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/* PIPAPO - PIle PAcket POlicies
*
* util.c - Convenience routines
*
* Author: Stefano Brivio <sbrivio@redhat.com>
* License: GPLv2
*/
#include <stdint.h>
#include <string.h>
#include <strings.h>
#include "pipapo.h"
/**
* set_bit() - Set single bit in arbitrary-sized word
* @data: Word
* @n: Bit number
*
* Equivalent to set_bit() in kernel.
*/
void set_bit(uint8_t *data, int n)
{
data[n / 8] |= 1 << (n % 8);
}
/**
* bit_sum() - Sum bit to arbitrary-sized word with carry
* @v: Word
* @n: Bit number
* @len: Word length
*/
void bit_sum(uint8_t *v, int n, int len)
{
int carry = 0, i;
for (i = len - 1 - n / 8; i >= 0; i--) {
if (carry)
v[i]++;
else
v[i] += 1 << (n % 8);
if (v[i])
break;
carry = 1;
}
}
/**
* bit_sub() - Subtract bit from arbitrary-sized word with carry
* @v: Word
* @n: Bit number
* @len: Word length
*/
void bit_sub(uint8_t *v, int n, int len)
{
int carry = 0, i;
for (i = len - 1 - n / 8; i >= 0; i--) {
if (carry)
v[i]--;
else
v[i] -= 1 << (n % 8);
if (v[i] != 0xff)
break;
carry = 1;
}
}
/**
* andmem() - AND two memory regions
* @dst: First operand and destination
* @src: Second operand
* @len: Length of memory region
*
* Equivalent to bitmap_and() in kernel.
*/
void andmem(uint8_t *dst, uint8_t *src, unsigned len)
{
while (len >= sizeof(long)) {
*(unsigned long *)dst &= *(unsigned long *)src;
dst += sizeof(long);
src += sizeof(long);
len -= sizeof(long);
}
while (len >= sizeof(int)) {
*(unsigned int *)dst &= *(unsigned int *)src;
dst += sizeof(int);
src += sizeof(int);
len -= sizeof(int);
}
while (len--) {
*dst &= *src;
dst++;
src++;
}
}
/**
* ffs_clear() - Find first bit set in memory region and clear it
* @data: Start of memory region
* @len: Length of memory region
* @offset: Starting offset in byte
*
* Similar purpose as for_each_set_bit_from() in kernel.
*
* Return: position of first set bit, if any, -1 otherwise
*/
int ffs_clear(uint8_t *data, unsigned int len, int byte_offset)
{
int tmp = 0, n, c = byte_offset;
data += byte_offset;
len -= byte_offset;
while (len) {
if (len >= sizeof(long)) {
n = ffsl(*(unsigned long *)data);
if (n--) {
*((unsigned long *)data) &= ~(1UL << n);
return n + c * 8;
}
len -= sizeof(long);
data += sizeof(long);
c += sizeof(long);
} else if (len >= sizeof(int)) {
n = ffs(*(unsigned int *)data);
if (n--) {
*((unsigned int *)data) &= ~(1U << n);
return n + c * 8;
}
len -= sizeof(int);
data += sizeof(int);
c += sizeof(int);
} else {
memcpy(&tmp, data, len);
n = ffs(tmp);
if (n--) {
data[n / 8] &= ~(1U << (n % 8));
return n + c * 8;
}
return -1;
}
}
return -1;
}
/**
* test_bit - Test bit in memory region
* @data: Memory region
* @n: Bit to be tested
*
* Equivalent to test_bit() in kernel.
*
* Return: 1 if bit set, 0 if bit unset.
*/
int test_bit(uint8_t *data, int n)
{
return !!(data[n / 8] & (1 << (n % 8)));
}
/**
* fold_bits() - Shift a bitmap region, removing a given amount of bits
* @data: Memory region
* @first: First bit to be removed
* @n: Amount of bits to be removed
* @len: Size of memory region
*
* Similar to bitmap_shift_left() in kernel, *not* equivalent to bitmap_fold().
* For example, with this bitmap, if start is 7 and n is 4:
*
* 1000 0110 1100 0001
* | | | |
* 7 0 15 8
*
* we are removing these four bits:
*
* x000 0110 1100 0xxx
* | | | |
* 7 0 15 8
*
* resulting in:
*
* 0000 0110 0000 1100
* | | | |
* 7 0 15 8
*/
void fold_bits(uint8_t *data, int first, int n, int len)
{
uint8_t keep, carry;
int i;
if (first % 8)
keep = data[first / 8] & (0xff >> (8 - first % 8));
else
keep = 0;
while (n) {
for (i = first / 8; i < len; i++) {
if (i < len - 1)
carry = data[i + 1] & 0x01;
else
carry = 0;
data[i] >>= 1;
data[i] |= carry << 7;
}
n--;
}
data[first / 8] &= 0xff << (first % 8);
data[first / 8] |= keep;
}
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