fix: handle odd-length hex in signed hexToBigInt / hexToNumber

[Kropiunig]

Summary

hexToBigInt (and hexToNumber) with signed: true crash on any odd-length hex value:

import { hexToBigInt } from 'viem'

hexToBigInt('0x1a4', { signed: true })
// RangeError: The number 1.5 cannot be converted to a BigInt because it is not an integer

This is the function's own @example (src/utils/encoding/fromHex.ts:124 documents it returning 420n). It also hits minimal-encoded JSON-RPC quantities, which are odd-length whenever the leading nibble is dropped (0x0, 0xf, 0x1a4, ...).

Root cause

src/utils/encoding/fromHex.ts:140:

const size = (hex.length - 2) / 2

For odd-length hex the byte size is fractional ('0x1a4' → 1.5), and the subsequent BigInt(size) throws. The unsigned path is unaffected — size is only used to compute the signed two's-complement bound.

Fix

Round the byte size up:

const size = Math.ceil((hex.length - 2) / 2)

An odd-length value is interpreted at its minimal byte width (0x1a4 ≙ 0x01a4, 2 bytes), so hexToBigInt('0x1a4', { signed: true }) now returns 420n as documented. Even-length inputs take the exact same path as before.

Test

Extended the args: signed tests in fromHex.test.ts with odd-length cases (0x0, 0xf, 0x1a4) for both hexToBigInt and hexToNumber. They fail on main with the RangeError above and pass with the fix.

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