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/*
* Memory Pool implementation logic.
*/
#include "git-compat-util.h"
#include "mem-pool.h"
#define BLOCK_GROWTH_SIZE (1024 * 1024 - sizeof(struct mp_block))
/*
* The inner union is an approximation for C11's max_align_t, and the
* struct + offsetof computes _Alignof. This can all just be replaced
* with _Alignof(max_align_t) if/when C11 is part of the baseline.
* Note that _Alignof(X) need not be the same as sizeof(X); it's only
* required to be a (possibly trivial) factor. They are the same for
* most architectures, but m68k for example has only 2-byte alignment
* for its 4-byte and 8-byte types, so using sizeof would waste space.
*
* Add more types to the union if the current set is insufficient.
*/
struct git_max_alignment {
char unalign;
union {
uintmax_t max_align_uintmax;
void *max_align_pointer;
} aligned;
};
#define GIT_MAX_ALIGNMENT offsetof(struct git_max_alignment, aligned)
/*
* Allocate a new mp_block and insert it after the block specified in
* `insert_after`. If `insert_after` is NULL, then insert block at the
* head of the linked list.
*/
static struct mp_block *mem_pool_alloc_block(struct mem_pool *pool,
size_t block_alloc,
struct mp_block *insert_after)
{
struct mp_block *p;
pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
p->next_free = (char *)p->space;
p->end = p->next_free + block_alloc;
if (insert_after) {
p->next_block = insert_after->next_block;
insert_after->next_block = p;
} else {
p->next_block = pool->mp_block;
pool->mp_block = p;
}
return p;
}
void mem_pool_init(struct mem_pool *pool, size_t initial_size)
{
memset(pool, 0, sizeof(*pool));
pool->block_alloc = BLOCK_GROWTH_SIZE;
if (initial_size > 0)
mem_pool_alloc_block(pool, initial_size, NULL);
}
void mem_pool_discard(struct mem_pool *pool, int invalidate_memory)
{
struct mp_block *block, *block_to_free;
block = pool->mp_block;
while (block)
{
block_to_free = block;
block = block->next_block;
if (invalidate_memory)
memset(block_to_free->space, 0xDD, ((char *)block_to_free->end) - ((char *)block_to_free->space));
free(block_to_free);
}
pool->mp_block = NULL;
pool->pool_alloc = 0;
}
void *mem_pool_alloc(struct mem_pool *pool, size_t len)
{
struct mp_block *p = NULL;
void *r;
/* round up to a 'GIT_MAX_ALIGNMENT' alignment */
if (len & (GIT_MAX_ALIGNMENT - 1))
len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
if (pool->mp_block &&
pool->mp_block->end - pool->mp_block->next_free >= len)
p = pool->mp_block;
if (!p) {
if (len >= (pool->block_alloc / 2))
return mem_pool_alloc_block(pool, len, pool->mp_block);
p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
}
r = p->next_free;
p->next_free += len;
return r;
}
void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
{
size_t len = st_mult(count, size);
void *r = mem_pool_alloc(pool, len);
memset(r, 0, len);
return r;
}
char *mem_pool_strdup(struct mem_pool *pool, const char *str)
{
size_t len = strlen(str) + 1;
char *ret = mem_pool_alloc(pool, len);
return memcpy(ret, str, len);
}
char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
{
char *p = memchr(str, '\0', len);
size_t actual_len = (p ? p - str : len);
char *ret = mem_pool_alloc(pool, actual_len+1);
ret[actual_len] = '\0';
return memcpy(ret, str, actual_len);
}
int mem_pool_contains(struct mem_pool *pool, void *mem)
{
struct mp_block *p;
/* Check if memory is allocated in a block */
for (p = pool->mp_block; p; p = p->next_block)
if ((mem >= ((void *)p->space)) &&
(mem < ((void *)p->end)))
return 1;
return 0;
}
void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
{
struct mp_block *p;
/* Append the blocks from src to dst */
if (dst->mp_block && src->mp_block) {
/*
* src and dst have blocks, append
* blocks from src to dst.
*/
p = dst->mp_block;
while (p->next_block)
p = p->next_block;
p->next_block = src->mp_block;
} else if (src->mp_block) {
/*
* src has blocks, dst is empty.
*/
dst->mp_block = src->mp_block;
} else {
/* src is empty, nothing to do. */
}
dst->pool_alloc += src->pool_alloc;
src->pool_alloc = 0;
src->mp_block = NULL;
}
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