On Tue, Nov 27, 2001 at 11:57:18PM +1100, Ben Stanley wrote:
> Here is the mmap patch for calculating CRCs quickly.
How about wrapping #warnings in #ifdef __GNUC__?
> This has fixed my slow CRC problem.
>
> It seems to work for me, but I think that Lars should put it into his
> check_crc test harness and check it a bit more before applying...
>
> In particular, I have not checked that you get the same CRC values using
> each iterator method.
> Lars, were you comparing the LyX CRC routine against the boost crc
> routine in that test code of yours which was generating different
> results? I'd be interested to see if you get the same result comparing
> lyx CRC with iterators and lyx CRC with mmap pointers (just iterators,
> really...) using your check_crc program.
>
> Ben.
> --- lyx-1.1.6fix3-orig/src/support/lyxsum.C Wed Jun 6 02:07:10 2001
> +++ lyx-1.1.6fix3/src/support/lyxsum.C Tue Nov 27 19:25:19 2001
> @@ -15,11 +15,33 @@
>
> #include <config.h>
>
> +#ifdef HAVE_MMAP
> +#warning lyx::sum() using mmap (lightning fast but untested)
> +#define USE_MMAP
> +#elif HAVE_DECL_ISTREAMBUF_ITERATOR
> +#warning lyx::sum() using istreambuf_iterator (fast)
> +#define USE_ISTREAMBUF_ITER
> +#define USE_STREAM
> +#else
> +#warning lyx::sum() using istream_iterator (slow as a snail)
> +#define USE_ISTREAM_ITER
> +#define USE_STREAM
> +#endif
> +
> +
> #include <fstream>
> #include <iterator>
>
> #include "support/lyxlib.h"
>
> +#ifdef USE_MMAP
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <sys/mman.h>
> +#endif
> +
> using std::ifstream;
> using std::ios;
>
> @@ -104,23 +126,56 @@
> }
>
>
> +
> // And this would be the file interface.
> unsigned long lyx::sum(string const & file)
> {
> +
> +#ifdef USE_STREAM
> std::ifstream ifs(file.c_str());
> if (!ifs) return 0;
> -
> -#ifdef HAVE_DECL_ISTREAMBUF_ITERATOR
> +#endif
> +
> + // Setups
> +
> +#ifdef USE_ISTREAMBUF_ITER
> // This is a lot faster...
> std::istreambuf_iterator<char> beg(ifs);
> std::istreambuf_iterator<char> end;
> -#else
> +#endif
> +
> +#ifdef USE_ISTREAM_ITER
> // than this.
> ifs.unsetf(std::ios::skipws);
> std::istream_iterator<char> beg(ifs);
> std::istream_iterator<char> end;
> #endif
>
> - return do_crc(beg, end);
> +#ifdef USE_MMAP
> + int fd = open(file.c_str(), O_RDONLY);
> + if( !fd ) return 0;
> +
> + struct stat info;
> + int st = fstat(fd, &info);
> +
> + void * mm = mmap(0, info.st_size, PROT_READ,
> + MAP_PRIVATE /*| MAP_ANON*/, fd, 0); // MAP_ANON is not POSIX
> + if (mm == MAP_FAILED) {
> + close(fd);
> + return 0;
> + }
> + char *beg = (char*)mm;
> + char *end = ((char*)mm)+info.st_size;
> +#endif
> +
> + // Do the CRC
> + unsigned long result = do_crc(beg,end);
> +
> + // Clean up
> +#ifdef USE_MMAP
> + munmap( mm, info.st_size );
> + close(fd);
> +#endif
> + return result;
> }
>
--
albert chin ([EMAIL PROTECTED])
