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[/] [c0or1k/] [trunk/] [conts/] [libl4/] [src/] [lib/] [bit.c] - Blame information for rev 2

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1 2 drasko 
/*
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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 <l4lib/lib/bit.h>
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#include <stdio.h>
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#include <l4/macros.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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