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# Lexical Scanner

## Name

Lexical Scanner -- a general purpose lexical scanner.

## Synopsis

    #include <glib.h>

    struct      GScanner;
    GScanner*   g_scanner_new                   (const GScannerConfig *config_templ);
    struct      GScannerConfig;

    void        g_scanner_input_file            (GScanner *scanner,
                                                 gint input_fd);
    void        g_scanner_sync_file_offset      (GScanner *scanner);
    void        g_scanner_input_text            (GScanner *scanner,
                                                 const	gchar *text,
                                                 guint text_len);
    GTokenType  g_scanner_peek_next_token       (GScanner *scanner);
    GTokenType  g_scanner_get_next_token        (GScanner *scanner);

    guint       g_scanner_cur_line              (GScanner *scanner);
    guint       g_scanner_cur_position          (GScanner *scanner);
    GTokenType  g_scanner_cur_token             (GScanner *scanner);
    GTokenValue g_scanner_cur_value             (GScanner *scanner);
    gboolean    g_scanner_eof                   (GScanner *scanner);

    guint       g_scanner_set_scope             (GScanner *scanner,
                                                 guint scope_id);
    void        g_scanner_scope_add_symbol      (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol,
                                                 gpointer value);
    void        g_scanner_scope_foreach_symbol  (GScanner *scanner,
                                                 guint scope_id,
                                                 GHFunc func,
                                                 gpointer user_data);
    gpointer    g_scanner_scope_lookup_symbol   (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol);
    void        g_scanner_scope_remove_symbol   (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol);

    #define     g_scanner_freeze_symbol_table   (scanner)
    #define     g_scanner_thaw_symbol_table     (scanner)
    gpointer    g_scanner_lookup_symbol         (GScanner *scanner,
                                                 const gchar *symbol);

    void        g_scanner_warn                  (GScanner *scanner,
                                                 const gchar *format,
                                                 ...);
    void        g_scanner_error                 (GScanner *scanner,
                                                 const gchar *format,
                                                 ...);
    void        g_scanner_unexp_token           (GScanner *scanner,
                                                 GTokenType expected_token,
                                                 const gchar *identifier_spec,
                                                 const gchar *symbol_spec,
                                                 const gchar *symbol_name,
                                                 const gchar *message,
                                                 gint is_error);
    void        (*GScannerMsgFunc)              (GScanner *scanner,
                                                 gchar *message,
                                                 gboolean error);

    void        g_scanner_destroy               (GScanner *scanner);

    enum        GTokenType;
    union       GTokenValue;
    enum        GErrorType;
    #define     G_CSET_a_2_z
    #define     G_CSET_A_2_Z
    #define     G_CSET_DIGITS
    #define     G_CSET_LATINC
    #define     G_CSET_LATINS

    #define     g_scanner_add_symbol            ( scanner, symbol, value )
    #define     g_scanner_remove_symbol         ( scanner, symbol )
    #define     g_scanner_foreach_symbol        ( scanner, func, data )

## Description

The GScanner and its associated functions provide a general purpose lexical scanner.

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.

## Details

### struct GScanner

    struct GScanner
    {
      /* unused fields */
      gpointer		user_data;
      guint			max_parse_errors;

      /* g_scanner_error() increments this field */
      guint			parse_errors;

      /* name of input stream, featured by the default message handler */
      const gchar		*input_name;

      /* quarked data */
      GData			*qdata;

      /* link into the scanner configuration */
      GScannerConfig	*config;

      /* fields filled in after g_scanner_get_next_token() */
      GTokenType		token;
      GTokenValue		value;
      guint			line;
      guint			position;

      /* fields filled in after g_scanner_peek_next_token() */
      GTokenType		next_token;
      GTokenValue		next_value;
      guint			next_line;
      guint			next_position;

      /* to be considered private */
      GHashTable		*symbol_table;
      gint			input_fd;
      const gchar		*text;
      const gchar		*text_end;
      gchar			*buffer;
      guint			scope_id;

      /* handler function for _warn and _error */
      GScannerMsgFunc	msg_handler;
    };

The data structure representing a lexical scanner.

You should set `input_name` 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.

The `user_data` and `max_parse_errors` fields are not used. If you need to associate extra data with the scanner you can place them here.

If you want to use your own message handler you can set the `msg_handler` field. The type of the message handler function is declared by GScannerMsgFunc.

### g_scanner_new ()

    GScanner*   g_scanner_new                   (const GScannerConfig *config_templ);

Creates a new GScanner. The `config_templ` structure specifies the initial settings of the scanner, which are copied into the GScanner `config` field. If you pass `NULL` then the default settings are used.

`config_templ` : | the initial scanner settings.
Returns : | the new GScanner.

### struct GScannerConfig

    struct GScannerConfig
    {
      /* Character sets
       */
      gchar		*cset_skip_characters;		/* default: " \t\n" */
      gchar		*cset_identifier_first;
      gchar		*cset_identifier_nth;
      gchar		*cpair_comment_single;		/* default: "#\n" */

      /* Should symbol lookup work case sensitive?
       */
      guint		case_sensitive : 1;

      /* Boolean values to be adjusted "on the fly"
       * to configure scanning behaviour.
       */
      guint		skip_comment_multi : 1;		/* C like comment */
      guint		skip_comment_single : 1;	/* single line comment */
      guint		scan_comment_multi : 1;		/* scan multi line comments? */
      guint		scan_identifier : 1;
      guint		scan_identifier_1char : 1;
      guint		scan_identifier_NULL : 1;
      guint		scan_symbols : 1;
      guint		scan_binary : 1;
      guint		scan_octal : 1;
      guint		scan_float : 1;
      guint		scan_hex : 1;			/* `0x0ff0' */
      guint		scan_hex_dollar : 1;		/* `$0ff0' */
      guint		scan_string_sq : 1;		/* string: 'anything' */
      guint		scan_string_dq : 1;		/* string: "\\-escapes!\n" */
      guint		numbers_2_int : 1;		/* bin, octal, hex => int */
      guint		int_2_float : 1;		/* int => G_TOKEN_FLOAT? */
      guint		identifier_2_string : 1;
      guint		char_2_token : 1;		/* return G_TOKEN_CHAR? */
      guint		symbol_2_token : 1;
      guint		scope_0_fallback : 1;		/* try scope 0 on lookups? */
      guint		padding_dummy;
    };

Specifies the GScanner settings.

`cset_skip_characters` specifies which characters should be skipped by the scanner (the default is the whitespace characters: space, tab, carriage-return and line-feed).

`cset_identifier_first` specifies the characters which can start identifiers (the default is G_CSET_a_2_z, "_", and G_CSET_A_2_Z).

`cset_identifier_nth` 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).

`cpair_comment_single` 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).

`case_sensitive` specifies if symbols are case sensitive (the default is `FALSE`).

`skip_comment_multi` specifies if multi-line comments are skipped and not returned as tokens (the default is `TRUE`).

`skip_comment_single` specifies if single-line comments are skipped and not returned as tokens (the default is `TRUE`).

`scan_comment_multi` specifies if multi-line comments are recognized (the default is `TRUE`).

`scan_identifier` specifies if identifiers are recognized (the default is `TRUE`).

`scan_identifier_1char` specifies if single-character identifiers are recognized (the default is `FALSE`).

`scan_identifier_NULL` specifies if `NULL` is reported as G_TOKEN_IDENTIFIER_NULL. (the default is `FALSE`).

`scan_symbols` specifies if symbols are recognized (the default is `TRUE`).

`scan_binary` specifies if binary numbers are recognized (the default is `FALSE`).

`scan_octal` specifies if octal numbers are recognized (the default is `TRUE`).

`scan_float` specifies if floating point numbers are recognized (the default is `TRUE`).

`scan_hex` specifies if hexadecimal numbers are recognized (the default is `TRUE`).

`scan_hex_dollar` specifies if '$' is recognized as a prefix for hexadecimal numbers (the default is `FALSE`).

`scan_string_sq` specifies if strings can be enclosed in single quotes (the default is `TRUE`).

`scan_string_dq` specifies if strings can be enclosed in double quotes (the default is `TRUE`).

`numbers_2_int` specifies if binary, octal and hexadecimal numbers are reported as G_TOKEN_INT (the default is `TRUE`).

`int_2_float` specifies if all numbers are reported as G_TOKEN_FLOAT (the default is `FALSE`).

`identifier_2_string` specifies if identifiers are reported as strings (the default is `FALSE`).

`char_2_token` specifies if characters are reported by setting `token = ch` or as G_TOKEN_CHAR (the default is `TRUE`).

`symbol_2_token` specifies if symbols are reported by setting `token = v_symbol` or as G_TOKEN_SYMBOL (the default is `FALSE`).

`scope_0_fallback` specifies if a symbol is searched for in the default scope in addition to the current scope (the default is `FALSE`).

### g_scanner_input_file ()

    void        g_scanner_input_file            (GScanner *scanner,
                                                 gint input_fd);

Prepares to scan a file.

`scanner` : | a GScanner.
`input_fd` : | a file descriptor.

### g_scanner_sync_file_offset ()

    void        g_scanner_sync_file_offset      (GScanner *scanner);

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.

`scanner` : | a GScanner.

### g_scanner_input_text ()

    void        g_scanner_input_text            (GScanner *scanner,
                                                 const	gchar *text,
                                                 guint text_len);

Prepares to scan a text buffer.

`scanner` : | a GScanner.
`text` : | the text buffer to scan.
`text_len` : | the length of the text buffer.

### g_scanner_peek_next_token ()

    GTokenType  g_scanner_peek_next_token       (GScanner *scanner);

Gets the next token, without removing it from the input stream. The token data is placed in the `next_token`, `next_value`, `next_line`, and `next_position` fields of the GScanner structure.

`scanner` : | a GScanner.
Returns : | the type of the token.

### g_scanner_get_next_token ()

    GTokenType  g_scanner_get_next_token        (GScanner *scanner);

Gets the next token, removing it from the input stream. The token data is placed in the `token`, `value`, `line`, and `position` fields of the GScanner structure.

`scanner` : | a GScanner.
Returns : | the type of the token.

### g_scanner_cur_line ()

    guint       g_scanner_cur_line              (GScanner *scanner);

Gets the current line in the input stream (counting from 1).

`scanner` : | a GScanner.
Returns : | the current line.

### g_scanner_cur_position ()

    guint       g_scanner_cur_position          (GScanner *scanner);

Gets the current position in the current line (counting from 0).

`scanner` : | a GScanner.
Returns : | the current position on the line.

### g_scanner_cur_token ()

    GTokenType  g_scanner_cur_token             (GScanner *scanner);

Gets the current token type. This is simply the `token` field in the GScanner structure.

`scanner` : | a GScanner.
Returns : | the current token type.

### g_scanner_cur_value ()

    GTokenValue g_scanner_cur_value             (GScanner *scanner);

Gets the current token value. This is simply the `value` field in the GScanner structure.

`scanner` : | a GScanner.
Returns : | the current token value.

### g_scanner_eof ()

    gboolean    g_scanner_eof                   (GScanner *scanner);

Returns `TRUE` if the scanner has reached the end of the file or text buffer.

`scanner` : | a GScanner.
Returns : | `TRUE` if the scanner has reached the end of the file or text buffer.

### g_scanner_set_scope ()

    guint       g_scanner_set_scope             (GScanner *scanner,
                                                 guint scope_id);

Sets the current scope.

`scanner` : | a GScanner.
`scope_id` : | the new scope id.
Returns : | the old scope id.

### g_scanner_scope_add_symbol ()

    void        g_scanner_scope_add_symbol      (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol,
                                                 gpointer value);

Adds a symbol to the given scope.

`scanner` : | a GScanner.
`scope_id` : | the scope id.
`symbol` : | the symbol to add.
`value` : | the value of the symbol.

### g_scanner_scope_foreach_symbol ()

    void        g_scanner_scope_foreach_symbol  (GScanner *scanner,
                                                 guint scope_id,
                                                 GHFunc func,
                                                 gpointer user_data);

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.

`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.

### g_scanner_scope_lookup_symbol ()

    gpointer    g_scanner_scope_lookup_symbol   (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol);

Looks up a symbol in a scope and return its value. If the symbol is not bound in the scope, `NULL` is returned.

`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.

### g_scanner_scope_remove_symbol ()

    void        g_scanner_scope_remove_symbol   (GScanner *scanner,
                                                 guint scope_id,
                                                 const gchar *symbol);

Removes a symbol from a scope.

`scanner` : | a GScanner.
`scope_id` : | the scope id.
`symbol` : | the symbol to remove.

### g_scanner_freeze_symbol_table()

    #define     g_scanner_freeze_symbol_table(scanner)

Warning
`g_scanner_freeze_symbol_table` is deprecated and should not be used in newly-written code.

This function is deprecated and will be removed in the next major release of GLib. It does nothing.

`scanner` : | a GScanner.

### g_scanner_thaw_symbol_table()

    #define     g_scanner_thaw_symbol_table(scanner)

Warning
`g_scanner_thaw_symbol_table` is deprecated and should not be used in newly-written code.

This function is deprecated and will be removed in the next major release of GLib. It does nothing.

`scanner` : | a GScanner.

### g_scanner_lookup_symbol ()

    gpointer    g_scanner_lookup_symbol         (GScanner *scanner,
                                                 const gchar *symbol);

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.

`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.

### g_scanner_warn ()

    void        g_scanner_warn                  (GScanner *scanner,
                                                 const gchar *format,
                                                 ...);

Outputs a warning message, via the GScanner message handler.

`scanner` : | a GScanner.
`format` : | the message format. See the `printf()` documentation.
`...` : | the parameters to insert into the format string.

### g_scanner_error ()

    void        g_scanner_error                 (GScanner *scanner,
                                                 const gchar *format,
                                                 ...);

Outputs an error message, via the GScanner message handler.

`scanner` : | a GScanner.
`format` : | the message format. See the `printf()` documentation.
`...` : | the parameters to insert into the format string.

### g_scanner_unexp_token ()

    void        g_scanner_unexp_token           (GScanner *scanner,
                                                 GTokenType expected_token,
                                                 const gchar *identifier_spec,
                                                 const gchar *symbol_spec,
                                                 const gchar *symbol_name,
                                                 const gchar *message,
                                                 gint is_error);

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.

`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.

### GScannerMsgFunc ()

    void        (*GScannerMsgFunc)              (GScanner *scanner,
                                                 gchar *message,
                                                 gboolean error);

Specifies the type of the message handler function.

`scanner` : | a GScanner.
`message` : | the message.
`error` : | `TRUE` if the message signals an error, `FALSE` if it signals a warning.

### g_scanner_destroy ()

    void        g_scanner_destroy               (GScanner *scanner);

Frees all memory used by the GScanner.

`scanner` : | a GScanner.

### enum GTokenType

    typedef enum
    {
      G_TOKEN_EOF			=   0,

      G_TOKEN_LEFT_PAREN		= '(',
      G_TOKEN_RIGHT_PAREN		= ')',
      G_TOKEN_LEFT_CURLY		= '{',
      G_TOKEN_RIGHT_CURLY		= '}',
      G_TOKEN_LEFT_BRACE		= '[',
      G_TOKEN_RIGHT_BRACE		= ']',
      G_TOKEN_EQUAL_SIGN		= '=',
      G_TOKEN_COMMA			= ',',

      G_TOKEN_NONE			= 256,

      G_TOKEN_ERROR,

      G_TOKEN_CHAR,
      G_TOKEN_BINARY,
      G_TOKEN_OCTAL,
      G_TOKEN_INT,
      G_TOKEN_HEX,
      G_TOKEN_FLOAT,
      G_TOKEN_STRING,

      G_TOKEN_SYMBOL,
      G_TOKEN_IDENTIFIER,
      G_TOKEN_IDENTIFIER_NULL,

      G_TOKEN_COMMENT_SINGLE,
      G_TOKEN_COMMENT_MULTI,
      G_TOKEN_LAST
    } GTokenType;

The possible types of token returned from each g_scanner_get_next_token() call.

`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

    union GTokenValue
    {
      gpointer	v_symbol;
      gchar		*v_identifier;
      gulong	v_binary;
      gulong	v_octal;
      gulong	v_int;
      gdouble	v_float;
      gulong	v_hex;
      gchar		*v_string;
      gchar		*v_comment;
      guchar	v_char;
      guint		v_error;
    };

A union holding the value of the token.

### enum GErrorType

    typedef enum
    {
      G_ERR_UNKNOWN,
      G_ERR_UNEXP_EOF,
      G_ERR_UNEXP_EOF_IN_STRING,
      G_ERR_UNEXP_EOF_IN_COMMENT,
      G_ERR_NON_DIGIT_IN_CONST,
      G_ERR_DIGIT_RADIX,
      G_ERR_FLOAT_RADIX,
      G_ERR_FLOAT_MALFORMED
    } GErrorType;

The possible errors, used in the `v_error` field of GTokenValue, when the token is a G_TOKEN_ERROR.

`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.

### G_CSET_a_2_z

    #define G_CSET_a_2_z	"abcdefghijklmnopqrstuvwxyz"

The set of lowercase ASCII alphabet characters. Used for specifying valid identifier characters in GScannerConfig.

### G_CSET_A_2_Z

    #define G_CSET_A_2_Z	"ABCDEFGHIJKLMNOPQRSTUVWXYZ"

The set of uppercase ASCII alphabet characters. Used for specifying valid identifier characters in GScannerConfig.

### G_CSET_DIGITS

    #define G_CSET_DIGITS	"0123456789"

The set of digits. Used for specifying valid identifier characters in GScannerConfig.

### G_CSET_LATINC

    #define     G_CSET_LATINC

The set of uppercase ISO 8859-1 alphabet characters which are not ASCII characters. Used for specifying valid identifier characters in GScannerConfig.

### G_CSET_LATINS

    #define     G_CSET_LATINS

The set of lowercase ISO 8859-1 alphabet characters which are not ASCII characters. Used for specifying valid identifier characters in GScannerConfig.

### g_scanner_add_symbol()

    #define     g_scanner_add_symbol( scanner, symbol, value )

Warning
`g_scanner_add_symbol` is deprecated and should not be used in newly-written code.

Adds a symbol to the default scope. Deprecated in favour of g_scanner_scope_add_symbol().

`scanner` : | a GScanner.
`symbol` : | the symbol to add.
`value` : | the value of the symbol.

### g_scanner_remove_symbol()

    #define     g_scanner_remove_symbol( scanner, symbol )

Warning
`g_scanner_remove_symbol` is deprecated and should not be used in newly-written code.

Removes a symbol from the default scope. Deprecated in favour of g_scanner_scope_remove_symbol().

`scanner` : | a GScanner.
`symbol` : | the symbol to remove.

### g_scanner_foreach_symbol()

    #define     g_scanner_foreach_symbol( scanner, func, data )

Warning
`g_scanner_foreach_symbol` is deprecated and should not be used in newly-written code.

Calls a function for each symbol in the default scope. Deprecated in favour of g_scanner_scope_foreach_symbol().

`scanner` : | a GScanner.
`func` : | the function to call with each symbol.
`data` : | data to pass to the function.

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