nostrdb/nostr_bech32: only parse up to raw bech32 buffers

We will be storing raw nostr bech32 buffers directly into nostrdb, so
adapt our bech32 code to reflect this.

When doing our content parsing pass, we will only look for strings and we
won't allocate any intermediate buffers. Only when we write this string
block to nostrdb will we actually allocate in our nostrdb output buffer
(no mallocs!)

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

nostrdb/src/block.h

@@ -0,0 +1,58 @@
+
+#ifndef NDB_BLOCK_H
+#define NDB_BLOCK_H
+
+#include "invoice.h"
+#include "str_block.h"
+#include "nostr_bech32.h"
+#include <inttypes.h>
+
+#pragma pack(push, 1)
+
+struct ndb_note_blocks {
+	unsigned char version;
+	unsigned char padding[3];
+
+	uint32_t words;
+	uint32_t num_blocks;
+	uint32_t blocks_size;
+	// future expansion
+	uint32_t reserved[4];
+	unsigned char blocks[0]; // see ndb_block definition
+};
+
+#pragma pack(pop)
+
+enum block_type {
+    BLOCK_HASHTAG        = 1,
+    BLOCK_TEXT           = 2,
+    BLOCK_MENTION_INDEX  = 3,
+    BLOCK_MENTION_BECH32 = 4,
+    BLOCK_URL            = 5,
+    BLOCK_INVOICE        = 6,
+};
+
+
+struct ndb_mention_bech32_block {
+	struct str_block str;
+	struct nostr_bech32 bech32;
+};
+
+struct invoice_block {
+	struct str_block invstr;
+	struct ndb_invoice invoice;
+	struct bolt11 *bolt11;
+};
+
+struct note_block {
+	enum block_type type;
+	union {
+		struct str_block str;
+		struct invoice_block invoice;
+		struct ndb_mention_bech32_block mention_bech32;
+		int mention_index;
+	} block;
+};
+
+
+#endif // NDB_BLOCK_H