,
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47 .copyin = generic_buffer_copyin_panic,
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48 };