/*
 * Copyright (C) 1998, 1999  Internet Software Consortium.
 * 
 * Permission to use, copy, modify, and 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

#include <config.h>

#include <string.h>

#include <isc/assertions.h>
#include <isc/buffer.h>

#define VALID_BUFFER(b)			((b) != NULL && \
					 (b)->magic == BUFFER_MAGIC)
#define BUFFER_MAGIC			0x42756621U	/* Buf!. */

void
isc_buffer_init(isc_buffer_t *b, void *base, unsigned int length,
		unsigned int type) {
	/*
	 * Make 'b' refer to the 'length'-byte region starting at base.
	 */

	REQUIRE(b != NULL);

	b->magic = BUFFER_MAGIC;
	b->type = type;
	b->base = base;
	b->length = length;
	b->used = 0;
	b->current = 0;
	b->active = 0;
}

void
isc_buffer_invalidate(isc_buffer_t *b) {
	/*
	 * Make 'b' an invalid buffer.
	 */

	REQUIRE(VALID_BUFFER(b));
	
	b->magic = 0;
	b->type = 0;
	b->base = NULL;
	b->length = 0;
	b->used = 0;
	b->current = 0;
	b->active = 0;
}

unsigned int
isc_buffer_type(isc_buffer_t *b) {
	/*
	 * The type of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));

	return (b->type);
}

void
isc_buffer_region(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	r->base = b->base;
	r->length = b->length;
}

void
isc_buffer_used(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the used region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	r->base = b->base;
	r->length = b->used;
}

void
isc_buffer_available(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the available region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	r->base = (unsigned char *)b->base + b->used;
	r->length = b->length - b->used;
}


void
isc_buffer_add(isc_buffer_t *b, unsigned int n) {
	/*
	 * Increase the 'used' region of 'b' by 'n' bytes.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(b->used + n <= b->length);

	b->used += n;
}

void
isc_buffer_subtract(isc_buffer_t *b, unsigned int n) {
	/*
	 * Decrease the 'used' region of 'b' by 'n' bytes.
	 */

	REQUIRE(VALID_BUFFER(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;
}

void
isc_buffer_clear(isc_buffer_t *b) {
	/*
	 * Make the used region empty.
	 */

	REQUIRE(VALID_BUFFER(b));

	b->used = 0;
	b->current = 0;
	b->active = 0;
}

void
isc_buffer_consumed(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the consumed region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	r->base = b->base;
	r->length = b->current;
}

void
isc_buffer_remaining(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the remaining region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	r->base = (unsigned char *)b->base + b->current;
	r->length = b->used - b->current;
}

void
isc_buffer_active(isc_buffer_t *b, isc_region_t *r) {
	/*
	 * Make 'r' refer to the active region of 'b'.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(r != NULL);

	if (b->current < b->active) {
		r->base = (unsigned char *)b->base + b->current;
		r->length = b->active - b->current;
	} else {
		r->base = NULL;
		r->length = 0;
	}
}

void
isc_buffer_setactive(isc_buffer_t *b, unsigned int n) {
	unsigned int active;

	/*
	 * Sets the end of the active region 'n' bytes after current.
	 */

	REQUIRE(VALID_BUFFER(b));
	active = b->current + n;
	REQUIRE(active <= b->used);

	b->active = active;
}

void
isc_buffer_first(isc_buffer_t *b) {
	/*
	 * Make the consumed region empty.
	 */

	REQUIRE(VALID_BUFFER(b));

	b->current = 0;
}

void
isc_buffer_forward(isc_buffer_t *b, unsigned int n) {
	/*
	 * Increase the 'consumed' region of 'b' by 'n' bytes.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(b->current + n <= b->used);

	b->current += n;
}

void
isc_buffer_back(isc_buffer_t *b, unsigned int n) {
	/*
	 * Decrease the 'consumed' region of 'b' by 'n' bytes.
	 */

	REQUIRE(VALID_BUFFER(b));
	REQUIRE(n <= b->current);

	b->current -= n;
}

void
isc_buffer_compact(isc_buffer_t *b) {
	unsigned int length;
	void *src;

	/*
	 * Compact the used region by moving the remaining region so it occurs
	 * at the start of the buffer.  The used region is shrunk by the size
	 * of the consumed region, and the consumed region is then made empty.
	 */

	REQUIRE(VALID_BUFFER(b));

	src = (unsigned char *)b->base + b->current;
	length = b->used - b->current;
	(void)memmove(b->base, src, (size_t)length);

	if (b->active > b->current)
		b->active -= b->current;
	else
		b->active = 0;
	b->current = 0;
	b->used = length;
}

isc_uint16_t
isc_buffer_getuint16(isc_buffer_t *b) {
	unsigned char *cp;
	isc_uint16_t result;

	/*
	 * Read an unsigned 16-bit integer in network byte order from 'b',
	 * convert it to host byte order, and return it.
	 */

	REQUIRE(VALID_BUFFER(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);
}

isc_uint32_t
isc_buffer_getuint32(isc_buffer_t *b) {
	unsigned char *cp;
	isc_uint32_t result;

	/*
	 * Read an unsigned 32-bit integer in network byte order from 'b',
	 * convert it to host byte order, and return it.
	 */

	REQUIRE(VALID_BUFFER(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);
}