/*
 * This file is part of LibParserUtils.
 * Licensed under the MIT License,
 *                http://www.opensource.org/licenses/mit-license.php
 * Copyright 2008 John-Mark Bell <jmb@netsurf-browser.org>
 */

#include <string.h>

#include <parserutils/utils/buffer.h>

#define DEFAULT_SIZE (4096)

/**
 * Create a memory buffer
 *
 * \param alloc  Memory (de)allocation function
 * \param pw     Pointer to client-specific private data
 * \return Pointer to memory buffer, or NULL on memory exhaustion
 */
parserutils_buffer *parserutils_buffer_create(parserutils_alloc alloc, void *pw)
{
	parserutils_buffer *buffer = 
			alloc(NULL, sizeof(parserutils_buffer), pw);

	if (buffer == NULL)
		return NULL;

	buffer->data = alloc(NULL, DEFAULT_SIZE, pw);
	if (buffer->data == NULL) {
		alloc(buffer, 0, pw);
		return NULL;
	}

	buffer->length = 0;
	buffer->allocated = DEFAULT_SIZE;

	buffer->alloc = alloc;
	buffer->pw = pw;

	return buffer;
}

/**
 * Destroy a memory buffer
 *
 * \param buffer  The buffer to destroy
 */
void parserutils_buffer_destroy(parserutils_buffer *buffer)
{
	if (buffer == NULL)
		return;

	buffer->alloc(buffer->data, 0, buffer->pw);
	buffer->alloc(buffer, 0, buffer->pw);
}

/**
 * Append data to a memory buffer
 *
 * \param buffer  The buffer to append to
 * \param data    The data to append
 * \param len     The length, in bytes, of the data to append
 * \return PARSERUTILS_OK on success, appropriate error otherwise.
 */
parserutils_error parserutils_buffer_append(parserutils_buffer *buffer, 
		const uint8_t *data, size_t len)
{
	while (len >= buffer->allocated - buffer->length) {
		parserutils_error error = parserutils_buffer_grow(buffer);
		if (error != PARSERUTILS_OK)
			return error;
	}

	memcpy(buffer->data + buffer->length, data, len);

	buffer->length += len;

	return PARSERUTILS_OK;
}

/**
 * Insert data into a memory buffer
 *
 * \param buffer  The buffer to insert into
 * \param offset  The offset into the buffer to insert at
 * \param data    The data to insert
 * \param len     The length, in bytes, of the data to insert
 * \return PARSERUTILS_OK on success, appropriate error otherwise
 */
parserutils_error parserutils_buffer_insert(parserutils_buffer *buffer, 
		size_t offset, const uint8_t *data, size_t len)
{
	if (offset > buffer->length)
		return PARSERUTILS_BADPARM;

	if (offset == buffer->length)
		return parserutils_buffer_append(buffer, data, len);

	while (len >= buffer->allocated - buffer->length) {
		parserutils_error error = parserutils_buffer_grow(buffer);
		if (error != PARSERUTILS_OK)
			return error;
	}

	memmove(buffer->data + buffer->length + len, 
			buffer->data + offset, buffer->length - offset);

	memcpy(buffer->data + offset, data, len);

	buffer->length += len;

	return PARSERUTILS_OK;
}

/**
 * Discard a section of a memory buffer
 *
 * \param buffer  The buffer to discard data from
 * \param offset  The offset into the buffer of the start of the section
 * \param len     The number of bytes to discard
 * \return PARSERUTILS_OK on success, appropriate error otherwise.
 */
parserutils_error parserutils_buffer_discard(parserutils_buffer *buffer, 
		size_t offset, size_t len)
{
	if (offset >= buffer->length || offset + len > buffer->length)
		return PARSERUTILS_BADPARM;

	memmove(buffer->data + offset, buffer->data + offset + len, 
			buffer->length - len);

	buffer->length -= len;

	return PARSERUTILS_OK;
}

/**
 * Extend the amount of space allocated for a memory buffer
 *
 * \param buffer  The buffer to extend
 * \return PARSERUTILS_OK on success, appropriate error otherwise.
 */
parserutils_error parserutils_buffer_grow(parserutils_buffer *buffer)
{
	uint8_t *temp = buffer->alloc(buffer->data, 
			buffer->allocated * 2, buffer->pw);
	if (temp == NULL)
		return PARSERUTILS_NOMEM;

	buffer->data = temp;
	buffer->allocated *= 2;

	return PARSERUTILS_OK;
}