snmp2rrd/linebuffer.c

/***************************************************************************
 *   Copyright (C) 03/2010 by Olaf Rempel                                  *
 *   razzor@kopf-tisch.de                                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; version 2 of the License                *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdarg.h>

#include "linebuffer.h"

#define MIN(a,b) (((a) < (b)) ? (a) : (b))

struct lbuf {
	size_t size;
	size_t pos;

	char *token;
	char data[0];
};

/*
 * creates linebuffer with given size
 */
struct lbuf * lbuf_create(size_t size)
{
	struct lbuf *buf = malloc(sizeof(struct lbuf) + size);
	if (buf == NULL)
		return NULL;

	buf->size = size;
	buf->pos = 0;
	return buf;
}

/*
 * frees the linebuffer and all data in it
 */
void lbuf_free(struct lbuf *buf)
{
	free(buf);
}

/*
 * clears the linebuffer
 * - returns the datasize it was holding
 */
int lbuf_clear(struct lbuf *buf)
{
	int oldpos = buf->pos;
	buf->pos = 0;
	return oldpos;
}

/*
 * get pointer to internal data
 * - returns pointer to datasize
 */
char * lbuf_getdata(struct lbuf *buf, size_t *len)
{
	if (len != NULL)
		*len = buf->pos;

	return buf->data;
}

/*
 * appends data to the buffer
 * - returns the number of bytes copied
 */
int lbuf_append(struct lbuf *buf, const char *src, size_t size)
{
	int len = MIN(buf->size - buf->pos, size);
	memcpy(buf->data + buf->pos, src, len);
	buf->pos += len;
	return len;
}

/*
 * reads as much data as it can get from a FD
 * - returns the number of bytes read, or -1 on error
 */
int lbuf_readfd(struct lbuf *buf, int fd)
{
	int len = read(fd, buf->data + buf->pos, buf->size - buf->pos);
	if (len <= 0)
		return -1;

	buf->pos += len;
	return len;
}

/*
 * parses as much data as it can get from a FD
 * parses means: backspaces remove one byte from the end of the buffer
 * - returns 0 on success, or -1 on error
 */
int lbuf_parsefd(struct lbuf *buf, int fd)
{
	char tmp[32];
	int len = read(fd, tmp, sizeof(tmp));
	if (len <= 0)
		return -1;

	int i;
	for (i = 0; i < len; i++) {
		/* "understand" backspace */
		if (tmp[i] == 0x08 && buf->pos > 0) {
			buf->pos--;

		/* copy */
		} else if (tmp[i] >= ' ' || tmp[i] == '\n') {
			*(buf->data + buf->pos++) = tmp[i];
		}

		if (buf->pos > buf->size)
			return -1;
	}
	/* TODO: return bytes appended to buffer? */
	return 0;
}

/*
 * writes as much data as it can to a FD
 * - returns the number of bytes written, or -1 on error
 */
int lbuf_writefd(struct lbuf *buf, int fd)
{
	int len = write(fd, buf->data, buf->pos);
	if (len <= 0)
		return -1;

	/* handle partial writes */
	if (len != buf->pos)
		memmove(buf->data, buf->data + len, buf->pos - len);

	buf->pos -= len;
	return len;
}

/*
 * append va_list to buffer
 * - returns number ob bytes appended, or -1 on error
 */
int lbuf_vprintf(struct lbuf *buf, const char *fmt, va_list az)
{
	int len = vsnprintf(buf->data + buf->pos, buf->size - buf->pos, fmt, az);
	if (len < 0 || len >= (buf->size - buf->pos))
		return -1;

	buf->pos += len;
	return len;
}

/*
 * printf into buffer
 * - returns number of bytes appended, or -1 on error
 */
int lbuf_printf(struct lbuf *buf, const char *fmt, ...)
{
	va_list az;

	va_start(az, fmt);
	int ret = lbuf_vprintf(buf, fmt, az);
	va_end(az);

	return ret;
}

/*
 * get next non-empty token
 * - returns pointer to next token
 * - returns NULL if no delimter is found in buffer
 */
char * lbuf_gettok(struct lbuf *buf, const char *delim)
{
	char *start = buf->data;
	char *end = buf->data + buf->pos;
	int dlen = strlen(delim);

	while (1) {
		buf->token = NULL;

		/* find first delimiter in buffer */
		int i;
		for (i = 0; i < dlen; i++) {
			char *tok = memchr(start, delim[i], end - start);
			if (tok != NULL && (tok < buf->token || buf->token == NULL))
				buf->token = tok;
		}

		/* nothing found */
		if (buf->token == NULL)
			return NULL;

		/* delimter found on start pos -> skip empty token */
		if (buf->token == start) {
			start++;
			if (start >= end)
				return NULL;
		} else {
			/* non-empty token found, exit */
			break;
		}
	}

	/* overwrite token, return start ptr */
	*(buf->token) = '\0';
	return start;
}

/*
 * release previous fetched line
 * - returns number of remaining bytes in buffer
 */
int lbuf_freetok(struct lbuf *buf)
{
	if (buf->token != NULL) {
		buf->pos -= (buf->token - buf->data) +1;
		memmove(buf->data, buf->token +1, buf->pos);
		buf->token = NULL;
	}
	return buf->pos;
}