/* malloc.c - C standard library routine. Copyright (c) 1989, 1993 Michael J. Haertel You may redistribute this library under the terms of the GNU Library General Public License (version 2 or any later version) as published by the Free Software Foundation. THIS SOFTWARE IS PROVIDED "AS IS" WITHOUT ANY EXPRESS OR IMPLIED WARRANTY. IN PARTICULAR, THE AUTHOR MAKES NO REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE. */ #define _GNU_SOURCE #include <features.h> #include <limits.h> #include <stddef.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include "malloc.h" #ifdef __UCLIBC_HAS_THREADS__ #include <pthread.h> extern pthread_mutex_t __malloclock; # define LOCK pthread_mutex_lock(&__malloclock) # define UNLOCK pthread_mutex_unlock(&__malloclock); #else # define LOCK # define UNLOCK #endif /* Resize the given region to the new size, returning a pointer to the (possibly moved) region. This is optimized for speed; some benchmarks seem to indicate that greater compactness is achieved by unconditionally allocating and copying to a new region. */ void * realloc (void *ptr, size_t size) { void *result, *previous; size_t block, blocks, type; size_t oldlimit; if (!ptr) return malloc(size); if (!size) { LOCK; __free_unlocked(ptr); result = __malloc_unlocked(0); UNLOCK; return(result); } LOCK; block = BLOCK(ptr); switch (type = _heapinfo[block].busy.type) { case 0: /* Maybe reallocate a large block to a small fragment. */ if (size <= BLOCKSIZE / 2) { if ((result = __malloc_unlocked(size)) != NULL) { memcpy(result, ptr, size); __free_unlocked(ptr); } UNLOCK; return result; } /* The new size is a large allocation as well; see if we can hold it in place. */ blocks = BLOCKIFY(size); if (blocks < _heapinfo[block].busy.info.size) { /* The new size is smaller; return excess memory to the free list. */ _heapinfo[block + blocks].busy.type = 0; _heapinfo[block + blocks].busy.info.size = _heapinfo[block].busy.info.size - blocks; _heapinfo[block].busy.info.size = blocks; __free_unlocked(ADDRESS(block + blocks)); UNLOCK; return ptr; } else if (blocks == _heapinfo[block].busy.info.size) { /* No size change necessary. */ UNLOCK; return ptr; } else { /* Won't fit, so allocate a new region that will. Free the old region first in case there is sufficient adjacent free space to grow without moving. */ blocks = _heapinfo[block].busy.info.size; /* Prevent free from actually returning memory to the system. */ oldlimit = _heaplimit; _heaplimit = 0; __free_unlocked(ptr); _heaplimit = oldlimit; result = __malloc_unlocked(size); if (!result) { /* Now we're really in trouble. We have to unfree the thing we just freed. Unfortunately it might have been coalesced with its neighbors. */ if (_heapindex == block) __malloc_unlocked(blocks * BLOCKSIZE); else { previous = __malloc_unlocked((block - _heapindex) * BLOCKSIZE); __malloc_unlocked(blocks * BLOCKSIZE); __free_unlocked(previous); } UNLOCK; return NULL; } if (ptr != result) memmove(result, ptr, blocks * BLOCKSIZE); UNLOCK; return result; } break; default: /* Old size is a fragment; type is logarithm to base two of the fragment size. */ if ((size > 1 << (type - 1)) && (size <= 1 << type)) { /* New size is the same kind of fragment. */ UNLOCK; return ptr; } else { /* New size is different; allocate a new space, and copy the lesser of the new size and the old. */ result = __malloc_unlocked(size); if (!result) { UNLOCK; return NULL; } memcpy(result, ptr, MIN(size, (size_t)(1 << type))); __free_unlocked(ptr); UNLOCK; return result; } break; } UNLOCK; }