Created
September 10, 2018 17:58
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class BitArray | |
attr_reader :size | |
attr_reader :field | |
include Enumerable | |
VERSION = "2.0.0" | |
def initialize(size, field = nil) | |
@size = size | |
@field = field || "\0" * (size / 8 + 1) | |
end | |
# Set a bit (1/0) | |
def []=(position, value) | |
if value == 1 | |
@field.setbyte(position >> 3, @field.getbyte(position >> 3) | (1 << (7 - position % 8))) | |
else | |
@field.setbyte(position >> 3, @field.getbyte(position >> 3) & ~(1 << (7 - position % 8))) | |
end | |
end | |
# Read a bit (1/0) | |
def [](position) | |
(@field.getbyte(position >> 3) & (1 << (7 - position % 8))) > 0 ? 1 : 0 | |
end | |
# Iterate over each bit | |
def each(&block) | |
@size.times { |position| yield self[position] } | |
end | |
# Returns the field as a string like "0101010100111100," etc. | |
def to_s | |
@field.bytes.collect { |ea| ("%08b" % ea) }.join[0, @size] | |
end | |
# Returns the total number of bits that are set | |
# (The technique used here is about 6 times faster than using each or inject direct on the bitfield) | |
def total_set | |
@field.bytes.inject(0) { |a, byte| a += byte & 1 and byte >>= 1 until byte == 0; a } | |
end | |
end |
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