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//
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// Copyright (c) 2011-2019 Canonical Ltd
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// Copyright (c) 2006-2010 Kirill Simonov
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy of
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// this software and associated documentation files (the "Software"), to deal in
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// the Software without restriction, including without limitation the rights to
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// use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
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// of the Software, and to permit persons to whom the Software is furnished to do
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// so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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package yaml
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import (
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	"io"
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)
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// Set the reader error and return 0.
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func yaml_parser_set_reader_error(parser *yaml_parser_t, problem string, offset int, value int) bool {
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	parser.error = yaml_READER_ERROR
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	parser.problem = problem
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	parser.problem_offset = offset
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	parser.problem_value = value
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	return false
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}
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// Byte order marks.
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const (
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	bom_UTF8    = "\xef\xbb\xbf"
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	bom_UTF16LE = "\xff\xfe"
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	bom_UTF16BE = "\xfe\xff"
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)
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// Determine the input stream encoding by checking the BOM symbol. If no BOM is
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// found, the UTF-8 encoding is assumed. Return 1 on success, 0 on failure.
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func yaml_parser_determine_encoding(parser *yaml_parser_t) bool {
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	// Ensure that we had enough bytes in the raw buffer.
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	for !parser.eof && len(parser.raw_buffer)-parser.raw_buffer_pos < 3 {
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		if !yaml_parser_update_raw_buffer(parser) {
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			return false
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		}
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	}
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	// Determine the encoding.
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	buf := parser.raw_buffer
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	pos := parser.raw_buffer_pos
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	avail := len(buf) - pos
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	if avail >= 2 && buf[pos] == bom_UTF16LE[0] && buf[pos+1] == bom_UTF16LE[1] {
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		parser.encoding = yaml_UTF16LE_ENCODING
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		parser.raw_buffer_pos += 2
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		parser.offset += 2
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	} else if avail >= 2 && buf[pos] == bom_UTF16BE[0] && buf[pos+1] == bom_UTF16BE[1] {
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		parser.encoding = yaml_UTF16BE_ENCODING
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		parser.raw_buffer_pos += 2
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		parser.offset += 2
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	} else if avail >= 3 && buf[pos] == bom_UTF8[0] && buf[pos+1] == bom_UTF8[1] && buf[pos+2] == bom_UTF8[2] {
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		parser.encoding = yaml_UTF8_ENCODING
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		parser.raw_buffer_pos += 3
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		parser.offset += 3
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	} else {
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		parser.encoding = yaml_UTF8_ENCODING
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	}
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	return true
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}
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// Update the raw buffer.
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func yaml_parser_update_raw_buffer(parser *yaml_parser_t) bool {
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	size_read := 0
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	// Return if the raw buffer is full.
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	if parser.raw_buffer_pos == 0 && len(parser.raw_buffer) == cap(parser.raw_buffer) {
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		return true
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	}
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	// Return on EOF.
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	if parser.eof {
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		return true
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	}
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	// Move the remaining bytes in the raw buffer to the beginning.
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	if parser.raw_buffer_pos > 0 && parser.raw_buffer_pos < len(parser.raw_buffer) {
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		copy(parser.raw_buffer, parser.raw_buffer[parser.raw_buffer_pos:])
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	}
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	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)-parser.raw_buffer_pos]
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	parser.raw_buffer_pos = 0
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	// Call the read handler to fill the buffer.
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	size_read, err := parser.read_handler(parser, parser.raw_buffer[len(parser.raw_buffer):cap(parser.raw_buffer)])
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	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)+size_read]
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	if err == io.EOF {
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		parser.eof = true
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	} else if err != nil {
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		return yaml_parser_set_reader_error(parser, "input error: "+err.Error(), parser.offset, -1)
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	}
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	return true
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}
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// Ensure that the buffer contains at least `length` characters.
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// Return true on success, false on failure.
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//
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// The length is supposed to be significantly less that the buffer size.
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func yaml_parser_update_buffer(parser *yaml_parser_t, length int) bool {
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	if parser.read_handler == nil {
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		panic("read handler must be set")
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	}
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	// [Go] This function was changed to guarantee the requested length size at EOF.
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	// The fact we need to do this is pretty awful, but the description above implies
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	// for that to be the case, and there are tests
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	// If the EOF flag is set and the raw buffer is empty, do nothing.
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	if parser.eof && parser.raw_buffer_pos == len(parser.raw_buffer) {
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		// [Go] ACTUALLY! Read the documentation of this function above.
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		// This is just broken. To return true, we need to have the
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		// given length in the buffer. Not doing that means every single
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		// check that calls this function to make sure the buffer has a
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		// given length is Go) panicking; or C) accessing invalid memory.
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		//return true
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	}
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	// Return if the buffer contains enough characters.
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	if parser.unread >= length {
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		return true
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	}
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	// Determine the input encoding if it is not known yet.
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	if parser.encoding == yaml_ANY_ENCODING {
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		if !yaml_parser_determine_encoding(parser) {
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			return false
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		}
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	}
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	// Move the unread characters to the beginning of the buffer.
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	buffer_len := len(parser.buffer)
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	if parser.buffer_pos > 0 && parser.buffer_pos < buffer_len {
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		copy(parser.buffer, parser.buffer[parser.buffer_pos:])
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		buffer_len -= parser.buffer_pos
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		parser.buffer_pos = 0
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	} else if parser.buffer_pos == buffer_len {
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		buffer_len = 0
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		parser.buffer_pos = 0
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	}
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	// Open the whole buffer for writing, and cut it before returning.
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	parser.buffer = parser.buffer[:cap(parser.buffer)]
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	// Fill the buffer until it has enough characters.
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	first := true
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	for parser.unread < length {
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		// Fill the raw buffer if necessary.
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		if !first || parser.raw_buffer_pos == len(parser.raw_buffer) {
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			if !yaml_parser_update_raw_buffer(parser) {
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				parser.buffer = parser.buffer[:buffer_len]
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				return false
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			}
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		}
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		first = false
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		// Decode the raw buffer.
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	inner:
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		for parser.raw_buffer_pos != len(parser.raw_buffer) {
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			var value rune
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			var width int
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			raw_unread := len(parser.raw_buffer) - parser.raw_buffer_pos
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			// Decode the next character.
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			switch parser.encoding {
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			case yaml_UTF8_ENCODING:
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				// Decode a UTF-8 character.  Check RFC 3629
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				// (http://www.ietf.org/rfc/rfc3629.txt) for more details.
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				//
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				// The following table (taken from the RFC) is used for
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				// decoding.
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				//
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				//    Char. number range |        UTF-8 octet sequence
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				//      (hexadecimal)    |              (binary)
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				//   --------------------+------------------------------------
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				//   0000 0000-0000 007F | 0xxxxxxx
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				//   0000 0080-0000 07FF | 110xxxxx 10xxxxxx
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				//   0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
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				//   0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
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				//
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				// Additionally, the characters in the range 0xD800-0xDFFF
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				// are prohibited as they are reserved for use with UTF-16
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				// surrogate pairs.
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				// Determine the length of the UTF-8 sequence.
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				octet := parser.raw_buffer[parser.raw_buffer_pos]
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				switch {
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				case octet&0x80 == 0x00:
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					width = 1
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				case octet&0xE0 == 0xC0:
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					width = 2
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				case octet&0xF0 == 0xE0:
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					width = 3
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				case octet&0xF8 == 0xF0:
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					width = 4
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				default:
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					// The leading octet is invalid.
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					return yaml_parser_set_reader_error(parser,
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						"invalid leading UTF-8 octet",
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						parser.offset, int(octet))
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				}
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				// Check if the raw buffer contains an incomplete character.
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				if width > raw_unread {
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					if parser.eof {
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						return yaml_parser_set_reader_error(parser,
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							"incomplete UTF-8 octet sequence",
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							parser.offset, -1)
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					}
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					break inner
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				}
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				// Decode the leading octet.
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				switch {
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				case octet&0x80 == 0x00:
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					value = rune(octet & 0x7F)
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				case octet&0xE0 == 0xC0:
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					value = rune(octet & 0x1F)
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				case octet&0xF0 == 0xE0:
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					value = rune(octet & 0x0F)
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				case octet&0xF8 == 0xF0:
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					value = rune(octet & 0x07)
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				default:
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					value = 0
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				}
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				// Check and decode the trailing octets.
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				for k := 1; k < width; k++ {
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					octet = parser.raw_buffer[parser.raw_buffer_pos+k]
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					// Check if the octet is valid.
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					if (octet & 0xC0) != 0x80 {
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						return yaml_parser_set_reader_error(parser,
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							"invalid trailing UTF-8 octet",
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							parser.offset+k, int(octet))
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					}
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					// Decode the octet.
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					value = (value << 6) + rune(octet&0x3F)
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				}
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				// Check the length of the sequence against the value.
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				switch {
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				case width == 1:
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				case width == 2 && value >= 0x80:
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				case width == 3 && value >= 0x800:
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				case width == 4 && value >= 0x10000:
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				default:
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					return yaml_parser_set_reader_error(parser,
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						"invalid length of a UTF-8 sequence",
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						parser.offset, -1)
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				}
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				// Check the range of the value.
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				if value >= 0xD800 && value <= 0xDFFF || value > 0x10FFFF {
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					return yaml_parser_set_reader_error(parser,
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						"invalid Unicode character",
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						parser.offset, int(value))
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				}
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			case yaml_UTF16LE_ENCODING, yaml_UTF16BE_ENCODING:
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				var low, high int
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				if parser.encoding == yaml_UTF16LE_ENCODING {
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					low, high = 0, 1
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				} else {
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					low, high = 1, 0
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				}
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				// The UTF-16 encoding is not as simple as one might
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				// naively think.  Check RFC 2781
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				// (http://www.ietf.org/rfc/rfc2781.txt).
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				//
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				// Normally, two subsequent bytes describe a Unicode
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				// character.  However a special technique (called a
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				// surrogate pair) is used for specifying character
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				// values larger than 0xFFFF.
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				//
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				// A surrogate pair consists of two pseudo-characters:
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				//      high surrogate area (0xD800-0xDBFF)
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				//      low surrogate area (0xDC00-0xDFFF)
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				//
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				// The following formulas are used for decoding
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				// and encoding characters using surrogate pairs:
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				//
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				//  U  = U' + 0x10000   (0x01 00 00 <= U <= 0x10 FF FF)
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				//  U' = yyyyyyyyyyxxxxxxxxxx   (0 <= U' <= 0x0F FF FF)
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				//  W1 = 110110yyyyyyyyyy
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				//  W2 = 110111xxxxxxxxxx
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				//
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				// where U is the character value, W1 is the high surrogate
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				// area, W2 is the low surrogate area.
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				// Check for incomplete UTF-16 character.
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				if raw_unread < 2 {
310
					if parser.eof {
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						return yaml_parser_set_reader_error(parser,
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							"incomplete UTF-16 character",
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							parser.offset, -1)
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					}
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					break inner
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				}
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				// Get the character.
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				value = rune(parser.raw_buffer[parser.raw_buffer_pos+low]) +
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					(rune(parser.raw_buffer[parser.raw_buffer_pos+high]) << 8)
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				// Check for unexpected low surrogate area.
323
				if value&0xFC00 == 0xDC00 {
324
					return yaml_parser_set_reader_error(parser,
325
						"unexpected low surrogate area",
326
						parser.offset, int(value))
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				}
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				// Check for a high surrogate area.
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				if value&0xFC00 == 0xD800 {
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					width = 4
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					// Check for incomplete surrogate pair.
334
					if raw_unread < 4 {
335
						if parser.eof {
336
							return yaml_parser_set_reader_error(parser,
337
								"incomplete UTF-16 surrogate pair",
338
								parser.offset, -1)
339
						}
340
						break inner
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					}
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343
					// Get the next character.
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					value2 := rune(parser.raw_buffer[parser.raw_buffer_pos+low+2]) +
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						(rune(parser.raw_buffer[parser.raw_buffer_pos+high+2]) << 8)
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347
					// Check for a low surrogate area.
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					if value2&0xFC00 != 0xDC00 {
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						return yaml_parser_set_reader_error(parser,
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							"expected low surrogate area",
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							parser.offset+2, int(value2))
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					}
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					// Generate the value of the surrogate pair.
355
					value = 0x10000 + ((value & 0x3FF) << 10) + (value2 & 0x3FF)
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				} else {
357
					width = 2
358
				}
359

360
			default:
361
				panic("impossible")
362
			}
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364
			// Check if the character is in the allowed range:
365
			//      #x9 | #xA | #xD | [#x20-#x7E]               (8 bit)
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			//      | #x85 | [#xA0-#xD7FF] | [#xE000-#xFFFD]    (16 bit)
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			//      | [#x10000-#x10FFFF]                        (32 bit)
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			switch {
369
			case value == 0x09:
370
			case value == 0x0A:
371
			case value == 0x0D:
372
			case value >= 0x20 && value <= 0x7E:
373
			case value == 0x85:
374
			case value >= 0xA0 && value <= 0xD7FF:
375
			case value >= 0xE000 && value <= 0xFFFD:
376
			case value >= 0x10000 && value <= 0x10FFFF:
377
			default:
378
				return yaml_parser_set_reader_error(parser,
379
					"control characters are not allowed",
380
					parser.offset, int(value))
381
			}
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			// Move the raw pointers.
384
			parser.raw_buffer_pos += width
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			parser.offset += width
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387
			// Finally put the character into the buffer.
388
			if value <= 0x7F {
389
				// 0000 0000-0000 007F . 0xxxxxxx
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				parser.buffer[buffer_len+0] = byte(value)
391
				buffer_len += 1
392
			} else if value <= 0x7FF {
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				// 0000 0080-0000 07FF . 110xxxxx 10xxxxxx
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				parser.buffer[buffer_len+0] = byte(0xC0 + (value >> 6))
395
				parser.buffer[buffer_len+1] = byte(0x80 + (value & 0x3F))
396
				buffer_len += 2
397
			} else if value <= 0xFFFF {
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				// 0000 0800-0000 FFFF . 1110xxxx 10xxxxxx 10xxxxxx
399
				parser.buffer[buffer_len+0] = byte(0xE0 + (value >> 12))
400
				parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 6) & 0x3F))
401
				parser.buffer[buffer_len+2] = byte(0x80 + (value & 0x3F))
402
				buffer_len += 3
403
			} else {
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				// 0001 0000-0010 FFFF . 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
405
				parser.buffer[buffer_len+0] = byte(0xF0 + (value >> 18))
406
				parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 12) & 0x3F))
407
				parser.buffer[buffer_len+2] = byte(0x80 + ((value >> 6) & 0x3F))
408
				parser.buffer[buffer_len+3] = byte(0x80 + (value & 0x3F))
409
				buffer_len += 4
410
			}
411

412
			parser.unread++
413
		}
414

415
		// On EOF, put NUL into the buffer and return.
416
		if parser.eof {
417
			parser.buffer[buffer_len] = 0
418
			buffer_len++
419
			parser.unread++
420
			break
421
		}
422
	}
423
	// [Go] Read the documentation of this function above. To return true,
424
	// we need to have the given length in the buffer. Not doing that means
425
	// every single check that calls this function to make sure the buffer
426
	// has a given length is Go) panicking; or C) accessing invalid memory.
427
	// This happens here due to the EOF above breaking early.
428
	for buffer_len < length {
429
		parser.buffer[buffer_len] = 0
430
		buffer_len++
431
	}
432
	parser.buffer = parser.buffer[:buffer_len]
433
	return true
434
}
435

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