+/*
+ * Byte order marks.
+ */
+
+#define BOM_UTF8 "\xef\xbb\xbf"
+#define BOM_UTF16LE "\xff\xfe"
+#define BOM_UTF16BE "\xfe\xff"
+
+/*
+ * Determine the input stream encoding by checking the BOM symbol. If no BOM is
+ * found, the UTF-8 encoding is assumed. Return 1 on success, 0 on failure.
+ */
+
+static int
+yaml_parser_determine_encoding(yaml_parser_t *parser)
+{
+ /* Ensure that we had enough bytes in the raw buffer. */
+
+ while (!parser->eof
+ && parser->raw_buffer.last - parser->raw_buffer.pointer < 3) {
+ if (!yaml_parser_update_raw_buffer(parser)) {
+ return 0;
+ }
+ }
+
+ /* Determine the encoding. */
+
+ if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
+ && !memcmp(parser->raw_buffer.pointer, BOM_UTF16LE, 2)) {
+ parser->encoding = YAML_UTF16LE_ENCODING;
+ parser->raw_buffer.pointer += 2;
+ parser->offset += 2;
+ }
+ else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 2
+ && !memcmp(parser->raw_buffer.pointer, BOM_UTF16BE, 2)) {
+ parser->encoding = YAML_UTF16BE_ENCODING;
+ parser->raw_buffer.pointer += 2;
+ parser->offset += 2;
+ }
+ else if (parser->raw_buffer.last - parser->raw_buffer.pointer >= 3
+ && !memcmp(parser->raw_buffer.pointer, BOM_UTF8, 3)) {
+ parser->encoding = YAML_UTF8_ENCODING;
+ parser->raw_buffer.pointer += 3;
+ parser->offset += 3;
+ }
+ else {
+ parser->encoding = YAML_UTF8_ENCODING;
+ }
+
+ return 1;
+}
+
+/*
+ * Update the raw buffer.
+ */
+
+static int
+yaml_parser_update_raw_buffer(yaml_parser_t *parser)
+{
+ size_t size_read = 0;
+
+ /* Return if the raw buffer is full. */
+
+ if (parser->raw_buffer.start == parser->raw_buffer.pointer
+ && parser->raw_buffer.last == parser->raw_buffer.end)
+ return 1;
+
+ /* Return on EOF. */
+
+ if (parser->eof) return 1;
+
+ /* Move the remaining bytes in the raw buffer to the beginning. */
+
+ if (parser->raw_buffer.start < parser->raw_buffer.pointer
+ && parser->raw_buffer.pointer < parser->raw_buffer.last) {
+ memmove(parser->raw_buffer.start, parser->raw_buffer.pointer,
+ parser->raw_buffer.last - parser->raw_buffer.pointer);
+ }
+ parser->raw_buffer.last -=
+ parser->raw_buffer.pointer - parser->raw_buffer.start;
+ parser->raw_buffer.pointer = parser->raw_buffer.start;
+
+ /* Call the read handler to fill the buffer. */
+
+ if (!parser->read_handler(parser->read_handler_data, parser->raw_buffer.last,
+ parser->raw_buffer.end - parser->raw_buffer.last, &size_read)) {
+ return yaml_parser_set_reader_error(parser, "input error",
+ parser->offset, -1);
+ }
+ parser->raw_buffer.last += size_read;
+ if (!size_read) {
+ parser->eof = 1;
+ }
+
+ return 1;
+}