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/******************************************************************************
* $Id$
*
* Project: MapServer
* Purpose: MapCache tile caching support file: OS-level locking support
* Author: Thomas Bonfort and the MapServer team.
*
******************************************************************************
* Copyright (c) 1996-2011 Regents of the University of Minnesota.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies of this Software or works derived from this Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*****************************************************************************/
#include "mapcache.h"
#include <apr_file_io.h>
#include <apr_strings.h>
#include <apr_time.h>
char* lock_filename_for_resource(mapcache_context *ctx, const char *resource)
{
char *saferes = apr_pstrdup(ctx->pool,resource);
char *safeptr = saferes;
while(*safeptr) {
if(*safeptr==' ' || *safeptr == '/' || *safeptr == '~' || *safeptr == '.') {
*safeptr = '#';
}
safeptr++;
}
return apr_psprintf(ctx->pool,"%s/"MAPCACHE_LOCKFILE_PREFIX"%s.lck",
ctx->config->lockdir,saferes);
}
int mapcache_lock_or_wait_for_resource(mapcache_context *ctx, char *resource)
{
char *lockname = lock_filename_for_resource(ctx,resource);
apr_file_t *lockfile;
apr_status_t rv;
/* create the lockfile */
rv = apr_file_open(&lockfile,lockname,APR_WRITE|APR_CREATE|APR_EXCL|APR_XTHREAD,APR_OS_DEFAULT,ctx->pool);
/* if the file already exists, wait for it to disappear */
/* TODO: check the lock isn't stale (i.e. too old) */
if( rv != APR_SUCCESS ) {
apr_finfo_t info;
rv = apr_stat(&info,lockname,0,ctx->pool);
#ifdef DEBUG
if(!APR_STATUS_IS_ENOENT(rv)) {
ctx->log(ctx, MAPCACHE_DEBUG, "waiting on resource lock %s", resource);
}
#endif
while(!APR_STATUS_IS_ENOENT(rv)) {
/* sleep for the configured number of micro-seconds (default is 1/100th of a second) */
apr_sleep(ctx->config->lock_retry_interval);
rv = apr_stat(&info,lockname,0,ctx->pool);
}
return MAPCACHE_FALSE;
} else {
/* we acquired the lock */
apr_file_close(lockfile);
return MAPCACHE_TRUE;
}
}
void mapcache_unlock_resource(mapcache_context *ctx, char *resource)
{
char *lockname = lock_filename_for_resource(ctx,resource);
apr_file_remove(lockname,ctx->pool);
}
/* vim: ts=2 sts=2 et sw=2
*/
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