Fixed-Length Types

For scenarios where you need buffers of a specific, unchanging size (like cryptographic hashes, IDs, or fixed-size protocol headers), the library provides specialized fixed-length buffer classes.

Available Types

The library includes several pre-defined fixed-length immutable buffers:

• Bytes16: 16 bytes (128 bits)
• Bytes20: 20 bytes (160 bits)
• Bytes24: 24 bytes (192 bits)
• Bytes32: 32 bytes (256 bits)
• Bytes40: 40 bytes (320 bits)
• Bytes64: 64 bytes (512 bits)

Usage

These classes are immutable and enforce their length during instantiation.

use Charcoal\Buffers\Types\Bytes32;

// Must be exactly 32 bytes
$hash = new Bytes32(hash('sha256', 'data', true)); 

Random Data

You can easily generate a fixed-length buffer filled with cryptographically secure random bytes:

$nonce = Bytes16::fromPrng();

Padded Initialization

If your input data is shorter than the required length, you can use setPadded() to left-pad it with null bytes (\0):

$padded = Bytes32::setPadded("short data");
echo $padded->length(); // 32

Utilities

Fixed-length buffers provide additional helper methods:

• isPadded(): Returns true if the buffer starts with a null byte.
• isEmpty(): Returns true if the buffer consists only of null bytes.
• getClean(): Returns the content with leading and/or trailing whitespace/null bytes trimmed.

Custom Fixed-Length Buffers

You can create your own fixed-length buffers by extending the FixedLengthImmutableBuffer abstract class:

use Charcoal\Buffers\Abstracts\FixedLengthImmutableBuffer;

final readonly class MyCustomBuffer extends FixedLengthImmutableBuffer
{
    protected const int FixedLengthBytes = 12;
}