Commit 411e9361 authored by Tony Gale's avatar Tony Gale
Browse files

Commit the correct version.


Commit the correct version.
parent 17cb4bb2
......@@ -1979,6 +1979,179 @@ showing the messages inside of a gtk window with your own handler
(inside of gtkmain.c).
</quote>
<!-- ----------------------------------------------------------------- -->
<sect1>What's a GScanner and how do I use one?
<p>
A GScanner will tokenize your text, that is, it'll return an integer
for every word or number that appears in its input stream, following
certain (customizable) rules to perform this translation.
You still need to write the parsing functions on your own though.
Here's a little test program supplied by Tim Janik that will parse
<verb>
<SYMBOL> = <OPTIONAL-MINUS> <NUMBER> ;
</verb>
constructs, while skipping "#\n" and "/**/" style comments.
<verb>
#include <glib.h>
/* some test text to be fed into the scanner */
static const gchar *test_text =
( "ping = 5;\n"
"/* slide in some \n"
" * comments, just for the\n"
" * fun of it \n"
" */\n"
"pong = -6; \n"
"\n"
"# the next value is a float\n"
"zonk = 0.7;\n"
"# redefine ping\n"
"ping = - 0.5;\n" );
/* define enumeration values to be returned for specific symbols */
enum {
SYMBOL_PING = G_TOKEN_LAST + 1,
SYMBOL_PONG = G_TOKEN_LAST + 2,
SYMBOL_ZONK = G_TOKEN_LAST + 3
};
/* symbol array */
static const struct {
gchar *symbol_name;
guint symbol_token;
} symbols[] = {
{ "ping", SYMBOL_PING, },
{ "pong", SYMBOL_PONG, },
{ "zonk", SYMBOL_ZONK, },
{ NULL, 0, },
}, *symbol_p = symbols;
static gfloat ping = 0;
static gfloat pong = 0;
static gfloat zonk = 0;
static guint
parse_symbol (GScanner *scanner)
{
guint symbol;
gboolean negate = FALSE;
/* expect a valid symbol */
g_scanner_get_next_token (scanner);
symbol = scanner->token;
if (symbol < SYMBOL_PING ||
symbol > SYMBOL_ZONK)
return G_TOKEN_SYMBOL;
/* expect '=' */
g_scanner_get_next_token (scanner);
if (scanner->token != '=')
return '=';
/* feature optional '-' */
g_scanner_peek_next_token (scanner);
if (scanner->next_token == '-')
{
g_scanner_get_next_token (scanner);
negate = !negate;
}
/* expect a float (ints are converted to floats on the fly) */
g_scanner_get_next_token (scanner);
if (scanner->token != G_TOKEN_FLOAT)
return G_TOKEN_FLOAT;
/* make sure the next token is a ';' */
if (g_scanner_peek_next_token (scanner) != ';')
{
/* not so, eat up the non-semicolon and error out */
g_scanner_get_next_token (scanner);
return ';';
}
/* assign value, eat the semicolon and exit successfully */
switch (symbol)
{
case SYMBOL_PING:
ping = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
case SYMBOL_PONG:
pong = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
case SYMBOL_ZONK:
zonk = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
}
g_scanner_get_next_token (scanner);
return G_TOKEN_NONE;
}
int
main (int argc, char *argv[])
{
GScanner *scanner;
guint expected_token;
scanner = g_scanner_new (NULL);
/* adjust lexing behaviour to suit our needs
*/
/* convert non-floats (octal values, hex values...) to G_TOKEN_INT */
scanner->config->numbers_2_int = TRUE;
/* convert G_TOKEN_INT to G_TOKEN_FLOAT */
scanner->config->int_2_float = TRUE;
/* don't return G_TOKEN_SYMBOL, but the symbol's value */
scanner->config->symbol_2_token = TRUE;
/* load symbols into the scanner */
while (symbol_p->symbol_name)
{
g_scanner_add_symbol (scanner,
symbol_p->symbol_name,
GINT_TO_POINTER (symbol_p->symbol_token));
symbol_p++;
}
/* feed in the text */
g_scanner_input_text (scanner, test_text, strlen (test_text));
/* give the error handler an idea on how the input is named */
scanner->input_name = "test text";
/* scanning loop, we parse the input untill it's end is reached,
* the scanner encountered a lexing error, or our sub routine came
* across invalid syntax
*/
do
{
expected_token = parse_symbol (scanner);
g_scanner_peek_next_token (scanner);
}
while (expected_token == G_TOKEN_NONE &&
scanner->next_token != G_TOKEN_EOF &&
scanner->next_token != G_TOKEN_ERROR);
/* give an error message upon syntax errors */
if (expected_token != G_TOKEN_NONE)
g_scanner_unexp_token (scanner, expected_token, NULL, "symbol", NULL, NULL, TRUE);
/* finsish parsing */
g_scanner_destroy (scanner);
/* print results */
g_print ("ping: %f\n", ping);
g_print ("pong: %f\n", pong);
g_print ("zonk: %f\n", zonk);
return 0;
}
</verb>
<!-- ***************************************************************** -->
<sect>GTK+ FAQ Contributions, Maintainers and Copyright
<p>
......
......@@ -1979,6 +1979,179 @@ showing the messages inside of a gtk window with your own handler
(inside of gtkmain.c).
</quote>
<!-- ----------------------------------------------------------------- -->
<sect1>What's a GScanner and how do I use one?
<p>
A GScanner will tokenize your text, that is, it'll return an integer
for every word or number that appears in its input stream, following
certain (customizable) rules to perform this translation.
You still need to write the parsing functions on your own though.
Here's a little test program supplied by Tim Janik that will parse
<verb>
<SYMBOL> = <OPTIONAL-MINUS> <NUMBER> ;
</verb>
constructs, while skipping "#\n" and "/**/" style comments.
<verb>
#include <glib.h>
/* some test text to be fed into the scanner */
static const gchar *test_text =
( "ping = 5;\n"
"/* slide in some \n"
" * comments, just for the\n"
" * fun of it \n"
" */\n"
"pong = -6; \n"
"\n"
"# the next value is a float\n"
"zonk = 0.7;\n"
"# redefine ping\n"
"ping = - 0.5;\n" );
/* define enumeration values to be returned for specific symbols */
enum {
SYMBOL_PING = G_TOKEN_LAST + 1,
SYMBOL_PONG = G_TOKEN_LAST + 2,
SYMBOL_ZONK = G_TOKEN_LAST + 3
};
/* symbol array */
static const struct {
gchar *symbol_name;
guint symbol_token;
} symbols[] = {
{ "ping", SYMBOL_PING, },
{ "pong", SYMBOL_PONG, },
{ "zonk", SYMBOL_ZONK, },
{ NULL, 0, },
}, *symbol_p = symbols;
static gfloat ping = 0;
static gfloat pong = 0;
static gfloat zonk = 0;
static guint
parse_symbol (GScanner *scanner)
{
guint symbol;
gboolean negate = FALSE;
/* expect a valid symbol */
g_scanner_get_next_token (scanner);
symbol = scanner->token;
if (symbol < SYMBOL_PING ||
symbol > SYMBOL_ZONK)
return G_TOKEN_SYMBOL;
/* expect '=' */
g_scanner_get_next_token (scanner);
if (scanner->token != '=')
return '=';
/* feature optional '-' */
g_scanner_peek_next_token (scanner);
if (scanner->next_token == '-')
{
g_scanner_get_next_token (scanner);
negate = !negate;
}
/* expect a float (ints are converted to floats on the fly) */
g_scanner_get_next_token (scanner);
if (scanner->token != G_TOKEN_FLOAT)
return G_TOKEN_FLOAT;
/* make sure the next token is a ';' */
if (g_scanner_peek_next_token (scanner) != ';')
{
/* not so, eat up the non-semicolon and error out */
g_scanner_get_next_token (scanner);
return ';';
}
/* assign value, eat the semicolon and exit successfully */
switch (symbol)
{
case SYMBOL_PING:
ping = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
case SYMBOL_PONG:
pong = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
case SYMBOL_ZONK:
zonk = negate ? - scanner->value.v_float : scanner->value.v_float;
break;
}
g_scanner_get_next_token (scanner);
return G_TOKEN_NONE;
}
int
main (int argc, char *argv[])
{
GScanner *scanner;
guint expected_token;
scanner = g_scanner_new (NULL);
/* adjust lexing behaviour to suit our needs
*/
/* convert non-floats (octal values, hex values...) to G_TOKEN_INT */
scanner->config->numbers_2_int = TRUE;
/* convert G_TOKEN_INT to G_TOKEN_FLOAT */
scanner->config->int_2_float = TRUE;
/* don't return G_TOKEN_SYMBOL, but the symbol's value */
scanner->config->symbol_2_token = TRUE;
/* load symbols into the scanner */
while (symbol_p->symbol_name)
{
g_scanner_add_symbol (scanner,
symbol_p->symbol_name,
GINT_TO_POINTER (symbol_p->symbol_token));
symbol_p++;
}
/* feed in the text */
g_scanner_input_text (scanner, test_text, strlen (test_text));
/* give the error handler an idea on how the input is named */
scanner->input_name = "test text";
/* scanning loop, we parse the input untill it's end is reached,
* the scanner encountered a lexing error, or our sub routine came
* across invalid syntax
*/
do
{
expected_token = parse_symbol (scanner);
g_scanner_peek_next_token (scanner);
}
while (expected_token == G_TOKEN_NONE &&
scanner->next_token != G_TOKEN_EOF &&
scanner->next_token != G_TOKEN_ERROR);
/* give an error message upon syntax errors */
if (expected_token != G_TOKEN_NONE)
g_scanner_unexp_token (scanner, expected_token, NULL, "symbol", NULL, NULL, TRUE);
/* finsish parsing */
g_scanner_destroy (scanner);
/* print results */
g_print ("ping: %f\n", ping);
g_print ("pong: %f\n", pong);
g_print ("zonk: %f\n", zonk);
return 0;
}
</verb>
<!-- ***************************************************************** -->
<sect>GTK+ FAQ Contributions, Maintainers and Copyright
<p>
......
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