gtsocial-umbx

decode.go (16993B)

---

 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package text
 
 import (
 	"bytes"
 	"fmt"
 	"io"
 	"strconv"
 	"unicode/utf8"
 
 	"google.golang.org/protobuf/internal/errors"
 )
 
 // Decoder is a token-based textproto decoder.
 type Decoder struct {
 	// lastCall is last method called, either readCall or peekCall.
 	// Initial value is readCall.
 	lastCall call
 
 	// lastToken contains the last read token.
 	lastToken Token
 
 	// lastErr contains the last read error.
 	lastErr error
 
 	// openStack is a stack containing the byte characters for MessageOpen and
 	// ListOpen kinds. The top of stack represents the message or the list that
 	// the current token is nested in. An empty stack means the current token is
 	// at the top level message. The characters '{' and '<' both represent the
 	// MessageOpen kind.
 	openStack []byte
 
 	// orig is used in reporting line and column.
 	orig []byte
 	// in contains the unconsumed input.
 	in []byte
 }
 
 // NewDecoder returns a Decoder to read the given []byte.
 func NewDecoder(b []byte) *Decoder {
 	return &Decoder{orig: b, in: b}
 }
 
 // ErrUnexpectedEOF means that EOF was encountered in the middle of the input.
 var ErrUnexpectedEOF = errors.New("%v", io.ErrUnexpectedEOF)
 
 // call specifies which Decoder method was invoked.
 type call uint8
 
 const (
 	readCall call = iota
 	peekCall
 )
 
 // Peek looks ahead and returns the next token and error without advancing a read.
 func (d *Decoder) Peek() (Token, error) {
 	defer func() { d.lastCall = peekCall }()
 	if d.lastCall == readCall {
 		d.lastToken, d.lastErr = d.Read()
 	}
 	return d.lastToken, d.lastErr
 }
 
 // Read returns the next token.
 // It will return an error if there is no valid token.
 func (d *Decoder) Read() (Token, error) {
 	defer func() { d.lastCall = readCall }()
 	if d.lastCall == peekCall {
 		return d.lastToken, d.lastErr
 	}
 
 	tok, err := d.parseNext(d.lastToken.kind)
 	if err != nil {
 		return Token{}, err
 	}
 
 	switch tok.kind {
 	case comma, semicolon:
 		tok, err = d.parseNext(tok.kind)
 		if err != nil {
 			return Token{}, err
 		}
 	}
 	d.lastToken = tok
 	return tok, nil
 }
 
 const (
 	mismatchedFmt = "mismatched close character %q"
 	unexpectedFmt = "unexpected character %q"
 )
 
 // parseNext parses the next Token based on given last kind.
 func (d *Decoder) parseNext(lastKind Kind) (Token, error) {
 	// Trim leading spaces.
 	d.consume(0)
 	isEOF := false
 	if len(d.in) == 0 {
 		isEOF = true
 	}
 
 	switch lastKind {
 	case EOF:
 		return d.consumeToken(EOF, 0, 0), nil
 
 	case bof:
 		// Start of top level message. Next token can be EOF or Name.
 		if isEOF {
 			return d.consumeToken(EOF, 0, 0), nil
 		}
 		return d.parseFieldName()
 
 	case Name:
 		// Next token can be MessageOpen, ListOpen or Scalar.
 		if isEOF {
 			return Token{}, ErrUnexpectedEOF
 		}
 		switch ch := d.in[0]; ch {
 		case '{', '<':
 			d.pushOpenStack(ch)
 			return d.consumeToken(MessageOpen, 1, 0), nil
 		case '[':
 			d.pushOpenStack(ch)
 			return d.consumeToken(ListOpen, 1, 0), nil
 		default:
 			return d.parseScalar()
 		}
 
 	case Scalar:
 		openKind, closeCh := d.currentOpenKind()
 		switch openKind {
 		case bof:
 			// Top level message.
 			// 	Next token can be EOF, comma, semicolon or Name.
 			if isEOF {
 				return d.consumeToken(EOF, 0, 0), nil
 			}
 			switch d.in[0] {
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		case MessageOpen:
 			// Next token can be MessageClose, comma, semicolon or Name.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case closeCh:
 				d.popOpenStack()
 				return d.consumeToken(MessageClose, 1, 0), nil
 			case otherCloseChar[closeCh]:
 				return Token{}, d.newSyntaxError(mismatchedFmt, ch)
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		case ListOpen:
 			// Next token can be ListClose or comma.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case ']':
 				d.popOpenStack()
 				return d.consumeToken(ListClose, 1, 0), nil
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			default:
 				return Token{}, d.newSyntaxError(unexpectedFmt, ch)
 			}
 		}
 
 	case MessageOpen:
 		// Next token can be MessageClose or Name.
 		if isEOF {
 			return Token{}, ErrUnexpectedEOF
 		}
 		_, closeCh := d.currentOpenKind()
 		switch ch := d.in[0]; ch {
 		case closeCh:
 			d.popOpenStack()
 			return d.consumeToken(MessageClose, 1, 0), nil
 		case otherCloseChar[closeCh]:
 			return Token{}, d.newSyntaxError(mismatchedFmt, ch)
 		default:
 			return d.parseFieldName()
 		}
 
 	case MessageClose:
 		openKind, closeCh := d.currentOpenKind()
 		switch openKind {
 		case bof:
 			// Top level message.
 			// Next token can be EOF, comma, semicolon or Name.
 			if isEOF {
 				return d.consumeToken(EOF, 0, 0), nil
 			}
 			switch ch := d.in[0]; ch {
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		case MessageOpen:
 			// Next token can be MessageClose, comma, semicolon or Name.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case closeCh:
 				d.popOpenStack()
 				return d.consumeToken(MessageClose, 1, 0), nil
 			case otherCloseChar[closeCh]:
 				return Token{}, d.newSyntaxError(mismatchedFmt, ch)
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		case ListOpen:
 			// Next token can be ListClose or comma
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case closeCh:
 				d.popOpenStack()
 				return d.consumeToken(ListClose, 1, 0), nil
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			default:
 				return Token{}, d.newSyntaxError(unexpectedFmt, ch)
 			}
 		}
 
 	case ListOpen:
 		// Next token can be ListClose, MessageStart or Scalar.
 		if isEOF {
 			return Token{}, ErrUnexpectedEOF
 		}
 		switch ch := d.in[0]; ch {
 		case ']':
 			d.popOpenStack()
 			return d.consumeToken(ListClose, 1, 0), nil
 		case '{', '<':
 			d.pushOpenStack(ch)
 			return d.consumeToken(MessageOpen, 1, 0), nil
 		default:
 			return d.parseScalar()
 		}
 
 	case ListClose:
 		openKind, closeCh := d.currentOpenKind()
 		switch openKind {
 		case bof:
 			// Top level message.
 			// Next token can be EOF, comma, semicolon or Name.
 			if isEOF {
 				return d.consumeToken(EOF, 0, 0), nil
 			}
 			switch ch := d.in[0]; ch {
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		case MessageOpen:
 			// Next token can be MessageClose, comma, semicolon or Name.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case closeCh:
 				d.popOpenStack()
 				return d.consumeToken(MessageClose, 1, 0), nil
 			case otherCloseChar[closeCh]:
 				return Token{}, d.newSyntaxError(mismatchedFmt, ch)
 			case ',':
 				return d.consumeToken(comma, 1, 0), nil
 			case ';':
 				return d.consumeToken(semicolon, 1, 0), nil
 			default:
 				return d.parseFieldName()
 			}
 
 		default:
 			// It is not possible to have this case. Let it panic below.
 		}
 
 	case comma, semicolon:
 		openKind, closeCh := d.currentOpenKind()
 		switch openKind {
 		case bof:
 			// Top level message. Next token can be EOF or Name.
 			if isEOF {
 				return d.consumeToken(EOF, 0, 0), nil
 			}
 			return d.parseFieldName()
 
 		case MessageOpen:
 			// Next token can be MessageClose or Name.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case closeCh:
 				d.popOpenStack()
 				return d.consumeToken(MessageClose, 1, 0), nil
 			case otherCloseChar[closeCh]:
 				return Token{}, d.newSyntaxError(mismatchedFmt, ch)
 			default:
 				return d.parseFieldName()
 			}
 
 		case ListOpen:
 			if lastKind == semicolon {
 				// It is not be possible to have this case as logic here
 				// should not have produced a semicolon Token when inside a
 				// list. Let it panic below.
 				break
 			}
 			// Next token can be MessageOpen or Scalar.
 			if isEOF {
 				return Token{}, ErrUnexpectedEOF
 			}
 			switch ch := d.in[0]; ch {
 			case '{', '<':
 				d.pushOpenStack(ch)
 				return d.consumeToken(MessageOpen, 1, 0), nil
 			default:
 				return d.parseScalar()
 			}
 		}
 	}
 
 	line, column := d.Position(len(d.orig) - len(d.in))
 	panic(fmt.Sprintf("Decoder.parseNext: bug at handling line %d:%d with lastKind=%v", line, column, lastKind))
 }
 
 var otherCloseChar = map[byte]byte{
 	'}': '>',
 	'>': '}',
 }
 
 // currentOpenKind indicates whether current position is inside a message, list
 // or top-level message by returning MessageOpen, ListOpen or bof respectively.
 // If the returned kind is either a MessageOpen or ListOpen, it also returns the
 // corresponding closing character.
 func (d *Decoder) currentOpenKind() (Kind, byte) {
 	if len(d.openStack) == 0 {
 		return bof, 0
 	}
 	openCh := d.openStack[len(d.openStack)-1]
 	switch openCh {
 	case '{':
 		return MessageOpen, '}'
 	case '<':
 		return MessageOpen, '>'
 	case '[':
 		return ListOpen, ']'
 	}
 	panic(fmt.Sprintf("Decoder: openStack contains invalid byte %c", openCh))
 }
 
 func (d *Decoder) pushOpenStack(ch byte) {
 	d.openStack = append(d.openStack, ch)
 }
 
 func (d *Decoder) popOpenStack() {
 	d.openStack = d.openStack[:len(d.openStack)-1]
 }
 
 // parseFieldName parses field name and separator.
 func (d *Decoder) parseFieldName() (tok Token, err error) {
 	defer func() {
 		if err == nil && d.tryConsumeChar(':') {
 			tok.attrs |= hasSeparator
 		}
 	}()
 
 	// Extension or Any type URL.
 	if d.in[0] == '[' {
 		return d.parseTypeName()
 	}
 
 	// Identifier.
 	if size := parseIdent(d.in, false); size > 0 {
 		return d.consumeToken(Name, size, uint8(IdentName)), nil
 	}
 
 	// Field number. Identify if input is a valid number that is not negative
 	// and is decimal integer within 32-bit range.
 	if num := parseNumber(d.in); num.size > 0 {
 		str := num.string(d.in)
 		if !num.neg && num.kind == numDec {
 			if _, err := strconv.ParseInt(str, 10, 32); err == nil {
 				return d.consumeToken(Name, num.size, uint8(FieldNumber)), nil
 			}
 		}
 		return Token{}, d.newSyntaxError("invalid field number: %s", str)
 	}
 
 	return Token{}, d.newSyntaxError("invalid field name: %s", errId(d.in))
 }
 
 // parseTypeName parses Any type URL or extension field name. The name is
 // enclosed in [ and ] characters. The C++ parser does not handle many legal URL
 // strings. This implementation is more liberal and allows for the pattern
 // ^[-_a-zA-Z0-9]+([./][-_a-zA-Z0-9]+)*`). Whitespaces and comments are allowed
 // in between [ ], '.', '/' and the sub names.
 func (d *Decoder) parseTypeName() (Token, error) {
 	startPos := len(d.orig) - len(d.in)
 	// Use alias s to advance first in order to use d.in for error handling.
 	// Caller already checks for [ as first character.
 	s := consume(d.in[1:], 0)
 	if len(s) == 0 {
 		return Token{}, ErrUnexpectedEOF
 	}
 
 	var name []byte
 	for len(s) > 0 && isTypeNameChar(s[0]) {
 		name = append(name, s[0])
 		s = s[1:]
 	}
 	s = consume(s, 0)
 
 	var closed bool
 	for len(s) > 0 && !closed {
 		switch {
 		case s[0] == ']':
 			s = s[1:]
 			closed = true
 
 		case s[0] == '/', s[0] == '.':
 			if len(name) > 0 && (name[len(name)-1] == '/' || name[len(name)-1] == '.') {
 				return Token{}, d.newSyntaxError("invalid type URL/extension field name: %s",
 					d.orig[startPos:len(d.orig)-len(s)+1])
 			}
 			name = append(name, s[0])
 			s = s[1:]
 			s = consume(s, 0)
 			for len(s) > 0 && isTypeNameChar(s[0]) {
 				name = append(name, s[0])
 				s = s[1:]
 			}
 			s = consume(s, 0)
 
 		default:
 			return Token{}, d.newSyntaxError(
 				"invalid type URL/extension field name: %s", d.orig[startPos:len(d.orig)-len(s)+1])
 		}
 	}
 
 	if !closed {
 		return Token{}, ErrUnexpectedEOF
 	}
 
 	// First character cannot be '.'. Last character cannot be '.' or '/'.
 	size := len(name)
 	if size == 0 || name[0] == '.' || name[size-1] == '.' || name[size-1] == '/' {
 		return Token{}, d.newSyntaxError("invalid type URL/extension field name: %s",
 			d.orig[startPos:len(d.orig)-len(s)])
 	}
 
 	d.in = s
 	endPos := len(d.orig) - len(d.in)
 	d.consume(0)
 
 	return Token{
 		kind:  Name,
 		attrs: uint8(TypeName),
 		pos:   startPos,
 		raw:   d.orig[startPos:endPos],
 		str:   string(name),
 	}, nil
 }
 
 func isTypeNameChar(b byte) bool {
 	return (b == '-' || b == '_' ||
 		('0' <= b && b <= '9') ||
 		('a' <= b && b <= 'z') ||
 		('A' <= b && b <= 'Z'))
 }
 
 func isWhiteSpace(b byte) bool {
 	switch b {
 	case ' ', '\n', '\r', '\t':
 		return true
 	default:
 		return false
 	}
 }
 
 // parseIdent parses an unquoted proto identifier and returns size.
 // If allowNeg is true, it allows '-' to be the first character in the
 // identifier. This is used when parsing literal values like -infinity, etc.
 // Regular expression matches an identifier: `^[_a-zA-Z][_a-zA-Z0-9]*`
 func parseIdent(input []byte, allowNeg bool) int {
 	var size int
 
 	s := input
 	if len(s) == 0 {
 		return 0
 	}
 
 	if allowNeg && s[0] == '-' {
 		s = s[1:]
 		size++
 		if len(s) == 0 {
 			return 0
 		}
 	}
 
 	switch {
 	case s[0] == '_',
 		'a' <= s[0] && s[0] <= 'z',
 		'A' <= s[0] && s[0] <= 'Z':
 		s = s[1:]
 		size++
 	default:
 		return 0
 	}
 
 	for len(s) > 0 && (s[0] == '_' ||
 		'a' <= s[0] && s[0] <= 'z' ||
 		'A' <= s[0] && s[0] <= 'Z' ||
 		'0' <= s[0] && s[0] <= '9') {
 		s = s[1:]
 		size++
 	}
 
 	if len(s) > 0 && !isDelim(s[0]) {
 		return 0
 	}
 
 	return size
 }
 
 // parseScalar parses for a string, literal or number value.
 func (d *Decoder) parseScalar() (Token, error) {
 	if d.in[0] == '"' || d.in[0] == '\'' {
 		return d.parseStringValue()
 	}
 
 	if tok, ok := d.parseLiteralValue(); ok {
 		return tok, nil
 	}
 
 	if tok, ok := d.parseNumberValue(); ok {
 		return tok, nil
 	}
 
 	return Token{}, d.newSyntaxError("invalid scalar value: %s", errId(d.in))
 }
 
 // parseLiteralValue parses a literal value. A literal value is used for
 // bools, special floats and enums. This function simply identifies that the
 // field value is a literal.
 func (d *Decoder) parseLiteralValue() (Token, bool) {
 	size := parseIdent(d.in, true)
 	if size == 0 {
 		return Token{}, false
 	}
 	return d.consumeToken(Scalar, size, literalValue), true
 }
 
 // consumeToken constructs a Token for given Kind from d.in and consumes given
 // size-length from it.
 func (d *Decoder) consumeToken(kind Kind, size int, attrs uint8) Token {
 	// Important to compute raw and pos before consuming.
 	tok := Token{
 		kind:  kind,
 		attrs: attrs,
 		pos:   len(d.orig) - len(d.in),
 		raw:   d.in[:size],
 	}
 	d.consume(size)
 	return tok
 }
 
 // newSyntaxError returns a syntax error with line and column information for
 // current position.
 func (d *Decoder) newSyntaxError(f string, x ...interface{}) error {
 	e := errors.New(f, x...)
 	line, column := d.Position(len(d.orig) - len(d.in))
 	return errors.New("syntax error (line %d:%d): %v", line, column, e)
 }
 
 // Position returns line and column number of given index of the original input.
 // It will panic if index is out of range.
 func (d *Decoder) Position(idx int) (line int, column int) {
 	b := d.orig[:idx]
 	line = bytes.Count(b, []byte("\n")) + 1
 	if i := bytes.LastIndexByte(b, '\n'); i >= 0 {
 		b = b[i+1:]
 	}
 	column = utf8.RuneCount(b) + 1 // ignore multi-rune characters
 	return line, column
 }
 
 func (d *Decoder) tryConsumeChar(c byte) bool {
 	if len(d.in) > 0 && d.in[0] == c {
 		d.consume(1)
 		return true
 	}
 	return false
 }
 
 // consume consumes n bytes of input and any subsequent whitespace or comments.
 func (d *Decoder) consume(n int) {
 	d.in = consume(d.in, n)
 	return
 }
 
 // consume consumes n bytes of input and any subsequent whitespace or comments.
 func consume(b []byte, n int) []byte {
 	b = b[n:]
 	for len(b) > 0 {
 		switch b[0] {
 		case ' ', '\n', '\r', '\t':
 			b = b[1:]
 		case '#':
 			if i := bytes.IndexByte(b, '\n'); i >= 0 {
 				b = b[i+len("\n"):]
 			} else {
 				b = nil
 			}
 		default:
 			return b
 		}
 	}
 	return b
 }
 
 // errId extracts a byte sequence that looks like an invalid ID
 // (for the purposes of error reporting).
 func errId(seq []byte) []byte {
 	const maxLen = 32
 	for i := 0; i < len(seq); {
 		if i > maxLen {
 			return append(seq[:i:i], "…"...)
 		}
 		r, size := utf8.DecodeRune(seq[i:])
 		if r > utf8.RuneSelf || (r != '/' && isDelim(byte(r))) {
 			if i == 0 {
 				// Either the first byte is invalid UTF-8 or a
 				// delimiter, or the first rune is non-ASCII.
 				// Return it as-is.
 				i = size
 			}
 			return seq[:i:i]
 		}
 		i += size
 	}
 	// No delimiter found.
 	return seq
 }
 
 // isDelim returns true if given byte is a delimiter character.
 func isDelim(c byte) bool {
 	return !(c == '-' || c == '+' || c == '.' || c == '_' ||
 		('a' <= c && c <= 'z') ||
 		('A' <= c && c <= 'Z') ||
 		('0' <= c && c <= '9'))
 }