/* IRCfs - IRC FileServ for *nix.
 * Copyright (C) 2002  Nick 'Zaf' Clifford <zaf@nrc.co.nz>
 * For licensing details, refer to the LICENSE file in the source 
 * code directory.
 */
#include "runtime.h"
#include "circbuf.h"

struct circbuf {
	POOL pool;
	char *buffer;
	size_t size;
	char *start, *end;
};

struct circbuf *circbuf_create(POOL parent, size_t bytes)
{
	POOL p;
	struct circbuf *cb;

	p = pool_new_n(parent,bytes + 64);
	cb = XMALLOC(p,struct circbuf);
	cb->pool = p;
	cb->buffer = (char *)palloc(cb->pool,(sizeof(char) * (bytes+1)));
	cb->start = cb->buffer;
	cb->end = cb->buffer;
	cb->size = bytes+1;
	return cb;
}

size_t circbuf_size(struct circbuf *cb)
{
	return cb->size-1;
}
size_t circbuf_bytes(struct circbuf *cb)
{
	if (cb->start <= cb->end) {
		return cb->end - cb->start;
	} else {
		/* size: 7 start: 6 end:3        
		 * 2345678
		 *  +  + 
		 * ^   ^^^
		 *  e  s   
		 * start: 3 end: 7 
		 * 2345678 
		 *  ^^^^
		 *  s   e
		 */
		return cb->size - (cb->start - cb->end);
	}
}
	
size_t circbuf_remaining(struct circbuf *cb)
{
	if (cb->start > cb->end) {
		return (cb->start-cb->end)-1;
	} else if (cb->start == cb->end) {
		return cb->size -1;
	} else {
		return cb->size - (cb->end - cb->start) -1;
	}
}
int circbuf_resize(struct circbuf *cb, size_t newsize)
{
	return -1;
}
int circbuf_add(struct circbuf *cb, const char *data, size_t size)
{
	char *cp,*test;
	size_t count=0;
	cp = cb->end;
	
	if (size == 0)
		return 0;

	do {
		size--;
		test = cb->start-1;
		if (test < cb->buffer)
			test = cb->buffer + cb->size -1;
		if (cp == test) 
			break;
		*cp = *data;
		cp++; data++;
		count++;
		if (cp >= cb->buffer + cb->size) 
			cp = cb->buffer;
	} while(size);
	if (cp == test)
		return -1;
	cb->end = cp;
	return count;
}

int circbuf_get(struct circbuf *cb, char *data, size_t size)
{
	char *cp;
	size_t count=0;
	cp = cb->start;
	while(size--) {
		if (cp == cb->end)
			break;
		*data = *cp;
		data++; cp++; count++;
		if (cp >= cb->buffer + cb->size)
			cp = cb->buffer;
	}
	cb->start = cp;
	return count;
}

int circbuf_get_till(struct circbuf *cb, char *data, size_t size, char ch)
{
	char *cp,f=0;
	size_t count=0;
	cp = cb->start;
	while(size--) {
		if (cp == cb->end)
			break;
		f = *data = *cp;
		data++; cp++; count++;
		if (cp >= cb->buffer + cb->size)
			cp = cb->buffer;
		if (f == ch)
			break;
	}
	if (f != ch)
		return -1;
	cb->start = cp;
	return count;

}

int circbuf_find_ch(struct circbuf *cb, char ch)
{
	char *cp;
	size_t count=0;
	cp = cb->start;
	while(*cp != ch) {
		if (cp == cb->end)
			break;
		cp++; count++;
		if (cp >= cb->buffer + cb->size)
			cp = cb->buffer;
	}
	if (*cp != ch)
		return -1;
	return count;
}

/* Get size bytes from buffer, but don't pop the bytes off */
int circbuf_peek(struct circbuf *cb, char *data, size_t size)
{
	char *cp;
	size_t count=0;
	cp = cb->start;
	while(size--) {
		if (cp == cb->end)
			break;
		*data = *cp;
		data++; cp++; count++;
		if (cp >= cb->buffer + cb->size)
			cp = cb->buffer;
	}
	return count;
}
/* Manually pop size bytes from buffer */
int circbuf_pop(struct circbuf *cb, size_t size)
{
	char *cp = cb->start;
	cp += size;
	while (cp > cb->buffer + cb->size) {
		cp = cp - cb->size;
	}
	cb->start = cp;
	return 0;	
}

void circbuf_destroy(struct circbuf *cb)
{
	pool_destroy(cb->pool);
}