tools/dsync-0.0/libdsync/contrib/slidingwindow.cc

   1 // -*- mode: cpp; mode: fold -*-
   2 // Description                                                          /*{{{*/
   3 // $Id: slidingwindow.cc,v 1.1 1999/11/05 05:47:06 jgg Exp $
   4 /* ######################################################################
   5
   6    Sliding Window - Implements a sliding buffer over a file.
   7
   8    It would be possible to implement an alternate version if
   9    _POSIX_MAPPED_FILES is not defined..
  10
  11    ##################################################################### */
  12                                                                         /*}}}*/
  13 // Include files                                                        /*{{{*/
  14 #ifdef __GNUG__
  15 #pragma implementation "dsync/slidingwindow.h"
  16 #endif
  17
  18 #include <dsync/slidingwindow.h>
  19 #include <dsync/error.h>
  20
  21 #include <sys/mman.h>
  22 #include <unistd.h>
  23                                                                         /*}}}*/
  24
  25 // SlidingWindow::SlidingWindow - Constructor                           /*{{{*/
  26 // ---------------------------------------------------------------------
  27 /* */
  28 SlidingWindow::SlidingWindow(FileFd &Fd,unsigned long MnSize) : Buffer(0),
  29                               MinSize(MnSize), Fd(Fd)
  30 {
  31    Offset = 0;
  32    Left = 0;
  33    PageSize = sysconf(_SC_PAGESIZE);
  34
  35    if (MinSize < 1024*1024)
  36       MinSize = 1024*1024;
  37    MinSize = Align(MinSize);
  38 }
  39                                                                         /*}}}*/
  40 // SlidingWindow::~SlidingWindow - Destructor                           /*{{{*/
  41 // ---------------------------------------------------------------------
  42 /* Just unmap the mapping */
  43 SlidingWindow::~SlidingWindow()
  44 {
  45    if (Buffer != 0)
  46    {
  47       if (munmap((char *)Buffer,Size) != 0)
  48          _error->Warning("Unable to munmap");
  49    }
  50 }
  51                                                                         /*}}}*/
  52 // SlidingWindow::Extend - Make Start - End longer                                                                      /*{{{*/
  53 // ---------------------------------------------------------------------
  54 /* Start == End when the file is exhausted, false is an IO error. */
  55 bool SlidingWindow::Extend(unsigned char *&Start,unsigned char *&End)
  56 {
  57    unsigned long Remainder = 0;
  58
  59    // Restart
  60    if (Start == 0 || Buffer == 0)
  61    {
  62       Offset = 0;
  63       Left = Fd.Size();
  64    }
  65    else
  66    {
  67       if (AlignDn((unsigned long)(Start - Buffer)) == 0)
  68          return _error->Error("SlidingWindow::Extend called with too small a 'Start'");
  69
  70       // Scanning is finished.
  71       if (Left < (off_t)Size)
  72       {
  73          End = Start;
  74          return true;
  75       }
  76
  77       Offset += AlignDn((unsigned long)(Start - Buffer));
  78       Left -= AlignDn((unsigned long)(Start - Buffer));
  79       Remainder = (Start - Buffer) % PageSize;
  80    }
  81
  82    // Release the old region
  83    if (Buffer != 0)
  84    {
  85       if (munmap((char *)Buffer,Size) != 0)
  86          return _error->Errno("munmap","Unable to munmap");
  87       Buffer = 0;
  88    }
  89
  90    // Maximize the amount that can be mapped
  91    if (Left < (off_t)MinSize)
  92       Size = Align(Left);
  93    else
  94       Size = MinSize;
  95
  96    // Map it
  97    Buffer = (unsigned char *)mmap(0,Size,PROT_READ,MAP_PRIVATE,Fd.Fd(),Offset);
  98    if (Buffer == (unsigned char *)-1)
  99       return _error->Errno("mmap","Couldn't make mmap %lu->%lu bytes",(unsigned long)Offset,
 100                            Size);
 101
 102    // Reposition
 103    if (Left < (off_t)Size)
 104       End = Buffer + Left;
 105    else
 106       End = Buffer + Size;
 107    Start = Buffer + Remainder;
 108    return true;
 109 }
 110                                                                         /*}}}*/