Class ScannerImpl

  • All Implemented Interfaces:
    java.util.Iterator<Token>, Scanner

    public final class ScannerImpl
    extends java.lang.Object
    implements Scanner
     Scanner produces tokens of the following types:
     STREAM-START
     STREAM-END
     COMMENT
     DIRECTIVE(name, value)
     DOCUMENT-START
     DOCUMENT-END
     BLOCK-SEQUENCE-START
     BLOCK-MAPPING-START
     BLOCK-END
     FLOW-SEQUENCE-START
     FLOW-MAPPING-START
     FLOW-SEQUENCE-END
     FLOW-MAPPING-END
     BLOCK-ENTRY
     FLOW-ENTRY
     KEY
     VALUE
     ALIAS(value)
     ANCHOR(value)
     TAG(value)
     SCALAR(value, plain, style)
     Read comments in the Scanner code for more details.
     
    • Field Detail

      • DIRECTIVE_PREFIX

        private static final java.lang.String DIRECTIVE_PREFIX
        See Also:
        Constant Field Values
      • EXPECTED_ALPHA_ERROR_PREFIX

        private static final java.lang.String EXPECTED_ALPHA_ERROR_PREFIX
        See Also:
        Constant Field Values
      • NOT_HEXA

        private static final java.util.regex.Pattern NOT_HEXA
        A regular expression matching characters which are not in the hexadecimal set (0-9, A-F, a-f).
      • tokens

        private final java.util.List<Token> tokens
      • indents

        private final ArrayStack<java.lang.Integer> indents
      • possibleSimpleKeys

        private final java.util.Map<java.lang.Integer,​SimpleKey> possibleSimpleKeys
      • done

        private boolean done
      • flowLevel

        private int flowLevel
      • lastToken

        private Token lastToken
      • tokensTaken

        private int tokensTaken
      • indent

        private int indent
      • allowSimpleKey

        private boolean allowSimpleKey
         A simple key is a key that is not denoted by the '?' indicator.
         Example of simple keys:
           ---
           block simple key: value
           ? not a simple key:
           : { flow simple key: value }
         We emit the KEY token before all keys, so when we find a potential
         simple key, we try to locate the corresponding ':' indicator.
         Simple keys should be limited to a single line and 1024 characters.
        
         Can a simple key start at the current position? A simple key may
         start:
         - at the beginning of the line, not counting indentation spaces
               (in block context),
         - after '{', '[', ',' (in the flow context),
         - after '?', ':', '-' (in the block context).
         In the block context, this flag also signifies if a block collection
         may start at the current position.
         
    • Constructor Detail

      • ScannerImpl

        @Deprecated
        public ScannerImpl​(StreamReader reader,
                           LoadSettings settings)
        Deprecated.
        use the other constructor with LoadSettings first
        Parameters:
        reader - - the input
        settings - - configurable options
      • ScannerImpl

        public ScannerImpl​(LoadSettings settings,
                           StreamReader reader)
        Create
        Parameters:
        settings - - configurable options
        reader - - the input
      • ScannerImpl

        @Deprecated
        public ScannerImpl​(StreamReader reader)
        Deprecated.
        it should be used with LoadSettings
        Parameters:
        reader - - the input
    • Method Detail

      • checkToken

        public boolean checkToken​(Token.ID... choices)
        Check whether the next token is one of the given types.
        Specified by:
        checkToken in interface Scanner
        Parameters:
        choices - token IDs to match with
        Returns:
        true if the next token is one of the given types. Returns false if no more tokens are available.
      • peekToken

        public Token peekToken()
        Return the next token, but do not delete it from the queue.
        Specified by:
        peekToken in interface Scanner
        Returns:
        The token that will be returned on the next call to Scanner.next()
      • hasNext

        public boolean hasNext()
        Specified by:
        hasNext in interface java.util.Iterator<Token>
      • next

        public Token next()
        Return the next token, removing it from the queue.
        Specified by:
        next in interface java.util.Iterator<Token>
        Specified by:
        next in interface Scanner
        Returns:
        the coming token
      • addToken

        private void addToken​(Token token)
      • addToken

        private void addToken​(int index,
                              Token token)
      • addAllTokens

        private void addAllTokens​(java.util.List<Token> tokens)
      • isBlockContext

        private boolean isBlockContext()
      • isFlowContext

        private boolean isFlowContext()
      • needMoreTokens

        private boolean needMoreTokens()
        Returns true if more tokens should be scanned.
      • fetchMoreTokens

        private void fetchMoreTokens()
        Fetch one or more tokens from the StreamReader.
      • nextPossibleSimpleKey

        private int nextPossibleSimpleKey()
        Return the number of the nearest possible simple key. Actually we don't need to loop through the whole dictionary.
      • stalePossibleSimpleKeys

        private void stalePossibleSimpleKeys()
         Remove entries that are no longer possible simple keys. According to
         the YAML specification, simple keys
         - should be limited to a single line,
         - should be no longer than 1024 characters.
         Disabling this procedure will allow simple keys of any length and
         height (may cause problems if indentation is broken though).
         
      • savePossibleSimpleKey

        private void savePossibleSimpleKey()
        The next token may start a simple key. We check if it's possible and save its position. This function is called for ALIAS, ANCHOR, TAG, SCALAR(flow), '[', and '{'.
      • removePossibleSimpleKey

        private void removePossibleSimpleKey()
        Remove the saved possible key position at the current flow level.
      • unwindIndent

        private void unwindIndent​(int col)
        * Handle implicitly ending multiple levels of block nodes by decreased indentation. This function becomes important on lines 4 and 7 of this example:
         1) book one:
         2)   part one:
         3)     chapter one
         4)   part two:
         5)     chapter one
         6)     chapter two
         7) book two:
         

        In flow context, tokens should respect indentation. Actually the condition should be `self.indent >= column` according to the spec. But this condition will prohibit intuitively correct constructions such 'as key : { }'

      • addIndent

        private boolean addIndent​(int column)
        Check if we need to increase indentation.
      • fetchStreamStart

        private void fetchStreamStart()
        We always add STREAM-START as the first token and STREAM-END as the last token.
      • fetchStreamEnd

        private void fetchStreamEnd()
      • fetchDirective

        private void fetchDirective()
        Fetch a YAML directive. Directives are presentation details that are interpreted as instructions to the processor. YAML defines two kinds of directives, YAML and TAG; all other types are reserved for future use.
      • fetchDocumentStart

        private void fetchDocumentStart()
        Fetch a document-start token ("---").
      • fetchDocumentEnd

        private void fetchDocumentEnd()
        Fetch a document-end token ("...").
      • fetchDocumentIndicator

        private void fetchDocumentIndicator​(boolean isDocumentStart)
        Fetch a document indicator, either "---" for "document-start", or else "..." for "document-end. The type is chosen by the given boolean.
      • fetchFlowSequenceStart

        private void fetchFlowSequenceStart()
      • fetchFlowMappingStart

        private void fetchFlowMappingStart()
      • fetchFlowCollectionStart

        private void fetchFlowCollectionStart​(boolean isMappingStart)
        Fetch a flow-style collection start, which is either a sequence or a mapping. The type is determined by the given boolean.

        A flow-style collection is in a format similar to JSON. Sequences are started by '[' and ended by ']'; mappings are started by '{' and ended by '}'.

        Parameters:
        isMappingStart - - true for mapping, false for sequence
      • fetchFlowSequenceEnd

        private void fetchFlowSequenceEnd()
      • fetchFlowMappingEnd

        private void fetchFlowMappingEnd()
      • fetchFlowCollectionEnd

        private void fetchFlowCollectionEnd​(boolean isMappingEnd)
        Fetch a flow-style collection end, which is either a sequence or a mapping. The type is determined by the given boolean.

        A flow-style collection is in a format similar to JSON. Sequences are started by '[' and ended by ']'; mappings are started by '{' and ended by '}'.

      • fetchFlowEntry

        private void fetchFlowEntry()
        Fetch an entry in the flow style. Flow-style entries occur either immediately after the start of a collection, or else after a comma.
      • fetchBlockEntry

        private void fetchBlockEntry()
        Fetch an entry in the block style.
      • fetchKey

        private void fetchKey()
        Fetch a key in a block-style mapping.
      • fetchValue

        private void fetchValue()
        Fetch a value in a block-style mapping.
      • fetchAlias

        private void fetchAlias()
        Fetch an alias, which is a reference to an anchor. Aliases take the format:
         *(anchor name)
         
      • fetchAnchor

        private void fetchAnchor()
        Fetch an anchor. Anchors take the form:
         &(anchor name)
         
      • fetchTag

        private void fetchTag()
        Fetch a tag. Tags take a complex form.
      • fetchLiteral

        private void fetchLiteral()
        Fetch a literal scalar, denoted with a vertical-bar. This is the type best used for source code and other content, such as binary data, which must be included verbatim.
      • fetchFolded

        private void fetchFolded()
        Fetch a folded scalar, denoted with a greater-than sign. This is the type best used for long content, such as the text of a chapter or description.
      • fetchBlockScalar

        private void fetchBlockScalar​(ScalarStyle style)
      • fetchSingle

        private void fetchSingle()
        Fetch a single-quoted (') scalar.
      • fetchDouble

        private void fetchDouble()
        Fetch a double-quoted (") scalar.
      • fetchFlowScalar

        private void fetchFlowScalar​(ScalarStyle style)
      • fetchPlain

        private void fetchPlain()
        Fetch a plain scalar.
      • checkDirective

        private boolean checkDirective()
        Returns true if the next thing on the reader is a directive, given that the leading '%' has already been checked.
      • checkDocumentStart

        private boolean checkDocumentStart()
        Returns true if the next thing on the reader is a document-start ("---"). A document-start is always followed immediately by a new line.
      • checkDocumentEnd

        private boolean checkDocumentEnd()
        Returns true if the next thing on the reader is a document-end ("..."). A document-end is always followed immediately by a new line.
      • checkBlockEntry

        private boolean checkBlockEntry()
        Returns true if the next thing on the reader is a block token.
      • checkKey

        private boolean checkKey()
        Returns true if the next thing on the reader is a key token. This is different in SnakeYAML -> '?' may start a token in the flow context
      • checkValue

        private boolean checkValue()
        Returns true if the next thing on the reader is a value token.
      • checkPlain

        private boolean checkPlain()
        Returns true if the next thing on the reader is a plain token.
      • scanToNextToken

        private void scanToNextToken()
         We ignore spaces, line breaks and comments.
         If we find a line break in the block context, we set the flag
         `allow_simple_key` on.
         The byte order mark is stripped if it's the first character in the
         stream. We do not yet support BOM inside the stream as the
         specification requires. Any such mark will be considered as a part
         of the document.
         TODO: We need to make tab handling rules more sane. A good rule is
           Tabs cannot precede tokens
           BLOCK-SEQUENCE-START, BLOCK-MAPPING-START, BLOCK-END,
           KEY(block), VALUE(block), BLOCK-ENTRY
         So the checking code is
           if :
               self.allow_simple_keys = False
         We also need to add the check for `allow_simple_keys == True` to
         `unwind_indent` before issuing BLOCK-END.
         Scanners for block, flow, and plain scalars need to be modified.
         
      • scanDirective

        private java.util.List<Token> scanDirective()
      • scanDirectiveName

        private java.lang.String scanDirectiveName​(java.util.Optional<Mark> startMark)
        Scan a directive name. Directive names are a series of non-space characters.
      • scanYamlDirectiveValue

        private java.util.List<java.lang.Integer> scanYamlDirectiveValue​(java.util.Optional<Mark> startMark)
      • scanYamlDirectiveNumber

        private java.lang.Integer scanYamlDirectiveNumber​(java.util.Optional<Mark> startMark)
        Read a %YAML directive number: this is either the major or the minor part. Stop reading at a non-digit character (usually either '.' or '\n').
      • scanTagDirectiveValue

        private java.util.List<java.lang.String> scanTagDirectiveValue​(java.util.Optional<Mark> startMark)

        Read a %TAG directive value:

         s-ignored-space+ c-tag-handle s-ignored-space+ ns-tag-prefix s-l-comments
         

      • scanTagDirectiveHandle

        private java.lang.String scanTagDirectiveHandle​(java.util.Optional<Mark> startMark)
        Scan a %TAG directive's handle. This is YAML's c-tag-handle.
        Parameters:
        startMark - - start
        Returns:
        the directive value
      • scanTagDirectivePrefix

        private java.lang.String scanTagDirectivePrefix​(java.util.Optional<Mark> startMark)
        Scan a %TAG directive's prefix. This is YAML's ns-tag-prefix.
      • scanDirectiveIgnoredLine

        private CommentToken scanDirectiveIgnoredLine​(java.util.Optional<Mark> startMark)
      • scanAnchor

        private Token scanAnchor​(boolean isAnchor)
         The YAML 1.2 specification does not restrict characters for anchors and
         aliases. This may lead to problems.
         see issue 485
         This implementation tries to follow RFC-0003
         
      • scanTag

        private Token scanTag()
        Scan a Tag property. A Tag property may be specified in one of three ways: c-verbatim-tag, c-ns-shorthand-tag, or c-ns-non-specific-tag

        c-verbatim-tag takes the form ! and must be delivered verbatim (as-is) to the application. In particular, verbatim tags are not subject to tag resolution.

        c-ns-shorthand-tag is a valid tag handle followed by a non-empty suffix. If the tag handle is a c-primary-tag-handle ('!') then the suffix must have all exclamation marks properly URI-escaped (%21); otherwise, the string will look like a named tag handle: !foo!bar would be interpreted as (handle="!foo!", suffix="bar").

        c-ns-non-specific-tag is always a lone '!'; this is only useful for plain scalars, where its specification means that the scalar MUST be resolved to have type tag:yaml.org,2002:str.

        TODO Note that this method does not enforce rules about local versus global tags!

      • scanBlockScalar

        private java.util.List<Token> scanBlockScalar​(ScalarStyle style)
      • scanBlockScalarIndicators

        private ScannerImpl.Chomping scanBlockScalarIndicators​(java.util.Optional<Mark> startMark)
        Scan a block scalar indicator. The block scalar indicator includes two optional components, which may appear in either order.

        A block indentation indicator is a non-zero digit describing the indentation level of the block scalar to follow. This indentation is an additional number of spaces relative to the current indentation level.

        A block chomping indicator is a + or -, selecting the chomping mode away from the default (clip) to either -(strip) or +(keep).

      • scanBlockScalarIgnoredLine

        private CommentToken scanBlockScalarIgnoredLine​(java.util.Optional<Mark> startMark)
        Scan to the end of the line after a block scalar has been scanned; the only things that are permitted at this time are comments and spaces.
      • scanBlockScalarIndentation

        private ScannerImpl.BreakIntentHolder scanBlockScalarIndentation()
        Scans for the indentation of a block scalar implicitly. This mechanism is used only if the block did not explicitly state an indentation to be used.
      • scanFlowScalar

        private Token scanFlowScalar​(ScalarStyle style)
        Scan a flow-style scalar. Flow scalars are presented in one of two forms; first, a flow scalar may be a double-quoted string; second, a flow scalar may be a single-quoted string.
         See the specification for details.
         Note that we loose indentation rules for quoted scalars. Quoted
         scalars don't need to adhere indentation because " and ' clearly
         mark the beginning and the end of them. Therefore we are less
         restrictive then the specification requires. We only need to check
         that document separators are not included in scalars.
         
      • scanFlowScalarNonSpaces

        private java.lang.String scanFlowScalarNonSpaces​(boolean doubleQuoted,
                                                         java.util.Optional<Mark> startMark)
        Scan some number of flow-scalar non-space characters.
      • scanFlowScalarSpaces

        private java.lang.String scanFlowScalarSpaces​(java.util.Optional<Mark> startMark)
      • scanFlowScalarBreaks

        private java.lang.String scanFlowScalarBreaks​(java.util.Optional<Mark> startMark)
      • scanPlain

        private Token scanPlain()
        Scan a plain scalar.

        See the specification for details. We add an additional restriction for the flow context: plain scalars in the flow context cannot contain ',', ':' and '?'. We also keep track of the `allow_simple_key` flag here. Indentation rules are loosed for the flow context.

      • atEndOfPlain

        private boolean atEndOfPlain()
      • scanPlainSpaces

        private java.lang.String scanPlainSpaces()
        See the specification for details. SnakeYAML and libyaml allow tabs inside plain scalar
      • scanTagHandle

        private java.lang.String scanTagHandle​(java.lang.String name,
                                               java.util.Optional<Mark> startMark)

        Scan a Tag handle. A Tag handle takes one of three forms:

         "!" (c-primary-tag-handle)
         "!!" (ns-secondary-tag-handle)
         "!(name)!" (c-named-tag-handle)
         

        Where (name) must be formatted as an ns-word-char.

         See the specification for details.
         For some strange reasons, the specification does not allow '_' in
         tag handles. I have allowed it anyway.
         
      • scanTagUri

        private java.lang.String scanTagUri​(java.lang.String name,
                                            CharConstants range,
                                            java.util.Optional<Mark> startMark)
        Scan a Tag URI. This scanning is valid for both local and global tag directives, because both appear to be valid URIs as far as scanning is concerned. The difference may be distinguished later, in parsing. This method will scan for ns-uri-char*, which covers both cases.

        This method performs no verification that the scanned URI conforms to any particular kind of URI specification.

      • scanUriEscapes

        private java.lang.String scanUriEscapes​(java.lang.String name,
                                                java.util.Optional<Mark> startMark)

        Scan a sequence of %-escaped URI escape codes and convert them into a String representing the unescaped values.

        This method fails for more than 256 bytes' worth of URI-encoded characters in a row. Is this possible? Is this a use-case?

      • scanLineBreak

        private java.util.Optional<java.lang.String> scanLineBreak()
        Scan a line break, transforming:
         '\r\n'   : '\n'
         '\r'     : '\n'
         '\n'     : '\n'
         '\x85'   : '\n'
         default : ''
         
        Returns:
        transformed character or empty string if no line break detected
      • makeTokenList

        private java.util.List<Token> makeTokenList​(Token... tokens)
        Ignore Comment token if they are null, or Comments should not be parsed
        Parameters:
        tokens - - token types
        Returns:
        tokens to be used
      • resetDocumentIndex

        public void resetDocumentIndex()
        Description copied from interface: Scanner
        Set the document index to 0 after a document end
        Specified by:
        resetDocumentIndex in interface Scanner