1 files changed, 20 insertions, 15 deletions

diff --git a/mempool/src/mempool.c b/mempool/src/mempool.c
index 679f124..1100dad 100644
--- a/mempool/src/mempool.c
+++ b/mempool/src/mempool.c
@@ -3,18 +3,14 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define NO_BLOCK ((size_t)-1)
-
-static inline size_t min(size_t a, size_t b) { return a < b ? a : b; }
-
 /// Initialize the free list.
 /// All of the blocks in the pool are assumed free.
 static void init_free_list(mempool* pool) {
   assert(pool);
   for (size_t i = 0; i < pool->num_blocks - 1; ++i) {
-    pool->block_info[i].next = i + 1;
+    pool->block_info[i].next_free = i + 1;
   }
-  pool->block_info[pool->num_blocks - 1].next = NO_BLOCK;
+  pool->block_info[pool->num_blocks - 1].next_free = 0;
 }
 
 bool mempool_make_(
@@ -27,6 +23,7 @@ bool mempool_make_(
   pool->block_size_bytes = block_size_bytes;
   pool->num_blocks       = num_blocks;
   pool->head             = 0;
+  pool->used             = 0;
 
   // Initialize blocks and block info.
   if (!block_info) {
@@ -66,6 +63,7 @@ void mempool_del_(mempool* pool) {
 void mempool_clear_(mempool* pool) {
   assert(pool);
   pool->head = 0;
+  pool->used = 0;
   memset(pool->blocks, 0, pool->num_blocks * pool->block_size_bytes);
   memset(pool->block_info, 0, pool->num_blocks * sizeof(BlockInfo));
   init_free_list(pool);
@@ -74,15 +72,18 @@ void mempool_clear_(mempool* pool) {
 void* mempool_alloc_(mempool* pool) {
   assert(pool);
 
-  if (pool->head == NO_BLOCK) {
-    return 0;
+  BlockInfo* head = &pool->block_info[pool->head];
+  if (head->used) {
+    return 0; // Pool is full.
   }
 
   // Allocate the block.
-  BlockInfo* head  = &pool->block_info[pool->head];
-  void*      block = &pool->blocks[pool->head * pool->block_size_bytes];
-  head->used       = true;
-  pool->head       = head->next;
+  void* block     = &pool->blocks[pool->head * pool->block_size_bytes];
+  head->used      = true;
+  head->next_used = pool->used;
+  pool->used      = pool->head;
+  pool->head      = head->next_free;
+  head->next_free = 0;
 
   return block;
 }
@@ -104,9 +105,13 @@ void mempool_free_(mempool* pool, void** block_ptr) {
   memset(*block_ptr, 0, pool->block_size_bytes);
 
   // Free the block and add it to the head of the free list.
-  info->used = false;
-  info->next = pool->head;
-  pool->head = block_index;
+  info->used      = false;
+  info->next_used = 0;
+  info->next_free = pool->head;
+  pool->head      = block_index;
+  if (pool->used == block_index) {
+    pool->used = 0;
+  }
 
   *block_ptr = 0;
 }