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-rw-r--r--src/malloc/mallocng/aligned_alloc.c57
1 files changed, 57 insertions, 0 deletions
diff --git a/src/malloc/mallocng/aligned_alloc.c b/src/malloc/mallocng/aligned_alloc.c
new file mode 100644
index 00000000..34116896
--- /dev/null
+++ b/src/malloc/mallocng/aligned_alloc.c
@@ -0,0 +1,57 @@
+#include <stdlib.h>
+#include <errno.h>
+#include "meta.h"
+
+void *aligned_alloc(size_t align, size_t len)
+{
+ if ((align & -align) != align) {
+ errno = EINVAL;
+ return 0;
+ }
+
+ if (len > SIZE_MAX - align || align >= (1ULL<<31)*UNIT) {
+ errno = ENOMEM;
+ return 0;
+ }
+
+ if (DISABLE_ALIGNED_ALLOC) {
+ errno = ENOMEM;
+ return 0;
+ }
+
+ if (align <= UNIT) align = UNIT;
+
+ unsigned char *p = malloc(len + align - UNIT);
+ struct meta *g = get_meta(p);
+ int idx = get_slot_index(p);
+ size_t stride = get_stride(g);
+ unsigned char *start = g->mem->storage + stride*idx;
+ unsigned char *end = g->mem->storage + stride*(idx+1) - IB;
+ size_t adj = -(uintptr_t)p & (align-1);
+
+ if (!adj) {
+ set_size(p, end, len);
+ return p;
+ }
+ p += adj;
+ uint32_t offset = (size_t)(p-g->mem->storage)/UNIT;
+ if (offset <= 0xffff) {
+ *(uint16_t *)(p-2) = offset;
+ p[-4] = 0;
+ } else {
+ // use a 32-bit offset if 16-bit doesn't fit. for this,
+ // 16-bit field must be zero, [-4] byte nonzero.
+ *(uint16_t *)(p-2) = 0;
+ *(uint32_t *)(p-8) = offset;
+ p[-4] = 1;
+ }
+ p[-3] = idx;
+ set_size(p, end, len);
+ // store offset to aligned enframing. this facilitates cycling
+ // offset and also iteration of heap for debugging/measurement.
+ // for extreme overalignment it won't fit but these are classless
+ // allocations anyway.
+ *(uint16_t *)(start - 2) = (size_t)(p-start)/UNIT;
+ start[-3] = 7<<5;
+ return p;
+}