u-boot/common/dlmalloc.c

221   INTERNAL_SIZE_T prev_size; /* Size of previous chunk (if free). */
239     in the front of each chunk and at the end.  This makes
244     An allocated chunk looks like this:
247     chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
248 	    |             Size of previous chunk, if allocated            | |
250 	    |             Size of chunk, in bytes                         |P|
257 	    |             Size of chunk                                     |
261     Where "chunk" is the front of the chunk for the purpose of most of
263     user.  "Nextchunk" is the beginning of the next contiguous chunk.
271     chunk-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
272 	    |             Size of previous chunk                            |
274     `head:' |             Size of chunk, in bytes                         |P|
276 	    |             Forward pointer to next chunk in list             |
278 	    |             Back pointer to previous chunk in list            |
284     `foot:' |             Size of chunk, in bytes                           |
288     chunk size (which is always a multiple of two words), is an in-use
289     bit for the *previous* chunk.  If that bit is *clear*, then the
290     word before the current chunk size contains the previous chunk
291     size, and can be used to find the front of the previous chunk.
292     (The very first chunk allocated always has this bit set,
295     Note that the `foot' of the current chunk is actually represented
296     as the prev_size of the NEXT chunk. (This makes it easier to
301      1. The special chunk `top', which doesn't bother using the
303 	next contiguous chunk that would have to index off it. (After
310 	never merged or traversed from any other chunk, they have no
320        consolidated chunk physically borders another one. Chunks in
322        approximately least recently used chunk.
332        order, which tends to give each chunk an equal opportunity to be
336     * `top': The top-most available chunk (i.e., the one bordering the
338        included in any bin, is used only if no other chunk is
343        most recently split (non-top) chunk. This bin is checked
380   Physical chunk operations
384 /* size field is or'ed with PREV_INUSE when previous adjacent chunk in use */
388 /* size field is or'ed with IS_MMAPPED if the chunk was obtained with mmap() */
407 /* Treat space at ptr + offset as a chunk */
423 /* extract inuse bit of previous chunk */
427 /* check for mmap()'ed chunk */
431 /* set/clear chunk as in use without otherwise disturbing */
469 /* Set size at footer (only when chunk is not in use) */
527 #define top            (av_[2])          /* The topmost chunk */
736   /* No checkable chunk is mmapped */
796     if an inuse chunk borders them and debug is on, it's worth doing them.
835   /* ... and was allocated at front of an available chunk */
865   Place chunk p of size s in its bin, in size order,
900 /* take a chunk off a list */
947    * there is no following chunk whose prev_size field could be used.
972    * in the prev_size field of the chunk; normally it is zero,
1058   Extend the top-most chunk by obtaining memory from system.
1072   INTERNAL_SIZE_T top_size;       /* new size of top chunk */
1111     /* Guarantee alignment of first new chunk made from this space */
1189 	 a chunk of exactly the right size is found, it is taken.
1191       2. The most recently remaindered chunk is used if it is big
1194 	 the remainder of the chunk used for the previous such request
1201 	 chunk big enough to fulfill the request, and splitting off
1204 	 recently used) chunk that fits is selected.
1206       4. If large enough, the chunk bordering the end of memory
1210 	 chunk since it can be extended to be as large as necessary
1229       chunk. (The implementation invariant is that prev_inuse is
1230       always true of any allocated chunk; i.e., that each allocated
1231       chunk borders either a previously allocated and still in-use chunk,
1242   mchunkptr victim;                  /* inspected/selected chunk */
1364      search for best fitting chunk by scanning bins in blockwidth units.
1393 	/* Find and use first big enough chunk ... */
1455   /* Try to use top chunk */
1494        2. If the chunk was allocated via mmap, it is release via munmap().
1496        3. If a returned chunk borders the current high end of memory,
1514   mchunkptr p;         /* chunk corresponding to mem */
1518   mchunkptr next;      /* next contiguous chunk */
1520   INTERNAL_SIZE_T prevsz; /* size of previous contiguous chunk */
1620     chunk can be extended, it is, else a malloc-copy-free sequence is
1621     taken.  There are several different ways that a chunk could be
1624        * Extending forward into following adjacent free chunk.
1630     size argument of zero (re)allocates a minimum-sized chunk.
1636     The old unix realloc convention of allowing the last-free'd chunk
1654   mchunkptr oldp;             /* chunk corresponding to oldmem */
1657   mchunkptr newp;             /* chunk to return */
1661   mchunkptr next;             /* next contiguous chunk after oldp */
1664   mchunkptr prev;             /* previous contiguous chunk before oldp */
1742       /* Forward into next chunk */
1784 	/* into next chunk */
1816     /* Avoid copy if newp is next chunk after oldp. */
1817     /* (This can only happen when new chunk is sbrk'ed.) */
1833  split:  /* split off extra room in old or expanded chunk */
1862     within that chunk that meets the alignment request, and then
1884   mchunkptr p;                /* corresponding chunk */
1886   mchunkptr newp;             /* chunk to return */
1905   /* Otherwise, ensure that it is at least a minimum chunk size */
1952     /* Fall through to original NULL check and chunk splitting logic */
1969       Find an aligned spot inside chunk.
1970       Since we need to give back leading space in a chunk of at
2057   calloc calls malloc, then zeroes out the allocated chunk.
2225     allocated chunk, which may be more than you requested (although