diff options
Diffstat (limited to 'bit-radix.c')
| -rw-r--r-- | bit-radix.c | 194 |
1 files changed, 194 insertions, 0 deletions
diff --git a/bit-radix.c b/bit-radix.c new file mode 100644 index 00000000..cd5913ad --- /dev/null +++ b/bit-radix.c @@ -0,0 +1,194 @@ +#include "kerncompat.h" +#include "radix-tree.h" + +#define BIT_ARRAY_BYTES 256 +#define BIT_RADIX_BITS_PER_ARRAY ((BIT_ARRAY_BYTES - sizeof(unsigned long)) * 8) + +int set_radix_bit(struct radix_tree_root *radix, unsigned long bit) +{ + unsigned long *bits; + unsigned long slot; + int bit_slot; + int ret; + + slot = bit / BIT_RADIX_BITS_PER_ARRAY; + bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY; + + bits = radix_tree_lookup(radix, slot); + if (!bits) { + bits = malloc(BIT_ARRAY_BYTES); + if (!bits) + return -ENOMEM; + memset(bits + 1, 0, BIT_ARRAY_BYTES - sizeof(unsigned long)); + bits[0] = slot; + radix_tree_preload(GFP_NOFS); + ret = radix_tree_insert(radix, slot, bits); + radix_tree_preload_end(); + if (ret) + return ret; + } + __set_bit(bit_slot, bits + 1); + return 0; +} + +int test_radix_bit(struct radix_tree_root *radix, unsigned long bit) +{ + unsigned long *bits; + unsigned long slot; + int bit_slot; + + slot = bit / BIT_RADIX_BITS_PER_ARRAY; + bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY; + + bits = radix_tree_lookup(radix, slot); + if (!bits) + return 0; + return test_bit(bit_slot, bits + 1); +} + +int clear_radix_bit(struct radix_tree_root *radix, unsigned long bit) +{ + unsigned long *bits; + unsigned long slot; + int bit_slot; + int i; + int empty = 1; + slot = bit / BIT_RADIX_BITS_PER_ARRAY; + bit_slot = bit % BIT_RADIX_BITS_PER_ARRAY; + + bits = radix_tree_lookup(radix, slot); + if (!bits) + return 0; + __clear_bit(bit_slot, bits + 1); + for (i = 1; i < BIT_ARRAY_BYTES / sizeof(unsigned long); i++) { + if (bits[i]) { + empty = 0; + break; + } + } + if (empty) { + bits = radix_tree_delete(radix, slot); + BUG_ON(!bits); + free(bits); + } + return 0; +} + +#define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) + +/** + * __ffs - find first bit in word. + * @word: The word to search + * + * Undefined if no bit exists, so code should check against 0 first. + */ +static unsigned long __ffs(unsigned long word) +{ + int num = 0; + +#if BITS_PER_LONG == 64 + if ((word & 0xffffffff) == 0) { + num += 32; + word >>= 32; + } +#endif + if ((word & 0xffff) == 0) { + num += 16; + word >>= 16; + } + if ((word & 0xff) == 0) { + num += 8; + word >>= 8; + } + if ((word & 0xf) == 0) { + num += 4; + word >>= 4; + } + if ((word & 0x3) == 0) { + num += 2; + word >>= 2; + } + if ((word & 0x1) == 0) + num += 1; + return num; +} + +/** + * find_next_bit - find the next set bit in a memory region + * @addr: The address to base the search on + * @offset: The bitnumber to start searching at + * @size: The maximum size to search + */ +unsigned long find_next_bit(const unsigned long *addr, unsigned long size, + unsigned long offset) +{ + const unsigned long *p = addr + BITOP_WORD(offset); + unsigned long result = offset & ~(BITS_PER_LONG-1); + unsigned long tmp; + + if (offset >= size) + return size; + size -= result; + offset %= BITS_PER_LONG; + if (offset) { + tmp = *(p++); + tmp &= (~0UL << offset); + if (size < BITS_PER_LONG) + goto found_first; + if (tmp) + goto found_middle; + size -= BITS_PER_LONG; + result += BITS_PER_LONG; + } + while (size & ~(BITS_PER_LONG-1)) { + if ((tmp = *(p++))) + goto found_middle; + result += BITS_PER_LONG; + size -= BITS_PER_LONG; + } + if (!size) + return result; + tmp = *p; + +found_first: + tmp &= (~0UL >> (BITS_PER_LONG - size)); + if (tmp == 0UL) /* Are any bits set? */ + return result + size; /* Nope. */ +found_middle: + return result + __ffs(tmp); +} + +int find_first_radix_bit(struct radix_tree_root *radix, unsigned long *retbits, + unsigned long start, int nr) +{ + unsigned long *bits; + unsigned long *gang[4]; + int found; + int ret; + int i; + int total_found = 0; + unsigned long slot; + + slot = start / BIT_RADIX_BITS_PER_ARRAY; + ret = radix_tree_gang_lookup(radix, (void **)gang, slot, + ARRAY_SIZE(gang)); + for (i = 0; i < ret && nr > 0; i++) { + found = 0; + bits = gang[i]; + while(nr > 0) { + found = find_next_bit(bits + 1, + BIT_RADIX_BITS_PER_ARRAY, + found); + if (found < BIT_RADIX_BITS_PER_ARRAY) { + *retbits = bits[0] * + BIT_RADIX_BITS_PER_ARRAY + found; + retbits++; + nr--; + total_found++; + found++; + } else + break; + } + } + return total_found; +} |