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Revision 1.3, Fri Aug 5 23:15:08 2016 UTC (4 years, 2 months ago) by schwarze
Branch: MAIN
Changes since 1.2: +7 -1 lines

The concept of endianness seems to be somewhat newfangled, so the
respective conversion functions are not yet properly standardized.
Rumour has it that POSIX is working on it, though.
For now, sprinkle some configuration glue.

/*	$Id: dbm_map.c,v 1.3 2016/08/05 23:15:08 schwarze Exp $ */
/*
 * Copyright (c) 2016 Ingo Schwarze <schwarze@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Low-level routines for the map-based version
 * of the mandoc database, for read-only access.
 * The interface is defined in "dbm_map.h".
 */
#include "config.h"

#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>

#if HAVE_ENDIAN
#include <endian.h>
#elif HAVE_SYS_ENDIAN
#include <sys/endian.h>
#elif HAVE_NTOHL
#include <arpa/inet.h>
#endif
#if HAVE_ERR
#include <err.h>
#endif
#include <errno.h>
#include <fcntl.h>
#include <regex.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "mansearch.h"
#include "dbm_map.h"
#include "dbm.h"

static struct stat	 st;
static char		*dbm_base;
static int		 ifd;
static int32_t		 max_offset;

/*
 * Open a disk-based database for read-only access.
 * Validate the file format as far as it is not mandoc-specific.
 * Return 0 on success.  Return -1 and set errno on failure.
 */
int
dbm_map(const char *fname)
{
	int		 save_errno;
	const int32_t	*magic;

	if ((ifd = open(fname, O_RDONLY)) == -1)
		return -1;
	if (fstat(ifd, &st) == -1)
		goto fail;
	if (st.st_size < 5) {
		warnx("dbm_map(%s): File too short", fname);
		errno = EFTYPE;
		goto fail;
	}
	if (st.st_size > INT32_MAX) {
		errno = EFBIG;
		goto fail;
	}
	if ((dbm_base = mmap(NULL, st.st_size, PROT_READ, MAP_SHARED,
	    ifd, 0)) == MAP_FAILED)
		goto fail;
	magic = dbm_getint(0);
	if (be32toh(*magic) != MANDOCDB_MAGIC) {
		warnx("dbm_map(%s): Bad initial magic %x (expected %x)",
		    fname, be32toh(*magic), MANDOCDB_MAGIC);
		errno = EFTYPE;
		goto fail;
	}
	magic = dbm_getint(1);
	if (be32toh(*magic) != MANDOCDB_VERSION) {
		warnx("dbm_map(%s): Bad version number %d (expected %d)",
		    fname, be32toh(*magic), MANDOCDB_VERSION);
		errno = EFTYPE;
		goto fail;
	}
	max_offset = be32toh(*dbm_getint(3)) + sizeof(int32_t);
	if (st.st_size != max_offset) {
		warnx("dbm_map(%s): Inconsistent file size %llu (expected %d)",
		    fname, st.st_size, max_offset);
		errno = EFTYPE;
		goto fail;
	}
	if ((magic = dbm_get(*dbm_getint(3))) == NULL) {
		errno = EFTYPE;
		goto fail;
	}
	if (be32toh(*magic) != MANDOCDB_MAGIC) {
		warnx("dbm_map(%s): Bad final magic %x (expected %x)",
		    fname, be32toh(*magic), MANDOCDB_MAGIC);
		errno = EFTYPE;
		goto fail;
	}
	return 0;

fail:
	save_errno = errno;
	close(ifd);
	errno = save_errno;
	return -1;
}

void
dbm_unmap(void)
{
	if (munmap(dbm_base, st.st_size) == -1)
		warn("dbm_unmap: munmap");
	if (close(ifd) == -1)
		warn("dbm_unmap: close");
	dbm_base = (char *)-1;
}

/*
 * Take a raw integer as it was read from the database.
 * Interpret it as an offset into the database file
 * and return a pointer to that place in the file.
 */
void *
dbm_get(int32_t offset)
{
	offset = be32toh(offset);
	if (offset < 0 || offset >= max_offset) {
		warnx("dbm_get: Database corrupt: offset %d > %d",
		    offset, max_offset);
		return NULL;
	}
	return dbm_base + offset;
}

/*
 * Assume the database starts with some integers.
 * Assume they are numbered starting from 0, increasing.
 * Get a pointer to one with the number "offset".
 */
int32_t *
dbm_getint(int32_t offset)
{
	return (int32_t *)dbm_base + offset;
}

/*
 * The reverse of dbm_get().
 * Take pointer into the database file
 * and convert it to the raw integer
 * that would be used to refer to that place in the file.
 */
int32_t
dbm_addr(const void *p)
{
	return htobe32((char *)p - dbm_base);
}

int
dbm_match(const struct dbm_match *match, const char *str)
{
	switch (match->type) {
	case DBM_EXACT:
		return strcmp(str, match->str) == 0;
	case DBM_SUB:
		return strcasestr(str, match->str) != NULL;
	case DBM_REGEX:
		return regexec(match->re, str, 0, NULL, 0) == 0;
	default:
		abort();
	}
}