ethers.js/src.ts/abi/coders/abstract-coder.ts

import {
    defineProperties, concat, getBytesCopy, getNumber, hexlify,
    toBeArray, toBigInt, toNumber,
    assert, assertArgument
} from "../../utils/index.js";

import type { BigNumberish, BytesLike } from "../../utils/index.js";

/**
 * @_ignore:
 */
export const WordSize: number = 32;
const Padding = new Uint8Array(WordSize);

// Properties used to immediate pass through to the underlying object
// - `then` is used to detect if an object is a Promise for await
const passProperties = [ "then" ];

const _guard = { };

function throwError(name: string, error: Error): never {
    const wrapped = new Error(`deferred error during ABI decoding triggered accessing ${ name }`);
    (<any>wrapped).error = error;
    throw wrapped;
}

/**
 *  A [[Result]] is a sub-class of Array, which allows accessing any
 *  of its values either positionally by its index or, if keys are
 *  provided by its name.
 *
 *  @_docloc: api/abi
 */
export class Result extends Array<any> {
    readonly #names: ReadonlyArray<null | string>;

    [ K: string | number ]: any

    /**
     *  @private
     */
    constructor(...args: Array<any>) {
        // To properly sub-class Array so the other built-in
        // functions work, the constructor has to behave fairly
        // well. So, in the event we are created via fromItems()
        // we build the read-only Result object we want, but on
        // any other input, we use the default constructor

        // constructor(guard: any, items: Array<any>, keys?: Array<null | string>);
        const guard = args[0];
        let items: Array<any> = args[1];
        let names: Array<null | string> = (args[2] || [ ]).slice();

        let wrap = true;
        if (guard !== _guard) {
            items = args;
            names = [ ];
            wrap = false;
        }

        // Can't just pass in ...items since an array of length 1
        // is a special case in the super.
        super(items.length);
        items.forEach((item, index) => { this[index] = item; });

        // Find all unique keys
        const nameCounts = names.reduce((accum, name) => {
            if (typeof(name) === "string") {
                accum.set(name, (accum.get(name) || 0) + 1);
            }
            return accum;
        }, <Map<string, number>>(new Map()));

        // Remove any key thats not unique
        this.#names = Object.freeze(items.map((item, index) => {
            const name = names[index];
            if (name != null && nameCounts.get(name) === 1) {
                return name;
            }
            return null;
        }));

        if (!wrap) { return; }

        // A wrapped Result is immutable
        Object.freeze(this);

        // Proxy indices and names so we can trap deferred errors
        return new Proxy(this, {
            get: (target, prop, receiver) => {
                if (typeof(prop) === "string") {

                    // Index accessor
                    if (prop.match(/^[0-9]+$/)) {
                        const index = getNumber(prop, "%index");
                        if (index < 0 || index >= this.length) {
                            throw new RangeError("out of result range");
                        }

                        const item = target[index];
                        if (item instanceof Error) {
                            throwError(`index ${ index }`, item);
                        }
                        return item;
                    }

                    // Pass important checks (like `then` for Promise) through
                    if (passProperties.indexOf(prop) >= 0) {
                        return Reflect.get(target, prop, receiver);
                    }

                    const value = target[prop];
                    if (value instanceof Function) {
                        // Make sure functions work with private variables
                        // See: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy#no_private_property_forwarding
                        return function(this: any, ...args: Array<any>) {
                            return value.apply((this === receiver) ? target: this, args);
                        };

                    } else if (!(prop in target)) {
                        // Possible name accessor
                        return target.getValue.apply((this === receiver) ? target: this, [ prop ]);
                    }
                }

                return Reflect.get(target, prop, receiver);
            }
        });
    }

    /**
     *  Returns the Result as a normal Array.
     *
     *  This will throw if there are any outstanding deferred
     *  errors.
     */
    toArray(): Array<any> {
        const result: Array<any> = [ ];
        this.forEach((item, index) => {
            if (item instanceof Error) { throwError(`index ${ index }`, item); }
            result.push(item);
        });
        return result;
    }

    /**
     *  Returns the Result as an Object with each name-value pair.
     *
     *  This will throw if any value is unnamed, or if there are
     *  any outstanding deferred errors.
     */
    toObject(): Record<string, any> {
        return this.#names.reduce((accum, name, index) => {
            assert(name != null, "value at index ${ index } unnamed", "UNSUPPORTED_OPERATION", {
                operation: "toObject()"
            });

            // Add values for names that don't conflict
            if (!(name in accum)) {
                accum[name] = this.getValue(name);
            }

            return accum;
        }, <Record<string, any>>{});
    }

    /**
     *  @_ignore
     */
    slice(start?: number | undefined, end?: number | undefined): Result {
        if (start == null) { start = 0; }
        if (start < 0) {
            start += this.length;
            if (start < 0) { start = 0; }
        }

        if (end == null) { end = this.length; }
        if (end < 0) {
            end += this.length;
            if (end < 0) { end = 0; }
        }
        if (end > this.length) { end = this.length; }

        const result: Array<any> = [ ], names: Array<null | string> = [ ];
        for (let i = start; i < end; i++) {
            result.push(this[i]);
            names.push(this.#names[i]);
        }

        return new Result(_guard, result, names);
    }

    /**
     *  @_ignore
     */
    filter(callback: (el: any, index: number, array: Result) => boolean, thisArg?: any): Result {
        const result: Array<any> = [ ], names: Array<null | string> = [ ];
        for (let i = 0; i < this.length; i++) {
            const item = this[i];
            if (item instanceof Error) {
                throwError(`index ${ i }`, item);
            }

            if (callback.call(thisArg, item, i, this)) {
                result.push(item);
                names.push(this.#names[i]);
            }
        }

        return new Result(_guard, result, names);
    }

    /**
     *  @_ignore
     */
    map<T extends any = any>(callback: (el: any, index: number, array: Result) => T, thisArg?: any): Array<T> {
        const result: Array<T> = [ ];
        for (let i = 0; i < this.length; i++) {
            const item = this[i];
            if (item instanceof Error) {
                throwError(`index ${ i }`, item);
            }

            result.push(callback.call(thisArg, item, i, this));
        }

        return result;
    }


    /**
     *  Returns the value for %%name%%.
     *
     *  Since it is possible to have a key whose name conflicts with
     *  a method on a [[Result]] or its superclass Array, or any
     *  JavaScript keyword, this ensures all named values are still
     *  accessible by name.
     */
    getValue(name: string): any {
        const index = this.#names.indexOf(name);
        if (index === -1) { return undefined; }

        const value = this[index];

        if (value instanceof Error) {
            throwError(`property ${ JSON.stringify(name) }`, (<any>value).error);
        }

        return value;
    }

    /**
     *  Creates a new [[Result]] for %%items%% with each entry
     *  also accessible by its corresponding name in %%keys%%.
     */
    static fromItems(items: Array<any>, keys?: Array<null | string>): Result {
        return new Result(_guard, items, keys);
    }
}

/**
 *  Returns all errors found in a [[Result]].
 *
 *  Since certain errors encountered when creating a [[Result]] do
 *  not impact the ability to continue parsing data, they are
 *  deferred until they are actually accessed. Hence a faulty string
 *  in an Event that is never used does not impact the program flow.
 *
 *  However, sometimes it may be useful to access, identify or
 *  validate correctness of a [[Result]].
 *
 *  @_docloc api/abi
 */
export function checkResultErrors(result: Result): Array<{ path: Array<string | number>, error: Error }> {
    // Find the first error (if any)
    const errors: Array<{ path: Array<string | number>, error: Error }> = [ ];

    const checkErrors = function(path: Array<string | number>, object: any): void {
        if (!Array.isArray(object)) { return; }
        for (let key in object) {
            const childPath = path.slice();
            childPath.push(key);

            try {
                 checkErrors(childPath, object[key]);
            } catch (error: any) {
                errors.push({ path: childPath, error: error });
            }
        }
    }
    checkErrors([ ], result);

    return errors;

}

function getValue(value: BigNumberish): Uint8Array {
    let bytes = toBeArray(value);

    assert (bytes.length <= WordSize, "value out-of-bounds",
        "BUFFER_OVERRUN", { buffer: bytes, length: WordSize, offset: bytes.length });

    if (bytes.length !== WordSize) {
        bytes = getBytesCopy(concat([ Padding.slice(bytes.length % WordSize), bytes ]));
    }

    return bytes;
}

/**
 *  @_ignore
 */
export abstract class Coder {

    // The coder name:
    //   - address, uint256, tuple, array, etc.
    readonly name!: string;

    // The fully expanded type, including composite types:
    //   - address, uint256, tuple(address,bytes), uint256[3][4][],  etc.
    readonly type!: string;

    // The localName bound in the signature, in this example it is "baz":
    //   - tuple(address foo, uint bar) baz
    readonly localName!: string;

    // Whether this type is dynamic:
    //  - Dynamic: bytes, string, address[], tuple(boolean[]), etc.
    //  - Not Dynamic: address, uint256, boolean[3], tuple(address, uint8)
    readonly dynamic!: boolean;

    constructor(name: string, type: string, localName: string, dynamic: boolean) {
        defineProperties<Coder>(this, { name, type, localName, dynamic }, {
            name: "string", type: "string", localName: "string", dynamic: "boolean"
        });
    }

    _throwError(message: string, value: any): never {
        assertArgument(false, message, this.localName, value);
    }

    abstract encode(writer: Writer, value: any): number;
    abstract decode(reader: Reader): any;

    abstract defaultValue(): any;
}

/**
 *  @_ignore
 */
export class Writer {
    // An array of WordSize lengthed objects to concatenation
    #data: Array<Uint8Array>;
    #dataLength: number;

    constructor() {
        this.#data = [ ];
        this.#dataLength = 0;
    }

    get data(): string {
        return concat(this.#data);
    }
    get length(): number { return this.#dataLength; }

    #writeData(data: Uint8Array): number {
        this.#data.push(data);
        this.#dataLength += data.length;
        return data.length;
    }

    appendWriter(writer: Writer): number {
        return this.#writeData(getBytesCopy(writer.data));
    }

    // Arrayish item; pad on the right to *nearest* WordSize
    writeBytes(value: BytesLike): number {
        let bytes = getBytesCopy(value);
        const paddingOffset = bytes.length % WordSize;
        if (paddingOffset) {
            bytes = getBytesCopy(concat([ bytes, Padding.slice(paddingOffset) ]))
        }
        return this.#writeData(bytes);
    }

    // Numeric item; pad on the left *to* WordSize
    writeValue(value: BigNumberish): number {
        return this.#writeData(getValue(value));
    }

    // Inserts a numeric place-holder, returning a callback that can
    // be used to asjust the value later
    writeUpdatableValue(): (value: BigNumberish) => void {
        const offset = this.#data.length;
        this.#data.push(Padding);
        this.#dataLength += WordSize;
        return (value: BigNumberish) => {
            this.#data[offset] = getValue(value);
        };
    }
}

/**
 *  @_ignore
 */
export class Reader {
    // Allows incomplete unpadded data to be read; otherwise an error
    // is raised if attempting to overrun the buffer. This is required
    // to deal with an old Solidity bug, in which event data for
    // external (not public thoguh) was tightly packed.
    readonly allowLoose!: boolean;

    readonly #data: Uint8Array;
    #offset: number;

    constructor(data: BytesLike, allowLoose?: boolean) {
        defineProperties<Reader>(this, { allowLoose: !!allowLoose });

        this.#data = getBytesCopy(data);

        this.#offset = 0;
    }

    get data(): string { return hexlify(this.#data); }
    get dataLength(): number { return this.#data.length; }
    get consumed(): number { return this.#offset; }
    get bytes(): Uint8Array { return new Uint8Array(this.#data); }

    #peekBytes(offset: number, length: number, loose?: boolean): Uint8Array {
        let alignedLength = Math.ceil(length / WordSize) * WordSize;
        if (this.#offset + alignedLength > this.#data.length) {
            if (this.allowLoose && loose && this.#offset + length <= this.#data.length) {
                alignedLength = length;
            } else {
                assert(false, "data out-of-bounds", "BUFFER_OVERRUN", {
                    buffer: getBytesCopy(this.#data),
                    length: this.#data.length,
                    offset: this.#offset + alignedLength
                });
            }
        }
        return this.#data.slice(this.#offset, this.#offset + alignedLength)
    }

    // Create a sub-reader with the same underlying data, but offset
    subReader(offset: number): Reader {
        return new Reader(this.#data.slice(this.#offset + offset), this.allowLoose);
    }

    // Read bytes
    readBytes(length: number, loose?: boolean): Uint8Array {
        let bytes = this.#peekBytes(0, length, !!loose);
        this.#offset += bytes.length;
        // @TODO: Make sure the length..end bytes are all 0?
        return bytes.slice(0, length);
    }

    // Read a numeric values
    readValue(): bigint {
        return toBigInt(this.readBytes(WordSize));
    }

    readIndex(): number {
        return toNumber(this.readBytes(WordSize));
    }
}