static char rcsid[] = "$Id: H:/drh/idioms/book/RCS/thread.doc,v 1.11 1997/02/21 19:50:51 drh Exp $";
#include <string.h>
#include "assert.h"
#include "mem.h"
#include "chan.h"
#include "sem.h"
#define T Chan_T
struct T {
	const void *ptr;
	int *size;
	Sem_T send, recv, sync;
};
T Chan_new(void) {
	T c;
	NEW(c);
	Sem_init(&c->send, 1);
	Sem_init(&c->recv, 0);
	Sem_init(&c->sync, 0);
	return c;
}
int Chan_send(Chan_T c, const void *ptr, int size) {
	assert(c);
	assert(ptr);
	assert(size >= 0);
	Sem_wait(&c->send);
	c->ptr = ptr;
	c->size = &size;
	Sem_signal(&c->recv);
	Sem_wait(&c->sync);
	return size;
}
int Chan_receive(Chan_T c, void *ptr, int size) {
	int n;
	assert(c);
	assert(ptr);
	assert(size >= 0);
	Sem_wait(&c->recv);
	n = *c->size;
	if (size < n)
		n = size;
	*c->size = n;
	if (n > 0)
		memcpy(ptr, c->ptr, n);
	Sem_signal(&c->sync);
	Sem_signal(&c->send);
	return n;
}