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

/**
 *  When sending values to or receiving values from a [[Contract]], the
 *  data is generally encoded using the [ABI standard](link-solc-abi).
 *
 *  The AbiCoder provides a utility to encode values to ABI data and
 *  decode values from ABI data.
 *
 *  Most of the time, developers should favour the [[Contract]] class,
 *  which further abstracts a lot of the finer details of ABI data.
 *
 *  @_section api/abi/abi-coder:ABI Encoding
 */

// See: https://github.com/ethereum/wiki/wiki/Ethereum-Contract-ABI

import { assertArgumentCount, assertArgument } from "../utils/index.js";

import { Coder, Reader, Result, Writer } from "./coders/abstract-coder.js";
import { AddressCoder } from "./coders/address.js";
import { ArrayCoder } from "./coders/array.js";
import { BooleanCoder } from "./coders/boolean.js";
import { BytesCoder } from "./coders/bytes.js";
import { FixedBytesCoder } from "./coders/fixed-bytes.js";
import { NullCoder } from "./coders/null.js";
import { NumberCoder } from "./coders/number.js";
import { StringCoder } from "./coders/string.js";
import { TupleCoder } from "./coders/tuple.js";
import { ParamType } from "./fragments.js";

import { getAddress } from "../address/index.js";
import { getBytes, hexlify, makeError } from "../utils/index.js";

import type {
    BytesLike,
    CallExceptionAction, CallExceptionError, CallExceptionTransaction
} from "../utils/index.js";

// https://docs.soliditylang.org/en/v0.8.17/control-structures.html
const PanicReasons: Map<number, string> = new Map();
PanicReasons.set(0x00, "GENERIC_PANIC");
PanicReasons.set(0x01, "ASSERT_FALSE");
PanicReasons.set(0x11, "OVERFLOW");
PanicReasons.set(0x12, "DIVIDE_BY_ZERO");
PanicReasons.set(0x21, "ENUM_RANGE_ERROR");
PanicReasons.set(0x22, "BAD_STORAGE_DATA");
PanicReasons.set(0x31, "STACK_UNDERFLOW");
PanicReasons.set(0x32, "ARRAY_RANGE_ERROR");
PanicReasons.set(0x41, "OUT_OF_MEMORY");
PanicReasons.set(0x51, "UNINITIALIZED_FUNCTION_CALL");

const paramTypeBytes = new RegExp(/^bytes([0-9]*)$/);
const paramTypeNumber = new RegExp(/^(u?int)([0-9]*)$/);


let defaultCoder: null | AbiCoder = null;


function getBuiltinCallException(action: CallExceptionAction, tx: { to?: null | string, from?: null | string, data?: string }, data: null | BytesLike, abiCoder: AbiCoder): CallExceptionError {
    let message = "missing revert data";

    let reason: null | string = null;
    const invocation = null;
    let revert: null | { signature: string, name: string, args: Array<any> } = null;

    if (data) {
        message = "execution reverted";

        const bytes = getBytes(data);
        data = hexlify(data);

        if (bytes.length === 0) {
            message += " (no data present; likely require(false) occurred";
            reason = "require(false)";

        } else if (bytes.length % 32 !== 4) {
            message += " (could not decode reason; invalid data length)";

        } else if (hexlify(bytes.slice(0, 4)) === "0x08c379a0") {
            // Error(string)
            try {
                reason = abiCoder.decode([ "string" ], bytes.slice(4))[0]
                revert = {
                    signature: "Error(string)",
                    name: "Error",
                    args: [ reason ]
                };
                message += `: ${ JSON.stringify(reason) }`;

            } catch (error) {
                message += " (could not decode reason; invalid string data)";
            }

        } else if (hexlify(bytes.slice(0, 4)) === "0x4e487b71") {
            // Panic(uint256)
            try {
                const code = Number(abiCoder.decode([ "uint256" ], bytes.slice(4))[0]);
                revert = {
                    signature: "Panic(uint256)",
                    name: "Panic",
                    args: [ code ]
                };
                reason = `Panic due to ${ PanicReasons.get(code) || "UNKNOWN" }(${ code })`;
                message += `: ${ reason }`;
            } catch (error) {
                message += " (could not decode panic code)";
            }
        } else {
            message += " (unknown custom error)";
        }
    }

    const transaction: CallExceptionTransaction = {
        to: (tx.to ? getAddress(tx.to): null),
        data: (tx.data || "0x")
    };
    if (tx.from) { transaction.from = getAddress(tx.from); }

    return makeError(message, "CALL_EXCEPTION", {
        action, data, reason, transaction, invocation, revert
    });
}

/**
  * About AbiCoder
  */
export class AbiCoder {

    #getCoder(param: ParamType): Coder {
        if (param.isArray()) {
            return new ArrayCoder(this.#getCoder(param.arrayChildren), param.arrayLength, param.name);
        }

        if (param.isTuple()) {
            return new TupleCoder(param.components.map((c) => this.#getCoder(c)), param.name);
        }

        switch (param.baseType) {
            case "address":
                return new AddressCoder(param.name);
            case "bool":
                return new BooleanCoder(param.name);
            case "string":
                return new StringCoder(param.name);
            case "bytes":
                return new BytesCoder(param.name);
            case "":
                return new NullCoder(param.name);
        }

        // u?int[0-9]*
        let match = param.type.match(paramTypeNumber);
        if (match) {
            let size = parseInt(match[2] || "256");
            assertArgument(size !== 0 && size <= 256 && (size % 8) === 0,
                "invalid " + match[1] + " bit length", "param", param);
            return new NumberCoder(size / 8, (match[1] === "int"), param.name);
        }

        // bytes[0-9]+
        match = param.type.match(paramTypeBytes);
        if (match) {
            let size = parseInt(match[1]);
            assertArgument(size !== 0 && size <= 32, "invalid bytes length", "param", param);
            return new FixedBytesCoder(size, param.name);
        }

        assertArgument(false, "invalid type", "type", param.type);
    }

    /**
     *  Get the default values for the given %%types%%.
     *
     *  For example, a ``uint`` is by default ``0`` and ``bool``
     *  is by default ``false``.
     */
    getDefaultValue(types: ReadonlyArray<string | ParamType>): Result {
        const coders: Array<Coder> = types.map((type) => this.#getCoder(ParamType.from(type)));
        const coder = new TupleCoder(coders, "_");
        return coder.defaultValue();
    }

    /**
     *  Encode the %%values%% as the %%types%% into ABI data.
     *
     *  @returns DataHexstring
     */
    encode(types: ReadonlyArray<string | ParamType>, values: ReadonlyArray<any>): string {
        assertArgumentCount(values.length, types.length, "types/values length mismatch");

        const coders = types.map((type) => this.#getCoder(ParamType.from(type)));
        const coder = (new TupleCoder(coders, "_"));

        const writer = new Writer();
        coder.encode(writer, values);
        return writer.data;
    }

    /**
     *  Decode the ABI %%data%% as the %%types%% into values.
     *
     *  If %%loose%% decoding is enabled, then strict padding is
     *  not enforced. Some older versions of Solidity incorrectly
     *  padded event data emitted from ``external`` functions.
     */
    decode(types: ReadonlyArray<string | ParamType>, data: BytesLike, loose?: boolean): Result {
        const coders: Array<Coder> = types.map((type) => this.#getCoder(ParamType.from(type)));
        const coder = new TupleCoder(coders, "_");
        return coder.decode(new Reader(data, loose));
    }

    /**
     *  Returns the shared singleton instance of a default [[AbiCoder]].
     *
     *  On the first call, the instance is created internally.
     */
    static defaultAbiCoder(): AbiCoder {
        if (defaultCoder == null) {
            defaultCoder = new AbiCoder();
        }
        return defaultCoder;
    }

    /**
     *  Returns an ethers-compatible [[CallExceptionError]] Error for the given
     *  result %%data%% for the [[CallExceptionAction]] %%action%% against
     *  the Transaction %%tx%%.
     */
    static getBuiltinCallException(action: CallExceptionAction, tx: { to?: null | string, from?: null | string, data?: string }, data: null | BytesLike): CallExceptionError {
        return getBuiltinCallException(action, tx, data, AbiCoder.defaultAbiCoder());
    }
}