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.TH RE2C 1 "" "" ""
.SH NAME
re2c \- convert regular expressions to C/C++ code
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.SH SYNOPSIS
.sp
\fBre2c [OPTIONS] FILE\fP
.SH DESCRIPTION
.sp
\fBre2c\fP is a lexer generator for C/C++. It finds regular expression
specifications inside of C/C++ comments and replaces them with a
hard\-coded DFA. The user must supply some interface code in order to
control and customize the generated DFA.
.SH OPTIONS
.INDENT 0.0
.TP
.B \fB\-? \-h \-\-help\fP
Show help message.
.TP
.B \fB\-b \-\-bit\-vectors\fP
Optimize conditional jumps using bit masks. Implies \fB\-s\fP\&.
.TP
.B \fB\-c \-\-conditions \-\-start\-conditions\fP
Enable support of Flex\-like "conditions": multiple interrelated lexers within one block.
Option \fB\-\-start\-conditions\fP is a legacy alias; use \fB\-\-conditions\fP instead.
.TP
.B \fB\-d \-\-debug\-output\fP
Emit \fBYYDEBUG\fP in the generated code.
\fBYYDEBUG\fP should be defined by the user in the form of a void function with two parameters:
\fBstate\fP (lexer state or \-1) and \fBsymbol\fP (current input symbol of type \fBYYCTYPE\fP).
.TP
.B \fB\-D \-\-emit\-dot\fP
Instead of normal output generate lexer graph in DOT format.
The output can be converted to PNG with the help of Graphviz (something like \fBdot \-Tpng \-odfa.png dfa.dot\fP).
Note that large graphs may crash Graphviz.
.TP
.B \fB\-e \-\-ecb\fP
Generate a lexer that reads input in EBCDIC encoding.
\fBre2c\fP assumes that character range is 0 \-\- 0xFF an character size is 1 byte.
.TP
.B \fB\-f \-\-storable\-state\fP
Generate a lexer which can store its inner state.
This is useful in push\-model lexers which are stopped by an outer program when there is not enough input,
and then resumed when more input becomes available.
In this mode users should additionally define
\fBYYGETSTATE ()\fP and \fBYYSETSTATE (state)\fP macros
and variables \fByych\fP, \fByyaccept\fP and the \fBstate\fP as part of the lexer state.
.TP
.B \fB\-F \-\-flex\-syntax\fP
Partial support for Flex syntax:
in this mode named definitions don\(aqt need the equal sign and the terminating semicolon,
and when used they must be surrounded by curly braces.
Names without curly braces are treated as double\-quoted strings.
.TP
.B \fB\-g \-\-computed\-gotos\fP
Optimize conditional jumps using non\-standard "computed goto" extension (must be supported by C/C++ compiler).
\fBre2c\fP generates jump tables only in complex cases with a lot of conditional branches.
Complexity threshold can be configured with \fBcgoto:threshold\fP configuration.
This option implies \fB\-b\fP\&.
.TP
.B \fB\-i \-\-no\-debug\-info\fP
Do not output \fB#line\fP information.
This is useful when the generated code is tracked by some version control system.
.TP
.B \fB\-o OUTPUT \-\-output=OUTPUT\fP
Specify the \fBOUTPUT\fP file.
.TP
.B \fB\-r \-\-reusable\fP
Allows reuse of \fBre2c\fP rules with \fB/*!rules:re2c */\fP and \fB/*!use:re2c */\fP blocks.
In this mode simple \fB/*!re2c */\fP blocks are not allowed
and exactly one \fB/*!rules:re2c */\fP block must be present.
The rules are saved and used by every \fB/*!use:re2c */\fP block that follows (which may add rules of their own).
This option allows one to reuse the same set of rules with different configurations.
.TP
.B \fB\-s \-\-nested\-ifs\fP
Use nested \fBif\fP statements instead of \fBswitch\fP statements in conditional jumps.
This usually results in more efficient code with non\-optimizing C/C++ compilers.
.TP
.B \fB\-t HEADER \-\-type\-header=HEADER\fP
Generate a \fBHEADER\fP file that contains enum with condition names.
Requires \fB\-c\fP option.
.TP
.B \fB\-T \-\-tags\fP
Enable submatch extraction with tags.
.TP
.B \fB\-P \-\-posix\-captures\fP
Enable submatch extraction with POSIX\-style capturing groups.
.TP
.B \fB\-u \-\-unicode\fP
Generate a lexer that reads input in UTF\-32 encoding.
\fBre2c\fP assumes that character range is 0 \-\- 0x10FFFF and character size is 4 bytes.
Implies \fB\-s\fP\&.
.TP
.B \fB\-v \-\-version\fP
Show version information.
.TP
.B \fB\-V \-\-vernum\fP
Show version information in \fBMMmmpp\fP format (major, minor, patch).
.TP
.B \fB\-w \-\-wide\-chars\fP
Generate a lexer that reads input in UCS\-2 encoding.
\fBre2c\fP assumes that character range is 0 \-\- 0xFFFF and character size is 2 bytes.
Implies \fB\-s\fP\&.
.TP
.B \fB\-x \-\-utf\-16\fP
Generate a lexer that reads input in UTF\-16 encoding.
\fBre2c\fP assumes that character range is 0 \-\- 0x10FFFF and character size is 2 bytes.
Implies \fB\-s\fP\&.
.TP
.B \fB\-8 \-\-utf\-8\fP
Generate a lexer that reads input in UTF\-8 encoding.
\fBre2c\fP assumes that character range is 0 \-\- 0x10FFFF and character size is 1 byte.
.TP
.B \fB\-\-case\-insensitive\fP
Treat single\-quoted and double\-quoted strings as case\-insensitive.
.TP
.B \fB\-\-case\-inverted\fP
Invert the meaning of single\-quoted and double\-quoted strings:
treat single\-quoted strings as case\-sensitive and double\-quoted strings as case\-insensitive.
.TP
.B \fB\-\-no\-generation\-date\fP
Suppress date output in the generated file.
.TP
.B \fB\-\-no\-lookahead\fP
Use TDFA(0) instead of TDFA(1).
This option only has effect with \fB\-\-tags\fP or \fB\-\-posix\-captures\fP options.
.TP
.B \fB\-\-no\-optimize\-tags\fP
Suppress optimization of tag variables (useful for debugging or benchmarking).
.TP
.B \fB\-\-no\-version\fP
Suppress version output in the generated file.
.TP
.B \fB\-\-encoding\-policy POLICY\fP
Define the way \fBre2c\fP treats Unicode surrogates.
\fBPOLICY\fP can be one of the following: \fBfail\fP (abort with an error when a surrogate is encountered),
\fBsubstitute\fP (silently replace surrogates with the error code point 0xFFFD),
\fBignore\fP (default, treat surrogates as normal code points).
The Unicode standard says that standalone surrogates are invalid,
but real\-world libraries and programs behave in different ways.
.TP
.B \fB\-\-input INPUT\fP
Specify \fBre2c\fP input API. \fBINPUT\fP can be either \fBdefault\fP or \fBcustom\fP (enables the use of generic API).
.TP
.B \fB\-S \-\-skeleton\fP
Ignore user\-defined interface code and generate a self\-contained "skeleton" program.
Additionally, generate input files with strings derived from the regular grammar
and compressed match results that are used to verify "skeleton" behavior on all inputs.
This option is useful for finding bugs in optimizations and code generation.
.TP
.B \fB\-\-empty\-class POLICY\fP
Define the way \fBre2c\fP treats empty character classes.
\fBPOLICY\fP can be one of the following: \fBmatch\-empty\fP (match empty input: illogical, but default behavior for backwards compatibility reasons),
\fBmatch\-none\fP (fail to match on any input),
\fBerror\fP (compilation error).
.TP
.B \fB\-\-dfa\-minimization ALGORITHM\fP
The internal algorithm used by re2c to minimize the DFA.
\fBALGORITHM\fP can be either \fBmoore\fP (Moore algorithm, the default) or \fBtable\fP (table filling algorithm).
Both algorithms should produce the same DFA up to states relabeling;
table filling is much slower and serves as a reference implementation.
.TP
.B \fB\-\-eager\-skip\fP
Make the generated lexer advance the input position "eagerly":
immediately after reading input symbol.
By default this happens after transition to the next state.
Implied by \fB\-\-no\-lookahead\fP\&.
.TP
.B \fB\-\-dump\-nfa\fP
Generate representation of NFA in DOT format and dump it on stderr.
.TP
.B \fB\-\-dump\-dfa\-raw\fP
Generate representation of DFA in DOT format under construction and dump it on stderr.
.TP
.B \fB\-\-dump\-dfa\-det\fP
Generate representation of DFA in DOT format immediately after determinization and dump it on stderr.
.TP
.B \fB\-\-dump\-dfa\-tagopt\fP
Generate representation of DFA in DOT format after tag optimizations and dump it on stderr.
.TP
.B \fB\-\-dump\-dfa\-min\fP
Generate representation of DFA in DOT format after minimization and dump it on stderr.
.TP
.B \fB\-\-dump\-adfa\fP
Generate representation of DFA in DOT format after tunneling and dump it on stderr.
.TP
.B \fB\-1 \-\-single\-pass\fP
Deprecated. Does nothing (single pass is the default now).
.UNINDENT
.INDENT 0.0
.TP
.B \fB\-W\fP
Turn on all warnings.
.TP
.B \fB\-Werror\fP
Turn warnings into errors. Note that this option alone
doesn\(aqt turn on any warnings; it only affects those warnings that have
been turned on so far or will be turned on later.
.TP
.B \fB\-W<warning>\fP
Turn on \fBwarning\fP\&.
.TP
.B \fB\-Wno\-<warning>\fP
Turn off \fBwarning\fP\&.
.TP
.B \fB\-Werror\-<warning>\fP
Turn on \fBwarning\fP and treat it as an error (this implies \fB\-W<warning>\fP).
.TP
.B \fB\-Wno\-error\-<warning>\fP
Don\(aqt treat this particular \fBwarning\fP as an error. This doesn\(aqt turn off
the warning itself.
.UNINDENT
.INDENT 0.0
.TP
.B \fB\-Wcondition\-order\fP
Warn if the generated program makes implicit
assumptions about condition numbering. One should use either the \fB\-t, \-\-type\-header\fP option or
the \fB/*!types:re2c*/\fP directive to generate a mapping of condition names to numbers and then use
the autogenerated condition names.
.TP
.B \fB\-Wempty\-character\-class\fP
Warn if a regular expression contains an empty
character class. Trying to match an empty character class makes no sense: it should always fail.
However, for backwards compatibility reasons \fBre2c\fP allows empty character classes and
treats them as empty strings. Use the \fB\-\-empty\-class\fP option to change the default
behavior.
.TP
.B \fB\-Wmatch\-empty\-string\fP
Warn if a rule is nullable (matches an empty string).
If the lexer runs in a loop and the empty match is unintentional,
the lexer may unexpectedly hang in an infinite loop.
.TP
.B \fB\-Wswapped\-range\fP
Warn if the lower bound of a range is greater than its upper
bound. The default behavior is to silently swap the range bounds.
.TP
.B \fB\-Wundefined\-control\-flow\fP
Warn if some input strings cause undefined
control flow in the lexer (the faulty patterns are reported). This is the
most dangerous and most common mistake. It can be easily fixed by adding
the default rule \fB*\fP which has the lowest priority, matches any code unit, and consumes
exactly one code unit.
.TP
.B \fB\-Wunreachable\-rules\fP
Warn about rules that are shadowed by other rules and will never match.
.TP
.B \fB\-Wuseless\-escape\fP
Warn if a symbol is escaped when it shouldn\(aqt be.
By default, re2c silently ignores such escapes, but this may as well indicate a
typo or an error in the escape sequence.
.TP
.B \fB\-Wnondeterministic\-tags\fP
Warn if a tag has \fBn\fP\-th degree of nondeterminism, where \fBn\fP is greater than 1.
.UNINDENT
.SH INTERFACE CODE
.sp
Below is the list of all symbols which may be used by the lexer in order to interact with the outer world.
These symbols should be defined by the user,
either in the form of inplace configurations,
or as C/C++ variables, functions, macros and other language constructs.
Which primitives are necessary depends on the particular use case.
.INDENT 0.0
.TP
.B \fByyaccept\fP
L\-value of unsigned integral type that is used to hold the number of the last matched rule.
Explicit definition by the user is necessary only with \fB\-f\fP \fB\-\-storable\-state\fP option.
.TP
.B \fBYYBACKUP ()\fP
Backup current input position (used only with \fB\-\-input custom\fP option).
.TP
.B \fBYYBACKUPCTX ()\fP
Backup current input position for trailing context (used only with  \fB\-\-input custom\fP option).
.TP
.B \fByych\fP
L\-value of type \fBYYCTYPE\fP that is used to hold current input character.
Explicit definition by the user is necessary only with \fB\-f\fP \fB\-\-storable\-state\fP option.
.TP
.B \fBYYCONDTYPE\fP
The type of \fIcondition\fP identifiers (used only with \fB\-c\fP \fB\-\-conditions\fP option).
Should be generated either with \fB/*!types:re2c*/\fP directive, or with \fB\-t\fP \fB\-\-type\-header\fP option.
.TP
.B \fBYYCTXMARKER\fP
L\-value of type \fBYYCTYPE *\fP that is used to backup input position of trailing context.
It is needed only if regular expressions use the lookahead operator \fB/\fP\&.
.TP
.B \fBYYCTYPE\fP
The type of the input characters (\fIcode units\fP).
Usually it should be \fBunsigned char\fP for ASCII, EBCDIC and UTF\-8 encodings,
\fBunsigned short\fP for UTF\-16 or UCS\-2 encodings,
and \fBunsigned int\fP for UTF\-32 encoding.
.TP
.B \fBYYCURSOR\fP
L\-value of type \fBYYCTYPE *\fP that is used as a pointer to the current input symbol.
Initially \fBYYCURSOR\fP points to the first character and is advanced by the lexer during matching.
When a rule matches, \fBYYCURSOR\fP points past the last character of the matched string.
.TP
.B \fBYYDEBUG (state, symbol)\fP
A function\-like primitive that is used to dump debug information (only used with \fB\-d\fP \fB\-\-debug\-output\fP option).
\fBYYDEBUG\fP should return no value and accept two arguments:
\fBstate\fP (either lexer state or \fB\-1\fP) and \fBsymbol\fP (current input symbol).
.TP
.B \fBYYFILL (n)\fP
A function\-like primitive that is called by the lexer when there is not enough input.
\fBYYFILL\fP should return no value and supply at least \fBn\fP additional characters.
Maximal value of \fBn\fP equals \fBYYMAXFILL\fP, which can be obtained with the \fB/*!max:re2c*/\fP directive.
.TP
.B \fBYYGETCONDITION ()\fP
R\-value of type \fBYYCONDTYPE\fP that represents current \fIcondition\fP identifier (used only with \fB\-c\fP \fB\-\-conditions\fP option).
.TP
.B \fBYYGETSTATE ()\fP
R\-value of signed integral type that represents current lexer state (used only with \fB\-f\fP \fB\-\-storable\-state\fP option).
Initial value of lexer state should be \fB\-1\fP\&.
.TP
.B \fBYYLESSTHAN (n)\fP
R\-value of boolean type that is \fBtrue\fP if and only if there is less than \fBn\fP input characters left (used only with  \fB\-\-input custom\fP option).
.TP
.B \fBYYLIMIT\fP
R\-value of type \fBYYCTYPE *\fP that marks the end of input (\fBYYLIMIT[\-1]\fP should be the last input character).
Lexer compares \fBYYCURSOR\fP and \fBYYLIMIT\fP in order to determine if there is enough input characters left.
.TP
.B \fBYYMARKER\fP
L\-value of type \fBYYCTYPE *\fP used to backup input position of successful match.
This might be necessary if there is an overlapping longer rule that might also match.
.TP
.B \fBYYMTAGP (t)\fP
Append current input position to the history of \fIm\-tag\fP \fBt\fP (used only with \fB\-T\fP \fB\-\-tags\fP option).
.TP
.B \fBYYMTAGN (t)\fP
Append default value to the history of \fIm\-tag\fP \fBt\fP (used only with \fB\-T\fP \fB\-\-tags\fP option).
.TP
.B \fBYYMAXFILL\fP
Integral constant that denotes maximal value of \fBYYFILL\fP argument
and is autogenerated by \fB/*!max:re2c*/\fP directive.
.TP
.B \fBYYMAXNMATCH\fP
Integral constant that denotes maximal number of capturing groups in a rule
and is autogenerated by \fB/*!maxnmatch:re2c*/\fP directive (used only with \fB\-\-posix\-captures\fP option).
.TP
.B \fByynmatch\fP
L\-value of unsigned integral type that is used to hold the number of capturing groups in the matching rule.
Used only with \fB\-P\fP \fB\-\-posix\-captures\fP option.
.TP
.B \fBYYPEEK ()\fP
R\-value of type \fBYYCTYPE\fP that denotes current input character (used only with \fB\-\-input custom\fP option).
.TP
.B \fByypmatch\fP
An array of l\-values that are used to hold the values of \fIs\-tags\fP
corresponding to the capturing parentheses in the matching rule.
The length of array must be at least \fByynmatch * 2\fP (ideally \fBYYMAXNMATCH * 2\fP).
Used only with \fB\-P\fP \fB\-\-posix\-captures\fP option.
.TP
.B \fBYYRESTORE ()\fP
Restore input position (used only with \fB\-\-input custom\fP option).
.TP
.B \fBYYRESTORECTX ()\fP
Restore input position from the value of trailing context (used only with \fB\-\-input custom\fP option).
.TP
.B \fBYYRESTORETAG (t)\fP
Restore input position from the value of \fIs\-tag\fP \fBt\fP (used only with \fB\-\-input custom\fP option).
.TP
.B \fBYYSETCONDITION (condition)\fP
Set current \fIcondition\fP identifier to \fBcondition\fP (used only with \fB\-c\fP \fB\-\-conditions\fP option).
.TP
.B \fBYYSETSTATE (state)\fP
Set current lexer state to \fBstate\fP (used only with \fB\-f\fP \fB\-\-storable\-state\fP option).
Parameter \fBstate\fP is of signed integral type.
.TP
.B \fBYYSKIP ()\fP
Advance input position to the next character (used only with generic API).
.TP
.B \fBYYSTAGP (t)\fP
Save current input position to \fIs\-tag\fP \fBt\fP (used only with \fB\-T\fP \fB\-\-tags\fP and \fB\-\-input custom\fP option).
.TP
.B \fBYYSTAGN (t)\fP
Save default value to \fIs\-tag\fP \fBt\fP (used only with \fB\-T\fP \fB\-\-tags\fP and \fB\-\-input custom\fP options).
.UNINDENT
.SH SYNTAX
.sp
A program can contain any number of \fBre2c\fP blocks.
Each block consists of a sequence of \fBRULES\fP, \fBNAMED DEFINITIONS\fP and \fBINPLACE CONFIGURATIONS\fP\&.
.SS RULES
.sp
Rules consist of a regular expression followed by a user\-defined action:
a block of C/C++ code that is executed in case of successful match.
Action can be either an arbitrary block of code enclosed in curly braces \fB{\fP and \fB}\fP
or a block of code without curly braces preceded with \fB:=\fP and ended with a newline that is not followed by a whitespace.
.sp
If multiple rules match, \fBre2c\fP prefers the longest match.
If rules match the same string, the earlier rule has priority.
.sp
There is one special kind of rule: the \fIdefault rule\fP with \fB*\fP instead of the regular expression.
It always has the lowest priority, matches any \fIcode unit\fP (either valid or invalid) and consumes exactly one \fIcode unit\fP\&.
Note that \fIdefault rule\fP is not the same as \fB[^]\fP, which
matches any valid \fIcode point\fP and can consume multiple \fIcode units\fP\&.
In case of variable\-length encodings \fB*\fP is the only possible way to match invalid input character.
.sp
If \fB\-c\fP \fB\-\-conditions\fP option is used, then rules have more complex form
described in the section about conditions.
.SS NAMED DEFINITIONS
.sp
Named definitions are of the form \fBname = regexp ;\fP
where \fBname\fP is an identifier that consists of letters, digits and underscores,
and \fBregexp\fP is a regular expression.
With \fB\-F\fP \fB\-\-flex\-syntax\fP option named definitions are also of the form \fBname regexp\fP\&.
Each name should be defined before it is used.
.SS INPLACE CONFIGURATIONS
.INDENT 0.0
.TP
.B \fBre2c:cgoto:threshold = 9;\fP
With \fB\-g\fP \fB\-\-computed\-gotos\fP option this value specifies
the complexity threshold that triggers the generation of jump tables rather
than nested \fBif\fP statements and bit masks.
.TP
.B \fBre2c:cond:divider = \(aq/* *********************************** */\(aq;\fP
Allows one to customize the divider for condition blocks. One can use \fB@@\fP to insert condition name.
.TP
.B \fBre2c:cond:divider@cond = @@;\fP
Specifies the placeholder that will be replaced with condition name in \fBre2c:cond:divider\fP\&.
.TP
.B \fBre2c:condenumprefix = yyc;\fP
Specifies the prefix used for condition identifiers.
.TP
.B \fBre2c:cond:goto@cond = @@;\fP
Specifies the placeholder that will be replaced with condition label in \fBre2c:cond:goto\fP\&.
.TP
.B \fBre2c:cond:goto = \(aqgoto @@;\(aq;\fP
Allows one to customize \fBgoto\fP statements used with \fB:=>\fP style rules.
One can use \fB@@\fP to insert the condition name.
.TP
.B \fBre2c:condprefix = yyc;\fP
Specifies the prefix used for condition labels.
.TP
.B \fBre2c:define:YYBACKUPCTX = \(aqYYBACKUPCTX\(aq;\fP
Replaces \fBYYBACKUPCTX\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYBACKUP = \(aqYYBACKUP\(aq;\fP
Replaces \fBYYBACKUP\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYCONDTYPE = \(aqYYCONDTYPE\(aq;\fP
Enumeration type used for condition identifiers.
.TP
.B \fBre2c:define:YYCTXMARKER = \(aqYYCTXMARKER\(aq;\fP
Replaces the \fBYYCTXMARKER\fP placeholder with the specified identifier.
.TP
.B \fBre2c:define:YYCTYPE = \(aqYYCTYPE\(aq;\fP
Replaces the \fBYYCTYPE\fP placeholder with the specified type.
.TP
.B \fBre2c:define:YYCURSOR = \(aqYYCURSOR\(aq;\fP
Replaces the \fBYYCURSOR\fP placeholder with the specified identifier.
.TP
.B \fBre2c:define:YYDEBUG = \(aqYYDEBUG\(aq;\fP
Replaces the \fBYYDEBUG\fP placeholder with the specified identifier.
.TP
.B \fBre2c:define:YYFILL@len = \(aq@@\(aq;\fP
Any occurrence of this text inside of a \fBYYFILL\fP will be replaced with the actual argument.
.TP
.B \fBre2c:define:YYFILL:naked = 0;\fP
Controls the argument in the parentheses after \fBYYFILL\fP and the following semicolon.
If zero, both the argument and the semicolon are omitted.
If non\-zero, the argument is generated unless \fBre2c:yyfill:parameter\fP is set to zero;
the semicolon is generated unconditionally.
.TP
.B \fBre2c:define:YYFILL = \(aqYYFILL\(aq;\fP
Define a substitution for \fBYYFILL\fP\&.
By default re2c generates an argument in parentheses and a semicolon after \fBYYFILL\fP\&.
If you need to make \fBYYFILL\fP an arbitrary statement rather than a call,
set \fBre2c:define:YYFILL:naked\fP to a non\-zero value.
.TP
.B \fBre2c:define:YYGETCONDITION:naked = 0;\fP
Controls the parentheses after \fBYYGETCONDITION\fP\&.
If zero, the parentheses are omitted. If non\-zero, the parentheses are generated.
.TP
.B \fBre2c:define:YYGETCONDITION = \(aqYYGETCONDITION\(aq;\fP
Substitution for \fBYYGETCONDITION\fP\&.
By default re2c generates parentheses after \fBYYGETCONDITION\fP\&.
Set \fBre2c:define:YYGETCONDITION:naked\fP to non\-zero in order to omit the parentheses.
.TP
.B \fBre2c:define:YYGETSTATE:naked = 0;\fP
Controls the parentheses that follow \fBYYGETSTATE\fP\&.
If zero, the parentheses are omitted. If non\-zero, they are generated.
.TP
.B \fBre2c:define:YYGETSTATE = \(aqYYGETSTATE\(aq;\fP
Substitution for \fBYYGETSTATE\fP\&.
By default re2c generates parentheses after \fBYYGETSTATE\fP\&.
Set \fBre2c:define:YYGETSTATE:naked\fP to non\-zero to omit the parentheses.
.TP
.B \fBre2c:define:YYLESSTHAN = \(aqYYLESSTHAN\(aq;\fP
Replaces \fBYYLESSTHAN\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYLIMIT = \(aqYYLIMIT\(aq;\fP
Replaces the \fBYYLIMIT\fP placeholder with the specified identifier.
.TP
.B \fBre2c:define:YYMARKER = \(aqYYMARKER\(aq;\fP
Replaces the \fBYYMARKER\fP placeholder with the specified identifier.
.TP
.B \fBre2c:define:YYMTAGN = \(aqYYMTAGN\(aq;\fP
Replaces \fBYYMTAGN\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYMTAGP = \(aqYYMTAGP\(aq;\fP
Replaces \fBYYMTAGP\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYPEEK = \(aqYYPEEK\(aq;\fP
Replaces \fBYYPEEK\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYRESTORECTX = \(aqYYRESTORECTX\(aq;\fP
Replaces \fBYYRESTORECTX\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYRESTORE = \(aqYYRESTORE\(aq;\fP
Replaces \fBYYRESTORE\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYRESTORETAG = \(aqYYRESTORETAG\(aq;\fP
Replaces \fBYYRESTORETAG\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYSETCONDITION@cond = \(aq@@\(aq;\fP
Any occurrence of this
text inside of \fBYYSETCONDITION\fP will be replaced with the actual argument.
.TP
.B \fBre2c:define:YYSETCONDITION:naked = 0;\fP
Controls the argument in parentheses
and the semicolon after \fBYYSETCONDITION\fP\&. If zero, both the argument and
the semicolon are omitted. If non\-zero, both the argument and the semicolon are
generated.
.TP
.B \fBre2c:define:YYSETCONDITION = \(aqYYSETCONDITION\(aq;\fP
Substitution for
\fBYYSETCONDITION\fP\&. By default re2c generates an argument in
parentheses followed by semicolon after \fBYYSETCONDITION\fP\&. If you need to make
\fBYYSETCONDITION\fP an arbitrary statement rather than a call, set
\fBre2c:define:YYSETCONDITION:naked\fP to non\-zero.
.TP
.B \fBre2c:define:YYSETSTATE:naked = 0;\fP
Controls the argument in parentheses and the
semicolon after \fBYYSETSTATE\fP\&. If zero, both argument and the semicolon are
omitted. If non\-zero, both the argument and the semicolon are generated.
.TP
.B \fBre2c:define:YYSETSTATE@state = \(aq@@\(aq;\fP
Any occurrence of this text
inside of \fBYYSETSTATE\fP will be replaced with the actual argument.
.TP
.B \fBre2c:define:YYSETSTATE = \(aqYYSETSTATE\(aq;\fP
Substitution for
\fBYYSETSTATE\fP\&. By default re2c generates an argument in parentheses
followed by a semicolon after \fBYYSETSTATE\fP\&. If you need to make \fBYYSETSTATE\fP an
arbitrary statement rather than a call, set
\fBre2c:define:YYSETSTATE:naked\fP to non\-zero.
.TP
.B \fBre2c:define:YYSKIP = \(aqYYSKIP\(aq;\fP
Replaces \fBYYSKIP\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYSTAGN = \(aqYYSTAGN\(aq;\fP
Replaces \fBYYSTAGN\fP identifier with the specified string.
.TP
.B \fBre2c:define:YYSTAGP = \(aqYYSTAGP\(aq;\fP
Replaces \fBYYSTAGP\fP identifier with the specified string.
.TP
.B \fBre2c:flags:8\fP or \fBre2c:flags:utf\-8\fP
Same as \fB\-8 \-\-utf\-8\fP command\-line option.
.TP
.B \fBre2c:flags:b\fP or \fBre2c:flags:bit\-vectors\fP
Same as \fB\-b \-\-bit\-vectors\fP command\-line option.
.TP
.B \fBre2c:flags:case\-insensitive = 0;\fP
Same as \fB\-\-case\-insensitive\fP command\-line option.
.TP
.B \fBre2c:flags:case\-inverted = 0;\fP
Same as \fB\-\-case\-inverted\fP command\-line option.
.TP
.B \fBre2c:flags:d\fP or \fBre2c:flags:debug\-output\fP
Same as \fB\-d \-\-debug\-output\fP command\-line option.
.TP
.B \fBre2c:flags:dfa\-minimization = \(aqmoore\(aq;\fP
Same as \fB\-\-dfa\-minimization\fP command\-line option.
.TP
.B \fBre2c:flags:eager\-skip = 0;\fP
Same as \fB\-\-eager\-skip\fP command\-line option.
.TP
.B \fBre2c:flags:e\fP or \fBre2c:flags:ecb\fP
Same as \fB\-e \-\-ecb\fP command\-line option.
.TP
.B \fBre2c:flags:empty\-class = \(aqmatch\-empty\(aq;\fP
Same as \fB\-\-empty\-class\fP command\-line option.
.TP
.B \fBre2c:flags:encoding\-policy = \(aqignore\(aq;\fP
Same as \fB\-\-encoding\-policy\fP command\-line option.
.TP
.B \fBre2c:flags:g\fP or \fBre2c:flags:computed\-gotos\fP
Same as \fB\-g \-\-computed\-gotos\fP command\-line option.
.TP
.B \fBre2c:flags:i\fP or \fBre2c:flags:no\-debug\-info\fP
Same as \fB\-i \-\-no\-debug\-info\fP command\-line option.
.TP
.B \fBre2c:flags:input = \(aqdefault\(aq;\fP
Same as \fB\-\-input\fP command\-line option.
.TP
.B \fBre2c:flags:lookahead = 1;\fP
Same as inverted \fB\-\-no\-lookahead\fP command\-line option.
.TP
.B \fBre2c:flags:optimize\-tags = 1;\fP
Same as inverted \fB\-\-no\-optimize\-tags\fP command\-line option.
.TP
.B \fBre2c:flags:P\fP or \fBre2c:flags:posix\-captures\fP
Same as \fB\-P \-\-posix\-captures\fP command\-line option.
.TP
.B \fBre2c:flags:s\fP or \fBre2c:flags:nested\-ifs\fP
Same as \fB\-s \-\-nested\-ifs\fP command\-line option.
.TP
.B \fBre2c:flags:T\fP or \fBre2c:flags:tags\fP
Same as \fB\-T \-\-tags\fP command\-line option.
.TP
.B \fBre2c:flags:u\fP or \fBre2c:flags:unicode\fP
Same as \fB\-u \-\-unicode\fP command\-line option.
.TP
.B \fBre2c:flags:w\fP or \fBre2c:flags:wide\-chars\fP
Same as \fB\-w \-\-wide\-chars\fP command\-line option.
.TP
.B \fBre2c:flags:x\fP or \fBre2c:flags:utf\-16\fP
Same as \fB\-x \-\-utf\-16\fP command\-line option.
.TP
.B \fBre2c:indent:string = \(aq\et\(aq;\fP
Specifies the string to use for indentation. Requires a string that contains
only whitespace (unless you need something else for external tools). The easiest
way to specify spaces is to enclose them in single or double quotes.
If you do  not want any indentation at all, you can set this to \(aq\(aq.
.TP
.B \fBre2c:indent:top = 0;\fP
Specifies the minimum amount of indentation to
use. Requires a numeric value greater than or equal to zero.
.TP
.B \fBre2c:labelprefix = \(aqyy\(aq;\fP
Allows one to change the prefix of numbered
labels. The default is \fByy\fP\&. Can be set any string that is valid in
a label name.
.TP
.B \fBre2c:label:yyFillLabel = \(aqyyFillLabel\(aq;\fP
Overrides the name of the \fByyFillLabel\fP label.
.TP
.B \fBre2c:label:yyNext = \(aqyyNext\(aq;\fP
Overrides the name of the \fByyNext\fP label.
.TP
.B \fBre2c:startlabel = 0;\fP
If set to a non zero integer, then the start
label of the next scanner block will be generated even if it isn\(aqt used by
the scanner itself. Otherwise, the normal \fByy0\fP\-like start label is only
generated if needed. If set to a text value, then a label with that
text will be generated regardless of whether the normal start label is
used or not. This setting is reset to 0 after a start label has been generated.
.TP
.B \fBre2c:state:abort = 0;\fP
When not zero and the \fB\-f\fP \fB\-\-storable\-state\fP switch is active, then
the \fBYYGETSTATE\fP block will contain a default case that aborts and a \-1
case will be used for initialization.
.TP
.B \fBre2c:state:nextlabel = 0;\fP
Used when \fB\-f\fP \fB\-\-storable\-state\fP is active to control
whether the \fBYYGETSTATE\fP block is followed by a \fByyNext:\fP label line.
Instead of using \fByyNext\fP, you can usually also use configuration
\fBstartlabel\fP to force a specific start label or default to \fByy0\fP as
a start label. Instead of using a dedicated label, it is often better to
separate the \fBYYGETSTATE\fP code from the actual scanner code by placing a
\fB/*!getstate:re2c*/\fP comment.
.TP
.B \fBre2c:tags:expression = \(aq@@\(aq;\fP
Allows one to customize the way re2c addresses tag variables:
by default it emits expressions of the form \fByyt<N>\fP,
but this might be inconvenient if tag variables are defined as fields in a struct,
or for any other reason require special accessors.
For example, setting \fBre2c:tags:expression = p\->@@\fP will result in \fBp\->yyt<N>\fP\&.
.TP
.B \fBre2c:tags:prefix = \(aqyyt\(aq;\fP
Allows one to override prefix of tag variables.
.TP
.B \fBre2c:variable:yyaccept = yyaccept;\fP
Overrides the name of the \fByyaccept\fP variable.
.TP
.B \fBre2c:variable:yybm = \(aqyybm\(aq;\fP
Overrides the name of the \fByybm\fP variable.
.TP
.B \fBre2c:variable:yych = \(aqyych\(aq;\fP
Overrides the name of the \fByych\fP variable.
.TP
.B \fBre2c:variable:yyctable = \(aqyyctable\(aq;\fP
When both \fB\-c\fP \fB\-\-conditions\fP and \fB\-g\fP \fB\-\-computed\-gotos\fP are active,
re2c will use this variable to generate a static jump table
for \fBYYGETCONDITION\fP\&.
.TP
.B \fBre2c:variable:yystable = \(aqyystable\(aq;\fP
Deprecated.
.TP
.B \fBre2c:variable:yytarget = \(aqyytarget\(aq;\fP
Overrides the name of the \fByytarget\fP variable.
.TP
.B \fBre2c:yybm:hex = 0;\fP
If set to zero, a decimal table will be used. Otherwise, a hexadecimal table will be generated.
.TP
.B \fBre2c:yych:conversion = 0;\fP
When this setting is non zero, re2c automatically generates
conversion code whenever yych gets read. In this case, the type must be
defined using \fBre2c:define:YYCTYPE\fP\&.
.TP
.B \fBre2c:yych:emit = 1;\fP
Set this to zero to suppress the generation of \fIyych\fP\&.
.TP
.B \fBre2c:yyfill:check = 1;\fP
This can be set to 0 to suppress the generations of
\fBYYCURSOR\fP and \fBYYLIMIT\fP based precondition checks. This option is useful when
\fBYYLIMIT + YYMAXFILL\fP is always accessible.
.TP
.B \fBre2c:yyfill:enable = 1;\fP
Set this to zero to suppress the generation of \fBYYFILL (n)\fP\&. When using this, be sure to verify that the generated
scanner does not read beyond the available input, as allowing such behavior might
introduce severe security issues to your programs.
.TP
.B \fBre2c:yyfill:parameter = 1;\fP
Controls the argument in the parentheses that follow \fBYYFILL\fP\&. If zero, the argument is omitted.
If non\-zero, the argument is generated unless \fBre2c:define:YYFILL:naked\fP is set to non\-zero.
.UNINDENT
.SS REGULAR EXPRESSIONS
.sp
re2c uses the following syntax for regular expressions:
.INDENT 0.0
.IP \(bu 2
\fB"foo"\fP case\-sensitive string literal
.IP \(bu 2
\fB\(aqfoo\(aq\fP case\-insensitive string literal
.IP \(bu 2
\fB[a\-xyz]\fP, \fB[^a\-xyz]\fP character class (possibly negated)
.IP \(bu 2
\fB\&.\fP any character except newline
.IP \(bu 2
\fBR \e S\fP difference of character classes \fBR\fP and \fBS\fP
.IP \(bu 2
\fBR*\fP zero or more occurrences of \fBR\fP
.IP \(bu 2
\fBR+\fP one or more occurrences of \fBR\fP
.IP \(bu 2
\fBR?\fP optional \fBR\fP
.IP \(bu 2
\fBR{n}\fP repetition of \fBR\fP exactly \fBn\fP times
.IP \(bu 2
\fBR{n,}\fP repetition of \fBR\fP at least \fBn\fP times
.IP \(bu 2
\fBR{n,m}\fP repetition of \fBR\fP from \fBn\fP to \fBm\fP times
.IP \(bu 2
\fB(R)\fP just \fBR\fP; parentheses are used to override precedence or for POSIX\-style submatch
.IP \(bu 2
\fBR S\fP concatenation: \fBR\fP followed by \fBS\fP
.IP \(bu 2
\fBR | S\fP alternative: \fBR or S\fP
.IP \(bu 2
\fBR / S\fP loohakead: \fBR\fP followed by \fBS\fP, but \fBS\fP is not consumed
.IP \(bu 2
\fBname\fP the regular expression defined as \fBname\fP (or literal string \fB"name"\fP in Flex compatibility mode)
.IP \(bu 2
\fB{name}\fP the regular expression defined as \fBname\fP in Flex compatibility mode
.IP \(bu 2
\fB@stag\fP an \fIs\-tag\fP: saves the last input position at which \fB@stag\fP matches in a variable named \fBstag\fP
.IP \(bu 2
\fB#mtag\fP an \fIm\-tag\fP: saves all input positions at which \fB#mtag\fP matches in a variable named \fBmtag\fP
.UNINDENT
.sp
Character classes and string literals may contain the following escape sequences:
\fB\ea\fP, \fB\eb\fP, \fB\ef\fP, \fB\en\fP, \fB\er\fP, \fB\et\fP, \fB\ev\fP, \fB\e\e\fP, octal escapes \fB\eooo\fP and hexadecimal escapes \fB\exhh\fP, \fB\euhhhh\fP and \fB\eUhhhhhhhh\fP\&.
.SH SUBMATCH EXTRACTION
.sp
\fBre2c\fP supports two kinds of submatch extraction.
.sp
The first option is \fB\-P \-\-posix\-captures\fP: it enables POSIX\-compliant capturing groups.
In this mode parentheses in regular expressions denote the beginning and the end of capturing groups;
the whole regular expression is group number zero.
The number of groups for the matching rule is stored in a variable \fByynmatch\fP,
and submatch results are stored in \fByypmatch\fP array.
Both \fByynmatch\fP and \fByypmatch\fP should be defined by the user;
note that \fByypmatch\fP size must be at least \fB[yynmatch * 2]\fP\&.
\fBre2c\fP provides a directive \fB/*!maxnmatch:re2c*/\fP that defines a constant \fBYYMAXNMATCH\fP: the maximal value of \fByynmatch\fP among all rules.
Note that \fBre2c\fP implements POSIX\-compliant disambiguation:
each subexpression matches as long as possible,
and subexpressions that start earlier in regular expression have priority over those starting later.
.sp
Second option is \fB\-T \-\-tags\fP\&.
With this option one can use standalone tags of the form \fB@stag\fP and \fB#mtag\fP instead of capturing parentheses,
where \fBstag\fP and \fBmtag\fP are arbitrary used\-defined names.
Tags can be used anywhere inside of a regular expression; semantically they are just position markers.
Tags of the form \fB@stag\fP are called \fIs\-tags\fP: they denote a single submatch value (the last input position where this tag matched).
Tags of the form \fB#mtag\fP are called \fIm\-tags\fP: they denote multiple submatch values (the whole history of repetitions of this tag).
All tags should be defined by the user as variables with the corresponding names.
With standalone tags \fBre2c\fP uses leftmost greedy disambiguation:
submatch positions correspond to the leftmost matching path through the regular expression.
.sp
With both \fB\-\-posix\-captures\fP and \fB\-\-tags\fP options \fBre2c\fP generates a number of tag variables
that are used by the lexer to track multiple possible versions of each tag
(multiple versions are caused by possible ambiguity of submatch).
When a rule matches, ambiguity is resolved and all tags of this rule (or capturing parentheses, which are also implemented as tags)
are initialized with the values of appropriate tag variables.
Note that there is no one\-to\-one correspondence between tag variables and tags:
the same tag variable may be reused for different tags, and one tag may require multiple tag variables to hold all its ambiguous versions.
The exact number of tag variables is unknown to the user; this number is determined by \fBre2c\fP\&.
However, tag variables should be defined by the user, because it might be necessary to update them in \fBYYFILL\fP
and store them between invocations of lexer with \fB\-\-storable\-state\fP option.
Therefore \fBre2c\fP provides directives \fB/*!stags:re2c ... */\fP and \fB/*!mtags:re2c ... */\fP
that can be used to declare, initialize and manipulate tag variables.
.sp
\fIS\-tags\fP must support the following operations:
.INDENT 0.0
.IP \(bu 2
save input position to \fIs\-tag\fP:
\fBt = YYCURSOR\fP with default API, or user\-defined operation \fBYYSTAGP (t)\fP with generic API
.IP \(bu 2
save default value to \fIs\-tag\fP:
\fBt = NULL\fP with default API, or user\-defined operation \fBYYSTAGN (t)\fP with generic API
.IP \(bu 2
copy one \fIs\-tag\fP to another:
\fBt1 = t2\fP
.UNINDENT
.sp
\fIM\-tags\fP must support the following operations:
.INDENT 0.0
.IP \(bu 2
append input position to \fIm\-tag\fP:
user\-defined operation \fBYYMTAGP (t)\fP with both default and generic API
.IP \(bu 2
append default value to \fIm\-tag\fP:
user\-defined operation \fBYYMTAGN (t)\fP with both default and generic API
.IP \(bu 2
copy one \fIm\-tag\fP to another:
\fBt1 = t2\fP
.UNINDENT
.sp
\fIS\-tags\fP can be implemented as scalar values (pointers or offsets).
\fIM\-tags\fP need a more complex representation, as they need to store a sequence of tag values.
The most naive and inefficient representation of \fIm\-tag\fP is a list (array, vector) of tag values;
a more efficient representation is to store all \fIm\-tags\fP in a prefix\-tree
represented as array of nodes \fB(v, p)\fP, where \fBv\fP is tag value and \fBp\fP is a pointer to parent node.
.sp
For further details see \fBhttp://re2c.org/examples/examples.html\fP page on the website
or \fBre2c/examples/\fP subdirectory of \fBre2c\fP distribution.
.SH STORABLE STATE
.sp
With \fB\-f\fP \fB\-\-storable\-state\fP option re2c generates a lexer that can
store its current state, return to the caller, and later resume operations exactly where it left off.
The default mode of operation in re2c is a "pull" model, where the lexer "pulls" more input whenever it needs it.
However, this mode of operation assumes that the lexer is the owner of the parsing loop, and that may not always be convenient.
.sp
Storable state is useful exactly for situations like that: it allows one to construct
lexers that work in a "push" model, where data is fed to the lexer chunk by chunk.
When the lexer needs more input, it stores its state and returns to the caller.
Later, when more input becomes available, it resumes operations exactly where it stopped.
.sp
Changes needed compared to the "pull" model:
.INDENT 0.0
.IP \(bu 2
Define \fBYYSETSTATE ()\fP and \fBYYGETSTATE (state)\fP\&.
.IP \(bu 2
Define \fByych\fP, \fByyaccept\fP and \fBstate\fP variables as a part of persistent lexer state.
\fBstate\fP should be initialized to \fB\-1\fP\&.
.IP \(bu 2
\fBYYFILL\fP should return to the outer program instead of trying to supply more input.
Return code should indicate that lexer needs more input.
.IP \(bu 2
The outer program should recognize situations when lexer needs more input
and respond appropriately.
.IP \(bu 2
Use \fB/*!getstate:re2c*/\fP directive if it is necessary to execute any code
before entering the lexer.
.IP \(bu 2
Use configurations \fBstate:abort\fP and \fBstate:nextlabel\fP to tweak the generated code.
.UNINDENT
.SH CONDITIONS
.sp
\fIConditions\fP are enabled with \fB\-c\fP \fB\-\-conditions\fP\&.
This option allows one to encode multiple interrelated lexers within the same re2c block.
.sp
Each lexer corresponds to a single \fIcondition\fP\&.
It starts with a label of the form \fByyc_name\fP,
where \fBname\fP is \fIcondition\fP name
and \fByyc\fP prefix can be adjusted with configuration \fBre2c:condprefix\fP\&.
Different lexers are separated with a comment \fB/* *********************************** */\fP
which can be adjusted with configuration \fBre2c:cond:divider\fP\&.
.sp
Furthermore, each \fIcondition\fP has a unique identifier of the form \fByycname\fP,
where \fBname\fP is condition name
and \fByyc\fP prefix can be adjusted with configuration \fBre2c:condenumprefix\fP\&.
Identifiers have the type \fBYYCONDTYPE\fP and should be generated with \fB/*!types:re2c*/\fP directive or \fB\-t\fP \fB\-\-type\-header\fP option.
Users shouldn\(aqt define these identifiers manually, as the order of \fIconditions\fP is not specified.
.sp
Before all \fIconditions\fP re2c generates entry code that checks the current \fIcondition\fP identifier
and transfers control flow to the start label of the active \fIcondition\fP\&.
After matching some rule of this \fIcondition\fP,
lexer may either transfer control flow back to the entry code (after executing the associated action and optionally setting another \fIcondition\fP with \fB=>\fP),
or use \fB:=>\fP shortcut and transition directly to the start label of another \fIcondition\fP (skipping the action and the entry code).
Configuration \fBre2c:cond:goto\fP allows one to change the default behavior.
.sp
Syntactically each rule must be preceded with a list of comma\-separated \fIcondition\fP names or a wildcard \fB*\fP
enclosed in angle brackets \fB<\fP and \fB>\fP\&.
Wildcard means "any condition" and is semantically equivalent to listing all condition names.
Here \fBregexp\fP is a regular expression, \fBdefault\fP refers to the \fIdefault rule\fP \fB*\fP,
and \fBaction\fP is a block of C/C++ code.
.INDENT 0.0
.IP \(bu 2
\fB<conditions\-or\-wildcard>  regexp\-or\-default                 action\fP
.IP \(bu 2
\fB<conditions\-or\-wildcard>  regexp\-or\-default  =>  condition  action\fP
.IP \(bu 2
\fB<conditions\-or\-wildcard>  regexp\-or\-default  :=> condition\fP
.UNINDENT
.sp
Rules with an exclamation mark \fB!\fP in front of condition list have a special meaning:
they have no regular expression,
and the associated action is merged as an entry code to actions of normal rules.
This might be a convenient place to peform a routine task that is common to all rules.
.INDENT 0.0
.IP \(bu 2
\fB<!conditions\-or\-wildcard>  action\fP
.UNINDENT
.sp
Another special form of rules with an empty condition list \fB<>\fP and no regular expression
allows one to specify an "entry condition" that can be used to execute code before entering the lexer.
It is semantically equivalent to a condition with number zero, name \fB0\fP and an empty regular expression.
.INDENT 0.0
.IP \(bu 2
\fB<>                 action\fP
.IP \(bu 2
\fB<>  =>  condition  action\fP
.IP \(bu 2
\fB<>  :=> condition\fP
.UNINDENT
.SH ENCODINGS
.sp
\fBre2c\fP supports the following encodings: ASCII (default), EBCDIC (\fB\-e\fP),
UCS\-2 (\fB\-w\fP), UTF\-16 (\fB\-x\fP), UTF\-32 (\fB\-u\fP) and UTF\-8 (\fB\-8\fP).
See also inplace configuration \fBre2c:flags\fP\&.
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The following concepts should be clarified when talking about encodings.
A \fIcode point\fP is an abstract number that represents a single symbol.
A \fIcode unit\fP is the smallest unit of memory, which is used in the
encoded text (it corresponds to one character in the input stream). One
or more code units may be needed to represent a single code point,
depending on the encoding. In a \fIfixed\-length\fP encoding, each code point
is represented with an equal number of code units. In \fIvariable\-length\fP
encodings, different code points can be represented with different number
of code units.
.INDENT 0.0
.IP \(bu 2
ASCII is a fixed\-length encoding. Its code space includes 0x100
code points, from 0 to 0xFF. A code point is represented with exactly one
1\-byte code unit, which has the same value as the code point. The size of
\fBYYCTYPE\fP must be 1 byte.
.IP \(bu 2
EBCDIC is a fixed\-length encoding. Its code space includes 0x100
code points, from 0 to 0xFF. A code point is represented with exactly
one 1\-byte code unit, which has the same value as the code point. The size
of \fBYYCTYPE\fP must be 1 byte.
.IP \(bu 2
UCS\-2 is a fixed\-length encoding. Its code space includes 0x10000
code points, from 0 to 0xFFFF. One code point is represented with
exactly one 2\-byte code unit, which has the same value as the code
point. The size of \fBYYCTYPE\fP must be 2 bytes.
.IP \(bu 2
UTF\-16 is a variable\-length encoding. Its code space includes all
Unicode code points, from 0 to 0xD7FF and from 0xE000 to 0x10FFFF. One
code point is represented with one or two 2\-byte code units. The size of
\fBYYCTYPE\fP must be 2 bytes.
.IP \(bu 2
UTF\-32 is a fixed\-length encoding. Its code space includes all
Unicode code points, from 0 to 0xD7FF and from 0xE000 to 0x10FFFF. One
code point is represented with exactly one 4\-byte code unit. The size of
\fBYYCTYPE\fP must be 4 bytes.
.IP \(bu 2
UTF\-8 is a variable\-length encoding. Its code space includes all
Unicode code points, from 0 to 0xD7FF and from 0xE000 to 0x10FFFF. One
code point is represented with a sequence of one, two, three, or four
1\-byte code units. The size of \fBYYCTYPE\fP must be 1 byte.
.UNINDENT
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In Unicode, values from range 0xD800 to 0xDFFF (surrogates) are not
valid Unicode code points. Any encoded sequence of code units that
would map to Unicode code points in the range 0xD800\-0xDFFF, is
ill\-formed. The user can control how \fBre2c\fP treats such ill\-formed
sequences with the \fB\-\-encoding\-policy <policy>\fP switch.
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For some encodings, there are code units that never occur in a valid
encoded stream (e.g., 0xFF byte in UTF\-8). If the generated scanner must
check for invalid input, the only correct way to do so is to use the default
rule (\fB*\fP). Note that the full range rule (\fB[^]\fP) won\(aqt catch invalid code units when a variable\-length encoding is used
(\fB[^]\fP means "any valid code point", whereas the default rule (\fB*\fP) means "any possible code unit").
.SH GENERIC API
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By default \fBre2c\fP operates on input using pointer\-like primitives
\fBYYCURSOR\fP, \fBYYMARKER\fP, \fBYYCTXMARKER\fP, and \fBYYLIMIT\fP\&.
Normally pointer\-like primitives are defined as variables of type \fBYYCTYPE*\fP,
but it is possible to use STL iterators or any other abstraction as long as it syntactically fits into the following use cases:
.INDENT 0.0
.IP \(bu 2
\fB++YYCURSOR;\fP
.IP \(bu 2
\fByych = *YYCURSOR;\fP
.IP \(bu 2
\fByych = *++YYCURSOR;\fP
.IP \(bu 2
\fByych = *(YYMARKER = YYCURSOR);\fP
.IP \(bu 2
\fByych = *(YYMARKER = ++YCURSOR);\fP
.IP \(bu 2
\fBYYMARKER = YYCURSOR;\fP
.IP \(bu 2
\fBYYMARKER = ++YYCURSOR;\fP
.IP \(bu 2
\fBYYCURSOR = YYMARKER;\fP
.IP \(bu 2
\fBYYCTXMARKER = YYCURSOR + 1;\fP
.IP \(bu 2
\fBYYCURSOR = YYCTXMARKER;\fP
.IP \(bu 2
\fBif (YYLIMIT <= YYCURSOR) ...\fP
.IP \(bu 2
\fBif ((YYLIMIT \- YYCURSOR) < n) ...\fP
.IP \(bu 2
\fBYYDEBUG (label, *YYCURSOR);\fP
.UNINDENT
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If this input model is too restrictive, then it is possible to use generic input API enabled with \fB\-\-input custom\fP option.
In this mode all input operations are expressed in terms of the primitives below.
These primitives can be defined in any suitable way; one doesn\(aqt have to stick to the pointer semantics.
For example, it is possible to read input directly from file without any buffering,
or to disable \fBYYFILL\fP mechanism and perform end\-of\-input checking on each input character from inside of \fBYYPEEK\fP or \fBYYSKIP\fP\&.
.INDENT 0.0
.IP \(bu 2
\fBYYPEEK ()\fP
.IP \(bu 2
\fBYYSKIP ()\fP
.IP \(bu 2
\fBYYBACKUP ()\fP
.IP \(bu 2
\fBYYBACKUPCTX ()\fP
.IP \(bu 2
\fBYYSTAGP (t)\fP
.IP \(bu 2
\fBYYSTAGN (t)\fP
.IP \(bu 2
\fBYYMTAGP (t)\fP
.IP \(bu 2
\fBYYMTAGN (t)\fP
.IP \(bu 2
\fBYYRESTORE ()\fP
.IP \(bu 2
\fBYYRESTORECTX ()\fP
.IP \(bu 2
\fBYYRESTORETAG (t)\fP
.IP \(bu 2
\fBYYLESSTHAN (n)\fP
.UNINDENT
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Default input model can be expressed in terms of generic API as follows
(except for \fBYMTAGP\fP and \fBYYMTAGN\fP, which have no default implementation):
.INDENT 0.0
.IP \(bu 2
\fB#define  YYPEEK ()         *YYCURSOR\fP
.IP \(bu 2
\fB#define  YYSKIP ()         ++YYCURSOR\fP
.IP \(bu 2
\fB#define  YYBACKUP ()       YYMARKER = YYCURSOR\fP
.IP \(bu 2
\fB#define  YYBACKUPCTX ()    YYCTXMARKER = YYCURSOR\fP
.IP \(bu 2
\fB#define  YYRESTORE ()      YYCURSOR = YYMARKER\fP
.IP \(bu 2
\fB#define  YYRESTORECTX ()   YYCURSOR = YYCTXMARKER\fP
.IP \(bu 2
\fB#define  YYRESTORERAG (t)  YYCURSOR = t\fP
.IP \(bu 2
\fB#define  YYLESSTHAN (n)    YYLIMIT \- YYCURSOR < n\fP
.IP \(bu 2
\fB#define  YYSTAGP (t)       t = YYCURSOR\fP
.IP \(bu 2
\fB#define  YYSTAGN (t)       t = NULL\fP
.UNINDENT
.SH SEE ALSO
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You can find more information about \fBre2c\fP at: \fI\%http://re2c.org\fP\&.
See also: flex(1), lex(1), quex (\fI\%http://quex.sourceforge.net\fP).
.SH AUTHORS
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Originaly written by Peter Bumbulis in 1993;
developed and maintained by Brain Young, Marcus Boerger, Dan Nuffer and Ulya Trofimovich.
Below is a (more or less) full list of contributors retrieved from the Git history and mailing lists:
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Abs62,
asmwarrior,
Ben Smith,
Brian Young,
CRCinAU,
Dan Nuffer,
Derick Rethans,
Dimitri John Ledkov,
Durimar,
Eldar Zakirov,
Emmanuel Mogenet,
Hartmut Kaiser,
jcfp,
Jean\-Claude Wippler,
Jeff Trull,
Jérôme Dumesnil,
Jesse Buesking,
joscherl,
Julian Andres Klode,
Marcus Boerger,
Mike Gilbert,
nuno\-lopes,
Oleksii Taran,
paulmcq,
Paulo Custodio,
Perry E. Metzger,
philippschaefer,
Ross Burton,
Rui Maciel,
Ryan Mast,
Samuel006,
Sergei Trofimovich,
sirzooro,
Tim Kelly,
Ulya Trofimovich
.SH VERSION INFORMATION
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This manpage describes \fBre2c\fP version 1.1.1, package date 30 Aug 2018.
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