src/add-ons/kernel/file_systems/exfat/DataStream.cpp

   1 /*
   2  * Copyright 2011, Haiku Inc. All rights reserved.
   3  * This file may be used under the terms of the MIT License.
   4  *
   5  * Authors:
   6  *              Jérôme Duval
   7  */
   8
   9
  10 #include "DataStream.h"
  11
  12 #include "Volume.h"
  13
  14
  15 //#define TRACE_EXFAT
  16 #ifdef TRACE_EXFAT
  17 #       define TRACE(x...) dprintf("\33[34mexfat:\33[0m " x)
  18 #else
  19 #       define TRACE(x...) ;
  20 #endif
  21 #define ERROR(x...)     dprintf("\33[34mexfat:\33[0m " x)
  22
  23
  24 DataStream::DataStream(Volume* volume, Inode* inode, off_t size)
  25         :
  26         kBlockSize(volume->BlockSize()),
  27         kClusterSize(volume->ClusterSize()),
  28         fVolume(volume),
  29         fInode(inode),
  30         fSize(size)
  31 {
  32         fNumBlocks = size == 0 ? 0 : ((size - 1) / kBlockSize) + 1;
  33 }
  34
  35
  36 DataStream::~DataStream()
  37 {
  38 }
  39
  40
  41 status_t
  42 DataStream::FindBlock(off_t pos, off_t& physical, off_t *_length)
  43 {
  44         if (pos >= fSize) {
  45                 TRACE("FindBlock: offset larger than size\n");
  46                 return B_ENTRY_NOT_FOUND;
  47         }
  48         cluster_t clusterIndex = pos / kClusterSize;
  49         uint32 offset = pos % kClusterSize;
  50
  51         cluster_t cluster = fInode->StartCluster();
  52         for (uint32 i = 0; i < clusterIndex; i++)
  53                 cluster = fInode->NextCluster(cluster);
  54         fsblock_t block;
  55         fVolume->ClusterToBlock(cluster, block);
  56         physical = block * kBlockSize + offset;
  57         for (uint32 i = 0; i < 64; i++) {
  58                 cluster_t extentEnd = fInode->NextCluster(cluster);
  59                 if (extentEnd == EXFAT_CLUSTER_END || extentEnd == cluster + 1)
  60                         break;
  61                 cluster = extentEnd;
  62         }
  63         *_length = min_c((cluster - clusterIndex + 1) * kClusterSize - offset,
  64                 fSize - pos);
  65         TRACE("inode %" B_PRIdINO ": cluster %" B_PRIu32 ", pos %" B_PRIdOFF ", %"
  66                 B_PRIdOFF "\n", fInode->ID(), clusterIndex, pos, physical);
  67         return B_OK;
  68 }
  69