getPredicateCodec

Call Signature

function getPredicateCodec<TFrom, TTo, TSize>(
    encodePredicate,
    decodePredicate,
    ifTrue,
    ifFalse,
): FixedSizeCodec<TFrom, TTo, TSize>;

Returns a codec that selects between two codecs based on predicates.

This codec uses boolean predicate functions to determine which of two codecs to use for encoding and decoding. If the encoding predicate returns true for a value, the ifTrue codec is used to encode it; otherwise ifFalse. Similarly, if the decoding predicate returns true for the bytes, the ifTrue codec is used to decode them.

Type Parameters

Type Parameter	Description
`TFrom`	The type of the value to encode.
`TTo`	The type of the value to decode.
`TSize` extends `number`	-

Parameters

Parameter	Type	Description
`encodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given value.
`decodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given byte array.
`ifTrue`	`FixedSizeCodec`<`TFrom`, `TTo`, `TSize`>	The codec to use when the respective predicate returns `true`.
`ifFalse`	`FixedSizeCodec`<`TFrom`, `TTo`, `TSize`>	The codec to use when the respective predicate returns `false`.

Returns

FixedSizeCodec<TFrom, TTo, TSize>

A Codec based on the provided codecs.

Example

Encoding and decoding small and large numbers differently.

const codec = getPredicateCodec(
  (n: number) => n < 256,
  bytes => bytes.length === 1,
  getU8Codec(),
  getU32Codec()
);
 
const smallBytes = codec.encode(42);
// 0x2a (encoded as u8)
 
const largeBytes = codec.encode(1000);
// 0xe8030000 (encoded as u32)
 
codec.decode(smallBytes); // 42
codec.decode(largeBytes); // 1000

See

Call Signature

function getPredicateCodec<TFrom, TTo>(
    encodePredicate,
    decodePredicate,
    ifTrue,
    ifFalse,
): FixedSizeCodec<TFrom, TTo>;

Returns a codec that selects between two codecs based on predicates.

Type Parameters

Type Parameter	Description
`TFrom`	The type of the value to encode.
`TTo`	The type of the value to decode.

Parameters

Parameter	Type	Description
`encodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given value.
`decodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given byte array.
`ifTrue`	`FixedSizeCodec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `true`.
`ifFalse`	`FixedSizeCodec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `false`.

Returns

FixedSizeCodec<TFrom, TTo>

A Codec based on the provided codecs.

Example

Encoding and decoding small and large numbers differently.

const codec = getPredicateCodec(
  (n: number) => n < 256,
  bytes => bytes.length === 1,
  getU8Codec(),
  getU32Codec()
);
 
const smallBytes = codec.encode(42);
// 0x2a (encoded as u8)
 
const largeBytes = codec.encode(1000);
// 0xe8030000 (encoded as u32)
 
codec.decode(smallBytes); // 42
codec.decode(largeBytes); // 1000

See

Call Signature

function getPredicateCodec<TFrom, TTo>(
    encodePredicate,
    decodePredicate,
    ifTrue,
    ifFalse,
): VariableSizeCodec<TFrom, TTo>;

Returns a codec that selects between two codecs based on predicates.

Type Parameters

Type Parameter	Description
`TFrom`	The type of the value to encode.
`TTo`	The type of the value to decode.

Parameters

Parameter	Type	Description
`encodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given value.
`decodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given byte array.
`ifTrue`	`VariableSizeCodec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `true`.
`ifFalse`	`VariableSizeCodec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `false`.

Returns

VariableSizeCodec<TFrom, TTo>

A Codec based on the provided codecs.

Example

Encoding and decoding small and large numbers differently.

const codec = getPredicateCodec(
  (n: number) => n < 256,
  bytes => bytes.length === 1,
  getU8Codec(),
  getU32Codec()
);
 
const smallBytes = codec.encode(42);
// 0x2a (encoded as u8)
 
const largeBytes = codec.encode(1000);
// 0xe8030000 (encoded as u32)
 
codec.decode(smallBytes); // 42
codec.decode(largeBytes); // 1000

See

Call Signature

function getPredicateCodec<TFrom, TTo>(
    encodePredicate,
    decodePredicate,
    ifTrue,
    ifFalse,
): Codec<TFrom, TTo>;

Returns a codec that selects between two codecs based on predicates.

Type Parameters

Type Parameter	Description
`TFrom`	The type of the value to encode.
`TTo`	The type of the value to decode.

Parameters

Parameter	Type	Description
`encodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given value.
`decodePredicate`	(`value`) => `boolean`	A function that returns `true` or `false` for a given byte array.
`ifTrue`	`Codec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `true`.
`ifFalse`	`Codec`<`TFrom`, `TTo`>	The codec to use when the respective predicate returns `false`.

Returns

Codec<TFrom, TTo>

A Codec based on the provided codecs.

Example

Encoding and decoding small and large numbers differently.

const codec = getPredicateCodec(
  (n: number) => n < 256,
  bytes => bytes.length === 1,
  getU8Codec(),
  getU32Codec()
);
 
const smallBytes = codec.encode(42);
// 0x2a (encoded as u8)
 
const largeBytes = codec.encode(1000);
// 0xe8030000 (encoded as u32)
 
codec.decode(smallBytes); // 42
codec.decode(largeBytes); // 1000

getPredicateCodec

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