/* * Ouroboros - Copyright (C) 2016 * * Bitmap implementation - taken partly from Linux kernel * * Sander Vrijders <sander.vrijders@intec.ugent.be> * Francesco Salvestrini <f.salvestrini@nextworks.it> * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License version 2 as * published by the Free Software Foundation. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #define OUROBOROS_PREFIX "bitmap" #include <ouroboros/bitmap.h> #include <ouroboros/logs.h> #include <assert.h> #include <stdlib.h> #include <string.h> #include <limits.h> #define BITS_PER_BYTE CHAR_BIT #define BITS_PER_LONG (sizeof(size_t) * BITS_PER_BYTE) #define BIT_WORD(nr) ((nr) / BITS_PER_LONG) #define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d)) #define BITS_TO_LONGS(nr) \ DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(size_t)) static size_t find_next_zero_bit(const size_t * addr, size_t nbits) { size_t tmp; size_t start = 0; size_t pos = 0; size_t mask; /* First find correct word */ tmp = ~addr[start]; while (!tmp) { start++; if (start >= (nbits / BITS_PER_LONG)) return nbits; tmp = ~addr[start]; } /* Find the free bit in the word */ mask = 1UL; while (!(tmp & mask)) { pos++; mask = 1UL << pos; } return (start * BITS_PER_LONG) + pos; } static void bitmap_zero(size_t * dst, size_t nbits) { size_t len = BITS_TO_LONGS(nbits) * sizeof(size_t); memset(dst, 0, len); } static void bitmap_clear(size_t * map, size_t start) { size_t * p = map + BIT_WORD(start); size_t mask = ~(1UL << (start % (BITS_PER_LONG))); *p &= mask; } static void bitmap_set(size_t * map, size_t start) { size_t * p = map + BIT_WORD(start); size_t mask = 1UL << (start % (BITS_PER_LONG)); *p |= mask; } struct bmp { ssize_t offset; size_t size; size_t * bitmap; }; struct bmp * bmp_create(size_t bits, ssize_t offset) { struct bmp * tmp; if (bits == 0) return NULL; tmp = malloc(sizeof(*tmp)); if (tmp == NULL) return NULL; tmp->bitmap = malloc(BITS_TO_LONGS(bits) * sizeof(size_t)); if (tmp->bitmap == NULL) { free(tmp); return NULL; } tmp->size = bits; tmp->offset = offset; bitmap_zero(tmp->bitmap, bits); return tmp; } int bmp_destroy(struct bmp * b) { if (b == NULL) return -1; if (b->bitmap == NULL) { free(b); return -1; } free(b->bitmap); free(b); return 0; } static ssize_t bad_id(struct bmp * b) { if (b == NULL) return -1; return b->offset - 1; } ssize_t bmp_allocate(struct bmp * b) { size_t id; if (b == NULL) return -1; id = find_next_zero_bit(b->bitmap, b->size); if (id >= b->size) return bad_id(b); bitmap_set(b->bitmap, id); return id + b->offset; } static bool is_id_valid(struct bmp * b, ssize_t id) { assert(b); if ((id < b->offset) || (id > (ssize_t) (b->offset + b->size))) return false; return true; } bool bmp_is_id_valid(struct bmp * b, ssize_t id) { if (b == NULL) return false; return is_id_valid(b, id); } int bmp_release(struct bmp * b, ssize_t id) { size_t rid; if (b == NULL) return -1; if (!is_id_valid(b, id)) return -1; rid = id - b->offset; bitmap_clear(b->bitmap, rid); return 0; }