fixCodecSize

fixCodecSize<TFrom, TTo, TSize>(codec, fixedBytes): FixedSizeCodec<TFrom, TTo, TSize>

Creates a fixed-size codec from a given codec.

The resulting codec ensures that both encoding and decoding operate on a fixed number of bytes. When encoding:

If the encoded value is larger than fixedBytes, it is truncated.
If it is smaller, it is padded with trailing zeroes.
If it is exactly fixedBytes, it remains unchanged.

When decoding:

Exactly fixedBytes bytes are read from the input.
If the nested decoder has a smaller fixed size, bytes are truncated or padded as necessary.

Type Parameters

Type Parameter	Description
`TFrom`	The type of the value to encode.
`TTo`	The type of the decoded value.
`TSize` extends `number`	The fixed size of the encoded value in bytes.

Parameters

Parameter	Type	Description
`codec`	`Codec`<`TFrom`, `TTo`>	The codec to wrap into a fixed-size codec.
`fixedBytes`	`TSize`	The fixed number of bytes to read/write.

Returns

FixedSizeCodec<TFrom, TTo, TSize>

A FixedSizeCodec that ensures both encoding and decoding conform to a fixed size.

Example

const codec = fixCodecSize(getUtf8Codec(), 4);
 
const bytes1 = codec.encode("Hello"); // 0x48656c6c (truncated)
const value1 = codec.decode(bytes1);  // "Hell"
 
const bytes2 = codec.encode("Hi");    // 0x48690000 (padded)
const value2 = codec.decode(bytes2);  // "Hi"
 
const bytes3 = codec.encode("Hiya");  // 0x48697961 (same length)
const value3 = codec.decode(bytes3);  // "Hiya"

Remarks

If you only need to enforce a fixed size for encoding, use fixEncoderSize. If you only need to enforce a fixed size for decoding, use fixDecoderSize.

const bytes = fixEncoderSize(getUtf8Encoder(), 4).encode("Hiya");
const value = fixDecoderSize(getUtf8Decoder(), 4).decode(bytes);