How do I decode bytes32 using Ethers.js

Question

I'm listening for an event:

OrdersMatched (bytes32 buyHash, bytes32 sellHash, index_topic_1 address maker, index_topic_2 address taker, uint256 price, index_topic_3 bytes32 metadata)

This is what I'm currently doing and I'm getting an error:

contract.on('OrdersMatched', (buyHash, sellHash, from, to, price, metadata) => {
    console.log('from', from)
    console.log('to', to)
    console.log('price', ethers.utils.formatUnits(price, 18)) // decode

    if (metadata !== '0x0000000000000000000000000000000000000000000000000000000000000000') {
      console.log('metadata', ethers.utils.parseBytes32String(metadata)) // decode bytes32 (doesn't work)
    }
    console.log('')
  })

error - uncaughtException: Error: invalid codepoint at offset 3; unexpected continuation byte (argument="bytes", value=Uint8Array(0x5c5321ae45550685308a405827575e3d6b4a84aa), code=INVALID_ARGUMENT, version=strings/5.4.0)

I'd love some help figuring out how to get this decoding.

Thanks!

Edit:

Logs of metadata and its type:

md 0x66fdd5e25ef9ddb305ba3c2aae1856ab9c6f2979000000000000000000000000

md type string

Answer 1

If the bytes32 is a valid utf8 byte string, then you are using the correct way for decoding:

ethers.utils.parseBytes32String(metadata)

However, not all bytes32 are valid utf8 byte strings (see code points).

In your example 0x66fdd5e25ef9ddb305ba3c2aae1856ab9c6f2979000000000000000000000000, this seems to contain 20 bytes, so I would just guess that this metadata could be an address. I just checked on etherscan, so this indeed is an address.

An address have any of 0 to 255 value in it's bytes, so it can contain invalid code points which are illegal UTF8 characters. That's why your parseBytes32String is triggering an error.

Answer 2

You can use ethers.utils.hexStripZeros()

ethers.utils.hexStripZeros(metadata, 32);