Created
November 12, 2011 18:23
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BitIO
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# | |
# BitIO utility. | |
# | |
class BitIO | |
include Enumerable | |
attr_accessor :bytepos, :bitpos | |
def initialize(text) | |
@text = text | |
@bytepos = 0 # Current byte position. | |
@bitpos = -1 # Current bit position ([7,6,5,4,3,2,1,0]). | |
@buffer = 0 # Contains current byte. | |
end | |
def self.open(text) | |
self.new text | |
end | |
private | |
def readbuf | |
return @buffer = nil if @text.bytesize <= @bytepos | |
@buffer = @text.getbyte(@bytepos) | |
@bytepos += 1 | |
@bitpos = 7 | |
end | |
public | |
def eof? | |
readbuf if @bitpos < 0 | |
@buffer == nil | |
end | |
# Reads a bit. | |
def getbit | |
readbuf if @bitpos < 0 | |
return nil if @buffer == nil | |
mask = 0x1 | |
bit = (@buffer >> @bitpos) & mask | |
@bitpos -= 1 | |
bit.to_s | |
end | |
# Reads n bits. | |
def readbits(n) | |
ret = "" | |
n.times do | |
ret << getbit.to_s | |
end | |
ret | |
end | |
def write str | |
@text <<= str | |
end | |
def rewind | |
@bytepos = 0 | |
@bitpos = -1 | |
end | |
def each | |
while !eof? do | |
yield getbit | |
end | |
end | |
# def to_s | |
# @text | |
# end | |
end | |
=begin | |
puts "[a] %08b" % "a".getbyte(0) | |
puts "[b] %08b" % "b".getbyte(0) | |
puts "[c] %08b" % "c".getbyte(0) | |
print "\n" | |
bitio = BitIO.new("abc") | |
puts "Init \"abc\"" | |
print "Read all: " | |
while (bit = bitio.getbit) != nil do | |
print bit | |
end | |
print "\n\n" | |
bitio.write("aa"); puts "write \"aa\"" | |
print "Read all: "; | |
bitio.each do |b| | |
print b | |
end | |
print "\n\n" | |
bitio.rewind; puts "rewind" | |
print "Read all: " | |
bitio.each do |b| | |
print b | |
end | |
print "\n\n" | |
bitio.rewind; puts "rewind" | |
puts "Read 4 bits: #{bitio.readbits 4}" | |
puts "Read 8 bits: #{bitio.readbits 8}" | |
puts "Read 5 bits: #{bitio.readbits 5}" | |
=end |
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