/*

 test.cc - disk test
 Uses C++ isms, so compile with 'CC test.cc -lposix4'
 
 This test program creates and fills a 4MB file, then processes
 the equivalent of 1000 TRANS_SIZE KB transactions.  A transaction involves
 writing TRANS_SIZE KB to the file, then calling pwrite().  When the end
 
 Input: file name , Transaction size, IO method ( fdatasync, directIO)
 Output: Average transaction time in us 
 
 */
 
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <fcntl.h>
 #include <string.h>
 #include <sys/time.h>
 
 
 #define MB	(1024*1024)
 #define K	(1024)
 #define PAGESIZE	(8192)
 #define BLOCKSIZE	(512)
 #define SLEEP_US	(2000)
 #define FILE_SIZE	(4 * MB)
 

 typedef long long hrtime_t;
 char * filename;
 char * IO_METHOD;
 unsigned int TRANS_SIZE ;
 int fd;
 char *trans;
 unsigned int cursor;
 unsigned int file_length;
 
 void open_file( int attr);
 void fill_file( unsigned int);
 void do_commit( unsigned int);
 
 main( int argc, char *argv[])
 {
     if ( argc < 4)
     {
      printf ("Usage: test.out [file name] [txn size] [fdatasync/directio]\n");
      exit(1);
     }

     hrtime_t start, delta;
     filename= argv[1];
     TRANS_SIZE = ((int)atoi(argv[2]) * K);
     IO_METHOD = argv[3];
    
     
     open_file( 0);
     file_length = FILE_SIZE;
    
     if (! strcmp(IO_METHOD, "directio") ) {
         printf("directio in use \n");
         directio(fd, DIRECTIO_ON);
      }
     
     else {
         if ( !strcmp(IO_METHOD, "fdatasync") ) {
             printf("fdatasync is in use \n");
             directio(fd, DIRECTIO_OFF);
          }
         else
           {printf ("Usage: test.out [file name] [txn size] [fdatasync/directIO]\n");
            exit(1);
           } 
        }
           

     trans= (char*) memalign( PAGESIZE, MB);
     unsigned char val = '4';
     memset( trans,(int)val , TRANS_SIZE);
     
    
     start= gethrtime();
   
     for ( int i=1000; i; i--) 
 	do_commit( TRANS_SIZE);
     
     delta= gethrtime() - start;
     printf( "%lld us\n", delta/1000LL/1000LL);
     close(fd);
 
     return 0;
 }
 
 void
 open_file( int attr)
 {
     fd= open( filename, O_RDWR | O_CREAT | attr, 0644);
      if ( fd == -1)  {
 	perror( filename);
 	exit(1);
     }
 }
 
 void
 fill_file( unsigned int length)
 {
     char *zero_block;
     zero_block= (char*) memalign( PAGESIZE, BLOCKSIZE);
     memset( zero_block, 0, BLOCKSIZE);
 
     for ( ; length; length-= BLOCKSIZE)
 	write( fd, zero_block, BLOCKSIZE);
     lseek( fd, 0, SEEK_SET);
     fdatasync(fd);
     free( zero_block);
 }
 
 void
 do_commit( unsigned int size)
 {
    hrtime_t start0;
    hrtime_t end0 ;
     
      start0= gethrtime();
 
       if ( pwrite( fd, trans, size, cursor) != size)  {
 	perror( "pwrite");
 	exit(1);
     }
       end0 = gethrtime() - start0;
       
     /* when directio is enabled - fdatasync has no effect */  
     fdatasync(fd); 
     
     cursor+= size;
     if ( cursor >= file_length)
 	cursor= 0;
 }