115 lines
3.1 KiB
C
115 lines
3.1 KiB
C
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#include <defs.h>
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#include <string.h>
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#include <bitmap.h>
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#include <kmalloc.h>
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#include <error.h>
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#include <assert.h>
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#define WORD_TYPE uint32_t
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#define WORD_BITS (sizeof(WORD_TYPE) * CHAR_BIT)
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struct bitmap {
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uint32_t nbits;
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uint32_t nwords;
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WORD_TYPE *map;
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};
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// bitmap_create - allocate a new bitmap object.
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struct bitmap *
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bitmap_create(uint32_t nbits) {
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static_assert(WORD_BITS != 0);
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assert(nbits != 0 && nbits + WORD_BITS > nbits);
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struct bitmap *bitmap;
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if ((bitmap = kmalloc(sizeof(struct bitmap))) == NULL) {
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return NULL;
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}
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uint32_t nwords = ROUNDUP_DIV(nbits, WORD_BITS);
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WORD_TYPE *map;
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if ((map = kmalloc(sizeof(WORD_TYPE) * nwords)) == NULL) {
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kfree(bitmap);
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return NULL;
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}
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bitmap->nbits = nbits, bitmap->nwords = nwords;
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bitmap->map = memset(map, 0xFF, sizeof(WORD_TYPE) * nwords);
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/* mark any leftover bits at the end in use(0) */
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if (nbits != nwords * WORD_BITS) {
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uint32_t ix = nwords - 1, overbits = nbits - ix * WORD_BITS;
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assert(nbits / WORD_BITS == ix);
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assert(overbits > 0 && overbits < WORD_BITS);
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for (; overbits < WORD_BITS; overbits ++) {
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bitmap->map[ix] ^= (1 << overbits);
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}
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}
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return bitmap;
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}
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// bitmap_alloc - locate a cleared bit, set it, and return its index.
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int
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bitmap_alloc(struct bitmap *bitmap, uint32_t *index_store) {
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WORD_TYPE *map = bitmap->map;
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uint32_t ix, offset, nwords = bitmap->nwords;
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for (ix = 0; ix < nwords; ix ++) {
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if (map[ix] != 0) {
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for (offset = 0; offset < WORD_BITS; offset ++) {
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WORD_TYPE mask = (1 << offset);
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if (map[ix] & mask) {
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map[ix] ^= mask;
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*index_store = ix * WORD_BITS + offset;
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return 0;
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}
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}
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assert(0);
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}
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}
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return -E_NO_MEM;
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}
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// bitmap_translate - according index, get the related word and mask
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static void
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bitmap_translate(struct bitmap *bitmap, uint32_t index, WORD_TYPE **word, WORD_TYPE *mask) {
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assert(index < bitmap->nbits);
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uint32_t ix = index / WORD_BITS, offset = index % WORD_BITS;
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*word = bitmap->map + ix;
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*mask = (1 << offset);
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}
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// bitmap_test - according index, get the related value (0 OR 1) in the bitmap
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bool
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bitmap_test(struct bitmap *bitmap, uint32_t index) {
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WORD_TYPE *word, mask;
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bitmap_translate(bitmap, index, &word, &mask);
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return (*word & mask);
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}
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// bitmap_free - according index, set related bit to 1
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void
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bitmap_free(struct bitmap *bitmap, uint32_t index) {
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WORD_TYPE *word, mask;
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bitmap_translate(bitmap, index, &word, &mask);
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assert(!(*word & mask));
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*word |= mask;
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}
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// bitmap_destroy - free memory contains bitmap
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void
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bitmap_destroy(struct bitmap *bitmap) {
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kfree(bitmap->map);
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kfree(bitmap);
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}
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// bitmap_getdata - return bitmap->map, return the length of bits to len_store
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void *
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bitmap_getdata(struct bitmap *bitmap, size_t *len_store) {
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if (len_store != NULL) {
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*len_store = sizeof(WORD_TYPE) * bitmap->nwords;
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}
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return bitmap->map;
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}
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