+/************************************************
+ * Helper functions for writing field callbacks *
+ ************************************************/
+
+/* Encode field header based on type and field number defined in the field
+ * structure. Call this from the callback before writing out field contents. */
+bool pb_encode_tag_for_field(pb_ostream_t *stream, const pb_field_t *field);
+
+/* Encode field header by manually specifing wire type. You need to use this
+ * if you want to write out packed arrays from a callback field. */
+bool pb_encode_tag(pb_ostream_t *stream, pb_wire_type_t wiretype, uint32_t field_number);
+
+/* Encode an integer in the varint format.
+ * This works for bool, enum, int32, int64, uint32 and uint64 field types. */
+bool pb_encode_varint(pb_ostream_t *stream, uint64_t value);
+
+/* Encode an integer in the zig-zagged svarint format.
+ * This works for sint32 and sint64. */
+bool pb_encode_svarint(pb_ostream_t *stream, int64_t value);
+
+/* Encode a string or bytes type field. For strings, pass strlen(s) as size. */
+bool pb_encode_string(pb_ostream_t *stream, const uint8_t *buffer, size_t size);
+
+/* Encode a fixed32, sfixed32 or float value.
+ * You need to pass a pointer to a 4-byte wide C variable. */
+bool pb_encode_fixed32(pb_ostream_t *stream, const void *value);
+
+/* Encode a fixed64, sfixed64 or double value.
+ * You need to pass a pointer to a 8-byte wide C variable. */
+bool pb_encode_fixed64(pb_ostream_t *stream, const void *value);
+
+/* Encode a submessage field.
+ * You need to pass the pb_field_t array and pointer to struct, just like
+ * with pb_encode(). This internally encodes the submessage twice, first to
+ * calculate message size and then to actually write it out.
+ */
+bool pb_encode_submessage(pb_ostream_t *stream, const pb_field_t fields[], const void *src_struct);