# ByteConverters

Low-level utility functions for serializing numbers and data structures to and from byte arrays in little-endian format.

## Import

```ts
import {
  toBytesU8, toBytesU32, toBytesU64, toBytesU512,
  toBytesString, fromBytesString,
  byteHash,
} from 'casper-js-sdk';
```

## Functions

### Integer Serialization

All integer functions produce little-endian `Uint8Array` output.

```ts
toBytesU8(value: BigNumberish): Uint8Array    // 1 byte
toBytesU16(value: BigNumberish): Uint8Array   // 2 bytes
toBytesI32(value: BigNumberish): Uint8Array   // 4 bytes, signed
toBytesU32(value: BigNumberish): Uint8Array   // 4 bytes
toBytesU64(value: BigNumberish): Uint8Array   // 8 bytes
toBytesI64(value: BigNumberish): Uint8Array   // 8 bytes, signed
toBytesU128(value: BigNumberish): Uint8Array  // variable-length
toBytesU256(value: BigNumberish): Uint8Array  // variable-length
toBytesU512(value: BigNumberish): Uint8Array  // variable-length
```

### String Serialization

Strings are serialized with a u32 length prefix (4 bytes) followed by UTF-8 bytes.

```ts
toBytesString(str: string): Uint8Array
fromBytesString(bytes: Uint8Array): string
```

### Array Serialization

```ts
toBytesArrayU8(arr: Uint8Array): Uint8Array  // u32 length + bytes
```

### Parsing

```ts
parseU16(bytes: Uint8Array): number
parseU32(bytes: Uint8Array): number
fromBytesU64(bytes: Uint8Array): BigNumber
```

### Hashing

```ts
byteHash(x: Uint8Array): Uint8Array  // Blake2b 256-bit hash
```

### DataView Helpers

```ts
writeInteger(view: DataView, offset: number, value: number): number
writeUShort(view: DataView, offset: number, value: number): number
writeBytes(view: DataView, offset: number, value: Uint8Array): number
expandBuffer(currentBuffer: ArrayBuffer, requiredSize: number): ArrayBuffer
```

### Factory

```ts
// Create a serializer for any integer type
toBytesNumber(bitSize: number, signed: boolean): (value: BigNumberish) => Uint8Array
```

## Usage

```ts
import { toBytesU32, toBytesU64, toBytesString, fromBytesString, byteHash } from 'casper-js-sdk';

// Serialize a u32
const bytes = toBytesU32(42);
// Uint8Array [42, 0, 0, 0]

// Serialize a string
const strBytes = toBytesString('hello');
// [5, 0, 0, 0, 104, 101, 108, 108, 111]

const str = fromBytesString(strBytes);
// 'hello'

// Compute a Blake2b hash
const hash = byteHash(new Uint8Array([1, 2, 3]));
// Uint8Array(32) [...]
```

## See Also

- [`Conversions`](/types/conversions) - Base64/hex encoding and CSPR↔motes conversion
- [`HexBytes`](/types/hex-bytes) - Hex string wrapper