/* * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC") * Copyright (C) 2000, 2001 Internet Software Consortium. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR * PERFORMANCE OF THIS SOFTWARE. */ /* $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 <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. */ lwres_uint8_t lwres_buffer_getuint8(lwres_buffer_t *b) { unsigned char *cp; lwres_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, lwres_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. */ lwres_uint16_t lwres_buffer_getuint16(lwres_buffer_t *b) { unsigned char *cp; lwres_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, lwres_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. */ lwres_uint32_t lwres_buffer_getuint32(lwres_buffer_t *b) { unsigned char *cp; lwres_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, lwres_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; memcpy(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; memcpy(base, cp, length); }