Module: LEB128
- Defined in:
- lib/leb128.rb
Overview
Includes a set of functions to encode and decode the LEB128 integer compression type.
Class Method Summary collapse
-
.decode_signed(io, index = 0) ⇒ Integer
Decode signed LEB128-compressed data into an integer.
-
.decode_unsigned(io, index = 0) ⇒ Integer
Decode unsigned LEB128-compressed data into an integer.
-
.encode_signed(value) ⇒ StringIO
Encode a signed integer into LEB128-compressed data.
-
.encode_unsigned(value) ⇒ StringIO
Encode an unsigned integer into LEB128-compressed data.
Class Method Details
.decode_signed(io, index = 0) ⇒ Integer
Decode signed LEB128-compressed data into an integer.
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# File 'lib/leb128.rb', line 90 def self.decode_signed(io, index = 0) io.pos = index raise(EOFError) if io.eof? value = 0 offset = 0 loop do byte = io.read(1).unpack('C')[0] value |= (byte & 0x7F) << offset offset += 7 if byte & 0x80 == 0 value |= -(1 << offset) unless byte & 0x40 == 0 break end end value end |
.decode_unsigned(io, index = 0) ⇒ Integer
Decode unsigned LEB128-compressed data into an integer.
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# File 'lib/leb128.rb', line 64 def self.decode_unsigned(io, index = 0) io.pos = index raise(EOFError) if io.eof? value = 0 offset = 0 loop do byte = io.read(1).unpack('C')[0] value |= (byte & 0x7F) << offset break if byte & 0x80 == 0 offset += 7 end value end |
.encode_signed(value) ⇒ StringIO
Encode a signed integer into LEB128-compressed data.
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# File 'lib/leb128.rb', line 38 def self.encode_signed(value) io = StringIO.new loop do byte = value & 0x7F value >>= 7 byte |= 0x80 unless (value == 0 && byte & 0x40 == 0) || (value == -1 && byte & 0x40 != 0) io.putc(byte) break if byte & 0x80 == 0 end io.pos = 0 io end |
.encode_unsigned(value) ⇒ StringIO
Encode an unsigned integer into LEB128-compressed data.
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# File 'lib/leb128.rb', line 13 def self.encode_unsigned(value) if value < 0 raise(ArgumentError, 'Cannot encode a negative integer to an unsigned LEB128') end io = StringIO.new loop do byte = value & 0x7F value >>= 7 byte |= 0x80 if value != 0 io.putc(byte) break if value == 0 end io.pos = 0 io end |