Add zone allocation, internal data structures, and README

Implement mmap-based zone allocation for TINY (<=128B) and SMALL
(<=1024B) categories. malloc now creates zones on demand and
returns a pointer to the first chunk.

1 files changed, 42 insertions, 0 deletions

diff --git a/src/zone.c b/src/zone.c
new file mode 100644
index 0000000..724237b
--- /dev/null
+++ b/src/zone.c
@@ -0,0 +1,42 @@
+/**
+ * @file   zone.c
+ * @brief  Zone allocation via mmap.
+ */
+
+#include "malloc_internal.h"
+#include <sys/mman.h>
+#include <unistd.h>
+
+static size_t
+_s_zone_size (size_t alloc_max)
+{
+  size_t chunk_size;
+  size_t total;
+  size_t page_size;
+
+  chunk_size = ALIGN (sizeof (t_chunk)) + ALIGN (alloc_max);
+  total = ALIGN (sizeof (t_zone)) + MIN_ALLOC_COUNT * chunk_size;
+  page_size = (size_t)getpagesize ();
+  return ((total + page_size - 1) & ~(page_size - 1));
+}
+
+t_zone *
+zone_new (size_t alloc_max)
+{
+  size_t zone_size;
+  t_zone *zone;
+  t_chunk *chunk;
+
+  zone_size = _s_zone_size (alloc_max);
+  zone = mmap (NULL, zone_size, PROT_READ | PROT_WRITE,
+               MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+  if (zone == MAP_FAILED)
+    return (NULL);
+  zone->next = NULL;
+  zone->size = zone_size;
+  chunk = (t_chunk *)((char *)zone + ALIGN (sizeof (t_zone)));
+  chunk->size = zone_size - ALIGN (sizeof (t_zone)) - ALIGN (sizeof (t_chunk));
+  chunk->next = NULL;
+  chunk->is_free = 1;
+  return (zone);
+}