xref: /third_party/icu/icu4c/source/common/rbbirpt.txt

#*****************************************************************************
#
#   Copyright (C) 2016 and later: Unicode, Inc. and others.
#   License & terms of use: http://www.unicode.org/copyright.html
#
#*****************************************************************************
#*****************************************************************************
#
#   Copyright (C) 2002-2016, International Business Machines Corporation and others.
#   All Rights Reserved.
#
#*****************************************************************************
#
#  file:  rbbirpt.txt
#  ICU Break Iterator Rule Parser State Table
#
#     This state table is used when reading and parsing a set of RBBI rules
#     The rule parser uses a state machine; the data in this file define the
#     state transitions that occur for each input character.
#
#     *** This file defines the RBBI rule grammar.   This is it.
#     *** The determination of what is accepted is here.
#
#     This file is processed by a perl script "rbbicst.pl" to produce initialized C arrays
#     that are then built with the rule parser.
#
#    perl rbbicst.pl    < rbbirpt.txt > rbbirpt.h

#
# Here is the syntax of the state definitions in this file:
#
#
#StateName:
#   input-char           n next-state           ^push-state     action    
#   input-char           n next-state           ^push-state     action    
#       |                |   |                      |             |
#       |                |   |                      |             |--- action to be performed by state machine
#       |                |   |                      |                  See function RBBIRuleScanner::doParseActions()
#       |                |   |                      |
#       |                |   |                      |--- Push this named state onto the state stack.
#       |                |   |                           Later, when next state is specified as "pop",
#       |                |   |                           the pushed state will become the current state.
#       |                |   |
#       |                |   |--- Transition to this state if the current input character matches the input
#       |                |        character or char class in the left hand column.  "pop" causes the next
#       |                |        state to be popped from the state stack.
#       |                |
#       |                |--- When making the state transition specified on this line, advance to the next
#       |                     character from the input only if 'n' appears here.
#       |
#       |--- Character or named character classes to test for.  If the current character being scanned
#            matches, perform the actions and go to the state specified on this line.
#            The input character is tested sequentally, in the order written.  The characters and
#            character classes tested for do not need to be mutually exclusive.  The first match wins.
#            




#
#  start state, scan position is at the beginning of the rules file, or in between two rules.
#
start:
    escaped                term                  ^break-rule-end    doExprStart                       
    white_space          n start                     
    '^'                  n start-after-caret     ^break-rule-end    doNoChain
    '$'                    scan-var-name         ^assign-or-rule    doExprStart
    '!'                  n rev-option                             
    ';'                  n start                                                  # ignore empty rules.
    eof                    exit              
    default                term                  ^break-rule-end    doExprStart
    
#
#  break-rule-end:  Returned from doing a break-rule expression.
#
break-rule-end:
    ';'	                 n start                                    doEndOfRule
    white_space          n break-rule-end
    default                errorDeath                               doRuleError
     
#
# start of a rule, after having seen a '^' (inhibits rule chain in).
#     Similar to the main 'start' state in most respects, except
#          - empty rule is an error.
#          - A second '^' is an error.
#
start-after-caret:
    escaped                term                                     doExprStart
    white_space          n start-after-caret
    '^'                    errorDeath                               doRuleError    # two '^'s
    '$'                    scan-var-name         ^term-var-ref      doExprStart
    ';'                    errorDeath                               doRuleError    # ^ ;
    eof                    errorDeath                               doRuleError
    default                term                                     doExprStart
 
#
#   !               We've just scanned a '!', indicating either a !!key word flag or a
#                   !Reverse rule.
#
rev-option:
    '!'                  n option-scan1   
    default                reverse-rule           ^break-rule-end   doReverseDir
    
option-scan1:
    name_start_char      n option-scan2                             doOptionStart
    default                errorDeath                               doRuleError
    
option-scan2:
    name_char            n option-scan2
    default                option-scan3                             doOptionEnd
    
option-scan3:
    ';'                  n start 
    white_space          n option-scan3 
    default                errorDeath                               doRuleError 
    

reverse-rule:
    default                term                   ^break-rule-end   doExprStart
    
    
#
#  term.  Eat through a single rule character, or a composite thing, which
#         could be a parenthesized expression, a variable name, or a Unicode Set.
#
term:
    escaped              n expr-mod                                 doRuleChar
    white_space          n term
    rule_char            n expr-mod                                 doRuleChar
    '['                    scan-unicode-set      ^expr-mod
    '('                  n term                  ^expr-mod          doLParen
    '$'                    scan-var-name         ^term-var-ref
    '.'                  n expr-mod                                 doDotAny
    default                errorDeath                               doRuleError
    
    

#
#  term-var-ref   We've just finished scanning a reference to a $variable.
#                 Check that the variable was defined.
#                 The variable name scanning is in common with assignment statements,
#                 so the check can't be done there.
term-var-ref:
    default                expr-mod                                 doCheckVarDef
    
    
#
#   expr-mod      We've just finished scanning a term, now look for the optional
#                 trailing '*', '?', '+'
#
expr-mod:
    white_space          n  expr-mod
    '*'                  n  expr-cont                               doUnaryOpStar
    '+'                  n  expr-cont                               doUnaryOpPlus
    '?'                  n  expr-cont                               doUnaryOpQuestion
    default                 expr-cont 
    
    
#
#  expr-cont      Expression, continuation.  At a point where additional terms are
#                                            allowed, but not required.
#
expr-cont:
    escaped                 term                                    doExprCatOperator
    white_space          n  expr-cont
    rule_char               term                                    doExprCatOperator
    '['                     term                                    doExprCatOperator
    '('                     term                                    doExprCatOperator
    '$'                     term                                    doExprCatOperator
    '.'                     term                                    doExprCatOperator
    '/'                     look-ahead                              doExprCatOperator
    '{'                  n  tag-open                                doExprCatOperator
    '|'                  n  term                                    doExprOrOperator
    ')'                  n  pop                                     doExprRParen
    default                 pop                                     doExprFinished
    

#
#   look-ahead    Scanning a '/', which identifies a break point, assuming that the
#                 remainder of the expression matches.
#
#                 Generate a parse tree as if this was a special kind of input symbol
#                 appearing in an otherwise normal concatenation expression.
#
look-ahead:
    '/'                   n expr-cont-no-slash                      doSlash
    default                 errorDeath


#
#  expr-cont-no-slash    Expression, continuation.  At a point where additional terms are
#                                            allowed, but not required.  Just like
#                                            expr-cont, above, except that no '/'
#                                            look-ahead symbol is permitted.
#
expr-cont-no-slash:
    escaped                 term                                    doExprCatOperator
    white_space          n  expr-cont
    rule_char               term                                    doExprCatOperator
    '['                     term                                    doExprCatOperator
    '('                     term                                    doExprCatOperator
    '$'                     term                                    doExprCatOperator
    '.'                     term                                    doExprCatOperator
    '|'                  n  term                                    doExprOrOperator
    ')'                  n  pop                                     doExprRParen
    default                 pop                                     doExprFinished


#
#   tags             scanning a '{', the opening delimiter for a tag that identifies
#                    the kind of match.  Scan the whole {dddd} tag, where d=digit
#
tag-open:
    white_space          n  tag-open
    digit_char              tag-value                               doStartTagValue
    default                 errorDeath                              doTagExpectedError
    
tag-value:
    white_space          n  tag-close
    '}'                     tag-close
    digit_char           n  tag-value                               doTagDigit
    default                 errorDeath                              doTagExpectedError
    
tag-close:
    white_space          n  tag-close
    '}'                  n  expr-cont-no-tag                        doTagValue
    default                 errorDeath                              doTagExpectedError
    
    
    
#
#  expr-cont-no-tag    Expression, continuation.  At a point where additional terms are
#                                            allowed, but not required.  Just like
#                                            expr-cont, above, except that no "{ddd}"
#                                            tagging is permitted.
#
expr-cont-no-tag:
    escaped                 term                                    doExprCatOperator
    white_space          n  expr-cont-no-tag
    rule_char               term                                    doExprCatOperator
    '['                     term                                    doExprCatOperator
    '('                     term                                    doExprCatOperator
    '$'                     term                                    doExprCatOperator
    '.'                     term                                    doExprCatOperator
    '/'                     look-ahead                              doExprCatOperator
    '|'                  n  term                                    doExprOrOperator
    ')'                  n  pop                                     doExprRParen
    default                 pop                                     doExprFinished
    
    


#
#   Variable Name Scanning.
#
#                    The state that branched to here must have pushed a return state
#                    to go to after completion of the variable name scanning.
#
#                    The current input character must be the $ that introduces the name.
#                    The $ is consumed here rather than in the state that first detected it
#                    so that the doStartVariableName action only needs to happen in one
#                    place (here), and the other states don't need to worry about it.
#
scan-var-name:
   '$'                  n scan-var-start                            doStartVariableName
   default                errorDeath


scan-var-start:
    name_start_char      n scan-var-body
    default                errorDeath                               doVariableNameExpectedErr
    
scan-var-body:
    name_char            n scan-var-body
    default                pop                                      doEndVariableName
    
    
    
#
#  scan-unicode-set   Unicode Sets are parsed by the the UnicodeSet class.
#                     Within the RBBI parser, after finding the first character
#                     of a Unicode Set, we just hand the rule input at that
#                     point of to the Unicode Set constructor, then pick
#                     up parsing after the close of the set.
#
#                     The action for this state invokes the UnicodeSet parser.
#
scan-unicode-set:
    '['                   n pop                                      doScanUnicodeSet
    'p'                   n pop                                      doScanUnicodeSet
    'P'                   n pop                                      doScanUnicodeSet
    default		    errorDeath 
    
    





#
#  assign-or-rule.   A $variable was encountered at the start of something, could be
#                    either an assignment statement or a rule, depending on whether an '='
#                    follows the variable name.  We get to this state when the variable name
#                    scanning does a return.
#
assign-or-rule:
    white_space          n assign-or-rule
    '='                  n term                  ^assign-end        doStartAssign   # variable was target of assignment
    default                term-var-ref          ^break-rule-end                    # variable was a term in a rule



#
#  assign-end        This state is entered when the end of the expression on the
#                    right hand side of an assignment is found.  We get here via
#                    a pop; this state is pushed when the '=' in an assignment is found.
#
#                    The only thing allowed at this point is a ';'.  The RHS of an
#                    assignment must look like a rule expression, and we come here
#                    when what is being scanned no longer looks like an expression.
#
assign-end:
    ';'                  n start                                    doEndAssign
    default                errorDeath                               doRuleErrorAssignExpr
    
    
    
#
# errorDeath.   This state is specified as the next state whenever a syntax error
#               in the source rules is detected.  Barring bugs, the state machine will never
#               actually get here, but will stop because of the action associated with the error.
#               But, just in case, this state asks the state machine to exit.
errorDeath:
    default              n errorDeath                               doExit