Class: Fat32::FileData

Inherits:
Object
  • Object
show all
Defined in:
lib/fs/fat32/file_data.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(dirEntry, bootSector) ⇒ FileData

Initialization



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# File 'lib/fs/fat32/file_data.rb', line 9

def initialize(dirEntry, bootSector)
  raise "Nil directory entry" if dirEntry.nil?
  raise "Nil boot sector" if bootSector.nil?

  @bs = bootSector
  @de = dirEntry
  rewind
end

Instance Attribute Details

#pos ⇒ Object (readonly)

Returns the value of attribute pos.



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# File 'lib/fs/fat32/file_data.rb', line 6

def pos
  @pos
end

Instance Method Details

#close ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 113

def close
  @de.close(@bs)
end

#firstCluster ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 22

def firstCluster
  return -1 if !@clusterMap || @clusterMap.size == 0
  @clusterMap[0]
end

#getCluster(vcn) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 96

def getCluster(vcn)
  lcn = getLCN(vcn)
  # puts "vcn=#{vcn}, lcn=#{lcn}" if $track_pos
  return MemoryBuffer.create(@bs.bytesPerCluster) if lcn == -1
  raise "LCN is nill" if lcn.nil?
  @bs.getCluster(lcn)
end

#getLCN(relClus) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 117

def getLCN(relClus)
  return -1 if relClus >= @clusterMap.size || @clusterMap.size == 0
  lcn = @clusterMap[relClus]
  if lcn.nil?
    # puts "LCN is nil for VCN #{relClus}; Map size is #{@clusterMap.size}, cluster map follows:"
    # puts @clusterMap.inspect
    raise "Bad cluster map."
  end
  lcn
end

#putCluster(vcn, buf) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 104

def putCluster(vcn, buf)
  lcn = getLCN(vcn)
  if lcn == -1
    lcn = @bs.allocClusters(@clusterMap.size == 0 ? 0 : @clusterMap[@clusterMap.size - 1])
    @clusterMap << lcn
  end
  @bs.writeClusters(lcn, buf)
end

#read(bytes = @de.length) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 38

def read(bytes = @de.length)
  return nil if @pos >= @de.length
  @clusterMap = @bs.mkClusterMap(@de.firstCluster) unless @clusterMap

  # Get start & end locs.
  bpc = @bs.bytesPerCluster
  startCluster, startOffset = @pos.divmod(bpc)
  endCluster, endOffset = (@pos + (bytes - 1)).divmod(bpc)

  # Single cluster.
  if startCluster == endCluster
    @pos += (endOffset - startOffset)
    return getCluster(startCluster)[startOffset..endOffset]
  end

  # Span clusters.
  out = MemoryBuffer.create(bytes)
  totalLen = 0
  (startCluster..endCluster).each do |clus|
    offset = 0; len = bpc
    if clus == startCluster
      offset = startOffset
      len -= offset
    end
    len -= (bpc - (endOffset + 1)) if clus == endCluster
    out[totalLen, len] = getCluster(clus)[offset, len]
    totalLen += len
    @pos += len
  end
  out[0..totalLen]
end

#rewind ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 18

def rewind
  @pos = 0
end

#seek(offset, method = IO::SEEK_SET) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 27

def seek(offset, method = IO::SEEK_SET)
  @pos = case method
         when IO::SEEK_SET then offset
         when IO::SEEK_CUR then @pos + offset
         when IO::SEEK_END then @de.length - offset
         end
  @pos = 0 if @pos < 0
  @pos = @de.length if @pos > @de.length
  @pos
end

#write(buf, bytes = buf.length) ⇒ Object 



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# File 'lib/fs/fat32/file_data.rb', line 70

def write(buf, bytes = buf.length)
  @clusterMap = @bs.mkClusterMap(@de.firstCluster) unless @clusterMap

  # Get start & end locs.
  bytesWritten = 0; bpc = @bs.bytesPerCluster
  startCluster, startOffset = @pos.divmod(bpc)
  endCluster, endOffset = (@pos + (bytes - 1)).divmod(bpc)

  # For each cluster, read, deposit & write.
  (startCluster..endCluster).each do |clus|
    offset = 0; len = bpc
    if clus == startCluster
      offset = startOffset
      len -= offset
    end
    len -= (bpc - (endOffset + 1)) if clus == endCluster
    current = getCluster(clus)
    current[startOffset, len] = buf[bytesWritten, len]
    putCluster(clus, current)
    @pos += len; bytesWritten += len
  end
  @de.length = @pos if @pos > @de.length
  @de.firstCluster = @clusterMap[0] if @de.firstCluster == 0
  bytesWritten
end