vendor/gopkg.in/yaml.v2/readerc.go - voltctl - Gitiles

 package yaml

 import (
 	"io"
 )

 // Set the reader error and return 0.
 func yaml_parser_set_reader_error(parser *yaml_parser_t, problem string, offset int, value int) bool {
 	parser.error = yaml_READER_ERROR
 	parser.problem = problem
 	parser.problem_offset = offset
 	parser.problem_value = value
 	return false
 }

 // Byte order marks.
 const (
 	bom_UTF8    = "\xef\xbb\xbf"
 	bom_UTF16LE = "\xff\xfe"
 	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.
 func yaml_parser_determine_encoding(parser *yaml_parser_t) bool {
 	// Ensure that we had enough bytes in the raw buffer.
 	for !parser.eof && len(parser.raw_buffer)-parser.raw_buffer_pos < 3 {
 		if !yaml_parser_update_raw_buffer(parser) {
 			return false
 		}
 	}

 	// Determine the encoding.
 	buf := parser.raw_buffer
 	pos := parser.raw_buffer_pos
 	avail := len(buf) - pos
 	if avail >= 2 && buf[pos] == bom_UTF16LE[0] && buf[pos+1] == bom_UTF16LE[1] {
 		parser.encoding = yaml_UTF16LE_ENCODING
 		parser.raw_buffer_pos += 2
 		parser.offset += 2
 	} else if avail >= 2 && buf[pos] == bom_UTF16BE[0] && buf[pos+1] == bom_UTF16BE[1] {
 		parser.encoding = yaml_UTF16BE_ENCODING
 		parser.raw_buffer_pos += 2
 		parser.offset += 2
 	} else if avail >= 3 && buf[pos] == bom_UTF8[0] && buf[pos+1] == bom_UTF8[1] && buf[pos+2] == bom_UTF8[2] {
 		parser.encoding = yaml_UTF8_ENCODING
 		parser.raw_buffer_pos += 3
 		parser.offset += 3
 	} else {
 		parser.encoding = yaml_UTF8_ENCODING
 	}
 	return true
 }

 // Update the raw buffer.
 func yaml_parser_update_raw_buffer(parser *yaml_parser_t) bool {
 	size_read := 0

 	// Return if the raw buffer is full.
 	if parser.raw_buffer_pos == 0 && len(parser.raw_buffer) == cap(parser.raw_buffer) {
 		return true
 	}

 	// Return on EOF.
 	if parser.eof {
 		return true
 	}

 	// Move the remaining bytes in the raw buffer to the beginning.
 	if parser.raw_buffer_pos > 0 && parser.raw_buffer_pos < len(parser.raw_buffer) {
 		copy(parser.raw_buffer, parser.raw_buffer[parser.raw_buffer_pos:])
 	}
 	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)-parser.raw_buffer_pos]
 	parser.raw_buffer_pos = 0

 	// Call the read handler to fill the buffer.
 	size_read, err := parser.read_handler(parser, parser.raw_buffer[len(parser.raw_buffer):cap(parser.raw_buffer)])
 	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)+size_read]
 	if err == io.EOF {
 		parser.eof = true
 	} else if err != nil {
 		return yaml_parser_set_reader_error(parser, "input error: "+err.Error(), parser.offset, -1)
 	}
 	return true
 }

 // Ensure that the buffer contains at least `length` characters.
 // Return true on success, false on failure.
 //
 // The length is supposed to be significantly less that the buffer size.
 func yaml_parser_update_buffer(parser *yaml_parser_t, length int) bool {
 	if parser.read_handler == nil {
 		panic("read handler must be set")
 	}

 	// [Go] This function was changed to guarantee the requested length size at EOF.
 	// The fact we need to do this is pretty awful, but the description above implies
 	// for that to be the case, and there are tests

 	// If the EOF flag is set and the raw buffer is empty, do nothing.
 	if parser.eof && parser.raw_buffer_pos == len(parser.raw_buffer) {
 		// [Go] ACTUALLY! Read the documentation of this function above.
 		// This is just broken. To return true, we need to have the
 		// given length in the buffer. Not doing that means every single
 		// check that calls this function to make sure the buffer has a
 		// given length is Go) panicking; or C) accessing invalid memory.
 		//return true
 	}

 	// Return if the buffer contains enough characters.
 	if parser.unread >= length {
 		return true
 	}

 	// Determine the input encoding if it is not known yet.
 	if parser.encoding == yaml_ANY_ENCODING {
 		if !yaml_parser_determine_encoding(parser) {
 			return false
 		}
 	}

 	// Move the unread characters to the beginning of the buffer.
 	buffer_len := len(parser.buffer)
 	if parser.buffer_pos > 0 && parser.buffer_pos < buffer_len {
 		copy(parser.buffer, parser.buffer[parser.buffer_pos:])
 		buffer_len -= parser.buffer_pos
 		parser.buffer_pos = 0
 	} else if parser.buffer_pos == buffer_len {
 		buffer_len = 0
 		parser.buffer_pos = 0
 	}

 	// Open the whole buffer for writing, and cut it before returning.
 	parser.buffer = parser.buffer[:cap(parser.buffer)]

 	// Fill the buffer until it has enough characters.
 	first := true
 	for parser.unread < length {

 		// Fill the raw buffer if necessary.
 		if !first || parser.raw_buffer_pos == len(parser.raw_buffer) {
 			if !yaml_parser_update_raw_buffer(parser) {
 				parser.buffer = parser.buffer[:buffer_len]
 				return false
 			}
 		}
 		first = false

 		// Decode the raw buffer.
 	inner:
 		for parser.raw_buffer_pos != len(parser.raw_buffer) {
 			var value rune
 			var width int

 			raw_unread := len(parser.raw_buffer) - parser.raw_buffer_pos

 			// Decode the next character.
 			switch parser.encoding {
 			case yaml_UTF8_ENCODING:
 				// Decode a UTF-8 character.  Check RFC 3629
 				// (http://www.ietf.org/rfc/rfc3629.txt) for more details.
 				//
 				// The following table (taken from the RFC) is used for
 				// decoding.
 				//
 				//    Char. number range |        UTF-8 octet sequence
 				//      (hexadecimal)    |              (binary)
 				//   --------------------+------------------------------------
 				//   0000 0000-0000 007F | 0xxxxxxx
 				//   0000 0080-0000 07FF | 110xxxxx 10xxxxxx
 				//   0000 0800-0000 FFFF | 1110xxxx 10xxxxxx 10xxxxxx
 				//   0001 0000-0010 FFFF | 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 				//
 				// Additionally, the characters in the range 0xD800-0xDFFF
 				// are prohibited as they are reserved for use with UTF-16
 				// surrogate pairs.

 				// Determine the length of the UTF-8 sequence.
 				octet := parser.raw_buffer[parser.raw_buffer_pos]
 				switch {
 				case octet&0x80 == 0x00:
 					width = 1
 				case octet&0xE0 == 0xC0:
 					width = 2
 				case octet&0xF0 == 0xE0:
 					width = 3
 				case octet&0xF8 == 0xF0:
 					width = 4
 				default:
 					// The leading octet is invalid.
 					return yaml_parser_set_reader_error(parser,
 						"invalid leading UTF-8 octet",
 						parser.offset, int(octet))
 				}

 				// Check if the raw buffer contains an incomplete character.
 				if width > raw_unread {
 					if parser.eof {
 						return yaml_parser_set_reader_error(parser,
 							"incomplete UTF-8 octet sequence",
 							parser.offset, -1)
 					}
 					break inner
 				}

 				// Decode the leading octet.
 				switch {
 				case octet&0x80 == 0x00:
 					value = rune(octet & 0x7F)
 				case octet&0xE0 == 0xC0:
 					value = rune(octet & 0x1F)
 				case octet&0xF0 == 0xE0:
 					value = rune(octet & 0x0F)
 				case octet&0xF8 == 0xF0:
 					value = rune(octet & 0x07)
 				default:
 					value = 0
 				}

 				// Check and decode the trailing octets.
 				for k := 1; k < width; k++ {
 					octet = parser.raw_buffer[parser.raw_buffer_pos+k]

 					// Check if the octet is valid.
 					if (octet & 0xC0) != 0x80 {
 						return yaml_parser_set_reader_error(parser,
 							"invalid trailing UTF-8 octet",
 							parser.offset+k, int(octet))
 					}

 					// Decode the octet.
 					value = (value << 6) + rune(octet&0x3F)
 				}

 				// Check the length of the sequence against the value.
 				switch {
 				case width == 1:
 				case width == 2 && value >= 0x80:
 				case width == 3 && value >= 0x800:
 				case width == 4 && value >= 0x10000:
 				default:
 					return yaml_parser_set_reader_error(parser,
 						"invalid length of a UTF-8 sequence",
 						parser.offset, -1)
 				}

 				// Check the range of the value.
 				if value >= 0xD800 && value <= 0xDFFF || value > 0x10FFFF {
 					return yaml_parser_set_reader_error(parser,
 						"invalid Unicode character",
 						parser.offset, int(value))
 				}

 			case yaml_UTF16LE_ENCODING, yaml_UTF16BE_ENCODING:
 				var low, high int
 				if parser.encoding == yaml_UTF16LE_ENCODING {
 					low, high = 0, 1
 				} else {
 					low, high = 1, 0
 				}

 				// The UTF-16 encoding is not as simple as one might
 				// naively think.  Check RFC 2781
 				// (http://www.ietf.org/rfc/rfc2781.txt).
 				//
 				// Normally, two subsequent bytes describe a Unicode
 				// character.  However a special technique (called a
 				// surrogate pair) is used for specifying character
 				// values larger than 0xFFFF.
 				//
 				// A surrogate pair consists of two pseudo-characters:
 				//      high surrogate area (0xD800-0xDBFF)
 				//      low surrogate area (0xDC00-0xDFFF)
 				//
 				// The following formulas are used for decoding
 				// and encoding characters using surrogate pairs:
 				//
 				//  U  = U' + 0x10000   (0x01 00 00 <= U <= 0x10 FF FF)
 				//  U' = yyyyyyyyyyxxxxxxxxxx   (0 <= U' <= 0x0F FF FF)
 				//  W1 = 110110yyyyyyyyyy
 				//  W2 = 110111xxxxxxxxxx
 				//
 				// where U is the character value, W1 is the high surrogate
 				// area, W2 is the low surrogate area.

 				// Check for incomplete UTF-16 character.
 				if raw_unread < 2 {
 					if parser.eof {
 						return yaml_parser_set_reader_error(parser,
 							"incomplete UTF-16 character",
 							parser.offset, -1)
 					}
 					break inner
 				}

 				// Get the character.
 				value = rune(parser.raw_buffer[parser.raw_buffer_pos+low]) +
 					(rune(parser.raw_buffer[parser.raw_buffer_pos+high]) << 8)

 				// Check for unexpected low surrogate area.
 				if value&0xFC00 == 0xDC00 {
 					return yaml_parser_set_reader_error(parser,
 						"unexpected low surrogate area",
 						parser.offset, int(value))
 				}

 				// Check for a high surrogate area.
 				if value&0xFC00 == 0xD800 {
 					width = 4

 					// Check for incomplete surrogate pair.
 					if raw_unread < 4 {
 						if parser.eof {
 							return yaml_parser_set_reader_error(parser,
 								"incomplete UTF-16 surrogate pair",
 								parser.offset, -1)
 						}
 						break inner
 					}

 					// Get the next character.
 					value2 := rune(parser.raw_buffer[parser.raw_buffer_pos+low+2]) +
 						(rune(parser.raw_buffer[parser.raw_buffer_pos+high+2]) << 8)

 					// Check for a low surrogate area.
 					if value2&0xFC00 != 0xDC00 {
 						return yaml_parser_set_reader_error(parser,
 							"expected low surrogate area",
 							parser.offset+2, int(value2))
 					}

 					// Generate the value of the surrogate pair.
 					value = 0x10000 + ((value & 0x3FF) << 10) + (value2 & 0x3FF)
 				} else {
 					width = 2
 				}

 			default:
 				panic("impossible")
 			}

 			// Check if the character is in the allowed range:
 			//      #x9 | #xA | #xD | [#x20-#x7E]               (8 bit)
 			//      | #x85 | [#xA0-#xD7FF] | [#xE000-#xFFFD]    (16 bit)
 			//      | [#x10000-#x10FFFF]                        (32 bit)
 			switch {
 			case value == 0x09:
 			case value == 0x0A:
 			case value == 0x0D:
 			case value >= 0x20 && value <= 0x7E:
 			case value == 0x85:
 			case value >= 0xA0 && value <= 0xD7FF:
 			case value >= 0xE000 && value <= 0xFFFD:
 			case value >= 0x10000 && value <= 0x10FFFF:
 			default:
 				return yaml_parser_set_reader_error(parser,
 					"control characters are not allowed",
 					parser.offset, int(value))
 			}

 			// Move the raw pointers.
 			parser.raw_buffer_pos += width
 			parser.offset += width

 			// Finally put the character into the buffer.
 			if value <= 0x7F {
 				// 0000 0000-0000 007F . 0xxxxxxx
 				parser.buffer[buffer_len+0] = byte(value)
 				buffer_len += 1
 			} else if value <= 0x7FF {
 				// 0000 0080-0000 07FF . 110xxxxx 10xxxxxx
 				parser.buffer[buffer_len+0] = byte(0xC0 + (value >> 6))
 				parser.buffer[buffer_len+1] = byte(0x80 + (value & 0x3F))
 				buffer_len += 2
 			} else if value <= 0xFFFF {
 				// 0000 0800-0000 FFFF . 1110xxxx 10xxxxxx 10xxxxxx
 				parser.buffer[buffer_len+0] = byte(0xE0 + (value >> 12))
 				parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 6) & 0x3F))
 				parser.buffer[buffer_len+2] = byte(0x80 + (value & 0x3F))
 				buffer_len += 3
 			} else {
 				// 0001 0000-0010 FFFF . 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
 				parser.buffer[buffer_len+0] = byte(0xF0 + (value >> 18))
 				parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 12) & 0x3F))
 				parser.buffer[buffer_len+2] = byte(0x80 + ((value >> 6) & 0x3F))
 				parser.buffer[buffer_len+3] = byte(0x80 + (value & 0x3F))
 				buffer_len += 4
 			}

 			parser.unread++
 		}

 		// On EOF, put NUL into the buffer and return.
 		if parser.eof {
 			parser.buffer[buffer_len] = 0
 			buffer_len++
 			parser.unread++
 			break
 		}
 	}
 	// [Go] Read the documentation of this function above. To return true,
 	// we need to have the given length in the buffer. Not doing that means
 	// every single check that calls this function to make sure the buffer
 	// has a given length is Go) panicking; or C) accessing invalid memory.
 	// This happens here due to the EOF above breaking early.
 	for buffer_len < length {
 		parser.buffer[buffer_len] = 0
 		buffer_len++
 	}
 	parser.buffer = parser.buffer[:buffer_len]
 	return true
 }
	package yaml

	import (
	"io"
	)

	// Set the reader error and return 0.
	func yaml_parser_set_reader_error(parser *yaml_parser_t, problem string, offset int, value int) bool {
	parser.error = yaml_READER_ERROR
	parser.problem = problem
	parser.problem_offset = offset
	parser.problem_value = value
	return false
	}

	// Byte order marks.
	const (
	bom_UTF8 = "\xef\xbb\xbf"
	bom_UTF16LE = "\xff\xfe"
	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.
	func yaml_parser_determine_encoding(parser *yaml_parser_t) bool {
	// Ensure that we had enough bytes in the raw buffer.
	for !parser.eof && len(parser.raw_buffer)-parser.raw_buffer_pos < 3 {
	if !yaml_parser_update_raw_buffer(parser) {
	return false
	}
	}

	// Determine the encoding.
	buf := parser.raw_buffer
	pos := parser.raw_buffer_pos
	avail := len(buf) - pos
	if avail >= 2 && buf[pos] == bom_UTF16LE[0] && buf[pos+1] == bom_UTF16LE[1] {
	parser.encoding = yaml_UTF16LE_ENCODING
	parser.raw_buffer_pos += 2
	parser.offset += 2
	} else if avail >= 2 && buf[pos] == bom_UTF16BE[0] && buf[pos+1] == bom_UTF16BE[1] {
	parser.encoding = yaml_UTF16BE_ENCODING
	parser.raw_buffer_pos += 2
	parser.offset += 2
	} else if avail >= 3 && buf[pos] == bom_UTF8[0] && buf[pos+1] == bom_UTF8[1] && buf[pos+2] == bom_UTF8[2] {
	parser.encoding = yaml_UTF8_ENCODING
	parser.raw_buffer_pos += 3
	parser.offset += 3
	} else {
	parser.encoding = yaml_UTF8_ENCODING
	}
	return true
	}

	// Update the raw buffer.
	func yaml_parser_update_raw_buffer(parser *yaml_parser_t) bool {
	size_read := 0

	// Return if the raw buffer is full.
	if parser.raw_buffer_pos == 0 && len(parser.raw_buffer) == cap(parser.raw_buffer) {
	return true
	}

	// Return on EOF.
	if parser.eof {
	return true
	}

	// Move the remaining bytes in the raw buffer to the beginning.
	if parser.raw_buffer_pos > 0 && parser.raw_buffer_pos < len(parser.raw_buffer) {
	copy(parser.raw_buffer, parser.raw_buffer[parser.raw_buffer_pos:])
	}
	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)-parser.raw_buffer_pos]
	parser.raw_buffer_pos = 0

	// Call the read handler to fill the buffer.
	size_read, err := parser.read_handler(parser, parser.raw_buffer[len(parser.raw_buffer):cap(parser.raw_buffer)])
	parser.raw_buffer = parser.raw_buffer[:len(parser.raw_buffer)+size_read]
	if err == io.EOF {
	parser.eof = true
	} else if err != nil {
	return yaml_parser_set_reader_error(parser, "input error: "+err.Error(), parser.offset, -1)
	}
	return true
	}

	// Ensure that the buffer contains at least `length` characters.
	// Return true on success, false on failure.
	//
	// The length is supposed to be significantly less that the buffer size.
	func yaml_parser_update_buffer(parser *yaml_parser_t, length int) bool {
	if parser.read_handler == nil {
	panic("read handler must be set")
	}

	// [Go] This function was changed to guarantee the requested length size at EOF.
	// The fact we need to do this is pretty awful, but the description above implies
	// for that to be the case, and there are tests

	// If the EOF flag is set and the raw buffer is empty, do nothing.
	if parser.eof && parser.raw_buffer_pos == len(parser.raw_buffer) {
	// [Go] ACTUALLY! Read the documentation of this function above.
	// This is just broken. To return true, we need to have the
	// given length in the buffer. Not doing that means every single
	// check that calls this function to make sure the buffer has a
	// given length is Go) panicking; or C) accessing invalid memory.
	//return true
	}

	// Return if the buffer contains enough characters.
	if parser.unread >= length {
	return true
	}

	// Determine the input encoding if it is not known yet.
	if parser.encoding == yaml_ANY_ENCODING {
	if !yaml_parser_determine_encoding(parser) {
	return false
	}
	}

	// Move the unread characters to the beginning of the buffer.
	buffer_len := len(parser.buffer)
	if parser.buffer_pos > 0 && parser.buffer_pos < buffer_len {
	copy(parser.buffer, parser.buffer[parser.buffer_pos:])
	buffer_len -= parser.buffer_pos
	parser.buffer_pos = 0
	} else if parser.buffer_pos == buffer_len {
	buffer_len = 0
	parser.buffer_pos = 0
	}

	// Open the whole buffer for writing, and cut it before returning.
	parser.buffer = parser.buffer[:cap(parser.buffer)]

	// Fill the buffer until it has enough characters.
	first := true
	for parser.unread < length {

	// Fill the raw buffer if necessary.
	if !first \|\| parser.raw_buffer_pos == len(parser.raw_buffer) {
	if !yaml_parser_update_raw_buffer(parser) {
	parser.buffer = parser.buffer[:buffer_len]
	return false
	}
	}
	first = false

	// Decode the raw buffer.
	inner:
	for parser.raw_buffer_pos != len(parser.raw_buffer) {
	var value rune
	var width int

	raw_unread := len(parser.raw_buffer) - parser.raw_buffer_pos

	// Decode the next character.
	switch parser.encoding {
	case yaml_UTF8_ENCODING:
	// Decode a UTF-8 character. Check RFC 3629
	// (http://www.ietf.org/rfc/rfc3629.txt) for more details.
	//
	// The following table (taken from the RFC) is used for
	// decoding.
	//
	// Char. number range \| UTF-8 octet sequence
	// (hexadecimal) \| (binary)
	// --------------------+------------------------------------
	// 0000 0000-0000 007F \| 0xxxxxxx
	// 0000 0080-0000 07FF \| 110xxxxx 10xxxxxx
	// 0000 0800-0000 FFFF \| 1110xxxx 10xxxxxx 10xxxxxx
	// 0001 0000-0010 FFFF \| 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
	//
	// Additionally, the characters in the range 0xD800-0xDFFF
	// are prohibited as they are reserved for use with UTF-16
	// surrogate pairs.

	// Determine the length of the UTF-8 sequence.
	octet := parser.raw_buffer[parser.raw_buffer_pos]
	switch {
	case octet&0x80 == 0x00:
	width = 1
	case octet&0xE0 == 0xC0:
	width = 2
	case octet&0xF0 == 0xE0:
	width = 3
	case octet&0xF8 == 0xF0:
	width = 4
	default:
	// The leading octet is invalid.
	return yaml_parser_set_reader_error(parser,
	"invalid leading UTF-8 octet",
	parser.offset, int(octet))
	}

	// Check if the raw buffer contains an incomplete character.
	if width > raw_unread {
	if parser.eof {
	return yaml_parser_set_reader_error(parser,
	"incomplete UTF-8 octet sequence",
	parser.offset, -1)
	}
	break inner
	}

	// Decode the leading octet.
	switch {
	case octet&0x80 == 0x00:
	value = rune(octet & 0x7F)
	case octet&0xE0 == 0xC0:
	value = rune(octet & 0x1F)
	case octet&0xF0 == 0xE0:
	value = rune(octet & 0x0F)
	case octet&0xF8 == 0xF0:
	value = rune(octet & 0x07)
	default:
	value = 0
	}

	// Check and decode the trailing octets.
	for k := 1; k < width; k++ {
	octet = parser.raw_buffer[parser.raw_buffer_pos+k]

	// Check if the octet is valid.
	if (octet & 0xC0) != 0x80 {
	return yaml_parser_set_reader_error(parser,
	"invalid trailing UTF-8 octet",
	parser.offset+k, int(octet))
	}

	// Decode the octet.
	value = (value << 6) + rune(octet&0x3F)
	}

	// Check the length of the sequence against the value.
	switch {
	case width == 1:
	case width == 2 && value >= 0x80:
	case width == 3 && value >= 0x800:
	case width == 4 && value >= 0x10000:
	default:
	return yaml_parser_set_reader_error(parser,
	"invalid length of a UTF-8 sequence",
	parser.offset, -1)
	}

	// Check the range of the value.
	if value >= 0xD800 && value <= 0xDFFF \|\| value > 0x10FFFF {
	return yaml_parser_set_reader_error(parser,
	"invalid Unicode character",
	parser.offset, int(value))
	}

	case yaml_UTF16LE_ENCODING, yaml_UTF16BE_ENCODING:
	var low, high int
	if parser.encoding == yaml_UTF16LE_ENCODING {
	low, high = 0, 1
	} else {
	low, high = 1, 0
	}

	// The UTF-16 encoding is not as simple as one might
	// naively think. Check RFC 2781
	// (http://www.ietf.org/rfc/rfc2781.txt).
	//
	// Normally, two subsequent bytes describe a Unicode
	// character. However a special technique (called a
	// surrogate pair) is used for specifying character
	// values larger than 0xFFFF.
	//
	// A surrogate pair consists of two pseudo-characters:
	// high surrogate area (0xD800-0xDBFF)
	// low surrogate area (0xDC00-0xDFFF)
	//
	// The following formulas are used for decoding
	// and encoding characters using surrogate pairs:
	//
	// U = U' + 0x10000 (0x01 00 00 <= U <= 0x10 FF FF)
	// U' = yyyyyyyyyyxxxxxxxxxx (0 <= U' <= 0x0F FF FF)
	// W1 = 110110yyyyyyyyyy
	// W2 = 110111xxxxxxxxxx
	//
	// where U is the character value, W1 is the high surrogate
	// area, W2 is the low surrogate area.

	// Check for incomplete UTF-16 character.
	if raw_unread < 2 {
	if parser.eof {
	return yaml_parser_set_reader_error(parser,
	"incomplete UTF-16 character",
	parser.offset, -1)
	}
	break inner
	}

	// Get the character.
	value = rune(parser.raw_buffer[parser.raw_buffer_pos+low]) +
	(rune(parser.raw_buffer[parser.raw_buffer_pos+high]) << 8)

	// Check for unexpected low surrogate area.
	if value&0xFC00 == 0xDC00 {
	return yaml_parser_set_reader_error(parser,
	"unexpected low surrogate area",
	parser.offset, int(value))
	}

	// Check for a high surrogate area.
	if value&0xFC00 == 0xD800 {
	width = 4

	// Check for incomplete surrogate pair.
	if raw_unread < 4 {
	if parser.eof {
	return yaml_parser_set_reader_error(parser,
	"incomplete UTF-16 surrogate pair",
	parser.offset, -1)
	}
	break inner
	}

	// Get the next character.
	value2 := rune(parser.raw_buffer[parser.raw_buffer_pos+low+2]) +
	(rune(parser.raw_buffer[parser.raw_buffer_pos+high+2]) << 8)

	// Check for a low surrogate area.
	if value2&0xFC00 != 0xDC00 {
	return yaml_parser_set_reader_error(parser,
	"expected low surrogate area",
	parser.offset+2, int(value2))
	}

	// Generate the value of the surrogate pair.
	value = 0x10000 + ((value & 0x3FF) << 10) + (value2 & 0x3FF)
	} else {
	width = 2
	}

	default:
	panic("impossible")
	}

	// Check if the character is in the allowed range:
	// #x9 \| #xA \| #xD \| [#x20-#x7E] (8 bit)
	// \| #x85 \| [#xA0-#xD7FF] \| [#xE000-#xFFFD] (16 bit)
	// \| [#x10000-#x10FFFF] (32 bit)
	switch {
	case value == 0x09:
	case value == 0x0A:
	case value == 0x0D:
	case value >= 0x20 && value <= 0x7E:
	case value == 0x85:
	case value >= 0xA0 && value <= 0xD7FF:
	case value >= 0xE000 && value <= 0xFFFD:
	case value >= 0x10000 && value <= 0x10FFFF:
	default:
	return yaml_parser_set_reader_error(parser,
	"control characters are not allowed",
	parser.offset, int(value))
	}

	// Move the raw pointers.
	parser.raw_buffer_pos += width
	parser.offset += width

	// Finally put the character into the buffer.
	if value <= 0x7F {
	// 0000 0000-0000 007F . 0xxxxxxx
	parser.buffer[buffer_len+0] = byte(value)
	buffer_len += 1
	} else if value <= 0x7FF {
	// 0000 0080-0000 07FF . 110xxxxx 10xxxxxx
	parser.buffer[buffer_len+0] = byte(0xC0 + (value >> 6))
	parser.buffer[buffer_len+1] = byte(0x80 + (value & 0x3F))
	buffer_len += 2
	} else if value <= 0xFFFF {
	// 0000 0800-0000 FFFF . 1110xxxx 10xxxxxx 10xxxxxx
	parser.buffer[buffer_len+0] = byte(0xE0 + (value >> 12))
	parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 6) & 0x3F))
	parser.buffer[buffer_len+2] = byte(0x80 + (value & 0x3F))
	buffer_len += 3
	} else {
	// 0001 0000-0010 FFFF . 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
	parser.buffer[buffer_len+0] = byte(0xF0 + (value >> 18))
	parser.buffer[buffer_len+1] = byte(0x80 + ((value >> 12) & 0x3F))
	parser.buffer[buffer_len+2] = byte(0x80 + ((value >> 6) & 0x3F))
	parser.buffer[buffer_len+3] = byte(0x80 + (value & 0x3F))
	buffer_len += 4
	}

	parser.unread++
	}

	// On EOF, put NUL into the buffer and return.
	if parser.eof {
	parser.buffer[buffer_len] = 0
	buffer_len++
	parser.unread++
	break
	}
	}
	// [Go] Read the documentation of this function above. To return true,
	// we need to have the given length in the buffer. Not doing that means
	// every single check that calls this function to make sure the buffer
	// has a given length is Go) panicking; or C) accessing invalid memory.
	// This happens here due to the EOF above breaking early.
	for buffer_len < length {
	parser.buffer[buffer_len] = 0
	buffer_len++
	}
	parser.buffer = parser.buffer[:buffer_len]
	return true
	}