forked from AuroraMiddleware/gtk
Commit the correct version.
Commit the correct version.
This commit is contained in:
Tony Gale
parent
17cb4bb2e6
commit
411e9361c2
@ -1979,6 +1979,179 @@ showing the messages inside of a gtk window with your own handler
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(inside of gtkmain.c).
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</quote>
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<!-- ----------------------------------------------------------------- -->
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<sect1>What's a GScanner and how do I use one?
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<p>
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A GScanner will tokenize your text, that is, it'll return an integer
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for every word or number that appears in its input stream, following
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certain (customizable) rules to perform this translation.
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You still need to write the parsing functions on your own though.
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Here's a little test program supplied by Tim Janik that will parse
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<verb>
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<SYMBOL> = <OPTIONAL-MINUS> <NUMBER> ;
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</verb>
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constructs, while skipping "#\n" and "/**/" style comments.
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<verb>
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#include <glib.h>
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/* some test text to be fed into the scanner */
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static const gchar *test_text =
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( "ping = 5;\n"
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"/* slide in some \n"
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" * comments, just for the\n"
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" * fun of it \n"
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" */\n"
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"pong = -6; \n"
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"\n"
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"# the next value is a float\n"
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"zonk = 0.7;\n"
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"# redefine ping\n"
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"ping = - 0.5;\n" );
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/* define enumeration values to be returned for specific symbols */
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enum {
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SYMBOL_PING = G_TOKEN_LAST + 1,
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SYMBOL_PONG = G_TOKEN_LAST + 2,
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SYMBOL_ZONK = G_TOKEN_LAST + 3
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};
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/* symbol array */
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static const struct {
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gchar *symbol_name;
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guint symbol_token;
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} symbols[] = {
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{ "ping", SYMBOL_PING, },
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{ "pong", SYMBOL_PONG, },
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{ "zonk", SYMBOL_ZONK, },
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{ NULL, 0, },
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}, *symbol_p = symbols;
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static gfloat ping = 0;
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static gfloat pong = 0;
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static gfloat zonk = 0;
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static guint
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parse_symbol (GScanner *scanner)
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{
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guint symbol;
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gboolean negate = FALSE;
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/* expect a valid symbol */
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g_scanner_get_next_token (scanner);
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symbol = scanner->token;
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if (symbol < SYMBOL_PING ||
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symbol > SYMBOL_ZONK)
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return G_TOKEN_SYMBOL;
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/* expect '=' */
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g_scanner_get_next_token (scanner);
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if (scanner->token != '=')
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return '=';
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/* feature optional '-' */
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g_scanner_peek_next_token (scanner);
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if (scanner->next_token == '-')
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{
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g_scanner_get_next_token (scanner);
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negate = !negate;
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}
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/* expect a float (ints are converted to floats on the fly) */
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g_scanner_get_next_token (scanner);
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if (scanner->token != G_TOKEN_FLOAT)
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return G_TOKEN_FLOAT;
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/* make sure the next token is a ';' */
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if (g_scanner_peek_next_token (scanner) != ';')
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{
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/* not so, eat up the non-semicolon and error out */
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g_scanner_get_next_token (scanner);
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return ';';
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}
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/* assign value, eat the semicolon and exit successfully */
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switch (symbol)
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{
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case SYMBOL_PING:
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ping = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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case SYMBOL_PONG:
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pong = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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case SYMBOL_ZONK:
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zonk = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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}
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g_scanner_get_next_token (scanner);
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return G_TOKEN_NONE;
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}
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int
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main (int argc, char *argv[])
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{
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GScanner *scanner;
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guint expected_token;
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scanner = g_scanner_new (NULL);
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/* adjust lexing behaviour to suit our needs
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*/
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/* convert non-floats (octal values, hex values...) to G_TOKEN_INT */
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scanner->config->numbers_2_int = TRUE;
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/* convert G_TOKEN_INT to G_TOKEN_FLOAT */
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scanner->config->int_2_float = TRUE;
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/* don't return G_TOKEN_SYMBOL, but the symbol's value */
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scanner->config->symbol_2_token = TRUE;
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/* load symbols into the scanner */
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while (symbol_p->symbol_name)
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{
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g_scanner_add_symbol (scanner,
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symbol_p->symbol_name,
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GINT_TO_POINTER (symbol_p->symbol_token));
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symbol_p++;
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}
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/* feed in the text */
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g_scanner_input_text (scanner, test_text, strlen (test_text));
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/* give the error handler an idea on how the input is named */
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scanner->input_name = "test text";
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/* scanning loop, we parse the input untill it's end is reached,
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* the scanner encountered a lexing error, or our sub routine came
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* across invalid syntax
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*/
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do
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{
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expected_token = parse_symbol (scanner);
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g_scanner_peek_next_token (scanner);
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}
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while (expected_token == G_TOKEN_NONE &&
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scanner->next_token != G_TOKEN_EOF &&
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scanner->next_token != G_TOKEN_ERROR);
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/* give an error message upon syntax errors */
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if (expected_token != G_TOKEN_NONE)
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g_scanner_unexp_token (scanner, expected_token, NULL, "symbol", NULL, NULL, TRUE);
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/* finsish parsing */
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g_scanner_destroy (scanner);
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/* print results */
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g_print ("ping: %f\n", ping);
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g_print ("pong: %f\n", pong);
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g_print ("zonk: %f\n", zonk);
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return 0;
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}
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</verb>
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<!-- ***************************************************************** -->
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<sect>GTK+ FAQ Contributions, Maintainers and Copyright
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<p>
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173
docs/gtkfaq.sgml
173
docs/gtkfaq.sgml
@ -1979,6 +1979,179 @@ showing the messages inside of a gtk window with your own handler
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(inside of gtkmain.c).
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</quote>
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<!-- ----------------------------------------------------------------- -->
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<sect1>What's a GScanner and how do I use one?
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<p>
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A GScanner will tokenize your text, that is, it'll return an integer
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for every word or number that appears in its input stream, following
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certain (customizable) rules to perform this translation.
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You still need to write the parsing functions on your own though.
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Here's a little test program supplied by Tim Janik that will parse
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<verb>
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<SYMBOL> = <OPTIONAL-MINUS> <NUMBER> ;
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</verb>
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constructs, while skipping "#\n" and "/**/" style comments.
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<verb>
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#include <glib.h>
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/* some test text to be fed into the scanner */
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static const gchar *test_text =
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( "ping = 5;\n"
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"/* slide in some \n"
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" * comments, just for the\n"
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" * fun of it \n"
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" */\n"
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"pong = -6; \n"
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"\n"
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"# the next value is a float\n"
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"zonk = 0.7;\n"
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"# redefine ping\n"
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"ping = - 0.5;\n" );
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/* define enumeration values to be returned for specific symbols */
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enum {
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SYMBOL_PING = G_TOKEN_LAST + 1,
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SYMBOL_PONG = G_TOKEN_LAST + 2,
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SYMBOL_ZONK = G_TOKEN_LAST + 3
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};
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/* symbol array */
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static const struct {
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gchar *symbol_name;
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guint symbol_token;
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} symbols[] = {
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{ "ping", SYMBOL_PING, },
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{ "pong", SYMBOL_PONG, },
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{ "zonk", SYMBOL_ZONK, },
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{ NULL, 0, },
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}, *symbol_p = symbols;
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static gfloat ping = 0;
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static gfloat pong = 0;
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static gfloat zonk = 0;
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static guint
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parse_symbol (GScanner *scanner)
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{
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guint symbol;
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gboolean negate = FALSE;
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/* expect a valid symbol */
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g_scanner_get_next_token (scanner);
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symbol = scanner->token;
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if (symbol < SYMBOL_PING ||
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symbol > SYMBOL_ZONK)
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return G_TOKEN_SYMBOL;
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/* expect '=' */
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g_scanner_get_next_token (scanner);
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if (scanner->token != '=')
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return '=';
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/* feature optional '-' */
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g_scanner_peek_next_token (scanner);
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if (scanner->next_token == '-')
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{
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g_scanner_get_next_token (scanner);
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negate = !negate;
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}
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/* expect a float (ints are converted to floats on the fly) */
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g_scanner_get_next_token (scanner);
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if (scanner->token != G_TOKEN_FLOAT)
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return G_TOKEN_FLOAT;
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/* make sure the next token is a ';' */
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if (g_scanner_peek_next_token (scanner) != ';')
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{
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/* not so, eat up the non-semicolon and error out */
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g_scanner_get_next_token (scanner);
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return ';';
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}
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/* assign value, eat the semicolon and exit successfully */
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switch (symbol)
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{
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case SYMBOL_PING:
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ping = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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case SYMBOL_PONG:
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pong = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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case SYMBOL_ZONK:
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zonk = negate ? - scanner->value.v_float : scanner->value.v_float;
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break;
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}
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g_scanner_get_next_token (scanner);
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return G_TOKEN_NONE;
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}
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int
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main (int argc, char *argv[])
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{
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GScanner *scanner;
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guint expected_token;
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scanner = g_scanner_new (NULL);
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/* adjust lexing behaviour to suit our needs
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*/
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/* convert non-floats (octal values, hex values...) to G_TOKEN_INT */
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scanner->config->numbers_2_int = TRUE;
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/* convert G_TOKEN_INT to G_TOKEN_FLOAT */
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scanner->config->int_2_float = TRUE;
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/* don't return G_TOKEN_SYMBOL, but the symbol's value */
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scanner->config->symbol_2_token = TRUE;
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/* load symbols into the scanner */
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while (symbol_p->symbol_name)
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{
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g_scanner_add_symbol (scanner,
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symbol_p->symbol_name,
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GINT_TO_POINTER (symbol_p->symbol_token));
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symbol_p++;
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}
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/* feed in the text */
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g_scanner_input_text (scanner, test_text, strlen (test_text));
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/* give the error handler an idea on how the input is named */
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scanner->input_name = "test text";
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/* scanning loop, we parse the input untill it's end is reached,
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* the scanner encountered a lexing error, or our sub routine came
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* across invalid syntax
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*/
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do
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{
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expected_token = parse_symbol (scanner);
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g_scanner_peek_next_token (scanner);
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}
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while (expected_token == G_TOKEN_NONE &&
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scanner->next_token != G_TOKEN_EOF &&
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scanner->next_token != G_TOKEN_ERROR);
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/* give an error message upon syntax errors */
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if (expected_token != G_TOKEN_NONE)
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g_scanner_unexp_token (scanner, expected_token, NULL, "symbol", NULL, NULL, TRUE);
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/* finsish parsing */
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g_scanner_destroy (scanner);
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/* print results */
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g_print ("ping: %f\n", ping);
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g_print ("pong: %f\n", pong);
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g_print ("zonk: %f\n", zonk);
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return 0;
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}
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</verb>
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<!-- ***************************************************************** -->
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<sect>GTK+ FAQ Contributions, Maintainers and Copyright
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<p>
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|
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Loading…
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Block a user