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;
+}