From: dyoung Date: Thu, 23 Sep 2004 21:27:18 +0000 (+0000) Subject: Add "cpack", a library for extracting 1-, 2-, 4-, and 8-octet words X-Git-Tag: tcpdump-3.9.1~280 X-Git-Url: https://git.tcpdump.org/tcpdump/commitdiff_plain/665b5651a8ac6a10de9cacbdb1af51134abcdb97 Add "cpack", a library for extracting 1-, 2-, 4-, and 8-octet words from a buffer. The cpack library expects for words to appear on their natural boundaries. The radiotap (802.11 + radio information) capture format uses cpack to extract the radio information fields. --- diff --git a/cpack.c b/cpack.c new file mode 100644 index 00000000..d2e765d4 --- /dev/null +++ b/cpack.c @@ -0,0 +1,143 @@ +/*- + * Copyright (c) 2003, 2004 David Young. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of David Young may not be used to endorse or promote + * products derived from this software without specific prior + * written permission. + * + * THIS SOFTWARE IS PROVIDED BY DAVID YOUNG ``AS IS'' AND ANY + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DAVID + * YOUNG BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED + * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY + * OF SUCH DAMAGE. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include +#include + +#include "cpack.h" +#include "extract.h" + +static u_int8_t * +cpack_next_boundary(u_int8_t *buf, u_int8_t *p, size_t alignment) +{ + size_t misalignment = (size_t)(p - buf) % alignment; + + if (misalignment == 0) + return p; + + return p + (alignment - misalignment); +} + +/* Advance to the next wordsize boundary. Return NULL if fewer than + * wordsize bytes remain in the buffer after the boundary. Otherwise, + * return a pointer to the boundary. + */ +static u_int8_t * +cpack_align_and_reserve(struct cpack_state *cs, size_t wordsize) +{ + u_int8_t *next; + + /* Ensure alignment. */ + next = cpack_next_boundary(cs->c_buf, cs->c_next, wordsize); + + /* Too little space for wordsize bytes? */ + if (next - cs->c_buf + wordsize > cs->c_len) + return NULL; + + return next; +} + +int +cpack_init(struct cpack_state *cs, u_int8_t *buf, size_t buflen) +{ + memset(cs, 0, sizeof(*cs)); + + cs->c_buf = buf; + cs->c_len = buflen; + cs->c_next = cs->c_buf; + + return 0; +} + +/* Unpack a 64-bit unsigned integer. */ +int +cpack_uint64(struct cpack_state *cs, u_int64_t *u) +{ + u_int8_t *next; + + if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL) + return -1; + + *u = EXTRACT_LE_64BITS(next); + + /* Move pointer past the u_int64_t. */ + cs->c_next = next + sizeof(*u); + return 0; +} + +/* Unpack a 32-bit unsigned integer. */ +int +cpack_uint32(struct cpack_state *cs, u_int32_t *u) +{ + u_int8_t *next; + + if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL) + return -1; + + *u = EXTRACT_LE_32BITS(next); + + /* Move pointer past the u_int32_t. */ + cs->c_next = next + sizeof(*u); + return 0; +} + +/* Unpack a 16-bit unsigned integer. */ +int +cpack_uint16(struct cpack_state *cs, u_int16_t *u) +{ + u_int8_t *next; + + if ((next = cpack_align_and_reserve(cs, sizeof(*u))) == NULL) + return -1; + + *u = EXTRACT_LE_16BITS(next); + + /* Move pointer past the u_int16_t. */ + cs->c_next = next + sizeof(*u); + return 0; +} + +/* Unpack an 8-bit unsigned integer. */ +int +cpack_uint8(struct cpack_state *cs, u_int8_t *u) +{ + /* No space left? */ + if (cs->c_next - cs->c_buf >= cs->c_len) + return -1; + + *u = *cs->c_next; + + /* Move pointer past the u_int8_t. */ + cs->c_next++; + return 0; +} diff --git a/cpack.h b/cpack.h new file mode 100644 index 00000000..14ed3769 --- /dev/null +++ b/cpack.h @@ -0,0 +1,51 @@ +/*- + * Copyright (c) 2003, 2004 David Young. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 3. The name of David Young may not be used to endorse or promote + * products derived from this software without specific prior + * written permission. + * + * THIS SOFTWARE IS PROVIDED BY DAVID YOUNG ``AS IS'' AND ANY + * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A + * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DAVID + * YOUNG BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED + * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY + * OF SUCH DAMAGE. + */ + +#ifndef _CPACK_H +#define _CPACK_H + +struct cpack_state { + u_int8_t *c_buf; + u_int8_t *c_next; + size_t c_len; +}; + +int cpack_init(struct cpack_state *, u_int8_t *, size_t); + +int cpack_uint8(struct cpack_state *, u_int8_t *); +int cpack_uint16(struct cpack_state *, u_int16_t *); +int cpack_uint32(struct cpack_state *, u_int32_t *); +int cpack_uint64(struct cpack_state *, u_int64_t *); + +#define cpack_int8(__s, __p) cpack_uint8((__s), (u_int8_t*)(__p)) +#define cpack_int16(__s, __p) cpack_uint16((__s), (u_int16_t*)(__p)) +#define cpack_int32(__s, __p) cpack_uint32((__s), (u_int32_t*)(__p)) +#define cpack_int64(__s, __p) cpack_uint64((__s), (u_int64_t*)(__p)) + +#endif /* _CPACK_H */