Sync to dtolnay/ryu master (#16)

Co-authored-by: Aphek <bilkow@tutanota.com>
Co-authored-by: David Tolnay <dtolnay@gmail.com>

Author: 3 people

.clippy.toml

@@ -0,0 +1 @@
+msrv = "1.31.0"

.github/workflows/ci.yml

@@ -39,5 +39,12 @@ jobs:
       - uses: dtolnay/rust-toolchain@nightly
         with:
           components: miri
-      - run: cargo miri setup
       - run: cargo miri test
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dtolnay/rust-toolchain@clippy
+      - run: cargo clippy -- -Dclippy::all -Dclippy::pedantic

README.md

@@ -21,7 +21,7 @@ C, [https://github.com/ulfjack/ryu][upstream].
 uses nothing from the Rust standard library so is usable from no_std crates.*
 
 [paper]: https://dl.acm.org/citation.cfm?id=3192369
-[upstream]: https://github.com/ulfjack/ryu/tree/1c413e127f8d02afd12eb6259bc80163722f1385
+[upstream]: https://github.com/ulfjack/ryu/tree/abf76d252bc97300354857e64e80d4a2bf664291
 
 ```toml
 [dependencies]

src/buffer/mod.rs

@@ -1,4 +1,6 @@
 use crate::raw;
+#[cfg(not(maybe_uninit))]
+use core::mem;
 #[cfg(maybe_uninit)]
 use core::mem::MaybeUninit;
 use core::{slice, str};

src/d2s_small_table.rs

@@ -22,7 +22,7 @@ use crate::common::*;
 #[cfg(not(integer128))]
 use crate::d2s_intrinsics::*;
 
-pub static DOUBLE_POW5_INV_SPLIT2: [(u64, u64); 13] = [
+pub static DOUBLE_POW5_INV_SPLIT2: [(u64, u64); 15] = [
     (1, 2305843009213693952),
     (5955668970331000884, 1784059615882449851),
     (8982663654677661702, 1380349269358112757),
@@ -36,6 +36,8 @@ pub static DOUBLE_POW5_INV_SPLIT2: [(u64, u64); 13] = [
     (12533209867169019542, 1418129833677084982),
     (5577825024675947042, 2194449627517475473),
     (11006974540203867551, 1697873161311732311),
+    (10313493231639821582, 1313665730009899186),
+    (12701016819766672773, 2032799256770390445),
 ];
 
 pub static POW5_INV_OFFSETS: [u32; 19] = [
@@ -112,7 +114,7 @@ pub unsafe fn compute_pow5(i: u32) -> (u64, u64) {
     let b0 = m as u128 * mul.0 as u128;
     let b2 = m as u128 * mul.1 as u128;
     let delta = pow5bits(i as i32) - pow5bits(base2 as i32);
-    debug_assert!(base < POW5_OFFSETS.len() as u32);
+    debug_assert!(i / 16 < POW5_OFFSETS.len() as u32);
     let shifted_sum = (b0 >> delta)
         + (b2 << (64 - delta))
         + ((*POW5_OFFSETS.get_unchecked((i / 16) as usize) >> ((i % 16) << 1)) & 3) as u128;
@@ -165,7 +167,7 @@ pub unsafe fn compute_pow5(i: u32) -> (u64, u64) {
     }
     // high1 | sum | low0
     let delta = pow5bits(i as i32) - pow5bits(base2 as i32);
-    debug_assert!(base < POW5_OFFSETS.len() as u32);
+    debug_assert!(i / 16 < POW5_OFFSETS.len() as u32);
     (
         shiftright128(low0, sum, delta as u32)
             + ((*POW5_OFFSETS.get_unchecked((i / 16) as usize) >> ((i % 16) << 1)) & 3) as u64,

src/lib.rs

@@ -66,10 +66,24 @@
 
 #![no_std]
 #![doc(html_root_url = "https://docs.rs/ryu-js/0.2.1")]
-#![cfg_attr(feature = "cargo-clippy", allow(renamed_and_removed_lints))]
-#![cfg_attr(
-    feature = "cargo-clippy",
-    allow(cast_lossless, many_single_char_names, unreadable_literal,)
+#![allow(
+    clippy::cast_lossless,
+    clippy::cast_possible_truncation,
+    clippy::cast_possible_wrap,
+    clippy::cast_sign_loss,
+    clippy::checked_conversions,
+    clippy::doc_markdown,
+    clippy::expl_impl_clone_on_copy,
+    clippy::if_not_else,
+    clippy::many_single_char_names,
+    clippy::missing_panics_doc,
+    clippy::module_name_repetitions,
+    clippy::must_use_candidate,
+    clippy::similar_names,
+    clippy::too_many_lines,
+    clippy::unreadable_literal,
+    clippy::unseparated_literal_suffix,
+    clippy::wildcard_imports
 )]
 
 mod buffer;

src/s2d.rs

@@ -202,12 +202,13 @@ pub fn s2d(buffer: &[u8]) -> Result<f64, Error> {
     let round_up = last_removed_bit != 0 && (!trailing_zeros || ((m2 >> shift) & 1) != 0);
 
     let mut ieee_m2 = (m2 >> shift).wrapping_add(round_up as u64);
-    if ieee_m2 == (1_u64 << (d2s::DOUBLE_MANTISSA_BITS + 1)) {
+    debug_assert!(ieee_m2 <= 1_u64 << (d2s::DOUBLE_MANTISSA_BITS + 1));
+    ieee_m2 &= (1_u64 << d2s::DOUBLE_MANTISSA_BITS) - 1;
+    if ieee_m2 == 0 && round_up {
         // Due to how the IEEE represents +/-Infinity, we don't need to check
         // for overflow here.
         ieee_e2 += 1;
     }
-    ieee_m2 &= (1_u64 << d2s::DOUBLE_MANTISSA_BITS) - 1;
     let ieee = ((((signed_m as u64) << d2s::DOUBLE_EXPONENT_BITS) | ieee_e2 as u64)
         << d2s::DOUBLE_MANTISSA_BITS)
         | ieee_m2;

src/s2f.rs

@@ -151,14 +151,28 @@ pub fn s2f(buffer: &[u8]) -> Result<f32, Error> {
             .wrapping_add(e10 as u32)
             .wrapping_sub(ceil_log2_pow5(-e10) as u32)
             .wrapping_sub(f2s::FLOAT_MANTISSA_BITS + 1) as i32;
+
+        // We now compute [m10 * 10^e10 / 2^e2] = [m10 / (5^(-e10) 2^(e2-e10))].
         let j = e2
             .wrapping_sub(e10)
             .wrapping_add(ceil_log2_pow5(-e10))
             .wrapping_sub(1)
             .wrapping_add(f2s::FLOAT_POW5_INV_BITCOUNT);
         m2 = mul_pow5_inv_div_pow2(m10, -e10 as u32, j);
 
-        multiple_of_power_of_5_32(m10, -e10 as u32)
+        // We also compute if the result is exact, i.e.,
+        //   [m10 / (5^(-e10) 2^(e2-e10))] == m10 / (5^(-e10) 2^(e2-e10))
+        //
+        // If e2-e10 >= 0, we need to check whether (5^(-e10) 2^(e2-e10))
+        // divides m10, which is the case iff pow5(m10) >= -e10 AND pow2(m10) >=
+        // e2-e10.
+        //
+        // If e2-e10 < 0, we have actually computed [m10 * 2^(e10 e2) /
+        // 5^(-e10)] above, and we need to check whether 5^(-e10) divides (m10 *
+        // 2^(e10-e2)), which is the case iff pow5(m10 * 2^(e10-e2)) = pow5(m10)
+        // >= -e10.
+        (e2 < e10 || (e2 - e10 < 32 && multiple_of_power_of_2_32(m10, (e2 - e10) as u32)))
+            && multiple_of_power_of_5_32(m10, -e10 as u32)
     };
 
     // Compute the final IEEE exponent.
@@ -193,12 +207,16 @@ pub fn s2f(buffer: &[u8]) -> Result<f32, Error> {
     let round_up = last_removed_bit != 0 && (!trailing_zeros || ((m2 >> shift) & 1) != 0);
 
     let mut ieee_m2 = (m2 >> shift).wrapping_add(round_up as u32);
-    if ieee_m2 == (1_u32 << (f2s::FLOAT_MANTISSA_BITS + 1)) {
+    debug_assert!(ieee_m2 <= 1_u32 << (f2s::FLOAT_MANTISSA_BITS + 1));
+    ieee_m2 &= (1_u32 << f2s::FLOAT_MANTISSA_BITS) - 1;
+    if ieee_m2 == 0 && round_up {
+        // Rounding up may overflow the mantissa.
+        // In this case we move a trailing zero of the mantissa into the
+        // exponent.
         // Due to how the IEEE represents +/-Infinity, we don't need to check
         // for overflow here.
         ieee_e2 += 1;
     }
-    ieee_m2 &= (1_u32 << f2s::FLOAT_MANTISSA_BITS) - 1;
     let ieee = ((((signed_m as u32) << f2s::FLOAT_EXPONENT_BITS) | ieee_e2 as u32)
         << f2s::FLOAT_MANTISSA_BITS)
         | ieee_m2;

tests/s2d_test.rs

@@ -78,6 +78,7 @@ fn test_basic() {
     assert_eq!(1.0, s2d(b"1e0").unwrap());
     assert_eq!(1.0, s2d(b"1E0").unwrap());
     assert_eq!(1.0, s2d(b"000001.000000").unwrap());
+    assert_eq!(0.2316419, s2d(b"0.2316419").unwrap());
 }
 
 #[test]
@@ -130,3 +131,20 @@ fn test_issue157() {
         s2d(b"1.2999999999999999E+154").unwrap(),
     );
 }
+
+#[test]
+fn test_issue173() {
+    // Denormal boundary
+    assert_eq!(
+        2.2250738585072012e-308,
+        s2d(b"2.2250738585072012e-308").unwrap(),
+    );
+    assert_eq!(
+        2.2250738585072013e-308,
+        s2d(b"2.2250738585072013e-308").unwrap(),
+    );
+    assert_eq!(
+        2.2250738585072014e-308,
+        s2d(b"2.2250738585072014e-308").unwrap(),
+    );
+}

tests/s2f_test.rs

@@ -75,4 +75,17 @@ fn test_min_max() {
 fn test_mantissa_rounding_overflow() {
     assert_eq!(1.0, s2f(b"0.999999999").unwrap());
     assert_eq!(f32::INFINITY, s2f(b"3.4028236e+38").unwrap());
+    assert_eq!(1.1754944e-38, s2f(b"1.17549430e-38").unwrap()); // FLT_MIN
+    assert_eq!(1.1754944e-38, s2f(b"1.17549431e-38").unwrap());
+    assert_eq!(1.1754944e-38, s2f(b"1.17549432e-38").unwrap());
+    assert_eq!(1.1754944e-38, s2f(b"1.17549433e-38").unwrap());
+    assert_eq!(1.1754944e-38, s2f(b"1.17549434e-38").unwrap());
+    assert_eq!(1.1754944e-38, s2f(b"1.17549435e-38").unwrap());
+}
+
+#[test]
+fn test_trailing_zeros() {
+    assert_eq!(26843550.0, s2f(b"26843549.5").unwrap());
+    assert_eq!(50000004.0, s2f(b"50000002.5").unwrap());
+    assert_eq!(99999992.0, s2f(b"99999989.5").unwrap());
 }