module BinData::IO::Common::UnSeekableStream

Manually keep track of offset for unseekable streams.

Public Instance Methods

num_bytes_remaining() click to toggle source

The number of bytes remaining in the input stream.

# File lib/bindata/io.rb, line 130
def num_bytes_remaining
  raise IOError, "stream is unseekable"
end
offset_raw() click to toggle source
# File lib/bindata/io.rb, line 125
def offset_raw
  @offset
end
with_readahead() { || ... } click to toggle source

All io calls in block are rolled back after this method completes.

# File lib/bindata/io.rb, line 136
def with_readahead
  mark = @offset
  @read_data = ""
  @in_readahead = true

  class << self
    alias_method :read_raw_without_readahead, :read_raw
    alias_method :read_raw, :read_raw_with_readahead
  end

  begin
    yield
  ensure
    @offset = mark
    @in_readahead = false
  end
end

Private Instance Methods

read_raw(n) click to toggle source
# File lib/bindata/io.rb, line 161
def read_raw(n)
  data = @raw_io.read(n)
  @offset += data.size if data
  data
end
read_raw_with_readahead(n) click to toggle source
# File lib/bindata/io.rb, line 167
def read_raw_with_readahead(n)
  data = ""

  unless @read_data.empty? || @in_readahead
    bytes_to_consume = [n, @read_data.length].min
    data += @read_data.slice!(0, bytes_to_consume)
    n -= bytes_to_consume

    if @read_data.empty?
      class << self
        alias_method :read_raw, :read_raw_without_readahead
      end
    end
  end

  raw_data = @raw_io.read(n)
  data += raw_data if raw_data

  if @in_readahead
    @read_data += data
  end

  @offset += data.size

  data
end
seek_raw(n) click to toggle source
# File lib/bindata/io.rb, line 199
def seek_raw(n)
  raise IOError, "stream is unseekable" if n < 0

  # NOTE: how do we seek on a writable stream?

  # skip over data in 8k blocks
  while n > 0
    bytes_to_read = [n, 8192].min
    read_raw(bytes_to_read)
    n -= bytes_to_read
  end
end
stream_init() click to toggle source
# File lib/bindata/io.rb, line 157
def stream_init
  @offset = 0
end
write_raw(data) click to toggle source
# File lib/bindata/io.rb, line 194
def write_raw(data)
  @offset += data.size
  @raw_io.write(data)
end