Blob.pod

=begin pod

=TITLE role Blob

=SUBTITLE Common interface for binary large objects

    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.

=head1 Methods

=head2 method new

    method new(*@codes)

Creates a C<Blob> from a list of integers.

=head2 method  Bool

    multi method Bool(Blob:D:)

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

=head2 method elems

    multi method elems(Blob:D:) returns Int:D

Returns the number of elements of the buffer.

=head2 method decode

    multi method decode(Blob:D: Str:D $encoding = 'UTF-8') returns Str:D

Applies an encoding to turn the blob into a L<Str|/type/Str>.

=head2 method subbuf

    method subbuf(Int $from, Int $len = self.elems) returns 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);    # Blob:0x<03 04 05 06>

=head2 method unpack

    method unpack(Blob:D: $template) returns List:D

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 are ignored.

So valid templates are for example C<"A4 C n*"> or 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" (big-endian) byte order into a single integer
    N       Extracts four elements and combines them in "network" (big-endian) 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

=end pod