build(ariadne): vendor serde crates

third_party/crates/itoa-1.0.18/src/u128_ext.rs

@@ -0,0 +1,22 @@
+#[cfg(feature = "no-panic")]
+use no_panic::no_panic;
+
+/// Multiply unsigned 128 bit integers, return upper 128 bits of the result
+#[inline]
+#[cfg_attr(feature = "no-panic", no_panic)]
+pub(crate) fn mulhi(x: u128, y: u128) -> u128 {
+    let x_lo = x as u64;
+    let x_hi = (x >> 64) as u64;
+    let y_lo = y as u64;
+    let y_hi = (y >> 64) as u64;
+
+    // handle possibility of overflow
+    let carry = (u128::from(x_lo) * u128::from(y_lo)) >> 64;
+    let m = u128::from(x_lo) * u128::from(y_hi) + carry;
+    let high1 = m >> 64;
+
+    let m_lo = m as u64;
+    let high2 = (u128::from(x_hi) * u128::from(y_lo) + u128::from(m_lo)) >> 64;
+
+    u128::from(x_hi) * u128::from(y_hi) + high1 + high2
+}