nostrdb/blocks: add note block iterator

This adds an api that walks along and pulls compact note block data out of
nostrdb.

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

nostrdb/src/block.c

@@ -0,0 +1,184 @@
+
+
+#include "nostrdb.h"
+#include "block.h"
+#include <stdlib.h>
+
+struct ndb_block_iterator {
+	const char *content;
+	struct ndb_blocks *blocks;
+	struct ndb_block block;
+	struct cursor cur;
+};
+
+int push_str_block(struct cursor *buf, const char *content, struct ndb_str_block *block) {
+	return cursor_push_varint(buf, block->str - content) &&
+	       cursor_push_varint(buf, block->len);
+}
+
+int pull_str_block(struct cursor *buf, const char *content, struct ndb_str_block *block) {
+	uint32_t start;
+	if (!cursor_pull_varint_u32(buf, &start))
+		return 0;
+
+	block->str = content + start;
+
+	return cursor_pull_varint_u32(buf, &block->len);
+}
+
+static int pull_nostr_bech32_type(struct cursor *cur, enum nostr_bech32_type *type)
+{
+	uint64_t inttype;
+	if (!cursor_pull_varint(cur, &inttype))
+		return 0;
+
+	if (inttype > NOSTR_BECH32_KNOWN_TYPES)
+		return 0;
+
+	*type = inttype;
+	return 1;
+}
+
+
+static int pull_bech32_mention(const char *content, struct cursor *cur, struct ndb_mention_bech32_block *block) {
+	uint16_t size;
+	unsigned char *start;
+	enum nostr_bech32_type type;
+
+	start = cur->p;
+
+	if (!pull_str_block(cur, content, &block->str))
+		return 0;
+
+	if (!cursor_pull_u16(cur, &size))
+		return 0;
+
+	if (!pull_nostr_bech32_type(cur, &type))
+		return 0;
+
+	if (!parse_nostr_bech32_buffer(cur, type, &block->bech32))
+		return 0;
+
+	cur->p = start + size;
+	return 1;
+}
+
+static int pull_invoice(const char *content, struct cursor *cur,
+			struct ndb_invoice_block *block)
+{
+	if (!pull_str_block(cur, content, &block->invstr))
+		return 0;
+
+	return ndb_decode_invoice(cur, &block->invoice);
+}
+
+static int pull_block_type(struct cursor *cur, enum ndb_block_type *type)
+{
+	uint32_t itype;
+	*type = 0;
+	if (!cursor_pull_varint_u32(cur, &itype))
+		return 0;
+
+	if (itype <= 0 || itype > NDB_NUM_BLOCK_TYPES)
+		return 0;
+
+	*type = itype;
+	return 1;
+}
+
+static int pull_block(const char *content, struct cursor *cur, struct ndb_block *block)
+{
+	unsigned char *start = cur->p;
+
+	if (!pull_block_type(cur, &block->type))
+		return 0;
+
+	switch (block->type) {
+	case BLOCK_HASHTAG:
+	case BLOCK_TEXT:
+	case BLOCK_URL:
+		if (!pull_str_block(cur, content, &block->block.str))
+			goto fail;
+		break;
+
+	case BLOCK_MENTION_INDEX:
+		if (!cursor_pull_varint_u32(cur, &block->block.mention_index))
+			goto fail;
+		break;
+
+	case BLOCK_MENTION_BECH32:
+		if (!pull_bech32_mention(content, cur, &block->block.mention_bech32))
+			goto fail;
+		break;
+
+	case BLOCK_INVOICE:
+		// we only push invoice strs here
+		if (!pull_invoice(content, cur, &block->block.invoice))
+			goto fail;
+		break;
+	}
+
+	return 1;
+fail:
+	cur->p = start;
+	return 0;
+}
+
+
+enum ndb_block_type ndb_get_block_type(struct ndb_block *block) {
+	return block->type;
+}
+
+// BLOCK ITERATORS
+struct ndb_block_iterator *ndb_blocks_iterate_start(const char *content, struct ndb_blocks *blocks) {
+	struct ndb_block_iterator *iter = malloc(sizeof(*iter));
+	if (!iter)
+		return NULL;
+
+	iter->blocks = blocks;
+	iter->content = content;
+
+	make_cursor((unsigned char *)blocks->blocks,
+		    blocks->blocks + blocks->blocks_size, &iter->cur);
+
+	return iter;
+}
+
+void ndb_blocks_iterate_free(struct ndb_block_iterator *iter)
+{
+	if (iter)
+		free(iter);
+}
+
+struct ndb_block *ndb_blocks_iterate_next(struct ndb_block_iterator *iter)
+{
+	while (iter->cur.p < iter->cur.end) {
+		if (!pull_block(iter->content, &iter->cur, &iter->block))
+			return NULL;
+		else
+			return &iter->block;
+	}
+
+	return NULL;
+}
+
+// STR BLOCKS
+struct ndb_str_block *ndb_block_str(struct ndb_block *block)
+{
+	switch (block->type) {
+	case BLOCK_HASHTAG:
+	case BLOCK_TEXT:
+	case BLOCK_URL:
+		return &block->block.str;
+	case BLOCK_MENTION_INDEX:
+		return NULL;
+	case BLOCK_MENTION_BECH32:
+		return &block->block.mention_bech32.str;
+	case BLOCK_INVOICE:
+		return &block->block.invoice.invstr;
+	}
+
+	return NULL;
+}
+//const char *ndb_str_block_ptr(struct ndb_str_block *);
+//uint32_t ndb_str_block_len(struct ndb_str_block *);