/*
* Copyright (c) 2012 Frantisek Princ
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* - The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/** @addtogroup libext4
* @{
*/
/**
* @file bitmap.c
* @brief Ext4 bitmap operations.
*/
#include <errno.h>
#include <block.h>
#include <stdint.h>
#include "ext4/bitmap.h"
/** Set bit in bitmap to 0 (free).
*
* Index must be checked by caller, if it's not out of bounds.
*
* @param bitmap Pointer to bitmap
* @param index Index of bit in bitmap
*
*/
void ext4_bitmap_free_bit(uint8_t *bitmap, uint32_t index)
{
uint32_t byte_index = index / 8;
uint32_t bit_index = index % 8;
uint8_t *target = bitmap + byte_index;
*target &= ~(1 << bit_index);
}
/** Free continous set of bits (set to 0).
*
* Index and count must be checked by caller, if they aren't out of bounds.
*
* @param bitmap Pointer to bitmap
* @param index Index of first bit to zeroed
* @param count Number of bits to be zeroed
*
*/
void ext4_bitmap_free_bits(uint8_t *bitmap, uint32_t index, uint32_t count)
{
uint8_t *target;
uint32_t idx = index;
uint32_t remaining = count;
uint32_t byte_index;
/* Align index to multiple of 8 */
while (((idx % 8) != 0) && (remaining > 0)) {
byte_index = idx / 8;
uint32_t bit_index = idx % 8;
target = bitmap + byte_index;
*target &= ~(1 << bit_index);
idx++;
remaining--;
}
/* For < 8 bits this check necessary */
if (remaining == 0)
return;
assert((idx % 8) == 0);
byte_index = idx / 8;
target = bitmap + byte_index;
/* Zero the whole bytes */
while (remaining >= 8) {
*target = 0;
idx += 8;
remaining -= 8;
target++;
}
assert(remaining < 8);
/* Zero remaining bytes */
while (remaining != 0) {
byte_index = idx / 8;
uint32_t bit_index = idx % 8;
target = bitmap + byte_index;
*target &= ~(1 << bit_index);
idx++;
remaining--;
}
}
/** Set bit in bitmap to 1 (used).
*
* @param bitmap Pointer to bitmap
* @param index Index of bit to set
*
*/
void ext4_bitmap_set_bit(uint8_t *bitmap, uint32_t index)
{
uint32_t byte_index = index / 8;
uint32_t bit_index = index % 8;
uint8_t *target = bitmap + byte_index;
*target |= 1 << bit_index;
}
/** Check if requested bit is free.
*
* @param bitmap Pointer to bitmap
* @param index Index of bit to be checked
*
* @return True if bit is free, else false
*
*/
bool ext4_bitmap_is_free_bit(uint8_t *bitmap, uint32_t index)
{
uint32_t byte_index = index / 8;
uint32_t bit_index = index % 8;
uint8_t *target = bitmap + byte_index;
if (*target & (1 << bit_index))
return false;
else
return true;
}
/** Try to find free byte and set the first bit as used.
*
* Walk through bitmap and try to find free byte (equal to 0).
* If byte found, set the first bit as used.
*
* @param bitmap Pointer to bitmap
* @param start Index of bit, where the algorithm will begin
* @param index Output value - index of bit (if found free byte)
* @param max Maximum index of bit in bitmap
*
* @return Error code
*
*/
errno_t ext4_bitmap_find_free_byte_and_set_bit(uint8_t *bitmap, uint32_t start,
uint32_t *index, uint32_t max)
{
uint32_t idx;
/* Align idx */
if (start % 8)
idx = start + (8 - (start % 8));
else
idx = start;
uint8_t *pos = bitmap + (idx / 8);
/* Try to find free byte */
while (idx < max) {
if (*pos == 0) {
*pos |= 1;
*index = idx;
return EOK;
}
idx += 8;
++pos;
}
/* Free byte not found */
return ENOSPC;
}
/** Try to find free bit and set it as used (1).
*
* Walk through bitmap and try to find any free bit.
*
* @param bitmap Pointer to bitmap
* @param start_idx Index of bit, where algorithm will begin
* @param index Output value - index of set bit (if found)
* @param max Maximum index of bit in bitmap
*
* @return Error code
*
*/
errno_t ext4_bitmap_find_free_bit_and_set(uint8_t *bitmap, uint32_t start_idx,
uint32_t *index, uint32_t max)
{
uint8_t *pos = bitmap + (start_idx / 8);
uint32_t idx = start_idx;
bool byte_part = false;
/* Check the rest of first byte */
while ((idx % 8) != 0) {
byte_part = true;
if ((*pos & (1 << (idx % 8))) == 0) {
*pos |= (1 << (idx % 8));
*index = idx;
return EOK;
}
++idx;
}
if (byte_part)
++pos;
/* Check the whole bytes (255 = 11111111 binary) */
while (idx < max) {
if ((*pos & 255) != 255) {
/* Free bit found */
break;
}
idx += 8;
++pos;
}
/* If idx < max, some free bit found */
if (idx < max) {
/* Check which bit from byte is free */
for (uint8_t i = 0; i < 8; ++i) {
if ((*pos & (1 << i)) == 0) {
/* Free bit found */
*pos |= (1 << i);
*index = idx;
return EOK;
}
idx++;
}
}
/* Free bit not found */
return ENOSPC;
}
/**
* @}
*/