nostrdb/blocks: add ndb_blocks_free

In some situations we will need to have owned note blocks. For
example, when we try to fetch note blocks from the database and it's not
there yet. We will need to parse the content on the spot and return an
owned copy, since it will not be immediately available in the database.

Add a new flag field to note blocks that lets us know if it's owned by
malloc or nostrdb.

We the add a free function that checks this flag and frees the object if
its set. If it is not set then it doesn nothing because it likely came
from the database.

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/src/block.c

@@ -201,3 +201,10 @@ struct nostr_bech32 *ndb_bech32_block(struct ndb_block *block) {
 size_t ndb_blocks_total_size(struct ndb_blocks *blocks) {
 	return blocks->total_size;
 }
+
+void ndb_blocks_free(struct ndb_blocks *blocks) {
+	if ((blocks->flags & NDB_BLOCK_FLAG_OWNED) != NDB_BLOCK_FLAG_OWNED)
+		return;
+
+	free(blocks);
+}

nostrdb/src/block.h

@@ -9,11 +9,14 @@
 #include "nostrdb.h"
 #include <inttypes.h>
 
+#define NDB_BLOCK_FLAG_OWNED 1
+
 #pragma pack(push, 1)
 
 struct ndb_blocks {
 	unsigned char version;
-	unsigned char padding[3];
+	unsigned char flags;
+	unsigned char padding[2];
 
 	uint32_t words;
 	uint32_t num_blocks;

nostrdb/src/content_parser.c

@@ -536,6 +536,7 @@ int ndb_parse_content(unsigned char *buf, int buf_size,
 	parser.blocks->words = 0;
 	parser.blocks->num_blocks = 0;
 	parser.blocks->blocks_size = 0;
+	parser.blocks->flags = 0;
 
 	blocks_start = start = parser.content.p;
 	while (parser.content.p < parser.content.end) {

nostrdb/src/nostrdb.h

@@ -471,6 +471,8 @@ int ndb_parse_content(unsigned char *buf, int buf_size,
 enum ndb_block_type ndb_block_type(struct ndb_blocks *blocks);
 size_t ndb_blocks_total_size(struct ndb_blocks *blocks);
 
+/// Free blocks if they are owned, safe to call on unowned blocks as well.
+void ndb_blocks_free(struct ndb_blocks *blocks);
 
 
 // BLOCK ITERATORS