Package org.yaml.snakeyaml.scanner

Class ScannerImpl

java.lang.Object
org.yaml.snakeyaml.scanner.ScannerImpl
All Implemented Interfaces:
Scanner
public final class ScannerImpl extends 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 Details

    • NOT_HEXA

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

    • ESCAPE_REPLACEMENTS

      public static final Map<Character,String> ESCAPE_REPLACEMENTS
      A mapping from an escaped character in the input stream to the string representation that they should be replaced with. YAML defines several common and a few uncommon escape sequences.
      See Also:

    • ESCAPE_CODES

      public static final Map<Character,Integer> ESCAPE_CODES
      A mapping from a character to a number of bytes to read-ahead for that escape sequence. These escape sequences are used to handle unicode escaping in the following formats, where H is a hexadecimal character: 
       \xHH         : escaped 8-bit Unicode character
 \uHHHH       : escaped 16-bit Unicode character
 \UHHHHHHHH   : escaped 32-bit Unicode character
      See Also:

    • reader

      private final StreamReader reader

    • done

      private boolean done

    • flowLevel

      private int flowLevel

    • tokens

      private final List<Token> tokens

    • lastToken

      private Token lastToken

    • tokensTaken

      private int tokensTaken

    • indent

      private int indent

    • indents

      private final ArrayStack<Integer> indents

    • parseComments

      private boolean parseComments

    • loaderOptions

      private final LoaderOptions loaderOptions

    • 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.

    • possibleSimpleKeys

      private final Map<Integer,SimpleKey> possibleSimpleKeys

  • Constructor Details

  • Method Details

    • setParseComments

      @Deprecated public ScannerImpl setParseComments(boolean parseComments)
      Deprecated.
      Please use LoaderOptions instead Set the scanner to ignore comments or parse them as a CommentToken.
      Parameters:
      parseComments - true to parse; false to ignore

    • isParseComments

      @Deprecated public boolean isParseComments()
      Deprecated.

    • 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.getToken()

    • getToken

      public Token getToken()
      Return the next token, removing it from the queue.
      Specified by:
      getToken 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(List<Token> tokens)

    • needMoreTokens

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

    • fetchMoreTokens

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

    • escapeChar

      private String escapeChar(String chRepresentation)
      This is implemented in CharConstants in SnakeYAML Engine

    • 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.
      See Also:

    • 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 -
      See Also:

    • 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 '}'.
      See Also:

    • 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.
      See Also:

    • fetchBlockEntry

      private void fetchBlockEntry()
      Fetch an entry in the block style.
      See Also:

    • fetchKey

      private void fetchKey()
      Fetch a key in a block-style mapping.
      See Also:

    • fetchValue

      private void fetchValue()
      Fetch a value in a block-style mapping.
      See Also:

    • fetchAlias

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

    • fetchAnchor

      private void fetchAnchor()
      Fetch an anchor. Anchors take the form: 
       invalid input: '&'(anchor name)
      See Also:

    • fetchTag

      private void fetchTag()
      Fetch a tag. Tags take a complex form.
      See Also:

    • 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.
      See Also:

    • 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.
      See Also:

    • fetchBlockScalar

      private void fetchBlockScalar(char style)
      Fetch a block scalar (literal or folded).
      Parameters:
      style -
      See Also:

    • fetchSingle

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

    • fetchDouble

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

    • fetchFlowScalar

      private void fetchFlowScalar(char style)
      Fetch a flow scalar (single- or double-quoted).
      Parameters:
      style -
      See Also:

    • 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.
      See Also:

    • 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.

    • 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 <TAB>:
       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.

    • scanComment

      private CommentToken scanComment(CommentType type)

    • scanDirective

      private List<Token> scanDirective()

    • scanDirectiveName

      private String scanDirectiveName(Mark startMark)
      Scan a directive name. Directive names are a series of non-space characters.
      See Also:

    • scanYamlDirectiveValue

      private List<Integer> scanYamlDirectiveValue(Mark startMark)

    • scanYamlDirectiveNumber

      private Integer scanYamlDirectiveNumber(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').
      See Also:

    • scanTagDirectiveValue

      private List<String> scanTagDirectiveValue(Mark startMark)

      Read a %TAG directive value: 

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

      See Also:

    • scanTagDirectiveHandle

      private String scanTagDirectiveHandle(Mark startMark)
      Scan a %TAG directive's handle. This is YAML's c-tag-handle.
      Parameters:
      startMark - - beginning of the handle
      Returns:
      scanned handle
      See Also:

    • scanTagDirectivePrefix

      private String scanTagDirectivePrefix(Mark startMark)
      Scan a %TAG directive's prefix. This is YAML's ns-tag-prefix.
      See Also:

    • scanDirectiveIgnoredLine

      private CommentToken scanDirectiveIgnoredLine(Mark startMark)

    • scanAnchor

      private Token scanAnchor(boolean isAnchor)
       The YAML 1.1 specification does not restrict characters for anchors and
 aliases. This may lead to problems.
 see https://bitbucket.org/snakeyaml/snakeyaml/issues/485/alias-names-are-too-permissive-compared-to
 This implementation tries to follow https://github.com/yaml/yaml-spec/blob/master/rfc/RFC-0003.md

    • 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 !<ns-uri-char+> 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 SnakeYaml incorrectly ignores c-ns-non-specific-tag right now.
      See Also:
      • 8.2. Node Tags TODO Note that this method does not enforce rules about local versus global tags!

    • scanBlockScalar

      private List<Token> scanBlockScalar(char style)

    • scanBlockScalarIndicators

      private ScannerImpl.Chomping scanBlockScalarIndicators(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).
      See Also:

    • scanBlockScalarIgnoredLine

      private CommentToken scanBlockScalarIgnoredLine(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 Object[] 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.
      See Also:

    • scanBlockScalarBreaks

      private Object[] scanBlockScalarBreaks(int indent)

    • scanFlowScalar

      private Token scanFlowScalar(char 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 Also:
      • 9.1. Flow Scalar Styles style/syntax 
         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 String scanFlowScalarNonSpaces(boolean doubleQuoted, Mark startMark)
      Scan some number of flow-scalar non-space characters.

    • scanFlowScalarSpaces

      private String scanFlowScalarSpaces(Mark startMark)

    • scanFlowScalarBreaks

      private String scanFlowScalarBreaks(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 String scanPlainSpaces()
      See the specification for details. SnakeYAML and libyaml allow tabs inside plain scalar

    • scanTagHandle

      private String scanTagHandle(String name, 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 Also:
      •  See the specification for details.
 For some strange reasons, the specification does not allow '_' in
 tag handles. I have allowed it anyway.

    • scanTagUri

      private String scanTagUri(String name, 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.

      See Also:

    • scanUriEscapes

      private String scanUriEscapes(String name, Mark startMark)

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

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

    • scanLineBreak

      private String scanLineBreak()
      Scan a line break, transforming: 
       '\r\n' : '\n'
 '\r' : '\n'
 '\n' : '\n'
 '\x85' : '\n'
 default : ''

    • makeTokenList

      private List<Token> makeTokenList(Token... tokens)