role Buf

Mutable buffer for binary data

role Buf[::T] does Blob[T] { ... }

A Buf is a mutable sequence of (usually unsigned) integers.

my $b = Buf.new(1, 2, 3);
$b[1] = 42;

Type graph

Type relations for Buf
perl6-type-graph Buf Buf Blob Blob Buf->Blob Positional Positional Stringy Stringy Blob->Positional Blob->Stringy

Stand-alone image: vector, raster

Routines supplied by role Blob

Buf does role Blob, which provides the following methods:

(Blob) method new

Defined as:

method new(*@codes)

Creates a Blob from a list of integers.

my $blob = Blob.new([1, 2, 3]);

(Blob) method Bool

Defined as:

multi method Bool(Blob:D:)

Returns 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␤»

(Blob) method elems

Defined as:

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

Returns the number of elements of the buffer.

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

(Blob) method decode

Defined as:

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

Applies an encoding to turn the blob into a Str.

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

(Blob) method subbuf

Defined as:

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

Extracts a part of the invocant buffer, starting from the index with elements $from, and taking $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>
say Blob.new(1..10).subbuf(*-2);     # Blob:0x<09 0a>
say Blob.new(1..10).subbuf(*-5,2);   # Blob:0x<06 07>

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

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

(Blob) method unpack

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

use experimental :pack;

Defined as:

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 * (which typically stands for "use up the rest of the Blob here"), or a positive integer (without a +).

Whitespace between template units is ignored.

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

The following letters are recognized:

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

Example:

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

(Blob) sub pack

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

use experimental :pack;
    sub pack(Str $template, *@items) returns Buf

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 unpack.

Routines supplied by role Positional

Buf does role Positional, which provides the following methods:

(Positional) method of

method of()

Returns the type constraint for elements of the positional container. Defaults to Mu.