Implement basic database locking

We're using advisory file locking via php_flock(), so the usual caveats
regarding multithreaded Windows SAPIs apply. We're applying blocking
locks automatically on creation and opening of databases, so that
existing code doesn't have to be changed to make use of the locking. If
users want to check whether an operation would block, flock() with
LOCK_NB can be used (leaving room for possible race-conditions, though).


git-svn-id: http://svn.php.net/repository/pecl/dbase/trunk@340803 c90b9560-bf6c-de11-be94-00142212c4b1

Author: cmb69

dbase.c

@@ -26,6 +26,7 @@
 #include "fopen_wrappers.h"
 #include "php_globals.h"
 #include "ext/standard/php_math.h"
+#include "ext/standard/flock_compat.h"
 
 #include <stdlib.h>
 
@@ -47,6 +48,7 @@ static void _close_dbase(zend_resource *rsrc)
 {
 	dbhead_t *dbhead = (dbhead_t *)rsrc->ptr;
 
+	php_flock(dbhead->db_fd, LOCK_UN);
 	close(dbhead->db_fd);
 	free_dbf_head(dbhead);
 }
@@ -516,6 +518,12 @@ PHP_FUNCTION(dbase_create)
 		RETURN_FALSE;
 	}
 
+	if (php_flock(fd, LOCK_EX)) {
+		php_error_docref(NULL, E_WARNING, "unable to lock database");
+		close(fd);
+		RETURN_FALSE;
+	}
+
 	num_fields = zend_hash_num_elements(fields);
 
 	if (num_fields <= 0) {

dbf_head.c

@@ -8,6 +8,7 @@
 #include <fcntl.h>
 
 #include "php.h"
+#include "ext/standard/flock_compat.h" 
 #include "dbf.h"
 
 void free_dbf_head(dbhead_t *dbh);
@@ -278,6 +279,11 @@ dbhead_t *dbf_open(char *dp, int o_flags)
 		return NULL;
 	}
 
+	if (php_flock(fd, (o_flags == O_RDWR ? LOCK_EX : LOCK_SH))) {
+		close(fd);
+		return NULL;
+	}
+
 	if ((dbh = get_dbf_head(fd)) ==	NULL) {
 		return NULL;
 	}

package.xml

@@ -10,9 +10,7 @@ http://pear.php.net/dtd/package-2.0.xsd">
 in dBase-format (dbf) databases.
 
 There is no support for indexes or memo fields. 
-There is no support for locking, too. 
-Two concurrent webserver processes modifying the 
-same dBase file will very likely ruin your database.
+The databases are automatically locked with blocking flock()s.
 
 dBase files are simple sequential files of fixed length records. 
 Records are appended to the end of the file and deleted records