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/*
This file is part of libmicrohttpd
(C) 2007 Daniel Pittman and Christian Grothoff
libmicrohttpd is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published
by the Free Software Foundation; either version 2, or (at your
option) any later version.
libmicrohttpd 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 libmicrohttpd; see the file COPYING. If not, write to the
Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.
*/
/**
* @file memorypool.c
* @brief memory pool
* @author Christian Grothoff
*/
#include "memorypool.h"
struct MemoryPool {
/**
* Pointer to the pool's memory
*/
char * memory;
/**
* Size of the pool.
*/
unsigned int size;
/**
* Offset of the first unallocated byte.
*/
unsigned int pos;
/**
* Offset of the last unallocated byte.
*/
unsigned int end;
/**
* 0 if pool was malloc'ed, 1 if mmapped.
*/
int is_mmap;
};
/**
* Create a memory pool.
*
* @param max maximum size of the pool
*/
struct MemoryPool * MHD_pool_create(unsigned int max) {
struct MemoryPool * pool;
pool = malloc(sizeof(struct MemoryPool));
if (pool == NULL)
return NULL;
pool->memory = MMAP(NULL, max, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS, -1, 0);
if ( (pool->memory == MAP_FAILED) ||
(pool->memory == NULL) ) {
pool->memory = malloc(max);
if (pool->memory == NULL) {
free(pool);
return NULL;
}
pool->is_mmap = 0;
} else {
pool->is_mmap = 1;
}
pool->pos = 0;
pool->end = max;
pool->size = max;
return pool;
}
/**
* Destroy a memory pool.
*/
void MHD_pool_destroy(struct MemoryPool * pool) {
if (pool == NULL)
return;
if (pool->is_mmap == 0)
free(pool->memory);
else
MUNMAP(pool->memory, pool->size);
free(pool);
}
/**
* Allocate size bytes from the pool.
* @return NULL if the pool cannot support size more
* bytes
*/
void * MHD_pool_allocate(struct MemoryPool * pool,
unsigned int size,
int from_end) {
void * ret;
if ( (pool->pos + size > pool->end) ||
(pool->pos + size < pool->pos) )
return NULL;
if (from_end == MHD_YES) {
ret = &pool->memory[pool->end - size];
pool->end -= size;
} else {
ret = &pool->memory[pool->pos];
pool->pos += size;
}
return ret;
}
/**
* Reallocate a block of memory obtained from the pool.
* This is particularly efficient when growing or
* shrinking the block that was last (re)allocated.
* If the given block is not the most recenlty
* (re)allocated block, the memory of the previous
* allocation may be leaked until the pool is
* destroyed (and copying the data maybe required).
*
* @param old the existing block
* @param old_size the size of the existing block
* @param new_size the new size of the block
* @return new address of the block, or
* NULL if the pool cannot support new_size
* bytes (old continues to be valid for old_size)
*/
void * MHD_pool_reallocate(struct MemoryPool * pool,
void * old,
unsigned int old_size,
unsigned int new_size) {
void * ret;
if ( (pool->end < old_size) ||
(pool->end < new_size) )
return NULL; /* unsatisfiable or bogus request */
if ( (pool->pos >= old_size) &&
(&pool->memory[pool->pos - old_size] == old) ) {
/* was the previous allocation - optimize! */
if (pool->pos + new_size - old_size <= pool->end) {
/* fits */
pool->pos += new_size - old_size;
if (new_size < old_size) /* shrinking - zero again! */
memset(&pool->memory[pool->pos],
0,
old_size - new_size);
return old;
}
/* does not fit */
return NULL;
}
if (new_size <= old_size)
return old; /* cannot shrink, no need to move */
if ( (pool->pos + new_size >= pool->pos) &&
(pool->pos + new_size <= pool->end) ) {
/* fits */
ret = &pool->memory[pool->pos];
memcpy(ret,
old,
old_size);
pool->pos += new_size;
return ret;
}
/* does not fit */
return NULL;
}
/* end of memorypool.c */
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