Implemented walker overlay that calculates decompressed size.

espReader/Reader.c

@@ -43,6 +43,7 @@ void print_type4(Type4 val);
 // Utilities
 Timestamp convert_ts(uint16_t ts);
 void print_callback(Node n, void *_);
+void dc_size_cb(Node n, void *dc_size_ptr);
 
 //
 // === FUNCTIONS ===
@@ -88,6 +89,33 @@ void print_callback(Node n, void *pt) {
 	}
 }
 
+size_t espr_decompressed_size(char *data, size_t size) {
+	size_t dc_size = 0;
+	espr_walk(data, size, dc_size_cb, &dc_size);
+	return dc_size;
+}
+
+void dc_size_cb(Node n, void *dc_size_ptr) {
+	size_t *dcsp = dc_size_ptr;
+	switch (n.type) {
+		case NT_GROUP:
+			// Only add header size for groups, internals will be walked
+			*dcsp += sizeof(Group);
+			break;
+		case NT_RECORD:
+			// Add the whole record and header, records are leaf-ish
+			*dcsp += sizeof(Record);
+			if (n.header.record->flags & COMPRESSED_FLAG) {
+				// Read decompressed size
+				*dcsp += *((uint32_t *)n.data);
+			} else
+				*dcsp += n.header.record->size;
+			break;
+		default:
+			assert(false); // invalid node type
+	}
+}
+
 /* Unknown data will be some concatenation of groups and records.
  *
  * `walk_concat` will call the appropriate walking function