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-= Packed \Data
-
-== Quick Reference
-
-These tables summarize the directives for packing and unpacking.
-
-=== For Integers
-
- Directive | Meaning
- --------------|---------------------------------------------------------------
- C | 8-bit unsigned (unsigned char)
- S | 16-bit unsigned, native endian (uint16_t)
- L | 32-bit unsigned, native endian (uint32_t)
- Q | 64-bit unsigned, native endian (uint64_t)
- J | pointer width unsigned, native endian (uintptr_t)
-
- c | 8-bit signed (signed char)
- s | 16-bit signed, native endian (int16_t)
- l | 32-bit signed, native endian (int32_t)
- q | 64-bit signed, native endian (int64_t)
- j | pointer width signed, native endian (intptr_t)
-
- S_ S! | unsigned short, native endian
- I I_ I! | unsigned int, native endian
- L_ L! | unsigned long, native endian
- Q_ Q! | unsigned long long, native endian
- | (raises ArgumentError if the platform has no long long type)
- J! | uintptr_t, native endian (same with J)
-
- s_ s! | signed short, native endian
- i i_ i! | signed int, native endian
- l_ l! | signed long, native endian
- q_ q! | signed long long, native endian
- | (raises ArgumentError if the platform has no long long type)
- j! | intptr_t, native endian (same with j)
-
- S> s> S!> s!> | each the same as the directive without >, but big endian
- L> l> L!> l!> | S> is the same as n
- I!> i!> | L> is the same as N
- Q> q> Q!> q!> |
- J> j> J!> j!> |
-
- S< s< S!< s!< | each the same as the directive without <, but little endian
- L< l< L!< l!< | S< is the same as v
- I!< i!< | L< is the same as V
- Q< q< Q!< q!< |
- J< j< J!< j!< |
-
- n | 16-bit unsigned, network (big-endian) byte order
- N | 32-bit unsigned, network (big-endian) byte order
- v | 16-bit unsigned, VAX (little-endian) byte order
- V | 32-bit unsigned, VAX (little-endian) byte order
-
- U | UTF-8 character
- w | BER-compressed integer
-
-=== For Floats
-
- Directive | Meaning
- ----------|--------------------------------------------------
- D d | double-precision, native format
- F f | single-precision, native format
- E | double-precision, little-endian byte order
- e | single-precision, little-endian byte order
- G | double-precision, network (big-endian) byte order
- g | single-precision, network (big-endian) byte order
-
-=== For Strings
-
- Directive | Meaning
- ----------|-----------------------------------------------------------------
- A | arbitrary binary string (remove trailing nulls and ASCII spaces)
- a | arbitrary binary string
- Z | null-terminated string
- B | bit string (MSB first)
- b | bit string (LSB first)
- H | hex string (high nibble first)
- h | hex string (low nibble first)
- u | UU-encoded string
- M | quoted-printable, MIME encoding (see RFC2045)
- m | base64 encoded string (RFC 2045) (default)
- | (base64 encoded string (RFC 4648) if followed by 0)
- P | pointer to a structure (fixed-length string)
- p | pointer to a null-terminated string
-
-=== Additional Directives for Packing
-
- Directive | Meaning
- ----------|----------------------------------------------------------------
- @ | moves to absolute position
- X | back up a byte
- x | null byte
-
-=== Additional Directives for Unpacking
-
- Directive | Meaning
- ----------|----------------------------------------------------------------
- @ | skip to the offset given by the length argument
- X | skip backward one byte
- x | skip forward one byte
-
-== Packing and Unpacking
-
-Certain Ruby core methods deal with packing and unpacking data:
-
-- Method Array#pack:
- Formats each element in array +self+ into a binary string;
- returns that string.
-- Method String#unpack:
- Extracts data from string +self+,
- forming objects that become the elements of a new array;
- returns that array.
-- Method String#unpack1:
- Does the same, but unpacks and returns only the first extracted object.
-
-Each of these methods accepts a string +template+,
-consisting of zero or more _directive_ characters,
-each followed by zero or more _modifier_ characters.
-
-Examples (directive <tt>'C'</tt> specifies 'unsigned character'):
-
- [65].pack('C') # => "A" # One element, one directive.
- [65, 66].pack('CC') # => "AB" # Two elements, two directives.
- [65, 66].pack('C') # => "A" # Extra element is ignored.
- [65].pack('') # => "" # No directives.
- [65].pack('CC') # Extra directive raises ArgumentError.
-
- 'A'.unpack('C') # => [65] # One character, one directive.
- 'AB'.unpack('CC') # => [65, 66] # Two characters, two directives.
- 'AB'.unpack('C') # => [65] # Extra character is ignored.
- 'A'.unpack('CC') # => [65, nil] # Extra directive generates nil.
- 'AB'.unpack('') # => [] # No directives.
-
-The string +template+ may contain any mixture of valid directives
-(directive <tt>'c'</tt> specifies 'signed character'):
-
- [65, -1].pack('cC') # => "A\xFF"
- "A\xFF".unpack('cC') # => [65, 255]
-
-The string +template+ may contain whitespace (which is ignored)
-and comments, each of which begins with character <tt>'#'</tt>
-and continues up to and including the next following newline:
-
- [0,1].pack(" C #foo \n C ") # => "\x00\x01"
- "\0\1".unpack(" C #foo \n C ") # => [0, 1]
-
-Any directive may be followed by either of these modifiers:
-
-- <tt>'*'</tt> - The directive is to be applied as many times as needed:
-
- [65, 66].pack('C*') # => "AB"
- 'AB'.unpack('C*') # => [65, 66]
-
-- Integer +count+ - The directive is to be applied +count+ times:
-
- [65, 66].pack('C2') # => "AB"
- [65, 66].pack('C3') # Raises ArgumentError.
- 'AB'.unpack('C2') # => [65, 66]
- 'AB'.unpack('C3') # => [65, 66, nil]
-
- Note: Directives in <tt>%w[A a Z m]</tt> use +count+ differently;
- see {String Directives}[rdoc-ref:packed_data.rdoc@String+Directives].
-
-If elements don't fit the provided directive, only least significant bits are encoded:
-
- [257].pack("C").unpack("C") # => [1]
-
-== Packing Method
-
-Method Array#pack accepts optional keyword argument
-+buffer+ that specifies the target string (instead of a new string):
-
- [65, 66].pack('C*', buffer: 'foo') # => "fooAB"
-
-The method can accept a block:
-
- # Packed string is passed to the block.
- [65, 66].pack('C*') {|s| p s } # => "AB"
-
-== Unpacking Methods
-
-Methods String#unpack and String#unpack1 each accept
-an optional keyword argument +offset+ that specifies an offset
-into the string:
-
- 'ABC'.unpack('C*', offset: 1) # => [66, 67]
- 'ABC'.unpack1('C*', offset: 1) # => 66
-
-Both methods can accept a block:
-
- # Each unpacked object is passed to the block.
- ret = []
- "ABCD".unpack("C*") {|c| ret << c }
- ret # => [65, 66, 67, 68]
-
- # The single unpacked object is passed to the block.
- 'AB'.unpack1('C*') {|ele| p ele } # => 65
-
-== \Integer Directives
-
-Each integer directive specifies the packing or unpacking
-for one element in the input or output array.
-
-=== 8-Bit \Integer Directives
-
-- <tt>'c'</tt> - 8-bit signed integer
- (like C <tt>signed char</tt>):
-
- [0, 1, 255].pack('c*') # => "\x00\x01\xFF"
- s = [0, 1, -1].pack('c*') # => "\x00\x01\xFF"
- s.unpack('c*') # => [0, 1, -1]
-
-- <tt>'C'</tt> - 8-bit unsigned integer
- (like C <tt>unsigned char</tt>):
-
- [0, 1, 255].pack('C*') # => "\x00\x01\xFF"
- s = [0, 1, -1].pack('C*') # => "\x00\x01\xFF"
- s.unpack('C*') # => [0, 1, 255]
-
-=== 16-Bit \Integer Directives
-
-- <tt>'s'</tt> - 16-bit signed integer, native-endian
- (like C <tt>int16_t</tt>):
-
- [513, -514].pack('s*') # => "\x01\x02\xFE\xFD"
- s = [513, 65022].pack('s*') # => "\x01\x02\xFE\xFD"
- s.unpack('s*') # => [513, -514]
-
-- <tt>'S'</tt> - 16-bit unsigned integer, native-endian
- (like C <tt>uint16_t</tt>):
-
- [513, -514].pack('S*') # => "\x01\x02\xFE\xFD"
- s = [513, 65022].pack('S*') # => "\x01\x02\xFE\xFD"
- s.unpack('S*') # => [513, 65022]
-
-- <tt>'n'</tt> - 16-bit network integer, big-endian:
-
- s = [0, 1, -1, 32767, -32768, 65535].pack('n*')
- # => "\x00\x00\x00\x01\xFF\xFF\x7F\xFF\x80\x00\xFF\xFF"
- s.unpack('n*')
- # => [0, 1, 65535, 32767, 32768, 65535]
-
-- <tt>'v'</tt> - 16-bit VAX integer, little-endian:
-
- s = [0, 1, -1, 32767, -32768, 65535].pack('v*')
- # => "\x00\x00\x01\x00\xFF\xFF\xFF\x7F\x00\x80\xFF\xFF"
- s.unpack('v*')
- # => [0, 1, 65535, 32767, 32768, 65535]
-
-=== 32-Bit \Integer Directives
-
-- <tt>'l'</tt> - 32-bit signed integer, native-endian
- (like C <tt>int32_t</tt>):
-
- s = [67305985, -50462977].pack('l*')
- # => "\x01\x02\x03\x04\xFF\xFE\xFD\xFC"
- s.unpack('l*')
- # => [67305985, -50462977]
-
-- <tt>'L'</tt> - 32-bit unsigned integer, native-endian
- (like C <tt>uint32_t</tt>):
-
- s = [67305985, 4244504319].pack('L*')
- # => "\x01\x02\x03\x04\xFF\xFE\xFD\xFC"
- s.unpack('L*')
- # => [67305985, 4244504319]
-
-- <tt>'N'</tt> - 32-bit network integer, big-endian:
-
- s = [0,1,-1].pack('N*')
- # => "\x00\x00\x00\x00\x00\x00\x00\x01\xFF\xFF\xFF\xFF"
- s.unpack('N*')
- # => [0, 1, 4294967295]
-
-- <tt>'V'</tt> - 32-bit VAX integer, little-endian:
-
- s = [0,1,-1].pack('V*')
- # => "\x00\x00\x00\x00\x01\x00\x00\x00\xFF\xFF\xFF\xFF"
- s.unpack('v*')
- # => [0, 0, 1, 0, 65535, 65535]
-
-=== 64-Bit \Integer Directives
-
-- <tt>'q'</tt> - 64-bit signed integer, native-endian
- (like C <tt>int64_t</tt>):
-
- s = [578437695752307201, -506097522914230529].pack('q*')
- # => "\x01\x02\x03\x04\x05\x06\a\b\xFF\xFE\xFD\xFC\xFB\xFA\xF9\xF8"
- s.unpack('q*')
- # => [578437695752307201, -506097522914230529]
-
-- <tt>'Q'</tt> - 64-bit unsigned integer, native-endian
- (like C <tt>uint64_t</tt>):
-
- s = [578437695752307201, 17940646550795321087].pack('Q*')
- # => "\x01\x02\x03\x04\x05\x06\a\b\xFF\xFE\xFD\xFC\xFB\xFA\xF9\xF8"
- s.unpack('Q*')
- # => [578437695752307201, 17940646550795321087]
-
-=== Platform-Dependent \Integer Directives
-
-- <tt>'i'</tt> - Platform-dependent width signed integer,
- native-endian (like C <tt>int</tt>):
-
- s = [67305985, -50462977].pack('i*')
- # => "\x01\x02\x03\x04\xFF\xFE\xFD\xFC"
- s.unpack('i*')
- # => [67305985, -50462977]
-
-- <tt>'I'</tt> - Platform-dependent width unsigned integer,
- native-endian (like C <tt>unsigned int</tt>):
-
- s = [67305985, -50462977].pack('I*')
- # => "\x01\x02\x03\x04\xFF\xFE\xFD\xFC"
- s.unpack('I*')
- # => [67305985, 4244504319]
-
-- <tt>'j'</tt> - Pointer-width signed integer, native-endian
- (like C <tt>intptr_t</tt>):
-
- s = [67305985, -50462977].pack('j*')
- # => "\x01\x02\x03\x04\x00\x00\x00\x00\xFF\xFE\xFD\xFC\xFF\xFF\xFF\xFF"
- s.unpack('j*')
- # => [67305985, -50462977]
-
-- <tt>'J'</tt> - Pointer-width unsigned integer, native-endian
- (like C <tt>uintptr_t</tt>):
-
- s = [67305985, 4244504319].pack('J*')
- # => "\x01\x02\x03\x04\x00\x00\x00\x00\xFF\xFE\xFD\xFC\x00\x00\x00\x00"
- s.unpack('J*')
- # => [67305985, 4244504319]
-
-=== Other \Integer Directives
-
-- <tt>'U'</tt> - UTF-8 character:
-
- s = [4194304].pack('U*')
- # => "\xF8\x90\x80\x80\x80"
- s.unpack('U*')
- # => [4194304]
-
-- <tt>'w'</tt> - BER-encoded integer
- (see {BER encoding}[https://en.wikipedia.org/wiki/X.690#BER_encoding]):
-
- s = [1073741823].pack('w*')
- # => "\x83\xFF\xFF\xFF\x7F"
- s.unpack('w*')
- # => [1073741823]
-
-=== Modifiers for \Integer Directives
-
-For the following directives, <tt>'!'</tt> or <tt>'_'</tt> modifiers may be
-suffixed as underlying platform’s native size.
-
-- <tt>'i'</tt>, <tt>'I'</tt> - C <tt>int</tt>, always native size.
-- <tt>'s'</tt>, <tt>'S'</tt> - C <tt>short</tt>.
-- <tt>'l'</tt>, <tt>'L'</tt> - C <tt>long</tt>.
-- <tt>'q'</tt>, <tt>'Q'</tt> - C <tt>long long</tt>, if available.
-- <tt>'j'</tt>, <tt>'J'</tt> - C <tt>intptr_t</tt>, always native size.
-
-Native size modifiers are silently ignored for always native size directives.
-
-The endian modifiers also may be suffixed in the directives above:
-
-- <tt>'>'</tt> - Big-endian.
-- <tt>'<'</tt> - Little-endian.
-
-== \Float Directives
-
-Each float directive specifies the packing or unpacking
-for one element in the input or output array.
-
-=== Single-Precision \Float Directives
-
-- <tt>'F'</tt> or <tt>'f'</tt> - Native format:
-
- s = [3.0].pack('F') # => "\x00\x00@@"
- s.unpack('F') # => [3.0]
-
-- <tt>'e'</tt> - Little-endian:
-
- s = [3.0].pack('e') # => "\x00\x00@@"
- s.unpack('e') # => [3.0]
-
-- <tt>'g'</tt> - Big-endian:
-
- s = [3.0].pack('g') # => "@@\x00\x00"
- s.unpack('g') # => [3.0]
-
-=== Double-Precision \Float Directives
-
-- <tt>'D'</tt> or <tt>'d'</tt> - Native format:
-
- s = [3.0].pack('D') # => "\x00\x00\x00\x00\x00\x00\b@"
- s.unpack('D') # => [3.0]
-
-- <tt>'E'</tt> - Little-endian:
-
- s = [3.0].pack('E') # => "\x00\x00\x00\x00\x00\x00\b@"
- s.unpack('E') # => [3.0]
-
-- <tt>'G'</tt> - Big-endian:
-
- s = [3.0].pack('G') # => "@\b\x00\x00\x00\x00\x00\x00"
- s.unpack('G') # => [3.0]
-
-A float directive may be infinity or not-a-number:
-
- inf = 1.0/0.0 # => Infinity
- [inf].pack('f') # => "\x00\x00\x80\x7F"
- "\x00\x00\x80\x7F".unpack('f') # => [Infinity]
-
- nan = inf/inf # => NaN
- [nan].pack('f') # => "\x00\x00\xC0\x7F"
- "\x00\x00\xC0\x7F".unpack('f') # => [NaN]
-
-== \String Directives
-
-Each string directive specifies the packing or unpacking
-for one byte in the input or output string.
-
-=== Binary \String Directives
-
-- <tt>'A'</tt> - Arbitrary binary string (space padded; count is width);
- +nil+ is treated as the empty string:
-
- ['foo'].pack('A') # => "f"
- ['foo'].pack('A*') # => "foo"
- ['foo'].pack('A2') # => "fo"
- ['foo'].pack('A4') # => "foo "
- [nil].pack('A') # => " "
- [nil].pack('A*') # => ""
- [nil].pack('A2') # => " "
- [nil].pack('A4') # => " "
-
- "foo\0".unpack('A') # => ["f"]
- "foo\0".unpack('A4') # => ["foo"]
- "foo\0bar".unpack('A10') # => ["foo\x00bar"] # Reads past "\0".
- "foo ".unpack('A') # => ["f"]
- "foo ".unpack('A4') # => ["foo"]
- "foo".unpack('A4') # => ["foo"]
-
- russian = "\u{442 435 441 442}" # => "тест"
- russian.size # => 4
- russian.bytesize # => 8
- [russian].pack('A') # => "\xD1"
- [russian].pack('A*') # => "\xD1\x82\xD0\xB5\xD1\x81\xD1\x82"
- russian.unpack('A') # => ["\xD1"]
- russian.unpack('A2') # => ["\xD1\x82"]
- russian.unpack('A4') # => ["\xD1\x82\xD0\xB5"]
- russian.unpack('A*') # => ["\xD1\x82\xD0\xB5\xD1\x81\xD1\x82"]
-
-- <tt>'a'</tt> - Arbitrary binary string (null padded; count is width):
-
- ["foo"].pack('a') # => "f"
- ["foo"].pack('a*') # => "foo"
- ["foo"].pack('a2') # => "fo"
- ["foo\0"].pack('a4') # => "foo\x00"
- [nil].pack('a') # => "\x00"
- [nil].pack('a*') # => ""
- [nil].pack('a2') # => "\x00\x00"
- [nil].pack('a4') # => "\x00\x00\x00\x00"
-
- "foo\0".unpack('a') # => ["f"]
- "foo\0".unpack('a4') # => ["foo\x00"]
- "foo ".unpack('a4') # => ["foo "]
- "foo".unpack('a4') # => ["foo"]
- "foo\0bar".unpack('a4') # => ["foo\x00"] # Reads past "\0".
-
-- <tt>'Z'</tt> - Same as <tt>'a'</tt>,
- except that null is added or ignored with <tt>'*'</tt>:
-
- ["foo"].pack('Z*') # => "foo\x00"
- [nil].pack('Z*') # => "\x00"
-
- "foo\0".unpack('Z*') # => ["foo"]
- "foo".unpack('Z*') # => ["foo"]
- "foo\0bar".unpack('Z*') # => ["foo"] # Does not read past "\0".
-
-=== Bit \String Directives
-
-- <tt>'B'</tt> - Bit string (high byte first):
-
- ['11111111' + '00000000'].pack('B*') # => "\xFF\x00"
- ['10000000' + '01000000'].pack('B*') # => "\x80@"
-
- ['1'].pack('B0') # => ""
- ['1'].pack('B1') # => "\x80"
- ['1'].pack('B2') # => "\x80\x00"
- ['1'].pack('B3') # => "\x80\x00"
- ['1'].pack('B4') # => "\x80\x00\x00"
- ['1'].pack('B5') # => "\x80\x00\x00"
- ['1'].pack('B6') # => "\x80\x00\x00\x00"
-
- "\xff\x00".unpack("B*") # => ["1111111100000000"]
- "\x01\x02".unpack("B*") # => ["0000000100000010"]
-
- "".unpack("B0") # => [""]
- "\x80".unpack("B1") # => ["1"]
- "\x80".unpack("B2") # => ["10"]
- "\x80".unpack("B3") # => ["100"]
-
-- <tt>'b'</tt> - Bit string (low byte first):
-
- ['11111111' + '00000000'].pack('b*') # => "\xFF\x00"
- ['10000000' + '01000000'].pack('b*') # => "\x01\x02"
-
- ['1'].pack('b0') # => ""
- ['1'].pack('b1') # => "\x01"
- ['1'].pack('b2') # => "\x01\x00"
- ['1'].pack('b3') # => "\x01\x00"
- ['1'].pack('b4') # => "\x01\x00\x00"
- ['1'].pack('b5') # => "\x01\x00\x00"
- ['1'].pack('b6') # => "\x01\x00\x00\x00"
-
- "\xff\x00".unpack("b*") # => ["1111111100000000"]
- "\x01\x02".unpack("b*") # => ["1000000001000000"]
-
- "".unpack("b0") # => [""]
- "\x01".unpack("b1") # => ["1"]
- "\x01".unpack("b2") # => ["10"]
- "\x01".unpack("b3") # => ["100"]
-
-=== Hex \String Directives
-
-- <tt>'H'</tt> - Hex string (high nibble first):
-
- ['10ef'].pack('H*') # => "\x10\xEF"
- ['10ef'].pack('H0') # => ""
- ['10ef'].pack('H3') # => "\x10\xE0"
- ['10ef'].pack('H5') # => "\x10\xEF\x00"
-
- ['fff'].pack('H3') # => "\xFF\xF0"
- ['fff'].pack('H4') # => "\xFF\xF0"
- ['fff'].pack('H5') # => "\xFF\xF0\x00"
- ['fff'].pack('H6') # => "\xFF\xF0\x00"
- ['fff'].pack('H7') # => "\xFF\xF0\x00\x00"
- ['fff'].pack('H8') # => "\xFF\xF0\x00\x00"
-
- "\x10\xef".unpack('H*') # => ["10ef"]
- "\x10\xef".unpack('H0') # => [""]
- "\x10\xef".unpack('H1') # => ["1"]
- "\x10\xef".unpack('H2') # => ["10"]
- "\x10\xef".unpack('H3') # => ["10e"]
- "\x10\xef".unpack('H4') # => ["10ef"]
- "\x10\xef".unpack('H5') # => ["10ef"]
-
-- <tt>'h'</tt> - Hex string (low nibble first):
-
- ['10ef'].pack('h*') # => "\x01\xFE"
- ['10ef'].pack('h0') # => ""
- ['10ef'].pack('h3') # => "\x01\x0E"
- ['10ef'].pack('h5') # => "\x01\xFE\x00"
-
- ['fff'].pack('h3') # => "\xFF\x0F"
- ['fff'].pack('h4') # => "\xFF\x0F"
- ['fff'].pack('h5') # => "\xFF\x0F\x00"
- ['fff'].pack('h6') # => "\xFF\x0F\x00"
- ['fff'].pack('h7') # => "\xFF\x0F\x00\x00"
- ['fff'].pack('h8') # => "\xFF\x0F\x00\x00"
-
- "\x01\xfe".unpack('h*') # => ["10ef"]
- "\x01\xfe".unpack('h0') # => [""]
- "\x01\xfe".unpack('h1') # => ["1"]
- "\x01\xfe".unpack('h2') # => ["10"]
- "\x01\xfe".unpack('h3') # => ["10e"]
- "\x01\xfe".unpack('h4') # => ["10ef"]
- "\x01\xfe".unpack('h5') # => ["10ef"]
-
-=== Pointer \String Directives
-
-- <tt>'P'</tt> - Pointer to a structure (fixed-length string):
-
- s = ['abc'].pack('P') # => "\xE0O\x7F\xE5\xA1\x01\x00\x00"
- s.unpack('P*') # => ["abc"]
- ".".unpack("P") # => []
- ("\0" * 8).unpack("P") # => [nil]
- [nil].pack("P") # => "\x00\x00\x00\x00\x00\x00\x00\x00"
-
-- <tt>'p'</tt> - Pointer to a null-terminated string:
-
- s = ['abc'].pack('p') # => "(\xE4u\xE5\xA1\x01\x00\x00"
- s.unpack('p*') # => ["abc"]
- ".".unpack("p") # => []
- ("\0" * 8).unpack("p") # => [nil]
- [nil].pack("p") # => "\x00\x00\x00\x00\x00\x00\x00\x00"
-
-=== Other \String Directives
-
-- <tt>'M'</tt> - Quoted printable, MIME encoding;
- text mode, but input must use LF and output LF;
- (see {RFC 2045}[https://www.ietf.org/rfc/rfc2045.txt]):
-
- ["a b c\td \ne"].pack('M') # => "a b c\td =\n\ne=\n"
- ["\0"].pack('M') # => "=00=\n"
-
- ["a"*1023].pack('M') == ("a"*73+"=\n")*14+"a=\n" # => true
- ("a"*73+"=\na=\n").unpack('M') == ["a"*74] # => true
- (("a"*73+"=\n")*14+"a=\n").unpack('M') == ["a"*1023] # => true
-
- "a b c\td =\n\ne=\n".unpack('M') # => ["a b c\td \ne"]
- "=00=\n".unpack('M') # => ["\x00"]
-
- "pre=31=32=33after".unpack('M') # => ["pre123after"]
- "pre=\nafter".unpack('M') # => ["preafter"]
- "pre=\r\nafter".unpack('M') # => ["preafter"]
- "pre=".unpack('M') # => ["pre="]
- "pre=\r".unpack('M') # => ["pre=\r"]
- "pre=hoge".unpack('M') # => ["pre=hoge"]
- "pre==31after".unpack('M') # => ["pre==31after"]
- "pre===31after".unpack('M') # => ["pre===31after"]
-
-- <tt>'m'</tt> - Base64 encoded string;
- count specifies input bytes between each newline,
- rounded down to nearest multiple of 3;
- if count is zero, no newlines are added;
- (see {RFC 4648}[https://www.ietf.org/rfc/rfc4648.txt]):
-
- [""].pack('m') # => ""
- ["\0"].pack('m') # => "AA==\n"
- ["\0\0"].pack('m') # => "AAA=\n"
- ["\0\0\0"].pack('m') # => "AAAA\n"
- ["\377"].pack('m') # => "/w==\n"
- ["\377\377"].pack('m') # => "//8=\n"
- ["\377\377\377"].pack('m') # => "////\n"
-
- "".unpack('m') # => [""]
- "AA==\n".unpack('m') # => ["\x00"]
- "AAA=\n".unpack('m') # => ["\x00\x00"]
- "AAAA\n".unpack('m') # => ["\x00\x00\x00"]
- "/w==\n".unpack('m') # => ["\xFF"]
- "//8=\n".unpack('m') # => ["\xFF\xFF"]
- "////\n".unpack('m') # => ["\xFF\xFF\xFF"]
- "A\n".unpack('m') # => [""]
- "AA\n".unpack('m') # => ["\x00"]
- "AA=\n".unpack('m') # => ["\x00"]
- "AAA\n".unpack('m') # => ["\x00\x00"]
-
- [""].pack('m0') # => ""
- ["\0"].pack('m0') # => "AA=="
- ["\0\0"].pack('m0') # => "AAA="
- ["\0\0\0"].pack('m0') # => "AAAA"
- ["\377"].pack('m0') # => "/w=="
- ["\377\377"].pack('m0') # => "//8="
- ["\377\377\377"].pack('m0') # => "////"
-
- "".unpack('m0') # => [""]
- "AA==".unpack('m0') # => ["\x00"]
- "AAA=".unpack('m0') # => ["\x00\x00"]
- "AAAA".unpack('m0') # => ["\x00\x00\x00"]
- "/w==".unpack('m0') # => ["\xFF"]
- "//8=".unpack('m0') # => ["\xFF\xFF"]
- "////".unpack('m0') # => ["\xFF\xFF\xFF"]
-
-- <tt>'u'</tt> - UU-encoded string:
-
- [""].pack("u") # => ""
- ["a"].pack("u") # => "!80``\n"
- ["aaa"].pack("u") # => "#86%A\n"
-
- "".unpack("u") # => [""]
- "#86)C\n".unpack("u") # => ["abc"]
-
-== Offset Directives
-
-- <tt>'@'</tt> - Begin packing at the given byte offset;
- for packing, null fill or shrink if necessary:
-
- [1, 2].pack("C@0C") # => "\x02"
- [1, 2].pack("C@1C") # => "\x01\x02"
- [1, 2].pack("C@5C") # => "\x01\x00\x00\x00\x00\x02"
- [*1..5].pack("CCCC@2C") # => "\x01\x02\x05"
-
- For unpacking, cannot to move to outside the string:
-
- "\x01\x00\x00\x02".unpack("C@3C") # => [1, 2]
- "\x00".unpack("@1C") # => [nil]
- "\x00".unpack("@2C") # Raises ArgumentError.
-
-- <tt>'X'</tt> - For packing, shrink for the given byte offset:
-
- [0, 1, 2].pack("CCXC") # => "\x00\x02"
- [0, 1, 2].pack("CCX2C") # => "\x02"
-
- For unpacking; rewind unpacking position for the given byte offset:
-
- "\x00\x02".unpack("CCXC") # => [0, 2, 2]
-
- Cannot to move to outside the string:
-
- [0, 1, 2].pack("CCX3C") # Raises ArgumentError.
- "\x00\x02".unpack("CX3C") # Raises ArgumentError.
-
-- <tt>'x'</tt> - Begin packing at after the given byte offset;
- for packing, null fill if necessary:
-
- [].pack("x0") # => ""
- [].pack("x") # => "\x00"
- [].pack("x8") # => "\x00\x00\x00\x00\x00\x00\x00\x00"
-
- For unpacking, cannot to move to outside the string:
-
- "\x00\x00\x02".unpack("CxC") # => [0, 2]
- "\x00\x00\x02".unpack("x3C") # => [nil]
- "\x00\x00\x02".unpack("x4C") # Raises ArgumentError
generated by cgit v1.2.3 (git 2.25.1) at 2026-05-29 19:33:14 +0000