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EVMJSON

JSON Precompile

Address: 0x0000000000000000000000000000000000001003

Parse JSON strings and extract typed data (bytes, uint256, arrays) from EVM contracts without external libraries.

Functions

FunctionDescription
extractAsBytes
function extractAsBytes(bytes input, string key) view returns (bytes)		Extract a value as bytes using a JSON key.
extractAsBytesList
function extractAsBytesList(bytes input, string key) view returns (bytes[])		Extract an array of bytes using a JSON key.
extractAsUint256
function extractAsUint256(bytes input, string key) view returns (uint256)		Parse a value as uint256; decimals are truncated.
extractAsBytesFromArray
function extractAsBytesFromArray(bytes input, uint16 arrayIndex) view returns (bytes)		Extract bytes from a JSON array by zero-based index.

Full Solidity Interface

/// Extract data as bytes using a JSON key.
/// @param input JSON data as bytes
/// @param key JSON key to extract
/// @return response Extracted bytes
function extractAsBytes(bytes memory input, string memory key) external view returns (bytes memory response);
 
/// Extract an array of bytes using a JSON key.
/// @param input JSON data as bytes
/// @param key JSON key to extract
/// @return response Array of extracted bytes
function extractAsBytesList(bytes memory input, string memory key) external view returns (bytes[] memory response);
 
/// Extract data as uint256 using a JSON key.
/// @param input JSON data as bytes
/// @param key JSON key to extract
/// @return response Extracted uint256
function extractAsUint256(bytes memory input, string memory key) external view returns (uint256 response);
 
/// Extract bytes from a JSON array by index.
/// @param input JSON data as bytes
/// @param arrayIndex Zero-based array index
/// @return response Extracted bytes from array element
function extractAsBytesFromArray(bytes memory input, uint16 arrayIndex) external view returns (bytes memory response);

Example

import { ethers } from 'ethers';
 
const JSON_PRECOMPILE = '0x0000000000000000000000000000000000001003';
const ABI = ['function extractAsBytes(bytes input, string key) view returns (bytes)', 'function extractAsUint256(bytes input, string key) view returns (uint256)', 'function extractAsBytesList(bytes input, string key) view returns (bytes[])', 'function extractAsBytesFromArray(bytes input, uint16 arrayIndex) view returns (bytes)'];
 
const provider = new ethers.JsonRpcProvider('https://evm-rpc.sei-apis.com');
const json = new ethers.Contract(JSON_PRECOMPILE, ABI, provider);
 
// Parse JSON response
const jsonData = ethers.toUtf8Bytes('{"price": "1.5", "assets": ["SEI", "USDC"]}');
 
const priceBytes = await json.extractAsBytes(jsonData, 'price');
const price = ethers.toUtf8String(priceBytes); // "1.5"
 
const priceUint = await json.extractAsUint256(jsonData, 'price'); // 1 (truncated)
 
const assetsBytes = await json.extractAsBytesList(jsonData, 'assets');
const assets = assetsBytes.map((b) => ethers.toUtf8String(b)); // ["SEI", "USDC"]

Key Notes

  • Input must be valid UTF-8 encoded JSON bytes
  • Returns empty bytes for missing keys (no revert)
  • extractAsUint256 truncates decimals; use extractAsBytes + parse for precision
  • Nested keys use dot notation: "data.user.balance"

Troubleshooting

ErrorCauseFix
invalid JSONMalformed UTF-8 or JSON syntax errorValidate JSON with JSON.parse() before encoding to bytes.
Empty resultKey does not exist in JSON objectVerify key spelling; use extractAsBytes to inspect raw response.
array index out of boundsIndex >= array lengthQuery array length first or use extractAsBytesList for all elements.

References

Last updated on
SoloP256