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import * as ethUtil from 'ethereumjs-util';
import * as Constants from '../utils/constants';
import { Queue } from '../utils/queue';
export class RawCalldata {
private static readonly _INITIAL_OFFSET = 0;
private readonly _value: Buffer;
private readonly _selector: string;
private readonly _scopes: Queue<number>;
private _offset: number; // tracks current offset into raw calldata; used for parsing
constructor(value: string | Buffer, hasSelectorPrefix: boolean = true) {
if (typeof value === 'string' && !value.startsWith('0x')) {
throw new Error(`Expected raw calldata to start with '0x'`);
}
const valueBuf = ethUtil.toBuffer(value);
if (hasSelectorPrefix) {
this._selector = ethUtil.bufferToHex(
valueBuf.slice(Constants.HEX_SELECTOR_BYTE_OFFSET_IN_CALLDATA, Constants.HEX_SELECTOR_LENGTH_IN_BYTES),
);
this._value = valueBuf.slice(Constants.HEX_SELECTOR_LENGTH_IN_BYTES); // disregard selector
} else {
this._selector = '0x';
this._value = valueBuf;
}
this._scopes = new Queue<number>();
this._scopes.push(RawCalldata._INITIAL_OFFSET);
this._offset = RawCalldata._INITIAL_OFFSET;
}
public popBytes(lengthInBytes: number): Buffer {
const value = this._value.slice(this._offset, this._offset + lengthInBytes);
this.setOffset(this._offset + lengthInBytes);
return value;
}
public popWord(): Buffer {
const wordInBytes = 32;
return this.popBytes(wordInBytes);
}
public popWords(length: number): Buffer {
const wordInBytes = 32;
return this.popBytes(length * wordInBytes);
}
public readBytes(from: number, to: number): Buffer {
const value = this._value.slice(from, to);
return value;
}
public setOffset(offsetInBytes: number): void {
this._offset = offsetInBytes;
}
public startScope(): void {
this._scopes.pushFront(this._offset);
}
public endScope(): void {
this._scopes.pop();
}
public getOffset(): number {
return this._offset;
}
public toAbsoluteOffset(relativeOffset: number): number {
const scopeOffset = this._scopes.peek();
if (scopeOffset === undefined) {
throw new Error(`Tried to access undefined scope.`);
}
const absoluteOffset = relativeOffset + scopeOffset;
return absoluteOffset;
}
public getSelector(): string {
return this._selector;
}
}
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