/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>

#include "backed_block.h"

struct backed_block {
	unsigned int block;
	unsigned int len;
	enum backed_block_type type;
	union {
		struct {
			void *data;
		} data;
		struct {
			char *filename;
			int64_t offset;
		} file;
		struct {
			uint32_t val;
		} fill;
	};
	struct backed_block *next;
};

struct backed_block_list {
	struct backed_block *data_blocks;
	struct backed_block *last_used;
};

struct backed_block *backed_block_iter_new(struct backed_block_list *bbl)
{
	return bbl->data_blocks;
}

struct backed_block *backed_block_iter_next(struct backed_block *bb)
{
	return bb->next;
}

unsigned int backed_block_len(struct backed_block *bb)
{
	return bb->len;
}

unsigned int backed_block_block(struct backed_block *bb)
{
	return bb->block;
}

void *backed_block_data(struct backed_block *bb)
{
	assert(bb->type == BACKED_BLOCK_DATA);
	return bb->data.data;
}

const char *backed_block_filename(struct backed_block *bb)
{
	assert(bb->type == BACKED_BLOCK_FILE);
	return bb->file.filename;
}

int64_t backed_block_file_offset(struct backed_block *bb)
{
	assert(bb->type == BACKED_BLOCK_FILE);
	return bb->file.offset;
}

uint32_t backed_block_fill_val(struct backed_block *bb)
{
	assert(bb->type == BACKED_BLOCK_FILL);
	return bb->fill.val;
}

enum backed_block_type backed_block_type(struct backed_block *bb)
{
	return bb->type;
}

struct backed_block_list *backed_block_list_new(void)
{
	struct backed_block_list *b = calloc(sizeof(struct backed_block_list), 1);

	return b;
}

void backed_block_list_destroy(struct backed_block_list *bbl)
{
	if (bbl->data_blocks) {
		struct backed_block *bb = bbl->data_blocks;
		while (bb) {
			struct backed_block *next = bb->next;
			if (bb->type == BACKED_BLOCK_FILE) {
				free(bb->file.filename);
			}

			free(bb);
			bb = next;
		}
	}

	free(bbl);
}

static int queue_bb(struct backed_block_list *bbl, struct backed_block *new_bb)
{
	struct backed_block *bb;

	if (bbl->data_blocks == NULL) {
		bbl->data_blocks = new_bb;
		return 0;
	}

	if (bbl->data_blocks->block > new_bb->block) {
		new_bb->next = bbl->data_blocks;
		bbl->data_blocks = new_bb;
		return 0;
	}

	/* Optimization: blocks are mostly queued in sequence, so save the
	   pointer to the last bb that was added, and start searching from
	   there if the next block number is higher */
	if (bbl->last_used && new_bb->block > bbl->last_used->block)
		bb = bbl->last_used;
	else
		bb = bbl->data_blocks;
	bbl->last_used = new_bb;

	for (; bb->next && bb->next->block < new_bb->block; bb = bb->next)
		;

	if (bb->next == NULL) {
		bb->next = new_bb;
	} else {
		new_bb->next = bb->next;
		bb->next = new_bb;
	}

	return 0;
}

/* Queues a fill block of memory to be written to the specified data blocks */
int backed_block_add_fill(struct backed_block_list *bbl, unsigned int fill_val,
		unsigned int len, unsigned int block)
{
	struct backed_block *bb = calloc(1, sizeof(struct backed_block));
	if (bb == NULL) {
		return -ENOMEM;
	}

	bb->block = block;
	bb->len = len;
	bb->type = BACKED_BLOCK_FILL;
	bb->fill.val = fill_val;
	bb->next = NULL;

	return queue_bb(bbl, bb);
}

/* Queues a block of memory to be written to the specified data blocks */
int backed_block_add_data(struct backed_block_list *bbl, void *data,
		unsigned int len, unsigned int block)
{
	struct backed_block *bb = calloc(1, sizeof(struct backed_block));
	if (bb == NULL) {
		return -ENOMEM;
	}

	bb->block = block;
	bb->len = len;
	bb->type = BACKED_BLOCK_DATA;
	bb->data.data = data;
	bb->next = NULL;

	return queue_bb(bbl, bb);
}

/* Queues a chunk of a file on disk to be written to the specified data blocks */
int backed_block_add_file(struct backed_block_list *bbl, const char *filename,
		int64_t offset, unsigned int len, unsigned int block)
{
	struct backed_block *bb = calloc(1, sizeof(struct backed_block));
	if (bb == NULL) {
		return -ENOMEM;
	}

	bb->block = block;
	bb->len = len;
	bb->type = BACKED_BLOCK_FILE;
	bb->file.filename = strdup(filename);
	bb->file.offset = offset;
	bb->next = NULL;

	return queue_bb(bbl, bb);
}