src/system/boot/loader/file_systems/fat/CachedBlock.cpp

   1 /*
   2  * Copyright 2008, Haiku, Inc.
   3  * Distributed under the terms of the MIT License.
   4  *
   5  * Authors:
   6  *              François Revol <revol@free.fr>
   7  */
   8
   9
  10 #include "CachedBlock.h"
  11
  12 #include <errno.h>
  13 #include <stdlib.h>
  14 #include <string.h>
  15 #include <unistd.h>
  16
  17 #include <util/kernel_cpp.h>
  18
  19
  20 using namespace FATFS;
  21
  22
  23 CachedBlock::CachedBlock(Volume &volume)
  24         :
  25         fVolume(volume),
  26         fBlockNumber(-1LL),
  27         fBlock(NULL)
  28 {
  29 }
  30
  31
  32 CachedBlock::CachedBlock(Volume &volume, off_t block)
  33         :
  34         fVolume(volume),
  35         fBlockNumber(-1LL),
  36         fBlock(NULL)
  37 {
  38         SetTo(block);
  39 }
  40
  41
  42 CachedBlock::~CachedBlock()
  43 {
  44         free(fBlock);
  45 }
  46
  47
  48 uint8 *
  49 CachedBlock::SetTo(off_t block)
  50 {
  51         status_t error = SetTo(block, READ);
  52         return error == B_OK ? fBlock : NULL;
  53 }
  54
  55
  56 status_t
  57 CachedBlock::SetTo(off_t blockNumber, uint32 flags)
  58 {
  59         if (fBlock == NULL) {
  60                 fBlock = (uint8*)malloc(BlockSize());
  61                 if (fBlock == NULL)
  62                         return B_NO_MEMORY;
  63         }
  64
  65         if (blockNumber != fBlockNumber)
  66                 flags |= FORCE;
  67
  68         fBlockNumber = blockNumber;
  69
  70         status_t error = B_OK;
  71
  72         if ((flags & READ) != 0) {
  73                 if ((flags & FORCE) != 0) {
  74                         ssize_t bytesRead = read_pos(fVolume.Device(),
  75                                 fBlockNumber << BlockShift(), fBlock, BlockSize());
  76                         if (bytesRead < 0)
  77                                 error = bytesRead;
  78                         else if (bytesRead < (ssize_t)BlockSize())
  79                                 error = B_ERROR;
  80                 }
  81         } else if ((flags & CLEAR) != 0)
  82                 memset(fBlock, 0, BlockSize());
  83
  84         if (error != B_OK)
  85                 fBlockNumber = -1;
  86
  87         return error;
  88 }
  89
  90
  91 status_t
  92 CachedBlock::Flush()
  93 {
  94         if (fBlockNumber < 0)
  95                 return B_BAD_VALUE;
  96
  97         ssize_t written = write_pos(fVolume.Device(), fBlockNumber << BlockShift(),
  98                 fBlock, BlockSize());
  99         if (written < 0)
 100                 return errno;
 101         if (written != (ssize_t)BlockSize())
 102                 return B_ERROR;
 103
 104         return B_OK;
 105 }