bag.c

来自「Object-Oriented Programming With ANSI-C这」· C语言 代码 · 共 84 行

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

#include "new.h"
#include "Set.h"
#include "Object.h"

struct Set { unsigned count; };
struct Object { unsigned count; struct Set * in; };

static const size_t _Set = sizeof(struct Set);
static const size_t _Object = sizeof(struct Object);

const void * Set = & _Set;
const void * Object = & _Object;

void * new (const void * type, ...)
{	const size_t size = * (const size_t *) type;
	void * p = calloc(1, size);

	assert(p);
	return p;
}

void delete (void * item)
{
	free(item);
}

void * add (void * _set, const void * _element)
{	struct Set * set = _set;
	struct Object * element = (void *) _element;

	assert(set);
	assert(element);

	if (! element -> in)
		element -> in = set;
	else
		assert(element -> in == set);
	++ element -> count, ++ set -> count;

	return element;
}

void * find (const void * _set, const void * _element)
{	const struct Object * element = _element;

	assert(_set);
	assert(element);

	return element -> in == _set ? (void *) element : 0;
}

int contains (const void * _set, const void * _element)
{
	return find(_set, _element) != 0;
}

void * drop (void * _set, const void * _element)
{	struct Set * set = _set;
	struct Object * element = find(set, _element);

	if (element)
	{	if (-- element -> count == 0)
			element -> in = 0;
		-- set -> count;
	}
	return element;
}

unsigned count (const void * _set)
{	const struct Set * set = _set;

	assert(set);
	return set -> count;
}

int differ (const void * a, const void * b)
{
	return a != b;
}