<!-- ##### SECTION Title ##### -->
Lexical Scanner

<!-- ##### SECTION Short_Description ##### -->
a general purpose lexical scanner

<!-- ##### SECTION Long_Description ##### -->
<para>
The #GScanner and its associated functions provide a general purpose
lexical scanner.
</para>

<!--
FIXME: really needs an example and more detail, but I don't completely
understand it myself. Look at gtkrc.c for some code using the scanner.
-->

<!-- ##### SECTION See_Also ##### -->
<para>

</para>

<!-- ##### SECTION Stability_Level ##### -->


<!-- ##### SECTION Image ##### -->


<!-- ##### STRUCT GScanner ##### -->
<para>
The data structure representing a lexical scanner.
</para>
<para>
You should set <structfield>input_name</structfield> after creating 
the scanner, since it is used by the default message handler when 
displaying warnings and errors. If you are scanning a file, the file 
name would be a good choice.
</para>
<para>
The <structfield>user_data</structfield> and
<structfield>max_parse_errors</structfield> fields are not used.
If you need to associate extra data with the scanner you can place them here.
</para>
<para>
If you want to use your own message handler you can set the
<structfield>msg_handler</structfield> field. The type of the message
handler function is declared by #GScannerMsgFunc.
</para>

@user_data: 
@max_parse_errors: 
@parse_errors: 
@input_name: 
@qdata: 
@config: 
@token:       token parsed by the last g_scanner_get_next_token()
@value:       value of the last token from g_scanner_get_next_token()
@line:        line number of the last token from g_scanner_get_next_token()
@position:    char number of the last token from g_scanner_get_next_token()
@next_token:    token parsed by the last g_scanner_peek_next_token()
@next_value:    value of the last token from g_scanner_peek_next_token()
@next_line:     line number of the last token from g_scanner_peek_next_token()
@next_position: char number of the last token from g_scanner_peek_next_token()
@symbol_table: 
@input_fd: 
@text: 
@text_end: 
@buffer: 
@scope_id: 
@msg_handler: function to handle GScanner message output

<!-- ##### STRUCT GScannerConfig ##### -->
<para>
Specifies the #GScanner parser configuration. Most settings can be changed during
the parsing phase and will affect the lexical parsing of the next unpeeked token.
</para>
<para>
<structfield>cset_skip_characters</structfield> specifies which characters
should be skipped by the scanner (the default is the whitespace characters:
space, tab, carriage-return and line-feed).
</para>
<para>
<structfield>cset_identifier_first</structfield> specifies the characters
which can start identifiers (the default is #G_CSET_a_2_z, "_", and 
#G_CSET_A_2_Z).
</para>
<para>
<structfield>cset_identifier_nth</structfield> specifies the characters
which can be used in identifiers, after the first character (the default 
is #G_CSET_a_2_z, "_0123456789", #G_CSET_A_2_Z, #G_CSET_LATINS,
#G_CSET_LATINC).
</para>
<para>
<structfield>cpair_comment_single</structfield> specifies the characters
at the start and end of single-line comments. The default is "#\n" which
means that single-line comments start with a '#' and continue until a '\n'
(end of line).
</para>
<para>
<structfield>case_sensitive</structfield> specifies if symbols are
case sensitive (the default is %FALSE).
</para>
<para>
<structfield>skip_comment_multi</structfield> specifies if multi-line
comments are skipped and not returned as tokens (the default is %TRUE).
</para>
<para>
<structfield>skip_comment_single</structfield> specifies if single-line
comments are skipped and not returned as tokens (the default is %TRUE).
</para>
<para>
<structfield>scan_comment_multi</structfield> specifies if multi-line
comments are recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_identifier</structfield> specifies if identifiers
are recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_identifier_1char</structfield> specifies if single-character
identifiers are recognized (the default is %FALSE).
</para>
<para>
<structfield>scan_identifier_NULL</structfield> specifies if 
<literal>NULL</literal> is reported as #G_TOKEN_IDENTIFIER_NULL.
(the default is %FALSE).
</para>
<para>
<structfield>scan_symbols</structfield> specifies if symbols are
recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_binary</structfield> specifies if binary numbers
are recognized (the default is %FALSE).
</para>
<para>
<structfield>scan_octal</structfield> specifies if octal numbers
are recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_float</structfield> specifies if floating point numbers
are recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_hex</structfield> specifies if hexadecimal numbers
are recognized (the default is %TRUE).
</para>
<para>
<structfield>scan_hex_dollar</structfield> specifies if '$' is recognized
as a prefix for hexadecimal numbers (the default is %FALSE).
</para>
<para>
<structfield>scan_string_sq</structfield> specifies if strings can be
enclosed in single quotes (the default is %TRUE).
</para>
<para>
<structfield>scan_string_dq</structfield> specifies if strings can be
enclosed in double quotes (the default is %TRUE).
</para>
<para>
<structfield>numbers_2_int</structfield> specifies if binary, octal and
hexadecimal numbers are reported as #G_TOKEN_INT (the default is %TRUE).
</para>
<para>
<structfield>int_2_float</structfield> specifies if all numbers are 
reported as #G_TOKEN_FLOAT (the default is %FALSE).
</para>
<para>
<structfield>identifier_2_string</structfield> specifies if identifiers
are reported as strings (the default is %FALSE).
</para>
<para>
<structfield>char_2_token</structfield> specifies if characters
are reported by setting <literal>token = ch</literal> or as #G_TOKEN_CHAR 
(the default is %TRUE).
</para>
<para>
<structfield>symbol_2_token</structfield> specifies if symbols 
are reported by setting <literal>token = v_symbol</literal> or as
#G_TOKEN_SYMBOL (the default is %FALSE).
</para>
<para>
<structfield>scope_0_fallback</structfield> specifies if a symbol 
is searched for in the default scope in addition to the current scope
(the default is %FALSE).
</para>

@cset_skip_characters: 
@cset_identifier_first: 
@cset_identifier_nth: 
@cpair_comment_single: 
@case_sensitive: 
@skip_comment_multi: 
@skip_comment_single: 
@scan_comment_multi: 
@scan_identifier: 
@scan_identifier_1char: 
@scan_identifier_NULL: 
@scan_symbols: 
@scan_binary: 
@scan_octal: 
@scan_float: 
@scan_hex: 
@scan_hex_dollar: 
@scan_string_sq: 
@scan_string_dq: 
@numbers_2_int: 
@int_2_float: 
@identifier_2_string: 
@char_2_token: 
@symbol_2_token: 
@scope_0_fallback: 
@store_int64: 
@padding_dummy: 

<!-- ##### FUNCTION g_scanner_new ##### -->
<para>
Creates a new #GScanner.
The @config_templ structure specifies the initial settings of the scanner,
which are copied into the #GScanner <structfield>config</structfield> field.
If you pass %NULL then the default settings are used.
</para>

@config_templ: the initial scanner settings.
@Returns: the new #GScanner.


<!-- ##### FUNCTION g_scanner_destroy ##### -->
<para>
Frees all memory used by the #GScanner.
</para>

@scanner: a #GScanner.


<!-- ##### FUNCTION g_scanner_input_file ##### -->
<para>
Prepares to scan a file.
</para>

@scanner: a #GScanner.
@input_fd: a file descriptor.


<!-- ##### FUNCTION g_scanner_sync_file_offset ##### -->
<para>
Rewinds the filedescriptor to the current buffer position and blows 
the file read ahead buffer. This is useful for third party uses of
the scanners filedescriptor, which hooks onto the current scanning 
position.
</para>

@scanner: a #GScanner.


<!-- ##### FUNCTION g_scanner_input_text ##### -->
<para>
Prepares to scan a text buffer.
</para>

@scanner: a #GScanner.
@text: the text buffer to scan.
@text_len: the length of the text buffer.


<!-- ##### FUNCTION g_scanner_peek_next_token ##### -->
<para>
Parses the next token, without removing it from the input stream.
The token data is placed in the
<structfield>next_token</structfield>,
<structfield>next_value</structfield>,
<structfield>next_line</structfield>, and
<structfield>next_position</structfield> fields of the #GScanner structure.
</para>
<para>
Note that, while the token is not removed from the input stream (i.e.
the next call to g_scanner_get_next_token() will return the same token),
it will not be reevaluated. This can lead to surprising results when
changing scope or the scanner configuration after peeking the next token.
Getting the next token after switching the scope or configuration will
return whatever was peeked before, regardless of any symbols that may
have been added or removed in the new scope. 
</para>

@scanner: a #GScanner.
@Returns: the type of the token.


<!-- ##### FUNCTION g_scanner_get_next_token ##### -->
<para>
Parses the next token just like g_scanner_peek_next_token() and also
removes it from the input stream.
The token data is placed in the
<structfield>token</structfield>,
<structfield>value</structfield>,
<structfield>line</structfield>, and
<structfield>position</structfield> fields of the #GScanner structure.
</para>

@scanner: a #GScanner.
@Returns: the type of the token.


<!-- ##### FUNCTION g_scanner_eof ##### -->
<para>
Returns %TRUE if the scanner has reached the end of the file or text buffer.
</para>

@scanner: a #GScanner.
@Returns: %TRUE if the scanner has reached the end of the file or text buffer.


<!-- ##### FUNCTION g_scanner_cur_line ##### -->
<para>
Returns the current line in the input stream (counting from 1).
This is the line of the last token parsed via g_scanner_get_next_token().
</para>

@scanner: a #GScanner.
@Returns: the current line.


<!-- ##### FUNCTION g_scanner_cur_position ##### -->
<para>
Returns the current position in the current line (counting from 0).
This is the position of the last token parsed via g_scanner_get_next_token().
</para>

@scanner: a #GScanner.
@Returns: the current position on the line.


<!-- ##### FUNCTION g_scanner_cur_token ##### -->
<para>
Gets the current token type.
This is simply the <structfield>token</structfield> field in the #GScanner
structure.
</para>

@scanner: a #GScanner.
@Returns: the current token type.


<!-- ##### FUNCTION g_scanner_cur_value ##### -->
<para>
Gets the current token value.
This is simply the <structfield>value</structfield> field in the #GScanner
structure.
</para>

@scanner: a #GScanner.
@Returns: the current token value.


<!-- ##### FUNCTION g_scanner_set_scope ##### -->
<para>
Sets the current scope.
</para>

@scanner: a #GScanner.
@scope_id: the new scope id.
@Returns: the old scope id.


<!-- ##### FUNCTION g_scanner_scope_add_symbol ##### -->
<para>
Adds a symbol to the given scope.
</para>

@scanner: a #GScanner.
@scope_id: the scope id.
@symbol: the symbol to add.
@value: the value of the symbol.


<!-- ##### FUNCTION g_scanner_scope_foreach_symbol ##### -->
<para>
Calls the given function for each of the symbol/value pairs in the 
given scope of the #GScanner. The function is passed the symbol and 
value of each pair, and the given @user_data parameter.
</para>

@scanner: a #GScanner.
@scope_id: the scope id.
@func: the function to call for each symbol/value pair.
@user_data: user data to pass to the function.


<!-- ##### FUNCTION g_scanner_scope_lookup_symbol ##### -->
<para>
Looks up a symbol in a scope and return its value. If the
symbol is not bound in the scope, %NULL is returned.
</para>

@scanner: a #GScanner.
@scope_id: the scope id.
@symbol: the symbol to look up.
@Returns: the value of @symbol in the given scope, or %NULL
if @symbol is not bound in the given scope.


<!-- ##### FUNCTION g_scanner_scope_remove_symbol ##### -->
<para>
Removes a symbol from a scope.
</para>

@scanner: a #GScanner.
@scope_id: the scope id.
@symbol: the symbol to remove.


<!-- ##### MACRO g_scanner_add_symbol ##### -->
<para>
Adds a symbol to the default scope.
</para>

@scanner: a #GScanner.
@symbol: the symbol to add.
@value: the value of the symbol.
@Deprecated: 2.2: Use g_scanner_scope_add_symbol() instead.


<!-- ##### MACRO g_scanner_remove_symbol ##### -->
<para>
Removes a symbol from the default scope.
</para>

@scanner: a #GScanner.
@symbol: the symbol to remove.
@Deprecated: 2.2: Use g_scanner_scope_remove_symbol() instead.


<!-- ##### MACRO g_scanner_foreach_symbol ##### -->
<para>
Calls a function for each symbol in the default scope.
</para>

@scanner: a #GScanner.
@func: the function to call with each symbol.
@data: data to pass to the function.
@Deprecated: 2.2: Use g_scanner_scope_foreach_symbol() instead.


<!-- ##### MACRO g_scanner_freeze_symbol_table ##### -->
<para>
There is no reason to use this macro, since it does nothing.
</para>

@scanner: a #GScanner.
@Deprecated: 2.2: This macro does nothing.


<!-- ##### MACRO g_scanner_thaw_symbol_table ##### -->
<para>
There is no reason to use this macro, since it does nothing.
</para>

@scanner: a #GScanner.
@Deprecated: 2.2: This macro does nothing.


<!-- ##### FUNCTION g_scanner_lookup_symbol ##### -->
<para>
Looks up a symbol in the current scope and return its value. If the
symbol is not bound in the current scope, %NULL is returned.
</para>

@scanner: a #GScanner.
@symbol: the symbol to look up.
@Returns: the value of @symbol in the current scope, or %NULL
if @symbol is not bound in the current scope.


<!-- ##### FUNCTION g_scanner_warn ##### -->
<para>
Outputs a warning message, via the #GScanner message handler.
</para>

@scanner: a #GScanner.
@format: the message format. See the <function>printf()</function>
documentation.
@Varargs: the parameters to insert into the format string.


<!-- ##### FUNCTION g_scanner_error ##### -->
<para>
Outputs an error message, via the #GScanner message handler.
</para>

@scanner: a #GScanner.
@format: the message format. See the <function>printf()</function>
documentation.
@Varargs: the parameters to insert into the format string.


<!-- ##### FUNCTION g_scanner_unexp_token ##### -->
<para>
Outputs a message through the scanner's msg_handler, resulting from an
unexpected token in the input stream.
Note that you should not call g_scanner_peek_next_token() followed by
g_scanner_unexp_token() without an intermediate call to
g_scanner_get_next_token(), as g_scanner_unexp_token() evaluates the
scanner's current token (not the peeked token) to construct part
of the message.
</para>

@scanner: a #GScanner.
@expected_token: the expected token.
@identifier_spec: a string describing how the scanner's user refers to
                  identifiers (%NULL defaults to "identifier").
                  This is used if @expected_token is #G_TOKEN_IDENTIFIER
                  or #G_TOKEN_IDENTIFIER_NULL.
@symbol_spec: a string describing how the scanner's user refers to
              symbols (%NULL defaults to "symbol").
              This is used if @expected_token is #G_TOKEN_SYMBOL or
              any token value greater than #G_TOKEN_LAST.
@symbol_name: the name of the symbol, if the scanner's current token
              is a symbol.
@message: a message string to output at the end of the warning/error, or %NULL.
@is_error: if %TRUE it is output as an error. If %FALSE it is output as a
           warning.


<!-- ##### USER_FUNCTION GScannerMsgFunc ##### -->
<para>
Specifies the type of the message handler function.
</para>

@scanner: a #GScanner.
@message: the message.
@error: %TRUE if the message signals an error, %FALSE if it 
  signals a warning.


<!-- ##### MACRO G_CSET_a_2_z ##### -->
<para>
The set of lowercase ASCII alphabet characters.
Used for specifying valid identifier characters in #GScannerConfig.
</para>


<!-- ##### MACRO G_CSET_A_2_Z ##### -->
<para>
The set of uppercase ASCII alphabet characters.
Used for specifying valid identifier characters in #GScannerConfig.
</para>


<!-- ##### MACRO G_CSET_DIGITS ##### -->
<para>
The set of digits.
Used for specifying valid identifier characters in #GScannerConfig.
</para>


<!-- ##### MACRO G_CSET_LATINC ##### -->
<para>
The set of uppercase ISO 8859-1 alphabet characters which are 
not ASCII characters. 
Used for specifying valid identifier characters in #GScannerConfig.
</para>


<!-- ##### MACRO G_CSET_LATINS ##### -->
<para>
The set of lowercase ISO 8859-1 alphabet characters which are 
not ASCII characters. 
Used for specifying valid identifier characters in #GScannerConfig.
</para>


<!-- ##### ENUM GTokenType ##### -->
<para>
The possible types of token returned from each g_scanner_get_next_token() call.
</para>

@G_TOKEN_EOF: the end of the file.
@G_TOKEN_LEFT_PAREN: a '(' character.
@G_TOKEN_LEFT_CURLY: a '{' character.
@G_TOKEN_RIGHT_CURLY: a '}' character.

<!-- ##### UNION GTokenValue ##### -->
<para>
A union holding the value of the token.
</para>


<!-- ##### ENUM GErrorType ##### -->
<para>
The possible errors, used in the <structfield>v_error</structfield> field
of #GTokenValue, when the token is a #G_TOKEN_ERROR.
</para>

@G_ERR_UNKNOWN: unknown error.
@G_ERR_UNEXP_EOF: unexpected end of file.
@G_ERR_UNEXP_EOF_IN_STRING: unterminated string constant.
@G_ERR_UNEXP_EOF_IN_COMMENT: unterminated comment.
@G_ERR_NON_DIGIT_IN_CONST: non-digit character in a number.
@G_ERR_DIGIT_RADIX: digit beyond radix in a number.
@G_ERR_FLOAT_RADIX: non-decimal floating point number.
@G_ERR_FLOAT_MALFORMED: malformed floating point number.