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Diffstat (limited to '')
| -rw-r--r-- | lib/lwres/lwbuffer.c | 356 |
1 files changed, 356 insertions, 0 deletions
diff --git a/lib/lwres/lwbuffer.c b/lib/lwres/lwbuffer.c new file mode 100644 index 0000000..9cdf5ed --- /dev/null +++ b/lib/lwres/lwbuffer.c @@ -0,0 +1,356 @@ +/* + * Copyright (C) Internet Systems Consortium, Inc. ("ISC") + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. + * + * See the COPYRIGHT file distributed with this work for additional + * information regarding copyright ownership. + */ + +/* $Id: lwbuffer.c,v 1.15 2007/06/19 23:47:22 tbox Exp $ */ + +/*! \file */ + +/** + * These functions provide bounds checked access to a region of memory + * where data is being read or written. They are based on, and similar + * to, the isc_buffer_ functions in the ISC library. + * + * A buffer is a region of memory, together with a set of related + * subregions. The used region and the available region are disjoint, and + * their union is the buffer's region. The used region extends from the + * beginning of the buffer region to the last used byte. The available + * region extends from one byte greater than the last used byte to the + * end of the buffer's region. The size of the used region can be changed + * using various buffer commands. Initially, the used region is empty. + * + * The used region is further subdivided into two disjoint regions: the + * consumed region and the remaining region. The union of these two + * regions is the used region. The consumed region extends from the + * beginning of the used region to the byte before the current offset (if + * any). The remaining region the current pointer to the end of the used + * region. The size of the consumed region can be changed using various + * buffer commands. Initially, the consumed region is empty. + * + * The active region is an (optional) subregion of the remaining region. + * It extends from the current offset to an offset in the remaining + * region. Initially, the active region is empty. If the current offset + * advances beyond the chosen offset, the active region will also be + * empty. + * + * + * \verbatim + * /------------entire length---------------\\ + * /----- used region -----\\/-- available --\\ + * +----------------------------------------+ + * | consumed | remaining | | + * +----------------------------------------+ + * a b c d e + * + * a == base of buffer. + * b == current pointer. Can be anywhere between a and d. + * c == active pointer. Meaningful between b and d. + * d == used pointer. + * e == length of buffer. + * + * a-e == entire length of buffer. + * a-d == used region. + * a-b == consumed region. + * b-d == remaining region. + * b-c == optional active region. + * \endverbatim + * + * lwres_buffer_init() initializes the lwres_buffer_t *b and assocates it + * with the memory region of size length bytes starting at location base. + * + * lwres_buffer_invalidate() marks the buffer *b as invalid. Invalidating + * a buffer after use is not required, but makes it possible to catch its + * possible accidental use. + * + * The functions lwres_buffer_add() and lwres_buffer_subtract() + * respectively increase and decrease the used space in buffer *b by n + * bytes. lwres_buffer_add() checks for buffer overflow and + * lwres_buffer_subtract() checks for underflow. These functions do not + * allocate or deallocate memory. They just change the value of used. + * + * A buffer is re-initialised by lwres_buffer_clear(). The function sets + * used , current and active to zero. + * + * lwres_buffer_first() makes the consumed region of buffer *p empty by + * setting current to zero (the start of the buffer). + * + * lwres_buffer_forward() increases the consumed region of buffer *b by n + * bytes, checking for overflow. Similarly, lwres_buffer_back() decreases + * buffer b's consumed region by n bytes and checks for underflow. + * + * lwres_buffer_getuint8() reads an unsigned 8-bit integer from *b and + * returns it. lwres_buffer_putuint8() writes the unsigned 8-bit integer + * val to buffer *b. + * + * lwres_buffer_getuint16() and lwres_buffer_getuint32() are identical to + * lwres_buffer_putuint8() except that they respectively read an unsigned + * 16-bit or 32-bit integer in network byte order from b. Similarly, + * lwres_buffer_putuint16() and lwres_buffer_putuint32() writes the + * unsigned 16-bit or 32-bit integer val to buffer b, in network byte + * order. + * + * Arbitrary amounts of data are read or written from a lightweight + * resolver buffer with lwres_buffer_getmem() and lwres_buffer_putmem() + * respectively. lwres_buffer_putmem() copies length bytes of memory at + * base to b. Conversely, lwres_buffer_getmem() copies length bytes of + * memory from b to base. + */ + +#include <config.h> + +#include <inttypes.h> +#include <string.h> + +#include <lwres/lwbuffer.h> + +#include "assert_p.h" + +void +lwres_buffer_init(lwres_buffer_t *b, void *base, unsigned int length) +{ + /* + * Make 'b' refer to the 'length'-byte region starting at base. + */ + + REQUIRE(b != NULL); + + b->magic = LWRES_BUFFER_MAGIC; + b->base = base; + b->length = length; + b->used = 0; + b->current = 0; + b->active = 0; +} + +/* Make 'b' an invalid buffer. */ +void +lwres_buffer_invalidate(lwres_buffer_t *b) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + + b->magic = 0; + b->base = NULL; + b->length = 0; + b->used = 0; + b->current = 0; + b->active = 0; +} + +/* Increase the 'used' region of 'b' by 'n' bytes. */ +void +lwres_buffer_add(lwres_buffer_t *b, unsigned int n) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used + n <= b->length); + + b->used += n; +} + +/* Decrease the 'used' region of 'b' by 'n' bytes. */ +void +lwres_buffer_subtract(lwres_buffer_t *b, unsigned int n) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used >= n); + + b->used -= n; + if (b->current > b->used) + b->current = b->used; + if (b->active > b->used) + b->active = b->used; +} + +/* Make the used region empty. */ +void +lwres_buffer_clear(lwres_buffer_t *b) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + + b->used = 0; + b->current = 0; + b->active = 0; +} + +/* Make the consumed region empty. */ +void +lwres_buffer_first(lwres_buffer_t *b) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + + b->current = 0; +} + +/* Increase the 'consumed' region of 'b' by 'n' bytes. */ +void +lwres_buffer_forward(lwres_buffer_t *b, unsigned int n) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->current + n <= b->used); + + b->current += n; +} + +/* Decrease the 'consumed' region of 'b' by 'n' bytes. */ +void +lwres_buffer_back(lwres_buffer_t *b, unsigned int n) +{ + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(n <= b->current); + + b->current -= n; +} + +/* Read an unsigned 8-bit integer from 'b' and return it. */ +uint8_t +lwres_buffer_getuint8(lwres_buffer_t *b) +{ + unsigned char *cp; + uint8_t result; + + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used - b->current >= 1); + + cp = b->base; + cp += b->current; + b->current += 1; + result = ((unsigned int)(cp[0])); + + return (result); +} + +/* Put an unsigned 8-bit integer */ +void +lwres_buffer_putuint8(lwres_buffer_t *b, uint8_t val) +{ + unsigned char *cp; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used + 1 <= b->length); + + cp = b->base; + cp += b->used; + b->used += 1; + cp[0] = (val & 0x00ff); +} + +/* Read an unsigned 16-bit integer in network byte order from 'b', convert it to host byte order, and return it. */ +uint16_t +lwres_buffer_getuint16(lwres_buffer_t *b) +{ + unsigned char *cp; + uint16_t result; + + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used - b->current >= 2); + + cp = b->base; + cp += b->current; + b->current += 2; + result = ((unsigned int)(cp[0])) << 8; + result |= ((unsigned int)(cp[1])); + + return (result); +} + +/* Put an unsigned 16-bit integer. */ +void +lwres_buffer_putuint16(lwres_buffer_t *b, uint16_t val) +{ + unsigned char *cp; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used + 2 <= b->length); + + cp = b->base; + cp += b->used; + b->used += 2; + cp[0] = (val & 0xff00) >> 8; + cp[1] = (val & 0x00ff); +} + +/* Read an unsigned 32-bit integer in network byte order from 'b', convert it to host byte order, and return it. */ +uint32_t +lwres_buffer_getuint32(lwres_buffer_t *b) +{ + unsigned char *cp; + uint32_t result; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used - b->current >= 4); + + cp = b->base; + cp += b->current; + b->current += 4; + result = ((unsigned int)(cp[0])) << 24; + result |= ((unsigned int)(cp[1])) << 16; + result |= ((unsigned int)(cp[2])) << 8; + result |= ((unsigned int)(cp[3])); + + return (result); +} + +/* Put an unsigned 32-bit integer. */ +void +lwres_buffer_putuint32(lwres_buffer_t *b, uint32_t val) +{ + unsigned char *cp; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used + 4 <= b->length); + + cp = b->base; + cp += b->used; + b->used += 4; + cp[0] = (unsigned char)((val & 0xff000000) >> 24); + cp[1] = (unsigned char)((val & 0x00ff0000) >> 16); + cp[2] = (unsigned char)((val & 0x0000ff00) >> 8); + cp[3] = (unsigned char)(val & 0x000000ff); +} + +/* copies length bytes of memory at base to b */ +void +lwres_buffer_putmem(lwres_buffer_t *b, const unsigned char *base, + unsigned int length) +{ + unsigned char *cp; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used + length <= b->length); + + cp = (unsigned char *)b->base + b->used; + memmove(cp, base, length); + b->used += length; +} + +/* copies length bytes of memory at b to base */ +void +lwres_buffer_getmem(lwres_buffer_t *b, unsigned char *base, + unsigned int length) +{ + unsigned char *cp; + + REQUIRE(LWRES_BUFFER_VALID(b)); + REQUIRE(b->used - b->current >= length); + + cp = b->base; + cp += b->current; + b->current += length; + + memmove(base, cp, length); +} |