Rickey Fehr
43 lines
1.4 KiB
C
43 lines
1.4 KiB
C
#include "pool.h"
|
|
|
|
void pool_bm_clear_idx(PoolBitmap *bm, int idx)
|
|
{
|
|
// Divide by 32 to get the word index
|
|
uint32_t i = idx >> 5;
|
|
// Get last 5-bits, same as a modulo (% 32) operation on positive numbers
|
|
uint32_t b = idx & 0x1F;
|
|
bm->w[i] &= ~((uint32_t)1 << b);
|
|
}
|
|
|
|
int pool_bm_get_free_idx(PoolBitmap *bm)
|
|
{
|
|
for (uint32_t i = 0; i < bm->nwords; i++)
|
|
{
|
|
uint32_t inv = ~bm->w[i];
|
|
|
|
// guard so we don't call `ctz` with 0, since __builtin_ctz(0) is undefined
|
|
// https://gcc.gnu.org/onlinedocs/gcc/Bit-Operation-Builtins.html#index-_005f_005fbuiltin_005fctz
|
|
//
|
|
// By using the bitwise inverse of the word, you can skip words that are full
|
|
// quickly (where the value is 0 or 'false' since all bits are '1', or 'in use'). Any value greater
|
|
// than 0 indicates there is a free slot. Then, when counting the trailing 0's, you can test very quickly
|
|
// where the first free slot is. This operation prevents looping through every bit of filled flags, and
|
|
// will instead operate only on the first word with free slots.
|
|
if (inv)
|
|
{
|
|
int bit = __builtin_ctz(inv);
|
|
bm->w[i] |= ((uint32_t)1 << bit);
|
|
int idx = i * POOL_BITS_PER_WORD + bit;
|
|
return (idx < bm->cap) ? idx : -1;
|
|
}
|
|
}
|
|
|
|
return -1;
|
|
}
|
|
|
|
|
|
#define POOL_ENTRY(name, capacity) \
|
|
POOL_DEFINE_TYPE(name, capacity);
|
|
#include POOLS_DEF_FILE
|
|
#undef POOL_ENTRY
|