Hi,
Now I am puzzled a bit.
It means DbDrop() only removes file entry from the directory
but does nothing with file contents. Am I right ?
OR if DbCloseArea() is issued prior to calling DbDrop(), it
removes the file entry as well as file contents.
To me it appears logical that DbDrop() must never be succeeded
unless file is closed, just like a disk file.
Open file can be deleted on all unix systems, but not windows. It is
very useful behaviour, for example if you want to delete (or replace by
new version) a running executable. The new version will be used next
time executable will be started. Actually I do not analyzed how DBDROP()
works. MEMIO implementetion is at file system level. Perhaps windows
like behaviour could be reached using some locking, but I'm not an
expert here. MEMIO uses file content (perhaps it can be called inode)
counter, after file is removed from directory and all open file handlers
are closed, file is removed from file system. Here is one nice sample:
=========
m...@linux:~/devel_exp/tmp> cat test1.c
#include "stdio.h"
#include "dirent.h"
static void dirlist( void );
int main( void )
{
FILE * file;
char buf[ 16 ];
if( ( file = fopen( "test1.txt", "w+" ) ) != NULL )
{
fwrite( "hello", 1, 5, file );
dirlist();
remove( "test1.txt" );
dirlist();
fseek( file, 0, 0 );
fread( buf, 1, 5, file );
printf( "File content: %.5s\n", buf );
fclose( file );
}
return 0;
}
static void dirlist( void )
{
DIR * dir;
struct dirent * d;
printf( "Dirlist:\n" );
if( ( dir = opendir( "." ) ) != NULL )
{
while( ( d = readdir( dir ) ) != NULL )
printf( " %s\n", d->d_name );
closedir( dir );
}
}
m...@linux:~/devel_exp/tmp> ./a.out
Dirlist:
test1.txt
test1.c
.
..
a.out
Dirlist:
test1.c
.
..
a.out
File content: hello
=========
Can you provide more insight how MEMIO be used and what
precautions one needs to take while adopting this protocol over
disk-files ?
Locking is not supported by MEMIO driver. Temporary file creation is not
supported because current IO driver architecture does not allow to
implement it. File system has a "plain root directory", i.e. all files
are placed in root and "/" or "\" character is just a common character
in file name. So, "mem:aaa", "mem:\\\", "mem:/../\/\..''\../*$?::::" all
are a valid file names.
Also, I have an idea some memory corruption exists. Sometimes we have a
strange behavior in a complex Windows applications, but I'm unable to
reproduce these errors in self contained samples or track them down
using valgrind.
Regards,
Mindaugas
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