samba-mirror/source3/smbwrapper/shared.c

/* 
   Unix SMB/CIFS implementation.
   SMB wrapper functions - shared variables
   Copyright (C) Andrew Tridgell 1998
   
   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 of the License, 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.
   
   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., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"

static int shared_fd;
static char *variables;
static int shared_size;

/***************************************************** 
setup the shared area 
*******************************************************/
void smbw_setup_shared(void)
{
	int fd;
	pstring name, s;

	slprintf(name,sizeof(name)-1, "%s/smbw.XXXXXX",tmpdir());

	fd = smb_mkstemp(name);

	if (fd == -1) goto failed;

	unlink(name);

	shared_fd = set_maxfiles(SMBW_MAX_OPEN);
	
	while (shared_fd && dup2(fd, shared_fd) != shared_fd) shared_fd--;

	if (shared_fd == 0) goto failed;

	close(fd);

	DEBUG(4,("created shared_fd=%d\n", shared_fd));

	slprintf(s,sizeof(s)-1,"%d", shared_fd);

	setenv("SMBW_HANDLE", s, 1);

	return;

 failed:
	perror("Failed to setup shared variable area ");
	exit(1);
}

static int locked;

/***************************************************** 
lock the shared variable area
*******************************************************/
static void lockit(void)
{
	if (shared_fd == 0) {
		char *p = getenv("SMBW_HANDLE");
		if (!p) {
			DEBUG(0,("ERROR: can't get smbw shared handle\n"));
			exit(1);
		}
		shared_fd = atoi(p);
	}
	if (locked==0 && 
	    fcntl_lock(shared_fd,SMB_F_SETLKW,0,1,F_WRLCK)==False) {
		DEBUG(0,("ERROR: can't get smbw shared lock (%s)\n", strerror(errno)));
		exit(1);
	}
	locked++;
}

/***************************************************** 
unlock the shared variable area
*******************************************************/
static void unlockit(void)
{
	locked--;
	if (locked == 0) {
		fcntl_lock(shared_fd,SMB_F_SETLK,0,1,F_UNLCK);
	}
}


/***************************************************** 
get a variable from the shared area
*******************************************************/
char *smbw_getshared(const char *name)
{
	int i;
	struct stat st;
	char *var;

	lockit();

	/* maybe the area has changed */
	if (fstat(shared_fd, &st)) goto failed;

	if (st.st_size != shared_size) {
		var = (char *)Realloc(variables, st.st_size);
		if (!var) goto failed;
		else variables = var;
		shared_size = st.st_size;
		lseek(shared_fd, 0, SEEK_SET);
		if (read(shared_fd, variables, shared_size) != shared_size) {
			goto failed;
		}
	}

	unlockit();

	i=0;
	while (i < shared_size) {
		char *n, *v;
		int l1, l2;

		l1 = SVAL(&variables[i], 0);
		l2 = SVAL(&variables[i], 2);

		n = &variables[i+4];
		v = &variables[i+4+l1];
		i += 4+l1+l2;

		if (strcmp(name,n)) {
			continue;
		}
		return v;
	}

	return NULL;

 failed:
	DEBUG(0,("smbw: shared variables corrupt (%s)\n", strerror(errno)));
	exit(1);
	return NULL;
}



/***************************************************** 
set a variable in the shared area
*******************************************************/
void smbw_setshared(const char *name, const char *val)
{
	int l1, l2;
	char *var;

	/* we don't allow variable overwrite */
	if (smbw_getshared(name)) return;

	lockit();

	l1 = strlen(name)+1;
	l2 = strlen(val)+1;

	var = (char *)Realloc(variables, shared_size + l1+l2+4);

	if (!var) {
		DEBUG(0,("out of memory in smbw_setshared\n"));
		exit(1);
	}
	
	variables = var;

	SSVAL(&variables[shared_size], 0, l1);
	SSVAL(&variables[shared_size], 2, l2);

	safe_strcpy(&variables[shared_size] + 4, name, l1-1);
	safe_strcpy(&variables[shared_size] + 4 + l1, val, l2-1);

	shared_size += l1+l2+4;

	lseek(shared_fd, 0, SEEK_SET);
	if (write(shared_fd, variables, shared_size) != shared_size) {
		DEBUG(0,("smbw_setshared failed (%s)\n", strerror(errno)));
		exit(1);
	}

	unlockit();
}


/*****************************************************************
return true if the passed fd is the SMBW_HANDLE
*****************************************************************/  
int smbw_shared_fd(int fd)
{
	return (shared_fd && shared_fd == fd);
}