/*
 * Copyright (c) 1985, 1989 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that: (1) source distributions retain this entire copyright
 * notice and comment, and (2) distributions including binaries display
 * the following acknowledgement:  ``This product includes software
 * developed by the University of California, Berkeley and its contributors''
 * in the documentation or other materials provided with the distribution
 * and in all advertising materials mentioning features or use of this
 * software. Neither the name of the University nor the names of its
 * contributors may be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#ifndef lint
static char Version[] = "@(#)file.c	e07@nikhef.nl (Eric Wassenaar) 991529";
#endif

#include "host.h"

#define MAXCACHENAME	(4+2+MAXDNAME)	/* NNNN/Xdomainname */

static char cachefilebuf[MAXCACHENAME+1];
static char *cachefile = NULL;	/* full name of real cache file */

static char tempcachebuf[MAXCACHENAME+1];
static char *tempcache = NULL;	/* full name of temporary cache file */

static int cachefd = -1;	/* cache file descriptor */

time_t cachetime = 0;		/* time of last cache modification */

/*
** CACHENAME -- Construct full name of cache file
** ----------------------------------------------
**
**	Returns:
**		Pointer to specified buffer.
**
**	Cache files are organized in a hashed directory structure,
**	with the 4-digit hash value as the name of the particular
**	directory. A single character prefixes the file name.
**	The cache is relative to the current working directory.
*/

char *
cachename(name, buf, prefix)
input char *name;			/* name of zone to process */
output char *buf;			/* where to store the file name */
input char prefix;			/* single char prefix for file name */
{
	register unsigned int hfunc;
	register char *p, *q;
	register char c;

/*
 * Construct the name of the hash directory.
 */
	for (hfunc = 0, p = name; (c = *p) != '\0'; p++)
	{
		hfunc = ((hfunc << 1) ^ (lowercase(c) & 0377)) % HASHSIZE;
	}

	(void) sprintf(buf, "%04u/%c", hfunc, prefix);

/*
 * Construct the full name of the cache file.
 * Make sure there are only reasonable characters in the file name.
 * Obviously there should be no further slashes in the name.
 */
	for (q = &buf[strlen(buf)], p = name; (c = *p) != '\0'; p++)
	{
		if (!is_alnum(c) && !in_string("-._", c))
			c = '?';

		*q++ = lowercase(c);
	}
	*q = '\0';

	return(buf);
}

/*
** CACHE_OPEN -- Open cache file for either read or write
** ------------------------------------------------------
**
**	Returns:
**		File descriptor if successfully opened.
**		-1 in case of errors.
**
**	Outputs:
**		Sets ``cachefd'' to the cache file descriptor.
**		Sets ``cachefile'' to the real cache file name.
**		Sets ``tempcache'' to the temp cache name in case
**		a fresh cache must be created, NULL for read only.
*/

int
cache_open(name, create)
input char *name;			/* name of zone to process */
input bool create;			/* set to create fresh file */
{
	struct stat st;
	register char *p;

	/* construct the name of the associated cache file */
	cachefile = cachename(name, cachefilebuf, 'C');

	/* temporary cache file is not needed when read only */
	tempcache = create ? cachename(name, tempcachebuf, 'T') : NULL;

/*
 * If selected for read only, the cache file must just exist.
 */
	if (!create)
	{
		cachefd = open(cachefile, O_RDONLY, 0);
		if (cachefd < 0)
		{
			if (errno != ENOENT)
				cache_perror("Cannot open", cachefile);
			return(-1);
		}

		/* save last modification time for later reference */
		cachetime = (fstat(cachefd, &st) >= 0) ? st.st_mtime : 0;

		return(cachefd);
	}

/*
 * If necessary, create the intermediate cache directories.
 */
	p = index(cachefile, '/');
	while (p != NULL)
	{
		if (p > cachefile)
		{
			*p = '\0';
			if (stat(cachefile, &st) < 0)
			{
				if (errno != ENOENT)
				{
					cache_perror("Cannot stat", cachefile);
					return(-1);
				}

				if (mkdir(cachefile, 0755) < 0)
				{
					if (errno == EEXIST)
						continue;
					cache_perror("Cannot mkdir", cachefile);
					return(-1);
				}
			}
			else if ((st.st_mode & S_IFMT) != S_IFDIR)
			{
				seterrno(ENOTDIR);
				cache_perror("Cannot create", cachefile);
				return(-1);
			}
			*p = '/';
		}

		p = index(p+1, '/');
	}

/*
 * Create a fresh temporary cache file. It will be renamed to the
 * real cache file after processing has been completed successfully.
 */
	cachefd = open(tempcache, O_WRONLY|O_CREAT|O_TRUNC, 0644);
	if (cachefd < 0)
	{
		cache_perror("Cannot open", tempcache);
		return(-1);
	}

	/* last modification time unused during cache write */
	cachetime = 0;

	return(cachefd);
}

/*
** CACHE_CLOSE -- Terminate cache file processing
** ----------------------------------------------
**
**	Returns:
**		Status result of close or rename, if appropriate.
**		0 on success, -1 on errors.
*/

int
cache_close(create)
input bool create;			/* set to create fresh file */
{
	int save_errno = errno;		/* preserve state */
	int status = 0;			/* result status */

	/* we must have a valid file */
	if (cachefd >= 0)
	{
		/* close the cache; this must succeed when writing */
		status = close(cachefd);
		if (status < 0 && tempcache != NULL)
		{
			cache_perror("Cannot close", tempcache);

			/* preserve existing cache; prevent rename */
			create = FALSE;
		}

		/* move temp cache to real cache if so requested */
		if ((tempcache != NULL) && create)
		{
			status = rename(tempcache, cachefile);
			if (status < 0)
			{
				cache_perror("Cannot rename", tempcache);
			}
		}
		else if (tempcache != NULL)
		{
			if (unlink(tempcache) < 0)
			{
				cache_perror("Cannot unlink", tempcache);
			}
		}
	}

	tempcache = NULL;
	cachefile = NULL;
	cachefd = -1;

	/* restore state */
	seterrno(save_errno);

	return(status);
}

/*
** CACHE_WRITE -- Write an answer buffer to the local disk cache
** -------------------------------------------------------------
**
**	Returns:
**		Length of buffer if successfully written.
**		-1 in case of failure (error message is issued).
**
**	The buffer is written in two steps: first a single word with
**	the length of the buffer, followed by the buffer itself.
**	Anticipate partial writes, probably not strictly necessary.
*/

int
cache_write(buf, bufsize)
input char *buf;			/* location of raw answer buffer */
input int bufsize;			/* length of answer buffer */
{
	u_short len;
	char *buffer;
	int buflen;
	register int n;

	/* we must have a valid file */
	if (cachefd < 0)
		return(0);

/*
 * Write the length of the answer buffer.
 */
	/* len = htons((u_short)bufsize); */
	putshort((u_short)bufsize, (u_char *)&len);

	buffer = (char *)&len;
	buflen = INT16SZ;

	while (buflen > 0 && (n = write(cachefd, buffer, buflen)) > 0)
	{
		buffer += n;
		buflen -= n;
	}

	if (buflen != 0)
	{
		if (errno == 0) seterrno(EIO);
		cache_perror("Cannot write answer length", tempcache);
		return(-1);
	}

/*
 * Write the answer buffer itself.
 */
	buffer = buf;
	buflen = bufsize;

	while (buflen > 0 && (n = write(cachefd, buffer, buflen)) > 0)
	{
		buffer += n;
		buflen -= n;
	}

	if (buflen != 0)
	{
		if (errno == 0) seterrno(EIO);
		cache_perror("Cannot write answer", tempcache);
		return(-1);
	}

	return(bufsize);
}

/*
** CACHE_READ -- Read an answer buffer from the local disk cache
** -------------------------------------------------------------
**
**	Returns:
**		Length of (untruncated) answer if successfully read.
**		-1 in case of failure (error message is issued).
**
**	The answer is read in two steps: first a single word which
**	gives the length of the buffer, followed by the buffer itself.
**	If the answer is too long to fit into the supplied buffer,
**	only the portion that fits will be stored, the residu will be
**	flushed, and the truncation flag will be set.
**
**	Note. The returned length is that of the *un*truncated answer,
**	however, and not the amount of data that is actually available.
**	This may give the caller a hint about new buffer reallocation.
*/

int
cache_read(buf, bufsize)
output char *buf;			/* location of buffer to store answer */
input int bufsize;			/* maximum size of answer buffer */
{
	u_short len;
	char *buffer;
	int buflen;
	int reslen;
	register int n;

	/* we must have a valid file */
	if (cachefd < 0)
		return(0);

/*
 * Read the length of answer buffer.
 */
	buffer = (char *)&len;
	buflen = INT16SZ;

	while (buflen > 0 && (n = read(cachefd, buffer, buflen)) > 0)
	{
		buffer += n;
		buflen -= n;
	}

	if (buflen != 0)
	{
		if (errno == 0) seterrno(EIO);
		cache_perror("Cannot read answer length", cachefile);
		return(-1);
	}

/*
 * Terminate if length is zero.
 */
	/* len = ntohs(len); */
	len = _getshort((u_char *)&len);
	if (len == 0)
		return(0);

/*
 * Check for truncation.
 * Do not chop the returned length in case of buffer overflow.
 */
	reslen = 0;
	if ((int)len > bufsize)
	{
		reslen = len - bufsize;
		/* len = bufsize; */
	}

/*
 * Read the answer buffer itself.
 * Truncate the answer is the supplied buffer is not big enough.
 */
	buffer = buf;
	buflen = (reslen > 0) ? bufsize : len;

	while (buflen > 0 && (n = read(cachefd, buffer, buflen)) > 0)
	{
		buffer += n;
		buflen -= n;
	}

	if (buflen != 0)
	{
		if (errno == 0) seterrno(EIO);
		cache_perror("Cannot read answer", cachefile);
		return(-1);
	}

/*
 * Discard the residu to keep subsequent reads in sync.
 */
	if (reslen > 0)
	{
		HEADER *bp = (HEADER *)buf;
		char resbuf[PACKETSZ];

		buffer = resbuf;
		buflen = (reslen < sizeof(resbuf)) ? reslen : sizeof(resbuf);

		while (reslen > 0 && (n = read(cachefd, buffer, buflen)) > 0)
		{
			reslen -= n;
			buflen = (reslen < sizeof(resbuf)) ? reslen : sizeof(resbuf);
		}

		if (reslen != 0)
		{
			if (errno == 0) seterrno(EIO);
			cache_perror("Cannot read residu", cachefile);
			return(-1);
		}

		/* set truncation flag */
		bp->tc = 1;
	}

	return(len);
}

/*
** CACHE_PERROR -- Issue perror message including file info
** --------------------------------------------------------
**
**	Returns:
**		None.
*/

void
cache_perror(message, filename)
input char *message;			/* extra message string */
input char *filename;			/* file name for perror */
{
	int save_errno = errno;		/* preserve state */

	/* prepend extra message */
	if (message != NULL)
		(void) fprintf(stderr, "%s ", message);

	/* issue actual message */
	seterrno(save_errno);
	perror(filename);

	/* restore state */
	seterrno(save_errno);
}