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https://github.com/drasko/codezero.git
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111 lines
2.2 KiB
C
111 lines
2.2 KiB
C
/*
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* Bit manipulation functions.
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*
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* Copyright (C) 2007 Bahadir Balban
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*/
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#include <lib/bit.h>
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#include <l4/macros.h>
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#include <l4/config.h>
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#include <stdio.h>
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#include INC_GLUE(memory.h)
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/* Emulation of ARM's CLZ (count leading zeroes) instruction */
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unsigned int __clz(unsigned int bitvector)
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{
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unsigned int x = 0;
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while((!(bitvector & ((unsigned)1 << 31))) && (x < 32)) {
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bitvector <<= 1;
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x++;
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}
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return x;
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}
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int find_and_set_first_free_bit(u32 *word, unsigned int limit)
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{
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int success = 0;
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int i;
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for(i = 0; i < limit; i++) {
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/* Find first unset bit */
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if (!(word[BITWISE_GETWORD(i)] & BITWISE_GETBIT(i))) {
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/* Set it */
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word[BITWISE_GETWORD(i)] |= BITWISE_GETBIT(i);
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success = 1;
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break;
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}
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}
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/* Return bit just set */
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if (success)
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return i;
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else
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return -1;
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}
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int find_and_set_first_free_contig_bits(u32 *word, unsigned int limit,
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int nbits)
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{
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int i = 0, first = 0, last = 0, found = 0;
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/* Can't allocate more than the limit */
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if (nbits > limit)
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return -1;
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/* This is a state machine that checks n contiguous free bits. */
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while (i + nbits <= limit) {
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first = i;
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last = i;
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while (!(word[BITWISE_GETWORD(last)] & BITWISE_GETBIT(last))) {
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last++;
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i++;
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if (last == first + nbits) {
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found = 1;
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break;
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}
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}
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if (found)
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break;
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i++;
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}
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/* If found, set the bits */
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if (found) {
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for (int x = first; x < first + nbits; x++)
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word[BITWISE_GETWORD(x)] |= BITWISE_GETBIT(x);
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return first;
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} else
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return -1;
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}
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int check_and_clear_bit(u32 *word, int bit)
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{
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/* Check that bit was set */
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if (word[BITWISE_GETWORD(bit)] & BITWISE_GETBIT(bit)) {
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word[BITWISE_GETWORD(bit)] &= ~BITWISE_GETBIT(bit);
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return 0;
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} else {
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printf("Trying to clear already clear bit\n");
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return -1;
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}
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}
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int check_and_set_bit(u32 *word, int bit)
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{
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/* Check that bit was clear */
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if (!(word[BITWISE_GETWORD(bit)] & BITWISE_GETBIT(bit))) {
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word[BITWISE_GETWORD(bit)] |= BITWISE_GETBIT(bit);
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return 0;
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} else {
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//printf("Trying to set already set bit\n");
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return -1;
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}
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}
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int check_and_clear_contig_bits(u32 *word, int first, int nbits)
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{
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for (int i = first; i < first + nbits; i++)
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if (check_and_clear_bit(word, i) < 0)
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return -1;
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return 0;
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}
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