/* gcc -O3 -o crc32 crc32.c -lz */

#include <stdio.h>
#include <zlib.h>
#include <errno.h>
#include <string.h>

int main( int argc, const char* argv[] )
{
  if ( argc != 2 )
  {
    fprintf( stderr, "Usage: crc32 <filename>\n" );
    return 1;
  }
  
  FILE* file = fopen( argv[ 1 ], "rb" );
  
  if ( file )
  {
    uLong crc = crc32( 0L, Z_NULL, 0 );
    
    for ( ;; )
    {
      Bytef buffer[ 16384 ];
      
      int numread = fread( (void*)buffer, 1, sizeof( buffer ), file );
      
      if ( numread > 0 )
      {
        crc = crc32( crc, buffer, numread );
      }
      else
      {
        break;
      }
    }
    
    fclose( file );
    
    printf( "%08x\n", crc );
    return 0;
  }
  
  fprintf( stderr, "Error opening input file: %s\n", strerror( errno ) );
  return 1;
}