+/* Read a single byte from input stream. buf may not be NULL.
+ * This is an optimization for the varint decoding. */
+static bool checkreturn pb_readbyte(pb_istream_t *stream, uint8_t *buf)
+{
+ if (!stream->bytes_left)
+ PB_RETURN_ERROR(stream, "end-of-stream");
+
+#ifndef PB_BUFFER_ONLY
+ if (!stream->callback(stream, buf, 1))
+ PB_RETURN_ERROR(stream, "io error");
+#else
+ *buf = *(uint8_t*)stream->state;
+ stream->state = (uint8_t*)stream->state + 1;
+#endif
+
+ stream->bytes_left--;
+
+ return true;
+}
+