diff options
Diffstat (limited to 'packages/utils/src/abi_encoder/calldata/calldata.ts')
| -rw-r--r-- | packages/utils/src/abi_encoder/calldata/calldata.ts | 243 |
1 files changed, 243 insertions, 0 deletions
diff --git a/packages/utils/src/abi_encoder/calldata/calldata.ts b/packages/utils/src/abi_encoder/calldata/calldata.ts new file mode 100644 index 000000000..5f3eee94a --- /dev/null +++ b/packages/utils/src/abi_encoder/calldata/calldata.ts @@ -0,0 +1,243 @@ +import * as ethUtil from 'ethereumjs-util'; +import * as _ from 'lodash'; + +import { constants } from '../utils/constants'; +import { EncodingRules } from '../utils/rules'; + +import { PointerCalldataBlock } from './blocks/pointer'; +import { SetCalldataBlock } from './blocks/set'; +import { CalldataBlock } from './calldata_block'; +import { CalldataIterator, ReverseCalldataIterator } from './iterator'; + +export class Calldata { + private readonly _rules: EncodingRules; + private _selector: string; + private _root: CalldataBlock | undefined; + + public constructor(rules: EncodingRules) { + this._rules = rules; + this._selector = ''; + this._root = undefined; + } + /** + * Sets the root calldata block. This block usually corresponds to a Method. + */ + public setRoot(block: CalldataBlock): void { + this._root = block; + } + /** + * Sets the selector to be prepended onto the calldata. + * If the root block was created by a Method then a selector will likely be set. + */ + public setSelector(selector: string): void { + if (!_.startsWith(selector, '0x')) { + throw new Error(`Expected selector to be hex. Missing prefix '0x'`); + } else if (selector.length !== constants.HEX_SELECTOR_LENGTH_IN_CHARS) { + throw new Error(`Invalid selector '${selector}'`); + } + this._selector = selector; + } + /** + * Iterates through the calldata blocks, starting from the root block, to construct calldata as a hex string. + * If the `optimize` flag is set then this calldata will be condensed, to save gas. + * If the `annotate` flag is set then this will return human-readable calldata. + * If the `annotate` flag is *not* set then this will return EVM-compatible calldata. + */ + public toString(): string { + // Sanity check: root block must be set + if (_.isUndefined(this._root)) { + throw new Error('expected root'); + } + // Optimize, if flag set + if (this._rules.optimize) { + this._optimize(); + } + // Set offsets + const iterator = new CalldataIterator(this._root); + let offset = 0; + for (const block of iterator) { + block.setOffset(offset); + offset += block.getSizeInBytes(); + } + // Generate hex string + const hexString = this._rules.annotate ? this._toHumanReadableCallData() : this._toEvmCompatibeCallDataHex(); + return hexString; + } + /** + * There are three types of calldata blocks: Blob, Set and Pointer. + * Scenarios arise where distinct pointers resolve to identical values. + * We optimize by keeping only one such instance of the identical value, and redirecting all pointers here. + * We keep the last such duplicate value because pointers can only be positive (they cannot point backwards). + * + * Example #1: + * function f(string[], string[]) + * f(["foo", "bar", "blitz"], ["foo", "bar", "blitz"]) + * The array ["foo", "bar", "blitz"] will only be included in the calldata once. + * + * Example #2: + * function f(string[], string) + * f(["foo", "bar", "blitz"], "foo") + * The string "foo" will only be included in the calldata once. + * + * Example #3: + * function f((string, uint, bytes), string, uint, bytes) + * f(("foo", 5, "0x05"), "foo", 5, "0x05") + * The string "foo" and bytes "0x05" will only be included in the calldata once. + * The duplicate `uint 5` values cannot be optimized out because they are static values (no pointer points to them). + * + * @TODO #1: + * This optimization strategy handles blocks that are exact duplicates of one another. + * But what if some block is a combination of two other blocks? Or a subset of another block? + * This optimization problem is not much different from the current implemetation. + * Instead of tracking "observed" hashes, at each node we would simply do pattern-matching on the calldata. + * This strategy would be applied after assigning offsets to the tree, rather than before (as in this strategy). + * Note that one consequence of this strategy is pointers may resolve to offsets that are not word-aligned. + * This shouldn't be a problem but further investigation should be done. + * + * @TODO #2: + * To be done as a follow-up to @TODO #1. + * Since we optimize from the bottom-up, we could be affecting the outcome of a later potential optimization. + * For example, what if by removing one duplicate value we miss out on optimizing another block higher in the tree. + * To handle this case, at each node we can store a candidate optimization in a priority queue (sorted by calldata size). + * At the end of traversing the tree, the candidate at the front of the queue will be the most optimal output. + * + */ + private _optimize(): void { + // Step 1/1 Create a reverse iterator (starts from the end of the calldata to the beginning) + if (_.isUndefined(this._root)) { + throw new Error('expected root'); + } + const iterator = new ReverseCalldataIterator(this._root); + // Step 2/2 Iterate over each block, keeping track of which blocks have been seen and pruning redundant blocks. + const blocksByHash: { [key: string]: CalldataBlock } = {}; + for (const block of iterator) { + // If a block is a pointer and its value has already been observed, then update + // the pointer to resolve to the existing value. + if (block instanceof PointerCalldataBlock) { + const dependencyBlockHashBuf = block.getDependency().computeHash(); + const dependencyBlockHash = ethUtil.bufferToHex(dependencyBlockHashBuf); + if (dependencyBlockHash in blocksByHash) { + const blockWithSameHash = blocksByHash[dependencyBlockHash]; + if (blockWithSameHash !== block.getDependency()) { + block.setAlias(blockWithSameHash); + } + } + continue; + } + // This block has not been seen. Record its hash. + const blockHashBuf = block.computeHash(); + const blockHash = ethUtil.bufferToHex(blockHashBuf); + if (!(blockHash in blocksByHash)) { + blocksByHash[blockHash] = block; + } + } + } + private _toEvmCompatibeCallDataHex(): string { + // Sanity check: must have a root block. + if (_.isUndefined(this._root)) { + throw new Error('expected root'); + } + // Construct an array of buffers (one buffer for each block). + const selectorBuffer = ethUtil.toBuffer(this._selector); + const valueBufs: Buffer[] = [selectorBuffer]; + const iterator = new CalldataIterator(this._root); + for (const block of iterator) { + valueBufs.push(block.toBuffer()); + } + // Create hex from buffer array. + const combinedBuffers = Buffer.concat(valueBufs); + const hexValue = ethUtil.bufferToHex(combinedBuffers); + return hexValue; + } + /** + * Returns human-readable calldata. + * + * Example: + * simpleFunction(string[], string[]) + * strings = ["Hello", "World"] + * simpleFunction(strings, strings) + * + * Output: + * 0xbb4f12e3 + * ### simpleFunction + * 0x0 0000000000000000000000000000000000000000000000000000000000000040 ptr<array1> (alias for array2) + * 0x20 0000000000000000000000000000000000000000000000000000000000000040 ptr<array2> + * + * 0x40 0000000000000000000000000000000000000000000000000000000000000002 ### array2 + * 0x60 0000000000000000000000000000000000000000000000000000000000000040 ptr<array2[0]> + * 0x80 0000000000000000000000000000000000000000000000000000000000000080 ptr<array2[1]> + * 0xa0 0000000000000000000000000000000000000000000000000000000000000005 array2[0] + * 0xc0 48656c6c6f000000000000000000000000000000000000000000000000000000 + * 0xe0 0000000000000000000000000000000000000000000000000000000000000005 array2[1] + * 0x100 576f726c64000000000000000000000000000000000000000000000000000000 + */ + private _toHumanReadableCallData(): string { + // Sanity check: must have a root block. + if (_.isUndefined(this._root)) { + throw new Error('expected root'); + } + // Constants for constructing annotated string + const offsetPadding = 10; + const valuePadding = 74; + const namePadding = 80; + const evmWordStartIndex = 0; + const emptySize = 0; + // Construct annotated calldata + let hexValue = `${this._selector}`; + let offset = 0; + const functionName: string = this._root.getName(); + const iterator = new CalldataIterator(this._root); + for (const block of iterator) { + // Process each block 1 word at a time + const size = block.getSizeInBytes(); + const name = block.getName(); + const parentName = block.getParentName(); + const prettyName = name.replace(`${parentName}.`, '').replace(`${functionName}.`, ''); + // Resulting line will be <offsetStr><valueStr><nameStr> + let offsetStr = ''; + let valueStr = ''; + let nameStr = ''; + let lineStr = ''; + if (size === emptySize) { + // This is a Set block with no header. + // For example, a tuple or an array with a defined length. + offsetStr = ' '.repeat(offsetPadding); + valueStr = ' '.repeat(valuePadding); + nameStr = `### ${prettyName.padEnd(namePadding)}`; + lineStr = `\n${offsetStr}${valueStr}${nameStr}`; + } else { + // This block has at least one word of value. + offsetStr = `0x${offset.toString(constants.HEX_BASE)}`.padEnd(offsetPadding); + valueStr = ethUtil + .stripHexPrefix( + ethUtil.bufferToHex( + block.toBuffer().slice(evmWordStartIndex, constants.EVM_WORD_WIDTH_IN_BYTES), + ), + ) + .padEnd(valuePadding); + if (block instanceof SetCalldataBlock) { + nameStr = `### ${prettyName.padEnd(namePadding)}`; + lineStr = `\n${offsetStr}${valueStr}${nameStr}`; + } else { + nameStr = ` ${prettyName.padEnd(namePadding)}`; + lineStr = `${offsetStr}${valueStr}${nameStr}`; + } + } + // This block has a value that is more than 1 word. + for (let j = constants.EVM_WORD_WIDTH_IN_BYTES; j < size; j += constants.EVM_WORD_WIDTH_IN_BYTES) { + offsetStr = `0x${(offset + j).toString(constants.HEX_BASE)}`.padEnd(offsetPadding); + valueStr = ethUtil + .stripHexPrefix( + ethUtil.bufferToHex(block.toBuffer().slice(j, j + constants.EVM_WORD_WIDTH_IN_BYTES)), + ) + .padEnd(valuePadding); + nameStr = ' '.repeat(namePadding); + lineStr = `${lineStr}\n${offsetStr}${valueStr}${nameStr}`; + } + // Append to hex value + hexValue = `${hexValue}\n${lineStr}`; + offset += size; + } + return hexValue; + } +} |