role Buf

Mutable buffer for binary data

role Buf[::Tdoes Blob[T{ ... }

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

my $b = Buf.new(123);
$b[1= 42;

Methods

method subbuf-rw

method subbuf-rw($from$length?)

A mutable version of subbuf that returns a Proxy functioning as a writable reference to a part of a buffer. Its first argument, $from specifies the index in the buffer from which a substitution should occur, and its last argument, $length specifies how many elements are to be replaced.

For example, to replace one element at index 3 with two elements, 100 and 101:

my Buf $b .= new(0..5);
$b.subbuf-rw(3,1= Buf.new(100101);
dd $b;        # OUTPUT: Buf $b = Buf.new(0,1,2,100,101,4,5) 

routine subbuf-rw

sub subbuf-rw(Buf:D $buf$from$length?)

Returns a writable reference to a part of a buffer. Similar to the subbuf-rw method:

my Buf $b .= new(1,2,3);
subbuf-rw($b,2,1= Buf.new(42);
dd $b;        # OUTPUT: Buf $b = Buf.new(1,2,42) 

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

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([123]);

(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([123]);
say $blob.Bool# OUTPUT: «True␤» 

(Blob) method Capture

Defined as:

method Capture(Blob:D --> Capture:D)

Equivalent to calling .List.Capture on the invocant.

(Blob) method elems

Defined as:

multi method elems(Blob:D: --> Int:D)

Returns the number of elements of the buffer.

my $blob = Blob.new([123]);
say $blob.elems# OUTPUT: «3␤» 

(Blob) 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([123]).bytes;      # OUTPUT: «3␤» 
say blob16.new([123]).bytes;    # OUTPUT: «6␤» 
say blob64.new([123]).bytes;    # OUTPUT: «24␤» 

(Blob) method decode

Defined as:

multi method decode(Blob:D: Str:D $encoding = 'UTF-8' --> 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␤» 

On malformed utf-8 .decode will throw X::AdHoc. To handle sloppy utf-8 use utf8-c8.

(Blob) method gist

Defined as:

method gist(Blob:D: --> Str:D)

Returns the string containing the "gist" of the Blob, listing up to the first 100 elements, separated by space, appending an ellipsis if the Blob has more than 100 elements.

put Blob.new(123).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 ...> 

(Blob) method subbuf

Defined as:

multi method subbuf(Int $fromInt $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 $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(24);    # 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 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>␤» 

(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 --> 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 --> 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.

(Blob) method reverse

Defined as:

method reverse(Blob:D: --> Blob:D)

Returns a Blob with all elements in reversed order.

say Blob.new([123]).reverse;    # OUTPUT: «Blob:0x<03 02 01>␤» 
say blob16.new([2]).reverse;        # OUTPUT: «Blob[uint16]:0x<02>␤» 
say buf32.new([1632]).reverse;    # OUTPUT: «Buf[uint32]:0x<20 10>␤» 

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.