tinyproxy/src/network.c

/* $Id: network.c,v 1.2 2003-07-31 23:38:28 rjkaes Exp $
 *
 * The functions found here are used for communicating across a
 * network.  They include both safe reading and writing (which are
 * the basic building blocks) along with two functions for
 * easily reading a line of text from the network, and a function
 * to write an arbitrary amount of data to the network.
 *
 * Copyright (C) 2002  Robert James Kaes (rjkaes@flarenet.com)
 *
 * 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; either version 2, or (at your option) any
 * later version.
 *
 * 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.
 */

#include "tinyproxy.h"

#include "heap.h"
#include "network.h"

/*
 * Write the buffer to the socket. If an EINTR occurs, pick up and try
 * again. Keep sending until the buffer has been sent.
 */
ssize_t
safe_write(int fd, const char *buffer, size_t count)
{
	ssize_t len;
	size_t bytestosend;

	assert(fd >= 0);
	assert(buffer != NULL);
	assert(count > 0);

	bytestosend = count;

	while (1) {
		len = send(fd, buffer, bytestosend, MSG_NOSIGNAL);

		if (len < 0) {
			if (errno == EINTR)
				continue;
			else
				return -errno;
		}

		if (len == bytestosend)
			break;

		buffer += len;
		bytestosend -= len;
	}

	return count;
}

/*
 * Matched pair for safe_write(). If an EINTR occurs, pick up and try
 * again.
 */
ssize_t
safe_read(int fd, char *buffer, size_t count)
{
	ssize_t len;

	do {
		len = read(fd, buffer, count);
	} while (len < 0 && errno == EINTR);

	return len;
}

/*
 * Send a "message" to the file descriptor provided. This handles the
 * differences between the various implementations of vsnprintf. This code
 * was basically stolen from the snprintf() man page of Debian Linux
 * (although I did fix a memory leak. :)
 */
int
write_message(int fd, const char *fmt, ...)
{
	ssize_t n;
	size_t size = (1024 * 8);	/* start with 8 KB and go from there */
	char *buf, *tmpbuf;
	va_list ap;

	if ((buf = (char*)safemalloc(size)) == NULL)
		return -1;

	while (1) {
		va_start(ap, fmt);
		n = vsnprintf(buf, size, fmt, ap);
		va_end(ap);

		/* If that worked, break out so we can send the buffer */
		if (n > -1 && n < size)
			break;

		/* Else, try again with more space */
		if (n > -1)
			/* precisely what is needed (glibc2.1) */
			size = n + 1;
		else
			/* twice the old size (glibc2.0) */
			size *= 2;

		if ((tmpbuf = (char*)saferealloc(buf, size)) == NULL) {
			safefree(buf);
			return -1;
		} else
			buf = tmpbuf;
	}

	if (safe_write(fd, buf, n) < 0) {
		safefree(buf);
		return -1;
	}

	safefree(buf);
	return 0;
}

/*
 * Read in a "line" from the socket. It might take a few loops through
 * the read sequence. The full string is allocate off the heap and stored
 * at the whole_buffer pointer. The caller needs to free the memory when
 * it is no longer in use. The returned line is NULL terminated.
 *
 * Returns the length of the buffer on success (not including the NULL
 * termination), 0 if the socket was closed, and -1 on all other errors.
 */
#define SEGMENT_LEN (512)
#define MAXIMUM_BUFFER_LENGTH (128 * 1024)
ssize_t
readline(int fd, char **whole_buffer)
{
	ssize_t whole_buffer_len;
	char buffer[SEGMENT_LEN];
	char *ptr;

	ssize_t ret;
	ssize_t diff;

	struct read_lines_s {
		char *data;
		size_t len;
		struct read_lines_s *next;
	};
	struct read_lines_s *first_line, *line_ptr;

	first_line =
		(struct read_lines_s*)safecalloc(sizeof(struct read_lines_s), 1);
	if (!first_line)
		return -ENOMEM;

	line_ptr = first_line;

	whole_buffer_len = 0;
	for (;;) {
		ret = recv(fd, buffer, SEGMENT_LEN, MSG_PEEK);
		if (ret <= 0)
			goto CLEANUP;

		ptr = (char*)memchr(buffer, '\n', ret);
		if (ptr)
			diff = ptr - buffer + 1;
		else
			diff = ret;

		whole_buffer_len += diff;

		/*
		 * Don't allow the buffer to grow without bound. If we
		 * get to more than MAXIMUM_BUFFER_LENGTH close.
		 */
		if (whole_buffer_len > MAXIMUM_BUFFER_LENGTH) {
			ret = -ERANGE;
			goto CLEANUP;
		}

		line_ptr->data = (char*)safemalloc(diff);
		if (!line_ptr->data) {
			ret = -ENOMEM;
			goto CLEANUP;
		}

		recv(fd, line_ptr->data, diff, 0);
		line_ptr->len = diff;

		if (ptr) {
			line_ptr->next = NULL;
			break;
		}

		line_ptr->next =
			(struct read_lines_s*)safecalloc(sizeof(struct read_lines_s), 1);
		if (!line_ptr->next) {
			ret = -ENOMEM;
			goto CLEANUP;
		}
		line_ptr = line_ptr->next;
	}

	*whole_buffer = (char*)safemalloc(whole_buffer_len + 1);
	if (!*whole_buffer) {
		ret = -ENOMEM;
		goto CLEANUP;
	}

	*(*whole_buffer + whole_buffer_len) = '\0';

	whole_buffer_len = 0;
	line_ptr = first_line;
	while (line_ptr) {
		memcpy(*whole_buffer + whole_buffer_len, line_ptr->data,
		       line_ptr->len);
		whole_buffer_len += line_ptr->len;

		line_ptr = line_ptr->next;
	}

	ret = whole_buffer_len;

      CLEANUP:
	do {
		line_ptr = first_line->next;
		if (first_line->data)
			safefree(first_line->data);
		safefree(first_line);
		first_line = line_ptr;
	} while (first_line);

	return ret;
}