1 files changed, 178 insertions, 0 deletions
diff --git a/mem-pool.c b/mem-pool.c
new file mode 100644
index 0000000..c34846d
--- /dev/null
+++ b/mem-pool.c
@@ -0,0 +1,178 @@
+/*
+ * Memory Pool implementation logic.
+ */
+
+#include "git-compat-util.h"
+#include "mem-pool.h"
+
+#define BLOCK_GROWTH_SIZE (1024 * 1024 - sizeof(struct mp_block))
+
+/*
+ * The inner union is an approximation for C11's max_align_t, and the
+ * struct + offsetof computes _Alignof. This can all just be replaced
+ * with _Alignof(max_align_t) if/when C11 is part of the baseline.
+ * Note that _Alignof(X) need not be the same as sizeof(X); it's only
+ * required to be a (possibly trivial) factor. They are the same for
+ * most architectures, but m68k for example has only 2-byte alignment
+ * for its 4-byte and 8-byte types, so using sizeof would waste space.
+ *
+ * Add more types to the union if the current set is insufficient.
+ */
+struct git_max_alignment {
+	char unalign;
+	union {
+		uintmax_t max_align_uintmax;
+		void *max_align_pointer;
+	} aligned;
+};
+#define GIT_MAX_ALIGNMENT offsetof(struct git_max_alignment, aligned)
+
+/*
+ * Allocate a new mp_block and insert it after the block specified in
+ * `insert_after`. If `insert_after` is NULL, then insert block at the
+ * head of the linked list.
+ */
+static struct mp_block *mem_pool_alloc_block(struct mem_pool *pool,
+					     size_t block_alloc,
+					     struct mp_block *insert_after)
+{
+	struct mp_block *p;
+
+	pool->pool_alloc += sizeof(struct mp_block) + block_alloc;
+	p = xmalloc(st_add(sizeof(struct mp_block), block_alloc));
+
+	p->next_free = (char *)p->space;
+	p->end = p->next_free + block_alloc;
+
+	if (insert_after) {
+		p->next_block = insert_after->next_block;
+		insert_after->next_block = p;
+	} else {
+		p->next_block = pool->mp_block;
+		pool->mp_block = p;
+	}
+
+	return p;
+}
+
+void mem_pool_init(struct mem_pool *pool, size_t initial_size)
+{
+	memset(pool, 0, sizeof(*pool));
+	pool->block_alloc = BLOCK_GROWTH_SIZE;
+
+	if (initial_size > 0)
+		mem_pool_alloc_block(pool, initial_size, NULL);
+}
+
+void mem_pool_discard(struct mem_pool *pool, int invalidate_memory)
+{
+	struct mp_block *block, *block_to_free;
+
+	block = pool->mp_block;
+	while (block)
+	{
+		block_to_free = block;
+		block = block->next_block;
+
+		if (invalidate_memory)
+			memset(block_to_free->space, 0xDD, ((char *)block_to_free->end) - ((char *)block_to_free->space));
+
+		free(block_to_free);
+	}
+
+	pool->mp_block = NULL;
+	pool->pool_alloc = 0;
+}
+
+void *mem_pool_alloc(struct mem_pool *pool, size_t len)
+{
+	struct mp_block *p = NULL;
+	void *r;
+
+	/* round up to a 'GIT_MAX_ALIGNMENT' alignment */
+	if (len & (GIT_MAX_ALIGNMENT - 1))
+		len += GIT_MAX_ALIGNMENT - (len & (GIT_MAX_ALIGNMENT - 1));
+
+	if (pool->mp_block &&
+	    pool->mp_block->end - pool->mp_block->next_free >= len)
+		p = pool->mp_block;
+
+	if (!p) {
+		if (len >= (pool->block_alloc / 2))
+			return mem_pool_alloc_block(pool, len, pool->mp_block);
+
+		p = mem_pool_alloc_block(pool, pool->block_alloc, NULL);
+	}
+
+	r = p->next_free;
+	p->next_free += len;
+	return r;
+}
+
+void *mem_pool_calloc(struct mem_pool *pool, size_t count, size_t size)
+{
+	size_t len = st_mult(count, size);
+	void *r = mem_pool_alloc(pool, len);
+	memset(r, 0, len);
+	return r;
+}
+
+char *mem_pool_strdup(struct mem_pool *pool, const char *str)
+{
+	size_t len = strlen(str) + 1;
+	char *ret = mem_pool_alloc(pool, len);
+
+	return memcpy(ret, str, len);
+}
+
+char *mem_pool_strndup(struct mem_pool *pool, const char *str, size_t len)
+{
+	char *p = memchr(str, '\0', len);
+	size_t actual_len = (p ? p - str : len);
+	char *ret = mem_pool_alloc(pool, actual_len+1);
+
+	ret[actual_len] = '\0';
+	return memcpy(ret, str, actual_len);
+}
+
+int mem_pool_contains(struct mem_pool *pool, void *mem)
+{
+	struct mp_block *p;
+
+	/* Check if memory is allocated in a block */
+	for (p = pool->mp_block; p; p = p->next_block)
+		if ((mem >= ((void *)p->space)) &&
+		    (mem < ((void *)p->end)))
+			return 1;
+
+	return 0;
+}
+
+void mem_pool_combine(struct mem_pool *dst, struct mem_pool *src)
+{
+	struct mp_block *p;
+
+	/* Append the blocks from src to dst */
+	if (dst->mp_block && src->mp_block) {
+		/*
+		 * src and dst have blocks, append
+		 * blocks from src to dst.
+		 */
+		p = dst->mp_block;
+		while (p->next_block)
+			p = p->next_block;
+
+		p->next_block = src->mp_block;
+	} else if (src->mp_block) {
+		/*
+		 * src has blocks, dst is empty.
+		 */
+		dst->mp_block = src->mp_block;
+	} else {
+		/* src is empty, nothing to do. */
+	}
+
+	dst->pool_alloc += src->pool_alloc;
+	src->pool_alloc = 0;
+	src->mp_block = NULL;
+}