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// Copyright © Aptos Foundation
// SPDX-License-Identifier: Apache-2.0
/* eslint-disable no-bitwise */
import { MAX_U32_NUMBER } from "./consts";
import { Uint8, Uint16, Uint32, Uint64, Uint128, Uint256 } from "../types";
/**
* This interface exists to define Deserializable<T> inputs for functions that
* deserialize a byte buffer into a type T.
* It is not intended to be implemented or extended, because Typescript has no support
* for static methods in interfaces.
*
* @template T - The type that this will deserialize into.
*/
export interface Deserializable<T> {
/**
* Deserializes the buffered bytes into an instance of the specified class type.
* This function provides an alternative syntax for deserialization, allowing users to call
* `deserializer.deserialize(MyClass)` instead of `MyClass.deserialize(deserializer)`.
*
* @param deserializer - The deserializer instance with the buffered bytes.
* @returns The deserialized value of class type T.
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([1, 2, 3]));
* const value = deserializer.deserialize(MyClass); // where MyClass has a `deserialize` function
* // value is now an instance of MyClass
* // equivalent to `const value = MyClass.deserialize(deserializer)`
* ```
*/
deserialize(deserializer: Deserializer): T;
}
/**
* A class that provides methods for deserializing various data types from a byte buffer.
* It supports deserialization of primitive types, strings, and complex objects using a BCS (Binary Common Serialization) layout.
*/
export class Deserializer {
private buffer: ArrayBuffer;
private offset: number;
/**
* Creates a new instance of the class with a copy of the provided data buffer.
* This prevents outside mutation of the buffer.
*
* @param data - The data to be copied into the internal buffer as a Uint8Array.
*/
constructor(data: Uint8Array) {
// copies data to prevent outside mutation of buffer.
this.buffer = new ArrayBuffer(data.length);
new Uint8Array(this.buffer).set(data, 0);
this.offset = 0;
}
/**
* Reads a specified number of bytes from the buffer and advances the offset.
*
* @param length - The number of bytes to read from the buffer.
* @throws Throws an error if the read operation exceeds the buffer's length.
*/
private read(length: number): ArrayBuffer {
if (this.offset + length > this.buffer.byteLength) {
throw new Error("Reached to the end of buffer");
}
const bytes = this.buffer.slice(this.offset, this.offset + length);
this.offset += length;
return bytes;
}
/**
* Returns the number of bytes remaining in the buffer.
*
* This information is useful to determine if there's more data to be read.
*
* @returns The number of bytes remaining in the buffer.
*/
remaining(): number {
return this.buffer.byteLength - this.offset;
}
/**
* Deserializes a UTF-8 encoded string from a byte array. It first reads the length of the string in bytes,
* followed by the actual byte content, and decodes it into a string.
*
* BCS layout for "string": string_length | string_content
* where string_length is a u32 integer encoded as a uleb128 integer, equal to the number of bytes in string_content.
*
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([8, 49, 50, 51, 52, 97, 98, 99, 100]));
* assert(deserializer.deserializeStr() === "1234abcd");
* ```
*/
deserializeStr(): string {
const value = this.deserializeBytes();
const textDecoder = new TextDecoder();
return textDecoder.decode(value);
}
/**
* @deprecated use `deserializeOption("string")` instead.
*
* The BCS layout for Optional<String> is 0 if none, else 1 followed by the string length and string content.
* @returns The deserialized string if it exists, otherwise undefined.
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([0x00]));
* assert(deserializer.deserializeOptionStr() === undefined);
* const deserializer = new Deserializer(new Uint8Array([1, 8, 49, 50, 51, 52, 97, 98, 99, 100]));
* assert(deserializer.deserializeOptionStr() === "1234abcd");
* ```
*/
deserializeOptionStr(): string | undefined {
return this.deserializeOption("string");
}
/**
* Deserializes an optional value from the buffer.
*
* The BCS layout for Optional<T> starts with a boolean byte (0 if none, 1 if some),
* followed by the value if present.
*
* @template T - The type of the value to deserialize
* @param type - Either a Deserializable class or one of the string literals: "string", "bytes", or "fixedBytes"
* @param len - Required length when type is "fixedBytes", ignored otherwise
* @returns The deserialized value if present, undefined otherwise
*
* @throws {Error} When "fixedBytes" is specified without a length
*
* @example
* ```typescript
* // Deserialize an optional string
* const deserializer = new Deserializer(new Uint8Array([1, 3, 97, 98, 99]));
* const optStr = deserializer.deserializeOption("string");
* // optStr === "abc"
*
* // Deserialize an optional custom type
* const deserializer = new Deserializer(new Uint8Array([0]));
* const optValue = deserializer.deserializeOption(MyClass);
* // optValue === undefined
*
* // Deserialize optional bytes
* const deserializer = new Deserializer(new Uint8Array([1, 3, 1, 2, 3]));
* const optBytes = deserializer.deserializeOption("bytes");
* // optBytes === Uint8Array[1, 2, 3]
*
* // Deserialize optional fixed bytes
* const deserializer = new Deserializer(new Uint8Array([1, 1, 2, 3, 4]));
* const optBytes = deserializer.deserializeOption("fixedBytes", 4);
* // optBytes === Uint8Array[1, 2, 3, 4]
* ```
*/
deserializeOption(type: "string"): string | undefined;
deserializeOption(type: "bytes"): Uint8Array | undefined;
deserializeOption(type: "fixedBytes", len: number): Uint8Array | undefined;
deserializeOption<T>(type: Deserializable<T>): T | undefined;
deserializeOption<T>(
type: Deserializable<T> | "string" | "bytes" | "fixedBytes",
len?: number,
): T | string | Uint8Array | undefined {
const exists = this.deserializeBool();
if (!exists) return undefined;
if (type === "string") {
return this.deserializeStr();
}
if (type === "bytes") {
return this.deserializeBytes();
}
if (type === "fixedBytes") {
if (len === undefined) {
throw new Error("Fixed bytes length not provided");
}
return this.deserializeFixedBytes(len);
}
return this.deserialize(type);
}
/**
* Deserializes an array of bytes.
*
* The BCS layout for "bytes" consists of a bytes_length followed by the bytes themselves, where bytes_length is a u32 integer
* encoded as a uleb128 integer, indicating the length of the bytes array.
*
* @returns {Uint8Array} The deserialized array of bytes.
*/
deserializeBytes(): Uint8Array {
const len = this.deserializeUleb128AsU32();
return new Uint8Array(this.read(len));
}
/**
* Deserializes an array of bytes of a specified length.
*
* @param len - The number of bytes to read from the source.
*/
deserializeFixedBytes(len: number): Uint8Array {
return new Uint8Array(this.read(len));
}
/**
* Deserializes a boolean value from a byte stream.
*
* The BCS layout for a boolean uses one byte, where "0x01" represents true and "0x00" represents false.
* An error is thrown if the byte value is not valid.
*
* @returns The deserialized boolean value.
* @throws Throws an error if the boolean value is invalid.
*/
deserializeBool(): boolean {
const bool = new Uint8Array(this.read(1))[0];
if (bool !== 1 && bool !== 0) {
throw new Error("Invalid boolean value");
}
return bool === 1;
}
/**
* Deserializes a uint8 number from the binary data.
*
* BCS layout for "uint8": One byte. Binary format in little-endian representation.
*
* @returns {number} The deserialized uint8 number.
*/
deserializeU8(): Uint8 {
return new DataView(this.read(1)).getUint8(0);
}
/**
* Deserializes a uint16 number from a binary format in little-endian representation.
*
* BCS layout for "uint16": Two bytes.
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([0x34, 0x12]));
* assert(deserializer.deserializeU16() === 4660);
* ```
*/
deserializeU16(): Uint16 {
return new DataView(this.read(2)).getUint16(0, true);
}
/**
* Deserializes a uint32 number from a binary format in little-endian representation.
*
* BCS layout for "uint32": Four bytes.
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([0x78, 0x56, 0x34, 0x12]));
* assert(deserializer.deserializeU32() === 305419896);
* ```
*/
deserializeU32(): Uint32 {
return new DataView(this.read(4)).getUint32(0, true);
}
/**
* Deserializes a uint64 number.
*
* This function combines two 32-bit values to return a 64-bit unsigned integer in little-endian representation.
* @example
* ```typescript
* const deserializer = new Deserializer(new Uint8Array([0x00, 0xEF, 0xCD, 0xAB, 0x78, 0x56, 0x34, 0x12]));
* assert(deserializer.deserializeU64() === 1311768467750121216);
* ```
*/
deserializeU64(): Uint64 {
const low = this.deserializeU32();
const high = this.deserializeU32();
// combine the two 32-bit values and return (little endian)
return BigInt((BigInt(high) << BigInt(32)) | BigInt(low));
}
/**
* Deserializes a uint128 number from its binary representation.
* This function combines two 64-bit values to return a single uint128 value in little-endian format.
*
* @returns {BigInt} The deserialized uint128 number.
*/
deserializeU128(): Uint128 {
const low = this.deserializeU64();
const high = this.deserializeU64();
// combine the two 64-bit values and return (little endian)
return BigInt((high << BigInt(64)) | low);
}
/**
* Deserializes a uint256 number from its binary representation.
*
* The BCS layout for "uint256" consists of thirty-two bytes in little-endian format.
*
* @returns {BigInt} The deserialized uint256 number.
*/
deserializeU256(): Uint256 {
const low = this.deserializeU128();
const high = this.deserializeU128();
// combine the two 128-bit values and return (little endian)
return BigInt((high << BigInt(128)) | low);
}
/**
* Deserializes a uleb128 encoded uint32 number.
*
* This function is used for interpreting lengths of variable-length sequences and tags of enum values in BCS encoding.
*
* @throws {Error} Throws an error if the parsed value exceeds the maximum uint32 number.
* @returns {number} The deserialized uint32 value.
*/
deserializeUleb128AsU32(): Uint32 {
let value: bigint = BigInt(0);
let shift = 0;
while (value < MAX_U32_NUMBER) {
const byte = this.deserializeU8();
value |= BigInt(byte & 0x7f) << BigInt(shift);
if ((byte & 0x80) === 0) {
break;
}
shift += 7;
}
if (value > MAX_U32_NUMBER) {
throw new Error("Overflow while parsing uleb128-encoded uint32 value");
}
return Number(value);
}
/**
* Helper function that primarily exists to support alternative syntax for deserialization.
* That is, if we have a `const deserializer: new Deserializer(...)`, instead of having to use
* `MyClass.deserialize(deserializer)`, we can call `deserializer.deserialize(MyClass)`.
*
* @example const deserializer = new Deserializer(new Uint8Array([1, 2, 3]));
* const value = deserializer.deserialize(MyClass); // where MyClass has a `deserialize` function
* // value is now an instance of MyClass
* // equivalent to `const value = MyClass.deserialize(deserializer)`
* @param cls The BCS-deserializable class to deserialize the buffered bytes into.
*
* @returns the deserialized value of class type T
*/
deserialize<T>(cls: Deserializable<T>): T {
// NOTE: `deserialize` in `cls.deserialize(this)` here is a static method defined in `cls`,
// It is separate from the `deserialize` instance method defined here in Deserializer.
return cls.deserialize(this);
}
/**
* Deserializes an array of BCS Deserializable values given an existing Deserializer instance with a loaded byte buffer.
*
* @param cls The BCS-deserializable class to deserialize the buffered bytes into.
* @returns An array of deserialized values of type T.
* @example
* // serialize a vector of addresses
* const addresses = new Array<AccountAddress>(
* AccountAddress.from("0x1"),
* AccountAddress.from("0x2"),
* AccountAddress.from("0xa"),
* AccountAddress.from("0xb"),
* );
* const serializer = new Serializer();
* serializer.serializeVector(addresses);
* const serializedBytes = serializer.toUint8Array();
*
* // deserialize the bytes into an array of addresses
* const deserializer = new Deserializer(serializedBytes);
* const deserializedAddresses = deserializer.deserializeVector(AccountAddress);
* // deserializedAddresses is now an array of AccountAddress instances
*/
deserializeVector<T>(cls: Deserializable<T>): Array<T> {
const length = this.deserializeUleb128AsU32();
const vector = new Array<T>();
for (let i = 0; i < length; i += 1) {
vector.push(this.deserialize(cls));
}
return vector;
}
}
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