const_fixed_from_int implementation that works on rustc 1.44
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src/lib.rs
29
src/lib.rs
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@ -590,27 +590,14 @@ fixed! {
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#[macro_export]
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macro_rules! const_fixed_from_int {
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($(const $NAME:ident: $Fixed:ty = $int:expr;)*) => { $(
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const $NAME: $Fixed = <$Fixed>::from_bits({
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let int = $int;
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// 0 should work even for no integer bits.
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if int == 0 {
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// Use int here to clearly ensure that the type of int is the inner type.
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int
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} else {
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// Fails to compile if int is not zero and there are no integer bits.
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let one_bits = <$Fixed>::from_bits(1).to_bits() << <$Fixed>::FRAC_NBITS;
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if one_bits > 0 {
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// one_bits is positive: multiplication overflows if int does not fit.
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int * one_bits
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} else if !int == 0 {
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// one_bits is negative minimum for signed inner type and int is -1.
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one_bits
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} else {
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// one_bits is negative minimum and int is not 0 or -1: overflow.
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1 / 0
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}
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}
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});
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const $NAME: $Fixed = {
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const FRAC: u32 = <$Fixed>::FRAC_NBITS;
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// Divide shift into two parts for cases where $Fixed cannot represent 1.
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// Use $Fixed as type because there isn't a const way to get the inner type.
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const ONE_A: $Fixed = <$Fixed>::from_bits(1 << FRAC / 2);
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const ONE_B: $Fixed = <$Fixed>::from_bits(1 << FRAC - FRAC / 2);
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<$Fixed>::from_bits($int * ONE_A.to_bits() * ONE_B.to_bits())
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};
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)* };
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}
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