From f8217d240d598f39f70047f7a623dd46312542c6 Mon Sep 17 00:00:00 2001
From: 3gg <3gg@shellblade.net>
Date: Sat, 4 Dec 2021 16:01:12 -0800
Subject: Initial commit.
---
listpool/src/listpool.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 78 insertions(+)
create mode 100644 listpool/src/listpool.c
(limited to 'listpool/src/listpool.c')
diff --git a/listpool/src/listpool.c b/listpool/src/listpool.c
new file mode 100644
index 0000000..9c86a3b
--- /dev/null
+++ b/listpool/src/listpool.c
@@ -0,0 +1,78 @@
+#include "listpool.h"
+
+#include <string.h>
+
+void listpool_make_(listpool* pool, list* nodes, void* blocks,
+ size_t num_blocks, size_t block_size_bytes) {
+ assert(pool);
+ pool->block_size_bytes = block_size_bytes;
+ pool->num_blocks = num_blocks;
+ pool->free = &nodes[0];
+ pool->used = 0;
+ pool->nodes = nodes;
+ pool->blocks = blocks;
+ list_make(nodes, num_blocks);
+ memset(blocks, 0, num_blocks * block_size_bytes);
+}
+
+void* listpool_alloc_(listpool* pool) {
+ assert(pool);
+ if (!pool->free) {
+ return 0;
+ }
+
+ const size_t index = pool->free - pool->nodes;
+ assert(index < pool->num_blocks);
+
+ list* free = pool->free;
+ pool->free = pool->free->next;
+
+ // pool->used is always the head of the used list, so prepend the new item to
+ // the list.
+ list* new_used = free;
+ new_used->prev = 0;
+ new_used->next = pool->used;
+ if (pool->used) {
+ pool->used->prev = new_used;
+ }
+ pool->used = new_used;
+
+ return pool->blocks + index * pool->block_size_bytes;
+}
+
+void listpool_free_(listpool* pool, void** block_ptr) {
+ assert(pool);
+ assert(block_ptr);
+
+ memset(*block_ptr, 0, pool->block_size_bytes);
+
+ const size_t index =
+ ((uint8_t*)*block_ptr - pool->blocks) / pool->block_size_bytes;
+ assert(index < pool->num_blocks);
+
+ list* item = &pool->nodes[index];
+
+ // We must remove the item from the used list first.
+ if (item->prev) {
+ item->prev->next = item->next;
+ }
+ if (item->next) {
+ item->next->prev = item->prev;
+ }
+ if (item == pool->used) {
+ pool->used = item->next;
+ }
+
+ // pool->free is always the head of the free list, so prepend the new item to
+ // the list. The item is now free to wire after removing it from the used
+ // list.
+ if (!pool->free) {
+ pool->free = item;
+ } else {
+ item->next = pool->free;
+ pool->free->prev = item;
+ pool->free = item;
+ }
+
+ *block_ptr = 0;
+}
--
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