=begin pod :kind("Type") :subkind("role") :category("composite")

=TITLE role Blob

=SUBTITLE Immutable buffer for binary data ('Binary Large OBject')

    role Blob[::T = uint8] does Positional[T] does Stringy { }

The C<Blob> role is an immutable interface to binary types, and offers a
list-like interface to lists of integers, typically unsigned integers.

However, it's a parameterized type, and you can instantiate with several
integer types:

=for code
my $b = Blob[int32].new(3, -3, 0xff32, -44);
say $b; # OUTPUT: «Blob[int32]:0x<03 -3 FF32 -2C>»

By default, C<Blob> uses 8-bit unsigned integers, that is, it is
equivalent to Blob[uint8]. Some other types of C<Blob>s which are used
often get their own class name.

X<|blob8>X<|blob16>X<|blob32>X<|blob64>
=begin table
blob8 | Blob[uint8]
blob16 | Blob[uint16]
blob32 | Blob[uint32]
blob64 | Blob[uint64]
=end table

You can use these in pretty much the same way you would with C<Blob>:

    my $blob = blob8.new(3, 6, 254);
    say $blob; # OUTPUT: «Blob[uint8]:0x<03 06 FE>␤»

=head1 Methods

=head2 method new

Defined as:

    multi method new(Blob:)
    multi method new(Blob: Blob:D $blob)
    multi method new(Blob: int @values)
    multi method new(Blob: @values)
    multi method new(Blob: *@values)


Creates an empty C<Blob>, or a new C<Blob> from another C<Blob>, or from a list
of integers or values (which will have to be coerced into integers):

    my $blob = Blob.new([1, 2, 3]);
    say Blob.new(<1 2 3>); # OUTPUT: «Blob:0x<01 02 03>␤»

=head2 method Bool

Defined as:

    multi method Bool(Blob:D:)

Returns C<False> if and only if the buffer is empty.

    my $blob = Blob.new();
    say $blob.Bool; # OUTPUT: «False␤»
    $blob = Blob.new([1, 2, 3]);
    say $blob.Bool; # OUTPUT: «True␤»

=head2 method Capture

Defined as:

    method Capture(Blob:D:)

Equivalent to calling L«C<.List.Capture>|/type/List#method_Capture»
on the invocant.

=head2 method elems

Defined as:

    multi method elems(Blob:D:)
    multi method elems(Blob:U: --> 1)

Returns the number of elements of the buffer.

    my $blob = Blob.new([1, 2, 3]);
    say $blob.elems; # OUTPUT: «3␤»

It will also return 1 on the class object.

=head2 method bytes

Defined as:

    method bytes(Blob:D: --> Int:D)

Returns the number of bytes used by the elements in the buffer.

    say Blob.new([1, 2, 3]).bytes;      # OUTPUT: «3␤»
    say blob16.new([1, 2, 3]).bytes;    # OUTPUT: «6␤»
    say blob64.new([1, 2, 3]).bytes;    # OUTPUT: «24␤»

=head2 method chars

Defined as:

    method chars(Blob:D:)

Throws C<X::Buf::AsStr> with C<chars> as payload.

=head2 method Str

Defined as:

    multi method Str(Blob:D:)

Throws C<X::Buf::AsStr> with C<Str> as payload. In order to convert to a C<Str>
you need to use L<C<.decode>|/routine/decode>.

=head2 method Stringy

Defined as:

    multi method Stringy(Blob:D:)

Throws C<X::Buf::AsStr> with C<Stringy> as payload.

=head2 method decode

Defined as:

    multi method decode(Blob:D: $encoding = self.encoding // "utf-8")

=for code :method
multi method decode(Blob:D: $encoding, Str :$replacement!,
                    Bool:D :$strict = False)

    multi method decode(Blob:D: $encoding, Bool:D :$strict = False)

Applies an encoding to turn the blob into a L<Str|/type/Str>; the encoding will
be UTF-8 by default.

    my Blob $blob = "string".encode('utf-8');
    say $blob.decode('utf-8'); # OUTPUT: «string␤»

On malformed utf-8 C<.decode> will throw X::AdHoc. To handle sloppy utf-8 use
L«C<utf8-c8>|/language/unicode#UTF8-C8».

=head2 method list

Defined as:

    multi method list(Blob:D:)

Returns a C<List> of integers:

    say "zipi".encode("ascii").list; # OUTPUT: «(122 105 112 105)␤»

=head2 method gist

Defined as:

    method gist(Blob:D: --> Str:D)

Returns the string containing the "gist" of the L<Blob|/type/Blob>,
B<listing up to the first 100> elements, separated by space, appending an
ellipsis if the L<Blob|/type/Blob> has more than 100 elements.

    put Blob.new(1, 2, 3).gist; # OUTPUT: «Blob:0x<01 02 03>␤»
    put Blob.new(1..2000).gist;
    # OUTPUT:
    # Blob:0x<01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F 10 11 12 13 14 15
    # 16 17 18 19 1A 1B 1C 1D 1E 1F 20 21 22 23 24 25 26 27 28 29 2A 2B 2C
    # 2D 2E 2F 30 31 32 33 34 35 36 37 38 39 3A 3B 3C 3D 3E 3F 40 41 42 43
    # 44 45 46 47 48 49 4A 4B 4C 4D 4E 4F 50 51 52 53 54 55 56 57 58 59 5A
    # 5B 5C 5D 5E 5F 60 61 62 63 64 ...>

=head2 method subbuf

Defined as:

    multi method subbuf(Int $from, Int $len = self.elems --> Blob:D)
    multi method subbuf(Range $range --> Blob:D)

Extracts a part of the invocant buffer, starting from the index with
elements C<$from>, and taking C<$len> elements (or less if the buffer is
shorter), and creates a new buffer as the result.

    say Blob.new(1..10).subbuf(2, 4);    # OUTPUT: «Blob:0x<03 04 05 06>␤»
    say Blob.new(1..10).subbuf(*-2);     # OUTPUT: «Blob:0x<09 0a>␤»
    say Blob.new(1..10).subbuf(*-5,2);   # OUTPUT: «Blob:0x<06 07>␤»

For convenience, also allows a C<Range> to be specified to indicate which
part of the invocant buffer you would like:

    say Blob.new(1..10).subbuf(2..5);    # OUTPUT: «Blob:0x<03 04 05 06>␤»

=head2 method allocate

Defined as:

    multi method allocate(Blob:U: Int:D $elements)
    multi method allocate(Blob:U: Int:D $elements, int $value)
    multi method allocate(Blob:U: Int:D $elements, Int:D \value)
    multi method allocate(Blob:U: Int:D $elements, Mu:D $got)
    multi method allocate(Blob:U: Int:D $elements, int @values)
    multi method allocate(Blob:U: Int:D $elements, Blob:D $blob)
    multi method allocate(Blob:U: Int:D $elements, @values)

Returns a newly created C<Blob> object with the given number of elements.
Optionally takes a second argument that indicates the pattern with which to fill
the C<Blob>: this can be a single (possibly native) integer value, or any
C<Iterable> that generates integer values, including another C<Blob>. The
pattern will be repeated if not enough values are given to fill the entire
C<Blob>.

    my Blob $b0 = Blob.allocate(10,0);
    $b0.say; # OUTPUT: «Blob:0x<00 00 00 00 00 00 00 00 00 00>␤»

If the pattern is a general C<Mu> value, it will fail.

=head2 method unpack

This method is considered B<experimental>, in order to use it you will need to
do:

    use experimental :pack;

Defined as:

    multi method unpack(Blob:D: Str:D $template)
    multi method unpack(Blob:D: @template)
    multi sub unpack(Blob:D \blob, Str:D $template)
    multi sub unpack(Blob:D \blob, @template)

Extracts features from the blob according to the template string, and
returns them as a list.

The template string consists of zero or more units that begin with an ASCII
letter, and are optionally followed by a quantifier.  The quantifier can be
C<*> (which typically stands for "use up the rest of the Blob here"), or a
positive integer (without a C<+>).

Whitespace between template units is ignored.

Examples of valid templates include C<"A4 C n*"> and C<"A*">.

The following letters are recognized:

=begin table

    Letter  Meaning
    ======  =======
    A       Extract a string, where each element of the Blob maps to a codepoint
    a       Same as A
    C       Extract an element from the blob as an integer
    H       Extracts a hex string
    L       Extracts four elements and returns them as a single unsigned integer
    n       Extracts two elements and combines them in "network" (BigEndian) byte order into a single integer
    N       Extracts four elements and combines them in "network" (BigEndian) byte order into a single integer
    S       Extracts two elements and returns them as a single unsigned integer
    v       Same as S
    V       Same as L
    x       Drop an element from the blob (that is, ignore it)
    Z       Same as A

=end table

Example:

    use experimental :pack;
    say Blob.new(1..10).unpack("C*");
    # OUTPUT: «(1 2 3 4 5 6 7 8 9 10)␤»

=head2 sub pack

This subroutine is considered B<experimental>,  in order to use it you will need
to do:

=for code
use experimental :pack;

=for code
multi sub pack(Str $template, *@items)
multi sub pack(@template, *@items)

Packs the given items according to the template and returns a buffer
containing the packed bytes.

The template string consists of zero or more units that begin with an ASCII
letter, and are optionally followed by a quantifier.  For details, see
L<unpack|/routine/unpack>.

=head2 method reverse

Defined as:

    method reverse(Blob:D: --> Blob:D)

Returns a Blob with all elements in reversed order.

    say Blob.new([1, 2, 3]).reverse;    # OUTPUT: «Blob:0x<03 02 01>␤»
    say blob16.new([2]).reverse;        # OUTPUT: «Blob[uint16]:0x<02>␤»
    say blob32.new([16, 32]).reverse;   # OUTPUT: «Blob[uint32]:0x<20 10>␤»

=head1 Methods on blob8 only (6.d, 2018.12 and later)

These methods are available on the blob8 (and C<buf8>) types only.  They allow
low level access to reading bytes from the underlying data and interpreting
them in different ways with regards to type (integer or floating point (num)),
size (8, 16, 32, 64 or 128 bits), signed or unsigned (for integer values) and
endianness (native, little and big endianness).  The returned values are
always expanded to a 64 bit native value where possible, and to a (big)
integer value if that is not possible.

Endianness must be indicated by using values of the L<Endian|/type/Endian>
enum as the B<second> parameter to these methods.  If no endianness is
specified, C<NativeEndian> will be assumed.  Other values are
C<LittleEndian> and C<BigEndian>.

=head2 method read-uint8

Defined as:

    method read-uint8(blob8:D: uint $pos, $endian = NativeEndian --> uint)

Returns an unsigned native integer value for the byte at the given position.
The C<$endian> parameter has no meaning, but is available for consistency.

=head2 method read-int8

Defined as:

    method read-int8(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<int> value for the byte at the given position.
The C<$endian> parameter has no meaning, but is available for consistency.

=head2 method read-uint16

Defined as:

    method read-uint16(blob8:D: uint $pos, $endian = NativeEndian --> uint)

Returns a native C<uint> value for the B<two> bytes starting at the
given position.

=head2 method read-int16

Defined as:

    method read-int16(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<int> value for the B<two> bytes starting at the given
position.

=head2 method read-uint32

Defined as:

    method read-uint32(blob8:D: uint $pos, $endian = NativeEndian --> uint)

Returns a native C<uint> value for the B<four> bytes starting at the
given position.

=head2 method read-int32

Defined as:

    method read-int32(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<int> value for the B<four> bytes starting at the given
position.

=head2 method read-uint64

Defined as:

    method read-uint64(blob8:D: uint $pos, $endian = NativeEndian --> UInt:D)

Returns an unsigned integer value for the B<eight> bytes starting at the
given position.

=head2 method read-int64

Defined as:

    method read-int64(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<int> value for the B<eight> bytes starting at the given
position.

=head2 method read-uint128

Defined as:

    method read-uint128(blob8:D: uint $pos, $endian = NativeEndian --> UInt:D)

Returns an unsigned integer value for the B<sixteen> bytes starting at the
given position.

=head2 method read-int128

Defined as:

    method read-int128(blob8:D: uint $pos, $endian = NativeEndian --> Int:D)

Returns an integer value for the B<sixteen> bytes starting at the given
position.

=head2 method read-num32

Defined as:

    method read-num32(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<num> value for the B<four> bytes starting at the given
position.

=head2 method read-num64

Defined as:

    method read-num64(blob8:D: uint $pos, $endian = NativeEndian --> int)

Returns a native C<num> value for the B<eight> bytes starting at the given
position.

=head1 Methods on blob8 only (6.d, 2019.03 and later)

=head2 method read-ubits

Defined as:

    method read-ubits(blob8:D: uint $pos, uint $bits --> UInt:D)

Returns an unsigned integer value for the B<bits> from the given B<bit> offset
and given number of bits.  The endianness of the bits is assumed to be
C<BigEndian>.

=head2 method read-bits

Defined as:

    method read-bits(blob8:D: uint $pos, uint $bits --> Int:D)

Returns a signed integer value for the B<bits> from the given B<bit> offset
and given number of bits.  The endianness of the bits is assumed to be
C<BigEndian>.

=end pod

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