From 28885e09ab01e668b604192e2a9b6b3a2ae00f0b Mon Sep 17 00:00:00 2001
From: Trevor Spiteri <tspiteri@ieee.org>
Date: Sat, 17 Aug 2019 17:55:50 +0200
Subject: [PATCH] make INT_NBITS and FRAC_NBITS constants public

---
 README.md          |  4 +++-
 RELEASES.md        |  1 +
 src/macros_frac.rs | 54 +++++++++++++++++++++++++++++++++++-----------
 3 files changed, 45 insertions(+), 14 deletions(-)

diff --git a/README.md b/README.md
index 6e8fb45..4499ffd 100644
--- a/README.md
+++ b/README.md
@@ -62,7 +62,10 @@ Various conversion methods are available:
         [`overflowing_mul_int`], [`overflowing_shl`],
         [`overflowing_shr`]
       * [`is_positive`], [`is_negative`]
+  * The associated constants [`INT_NBITS`] and [`FRAC_NBITS`] were added.
 
+[`FRAC_NBITS`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#associatedconstant.FRAC_NBITS
+[`INT_NBITS`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#associatedconstant.INT_NBITS
 [`count_ones`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.count_ones
 [`count_zeros`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.count_zeros
 [`from_bits`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.from_bits
@@ -86,7 +89,6 @@ Various conversion methods are available:
 [`wrapping_neg`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.wrapping_neg
 [`wrapping_shl`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.wrapping_shl
 [`wrapping_shr`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.wrapping_shr
-[`wrapping_sub`]: https://docs.rs/fixed/0.4.2/fixed/struct.FixedI32.html#method.wrapping_sub
 
 ### Version 0.4.2 news (2019-08-16)
 
diff --git a/RELEASES.md b/RELEASES.md
index 51012d9..4c3d8f9 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -18,6 +18,7 @@ Version 0.4.3 (unreleased)
 	  * `overflowing_neg`, `overflowing_add`, `overflowing_sub`,
         `overflowing_mul_int`, `overflowing_shl`, `overflowing_shr`
       * `is_positive`, `is_negative`
+  * The associated constants `INT_NBITS` and `FRAC_NBITS` were added.
 
 Version 0.4.2 (2019-08-16)
 ==========================
diff --git a/src/macros_frac.rs b/src/macros_frac.rs
index aa7ee9d..6b81b09 100644
--- a/src/macros_frac.rs
+++ b/src/macros_frac.rs
@@ -20,6 +20,47 @@ macro_rules! fixed_frac {
         $UInner:ty, $Signedness:tt
     ) => {
         impl<Frac: $LeEqU> $Fixed<Frac> {
+            comment!(
+                "The number of integer bits.
+
+# Examples
+
+```rust
+use fixed::{frac::U6, ", $s_fixed, "};
+type Fix = ", $s_fixed, "<U6>;
+assert_eq!(Fix::INT_NBITS, ", $s_nbits, " - 6);
+```
+";
+                pub const INT_NBITS: u32 = mem::size_of::<$Inner>() as u32 * 8 - Self::FRAC_NBITS;
+            );
+
+            comment!(
+                "The number of fractional bits.
+
+# Examples
+
+```rust
+use fixed::{frac::U6, ", $s_fixed, "};
+type Fix = ", $s_fixed, "<U6>;
+assert_eq!(Fix::FRAC_NBITS, 6);
+```
+";
+                pub const FRAC_NBITS: u32 = Frac::U32;
+            );
+
+            // some other useful constants for internal use:
+
+            const INT_MASK: $Inner =
+                !0 << (Self::FRAC_NBITS / 2) << (Self::FRAC_NBITS - Self::FRAC_NBITS / 2);
+            const FRAC_MASK: $Inner = !Self::INT_MASK;
+
+            // 0 when FRAC_NBITS = 0
+            const INT_LSB: $Inner = Self::INT_MASK ^ (Self::INT_MASK << 1);
+
+            // 0 when INT_NBITS = 0
+            const FRAC_MSB: $Inner =
+                Self::FRAC_MASK ^ ((Self::FRAC_MASK as $UInner) >> 1) as $Inner;
+
             comment!(
                 "Returns the number of integer bits.
 
@@ -301,19 +342,6 @@ assert_eq!(Fix::max_value().overflowing_div(quarter), (wrapped, true));
             );
 
             fixed_deprecated! { $Fixed($Inner) }
-
-            // some useful constants
-            const INT_NBITS: u32 = mem::size_of::<$Inner>() as u32 * 8 - Self::FRAC_NBITS;
-            // split shift in two parts to avoid overflow when INT_NBITS = 0
-            const INT_MASK: $Inner =
-                !0 << (Self::FRAC_NBITS / 2) << (Self::FRAC_NBITS - Self::FRAC_NBITS / 2);
-            const INT_LSB: $Inner = Self::INT_MASK ^ (Self::INT_MASK << 1);
-            // 0 when FRAC_NBITS = 0
-            const FRAC_NBITS: u32 = Frac::U32;
-            const FRAC_MASK: $Inner = !Self::INT_MASK;
-            // 0 when INT_NBITS = 0
-            const FRAC_MSB: $Inner =
-                Self::FRAC_MASK ^ ((Self::FRAC_MASK as $UInner) >> 1) as $Inner;
         }
     };
 }