Re: [sqlite] A memvfs for loading/saving database from buffer

[stephen liu]

http://spserver.googlecode.com/files/spmemvfs-0.1.src.tar.gz

Changes:
* Modify the save callback, transfer the ownership of the buffer to callback
function
* Add a buffer map to pass buffer between application and sqlite3 vfs

The demo code:

static void * load( void * arg, const char * path, int * len )
{
    spmembuffer_map_t * themap = (spmembuffer_map_t*)arg;
    char * ret = spmembuffer_map_take( themap, path, len );
    return ret;
}

static int save( void * arg, const char * path, char * buffer, int len )
{
    spmembuffer_map_t * themap = (spmembuffer_map_t*)arg;
    return spmembuffer_map_put( themap, path, buffer, len );
}

int main( int argc, char * argv[] )
{
    spmembuffer_map_t * themap = spmembuffer_map_new();
    spmemvfs_cb_t cb = { themap, load, save };
    const char * path = "abc.db";

    spmemvfs_init( &cb );

    // load membuffer from file, put it into themap
    {
        char * buffer = NULL;
        int len = 0;
        buffer = read_buffer_from_file( path, &len );
        spmembuffer_map_put( themap, path, buffer, len );
    }

    // open sqlite by sqlite3_open_v2
    {
        sqlite3 * dbHandle = NULL;
        char errcode = sqlite3_open_v2( path, &dbHandle,
            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, SPMEMVFS_NAME );

        // do wahtever you want
        ......
    }

    // get membuffer from themap, save it to file
    {
        int len = 0;
        char * buffer = (char*)spmembuffer_map_take( themap, path, &len );
        save_buffer_to_file( path, buffer, len );
        free( buffer );
    }

    spmembuffer_map_del( themap );

    return 0;
}
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