fix: handle odd-length hex in signed hexToBigInt / hexToNumber (#4913)

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

* chore: shorten signed hex changeset

---------

Co-authored-by: jxom <7336481+jxom@users.noreply.github.com>

Author: Kropiunig

.changeset/signed-odd-length-hex.md

@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Fixed signed `hexToBigInt` and `hexToNumber` calls with odd-length hex values.

src/utils/encoding/fromHex.test.ts

@@ -46,6 +46,10 @@ describe('converts hex to number', () => {
     expect(hexToNumber('0x00027760a62ec2ac', { signed: true })).toBe(
       694206942069420,
     )
+
+    // odd-length hex
+    expect(hexToNumber('0x0', { signed: true })).toBe(0)
+    expect(hexToNumber('0x1a4', { signed: true })).toBe(420)
   })
 
   test('args: size', () => {
@@ -129,6 +133,11 @@ describe('converts hex to bigint', () => {
         { signed: true },
       ),
     ).toBe(-12312312312312312412n)
+
+    // odd-length hex
+    expect(hexToBigInt('0x0', { signed: true })).toBe(0n)
+    expect(hexToBigInt('0xf', { signed: true })).toBe(15n)
+    expect(hexToBigInt('0x1a4', { signed: true })).toBe(420n)
   })
 
   test('args: size', () => {

src/utils/encoding/fromHex.ts

@@ -137,7 +137,7 @@ export function hexToBigInt(hex: Hex, opts: HexToBigIntOpts = {}): bigint {
   const value = BigInt(hex)
   if (!signed) return value
 
-  const size = (hex.length - 2) / 2
+  const size = Math.ceil((hex.length - 2) / 2)
   const max = (1n << (BigInt(size) * 8n - 1n)) - 1n
   if (value <= max) return value