class BinData::IO::Read

Create a new IO Read wrapper around io. io must provide read, pos if reading the current stream position and seek if setting the current stream position. If io is a string it will be automatically wrapped in an StringIO object.

The IO can handle bitstreams in either big or little endian format.

M  byte1   L      M  byte2   L
S 76543210 S      S fedcba98 S
B          B      B          B

In big endian format:

readbits(6), readbits(5) #=> [765432, 10fed]

In little endian format:

readbits(6), readbits(5) #=> [543210, a9876]

Public Class Methods

new(io) click to toggle source

# File lib/bindata/io.rb, line 239
def initialize(io)
  super(io)

  # bits when reading
  @rnbits  = 0
  @rval    = 0
  @rendian = nil
end

Public Instance Methods

offset() click to toggle source

Returns the current offset of the io stream. Offset will be rounded up when reading bitfields.

# File lib/bindata/io.rb, line 259
def offset
  offset_raw
end

read_all_bytes() click to toggle source

Reads all remaining bytes from the stream.

# File lib/bindata/io.rb, line 280
def read_all_bytes
  reset_read_bits
  read
end

readbits(nbits, endian) click to toggle source

Reads exactly nbits bits from the stream. endian specifies whether the bits are stored in :big or :little endian format.

# File lib/bindata/io.rb, line 287
def readbits(nbits, endian)
  if @rendian != endian
    # don't mix bits of differing endian
    reset_read_bits
    @rendian = endian
  end

  if endian == :big
    read_big_endian_bits(nbits)
  else
    read_little_endian_bits(nbits)
  end
end

readbytes(n) click to toggle source

Reads exactly n bytes from io.

If the data read is nil an EOFError is raised.

If the data read is too short an IOError is raised.

# File lib/bindata/io.rb, line 274
def readbytes(n)
  reset_read_bits
  read(n)
end

reset_read_bits() click to toggle source

Discards any read bits so the stream becomes aligned at the next byte boundary.

# File lib/bindata/io.rb, line 303
def reset_read_bits
  @rnbits = 0
  @rval   = 0
end

seekbytes(n) click to toggle source

Seek n bytes from the current position in the io stream.

# File lib/bindata/io.rb, line 264
def seekbytes(n)
  reset_read_bits
  seek(n)
end

with_buffer(n) { || ... } click to toggle source

Sets a buffer of n bytes on the io stream. Any reading or seeking calls inside the block will be contained within this buffer.

# File lib/bindata/io.rb, line 250
def with_buffer(n)
  with_buffer_common(n) do
    yield
    read
  end
end