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Native::Packing cpan:WARRINGD last updated on 2021-01-12

README.md
Native-Packing-raku
===============

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## Description

Native::Packing is a simple solution for structured reading
and writing of binary numerical data.

## Example

```
use v6;
use Native::Packing :Endian;

# open a GIF read the header
my class LogicalDescriptor
    does Native::Packing[Endian::Vax] {

    has uint16 $.width;
    has uint16 $.height;
    has uint8  $.flags;
    has uint8  $.bgColorIndex;
    has uint8  $.aspect;
}

my $fh = "t/lightbulb.gif".IO.open( :r, :bin);
my $offset = 6;  # skip GIF header

my LogicalDescriptor $screen .= read: $fh, :$offset;
say "GIF has size {$screen.width} X {$screen.height}";
```

It currently handles records containing native integers (`int8`, `uint8`, `int16`, etc),
numerics (`num32`, `num64`) and sub-records of type `Native::Packing`.

- Data may read be and written to binary files, via the `read` and `write` methods

-  Or read and written to buffers via the `unpack` and `pack` methods.

## Endianess

The two fixed modes are:

- Vax (big endian) - least significant byte written first

- Network (little endian) - most significant byte written first

The endianess of the binary format needs to be known to correctly
read and write to it.

There is also a platform-dependant `Host` mode. This will read and write
binary data in the same endianess as the host computer.

Endian Examples:

```
use Native::Packing :Endian;
class C { has int16 $.a }
my $c = C.new: :a(42);
say ($c but Native::Packing[Vax]).pack;     # Buf[uint8]:0x<2a 00>
say ($c but Native::Packing[Network]).pack; # Buf[uint8]:0x<00 2a>
say ($c but Native::Packing[Host]).pack;    # Depends on your host

```