lwbuffer.c revision 70e5a7403f0e0a3bd292b8287c5fed5772c15270
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews/*
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * Copyright (C) 2004, 2005, 2007 Internet Systems Consortium, Inc. ("ISC")
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * Copyright (C) 2000, 2001 Internet Software Consortium.
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews *
0c27b3fe77ac1d5094ba3521e8142d9e7973133fMark Andrews * Permission to use, copy, modify, and/or distribute this software for any
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * purpose with or without fee is hereby granted, provided that the above
0f467ed4d4a732003941247d26f05596e25f357bAutomatic Updater * copyright notice and this permission notice appear in all copies.
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt *
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * PERFORMANCE OF THIS SOFTWARE.
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt */
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt/* $Id: lwbuffer.c,v 1.15 2007/06/19 23:47:22 tbox Exp $ */
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt/*! \file */
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt/**
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * These functions provide bounds checked access to a region of memory
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * where data is being read or written. They are based on, and similar
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * to, the isc_buffer_ functions in the ISC library.
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt *
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * A buffer is a region of memory, together with a set of related
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * subregions. The used region and the available region are disjoint, and
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * their union is the buffer's region. The used region extends from the
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * beginning of the buffer region to the last used byte. The available
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * region extends from one byte greater than the last used byte to the
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * end of the buffer's region. The size of the used region can be changed
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt * using various buffer commands. Initially, the used region is empty.
79ce3a9e82384cc31fd6b86be8f3d1474fcfd9f4Evan Hunt *
* 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);
}