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-rw-r--r--libc/stdlib/malloc/heap.h66
-rw-r--r--libc/stdlib/malloc/heap_free.c61
2 files changed, 74 insertions, 53 deletions
diff --git a/libc/stdlib/malloc/heap.h b/libc/stdlib/malloc/heap.h
index 589bf42b0..5207afe8e 100644
--- a/libc/stdlib/malloc/heap.h
+++ b/libc/stdlib/malloc/heap.h
@@ -115,14 +115,68 @@ static void HEAP_DEBUG (struct heap *heap, const char *str)
extern inline void
__heap_unlink_free_area (struct heap *heap, struct heap_free_area *fa)
{
- if (fa->next)
- fa->next->prev = fa->prev;
- if (fa->prev)
- fa->prev->next = fa->next;
- else
- heap->free_areas = fa->next;
+ if (fa->next)
+ fa->next->prev = fa->prev;
+ if (fa->prev)
+ fa->prev->next = fa->next;
+ else
+ heap->free_areas = fa->next;
+}
+
+/* Link the free-area FA between the existing free-area's PREV and NEXT in
+ HEAP. PREV and NEXT may be 0; if PREV is 0, FA is installed as the
+ first free-area. */
+extern inline void
+__heap_link_free_area (struct heap *heap, struct heap_free_area *fa,
+ struct heap_free_area *prev,
+ struct heap_free_area *next)
+{
+ fa->next = next;
+ fa->prev = prev;
+
+ if (prev)
+ prev->next = fa;
+ else
+ heap->free_areas = fa;
+ if (next)
+ next->prev = fa;
}
+/* Update the mutual links between the free-areas PREV and FA in HEAP.
+ PREV may be 0, in which case FA is installed as the first free-area (but
+ FA may not be 0). */
+extern inline void
+__heap_link_free_area_after (struct heap *heap,
+ struct heap_free_area *fa,
+ struct heap_free_area *prev)
+{
+ if (prev)
+ prev->next = fa;
+ else
+ heap->free_areas = fa;
+ fa->prev = prev;
+}
+
+/* Add a new free-area MEM, of length SIZE, in between the existing
+ free-area's PREV and NEXT in HEAP, and return a pointer to its header.
+ PREV and NEXT may be 0; if PREV is 0, MEM is installed as the first
+ free-area. */
+extern inline struct heap_free_area *
+__heap_add_free_area (struct heap *heap, void *mem, size_t size,
+ struct heap_free_area *prev,
+ struct heap_free_area *next)
+{
+ struct heap_free_area *fa = (struct heap_free_area *)
+ ((char *)mem + size - sizeof (struct heap_free_area));
+
+ fa->size = size;
+
+ __heap_link_free_area (heap, fa, prev, next);
+
+ return fa;
+}
+
+
/* Allocate SIZE bytes from the front of the free-area FA in HEAP, and
return the amount actually allocated (which may be more than SIZE). */
extern inline size_t
diff --git a/libc/stdlib/malloc/heap_free.c b/libc/stdlib/malloc/heap_free.c
index ac7e00be3..e958f920d 100644
--- a/libc/stdlib/malloc/heap_free.c
+++ b/libc/stdlib/malloc/heap_free.c
@@ -20,7 +20,7 @@
struct heap_free_area *
__heap_free (struct heap *heap, void *mem, size_t size)
{
- struct heap_free_area *prev_fa, *fa, *new_fa;
+ struct heap_free_area *prev_fa, *fa;
void *end = (char *)mem + size;
__heap_lock (heap);
@@ -31,10 +31,9 @@ __heap_free (struct heap *heap, void *mem, size_t size)
for (prev_fa = 0, fa = heap->free_areas; fa; prev_fa = fa, fa = fa->next)
{
size_t fa_size = fa->size;
- void *fa_end = HEAP_FREE_AREA_END (fa);
void *fa_mem = HEAP_FREE_AREA_START (fa);
- if (fa_mem == end)
+ if (end == fa_mem)
/* FA is just after MEM, grow down to encompass it. */
{
fa_size += size;
@@ -43,20 +42,15 @@ __heap_free (struct heap *heap, void *mem, size_t size)
if (prev_fa && fa_mem - size == HEAP_FREE_AREA_END (prev_fa))
/* Yup; merge PREV_FA's info into FA. */
{
- struct heap_free_area *pp = prev_fa->prev;
fa_size += prev_fa->size;
- if (pp)
- pp->next = fa;
- else
- heap->free_areas = fa;
- fa->prev = pp;
+ __heap_link_free_area_after (heap, fa, prev_fa->prev);
}
fa->size = fa_size;
goto done;
}
- else if (fa_end == mem)
+ else if (HEAP_FREE_AREA_END (fa) == mem)
/* FA is just before MEM, expand to encompass it. */
{
struct heap_free_area *next_fa = fa->next;
@@ -64,33 +58,22 @@ __heap_free (struct heap *heap, void *mem, size_t size)
fa_size += size;
/* See if FA can now be merged with its successor. */
- if (next_fa && fa_end + size == HEAP_FREE_AREA_START (next_fa))
+ if (next_fa && mem + size == HEAP_FREE_AREA_START (next_fa))
{
/* Yup; merge FA's info into NEXT_FA. */
fa_size += next_fa->size;
- if (prev_fa)
- prev_fa->next = next_fa;
- else
- heap->free_areas = next_fa;
- next_fa->prev = prev_fa;
+ __heap_link_free_area_after (heap, next_fa, prev_fa);
fa = next_fa;
}
else
/* FA can't be merged; move the descriptor for it to the tail-end
of the memory block. */
{
- new_fa = (struct heap_free_area *)((char *)fa + size);
- /* Update surrounding free-areas to point to FA's new address. */
- if (prev_fa)
- prev_fa->next = new_fa;
- else
- heap->free_areas = new_fa;
- if (next_fa)
- next_fa->prev = new_fa;
- /* Fill in the moved descriptor. */
- new_fa->prev = prev_fa;
- new_fa->next = next_fa;
- fa = new_fa;
+ /* The new descriptor is at the end of the extended block,
+ SIZE bytes later than the old descriptor. */
+ fa = (struct heap_free_area *)((char *)fa + size);
+ /* Update links with the neighbors in the list. */
+ __heap_link_free_area (heap, fa, prev_fa, next_fa);
}
fa->size = fa_size;
@@ -99,28 +82,12 @@ __heap_free (struct heap *heap, void *mem, size_t size)
}
else if (fa_mem > mem)
/* We've reached the right spot in the free-list without finding an
- adjacent free-area, so add a new free area to hold MEM. */
+ adjacent free-area, so continue below to add a new free area. */
break;
}
- /* Make a new free-list entry. */
-
- /* NEW_FA initially holds only MEM. */
- new_fa = (struct heap_free_area *)
- ((char *)mem + size - sizeof (struct heap_free_area));
- new_fa->size = size;
- new_fa->next = fa;
- new_fa->prev = prev_fa;
-
- /* Insert NEW_FA in the free-list between PREV_FA and FA. */
- if (prev_fa)
- prev_fa->next = new_fa;
- else
- heap->free_areas = new_fa;
- if (fa)
- fa->prev = new_fa;
-
- fa = new_fa;
+ /* Make MEM into a new free-list entry. */
+ fa = __heap_add_free_area (heap, mem, size, prev_fa, fa);
done:
HEAP_DEBUG (heap, "after __heap_free");
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-24 23:02:07 +0000