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C Object Oriented Programming Example
#include <stdio.h>
#include <stdlib.h>
#include <regex.h>
#include <stdbool.h>
#include <fnmatch.h>
#include <stddef.h>
#define container_of(ptr, type, member) \
((type *)((char *)(ptr) - offsetof(type, member)))
/* Filter API */
struct filter {
struct filter_vtable *vtable;
};
struct filter_vtable {
bool (*match)(struct filter *, const char *);
void (*free)(struct filter *);
struct filter *(*clone)(struct filter *);
};
bool filter_match(struct filter *filter, const char *string)
{
return filter->vtable->match(filter, string);
}
void filter_free(struct filter *filter)
{
return filter->vtable->free(filter);
}
struct filter *filter_clone(struct filter *filter)
{
return filter->vtable->clone(filter);
}
/* Regex Filter */
struct filter *filter_regex_create(const char *pattern);
struct filter_regex {
regex_t regex;
const char *pattern;
struct filter filter;
};
static bool
method_match_regex(struct filter *f, const char *string)
{
struct filter_regex *regex = container_of(f, struct filter_regex, filter);
return regexec(&regex->regex, string, 0, NULL, 0) == 0;
}
static void
method_free_regex(struct filter *f)
{
struct filter_regex *regex = container_of(f, struct filter_regex, filter);
regfree(&regex->regex);
free(f);
}
static struct filter *
method_clone_regex(struct filter *f)
{
struct filter_regex *regex = container_of(f, struct filter_regex, filter);
return filter_regex_create(regex->pattern);
}
struct filter_vtable filter_regex_vtable = {
method_match_regex, method_free_regex, method_clone_regex
};
struct filter *filter_regex_create(const char *pattern)
{
struct filter_regex *regex = malloc(sizeof(*regex));
regex->pattern = pattern;
regcomp(&regex->regex, pattern, REG_EXTENDED);
regex->filter.vtable = &filter_regex_vtable;
return &regex->filter;
}
/* Glob Filter */
struct filter *filter_glob_create(const char *pattern);
struct filter_glob {
struct filter filter;
const char *pattern;
};
static bool
method_match_glob(struct filter *f, const char *string)
{
struct filter_glob *glob = (struct filter_glob *) f;
return fnmatch(glob->pattern, string, 0) == 0;
}
static void
method_free_glob(struct filter *f)
{
free(f);
}
static struct filter *
method_clone_glob(struct filter *f)
{
struct filter_glob *glob = (struct filter_glob *) f;
return filter_glob_create(glob->pattern);
}
struct filter_vtable filter_glob_vtable = {
method_match_glob, method_free_glob, method_clone_glob
};
struct filter *filter_glob_create(const char *pattern)
{
struct filter_glob *glob = malloc(sizeof(*glob));
glob->pattern = pattern;
glob->filter.vtable = &filter_glob_vtable;
return &glob->filter;
}
/* AND Filter */
struct filter *filter_and(struct filter *a, struct filter *b);
struct filter_and {
struct filter filter;
struct filter *sub[2];
};
static bool
method_match_and (struct filter *f, const char *s)
{
struct filter_and *and = (struct filter_and *) f;
return filter_match(and->sub[0], s) && filter_match(and->sub[1], s);
}
static void
method_free_and(struct filter *f)
{
struct filter_and *and = (struct filter_and *) f;
filter_free(and->sub[0]);
filter_free(and->sub[1]);
free(f);
}
static struct filter *
method_clone_and(struct filter *f)
{
struct filter_and *and = (struct filter_and *) f;
return filter_and(filter_clone(and->sub[0]), filter_clone(and->sub[1]));
}
struct filter_vtable filter_and_vtable = {
method_match_and, method_free_and, method_clone_and
};
struct filter *filter_and(struct filter *a, struct filter *b)
{
struct filter_and *and = malloc(sizeof(*and));
and->sub[0] = a;
and->sub[1] = b;
and->filter.vtable = &filter_and_vtable;
return &and->filter;
}
/* Constant Filters */
static bool
method_match_any(struct filter *f, const char *string)
{
return true;
}
static bool
method_match_none(struct filter *f, const char *string)
{
return false;
}
static void
method_free_noop(struct filter *f)
{
}
static struct
filter *method_clone_noop(struct filter *f)
{
return f;
}
struct filter_vtable filter_any_vtable = {
method_match_any, method_free_noop, method_clone_noop
};
struct filter_vtable filter_none_vtable = {
method_match_none, method_free_noop, method_clone_noop
};
struct filter FILTER_ANY = { &filter_any_vtable };
struct filter FILTER_NONE = { &filter_none_vtable };
/* Test Program */
void pass_match(FILE *input, FILE *output, struct filter *filter)
{
char line[4096];
while (fgets(line, sizeof(line), input))
if (filter_match(filter, line))
fputs(line, output);
}
int main(int argc, char **argv)
{
struct filter *filter = &FILTER_ANY;
for (char **p = argv + 1; *p; p++)
filter = filter_and(filter, filter_glob_create(*p));
pass_match(stdin, stdout, filter);
filter_free(filter);
return 0;
}
CFLAGS = -std=c99 -Wall
main : main.o
.PHONY : test clean
test : main
./$^ "*regex*" "*vtable*" < main.c
clean :
$(RM) main *.o
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