mv std libs to library/

library/core/src/fmt/float.rs

@@ -0,0 +1,207 @@
+use crate::fmt::{Debug, Display, Formatter, LowerExp, Result, UpperExp};
+use crate::mem::MaybeUninit;
+use crate::num::flt2dec;
+
+// Don't inline this so callers don't use the stack space this function
+// requires unless they have to.
+#[inline(never)]
+fn float_to_decimal_common_exact<T>(
+    fmt: &mut Formatter<'_>,
+    num: &T,
+    sign: flt2dec::Sign,
+    precision: usize,
+) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    // SAFETY: Possible undefined behavior, see FIXME(#53491)
+    unsafe {
+        let mut buf = MaybeUninit::<[u8; 1024]>::uninit(); // enough for f32 and f64
+        let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 4]>::uninit();
+        // FIXME(#53491): This is calling `get_mut` on an uninitialized
+        // `MaybeUninit` (here and elsewhere in this file). Revisit this once
+        // we decided whether that is valid or not.
+        // We can do this only because we are libstd and coupled to the compiler.
+        // (FWIW, using `freeze` would not be enough; `flt2dec::Part` is an enum!)
+        let formatted = flt2dec::to_exact_fixed_str(
+            flt2dec::strategy::grisu::format_exact,
+            *num,
+            sign,
+            precision,
+            buf.get_mut(),
+            parts.get_mut(),
+        );
+        fmt.pad_formatted_parts(&formatted)
+    }
+}
+
+// Don't inline this so callers that call both this and the above won't wind
+// up using the combined stack space of both functions in some cases.
+#[inline(never)]
+fn float_to_decimal_common_shortest<T>(
+    fmt: &mut Formatter<'_>,
+    num: &T,
+    sign: flt2dec::Sign,
+    precision: usize,
+) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    // SAFETY: Possible undefined behavior, see FIXME(#53491)
+    unsafe {
+        // enough for f32 and f64
+        let mut buf = MaybeUninit::<[u8; flt2dec::MAX_SIG_DIGITS]>::uninit();
+        let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 4]>::uninit();
+        // FIXME(#53491)
+        let formatted = flt2dec::to_shortest_str(
+            flt2dec::strategy::grisu::format_shortest,
+            *num,
+            sign,
+            precision,
+            buf.get_mut(),
+            parts.get_mut(),
+        );
+        fmt.pad_formatted_parts(&formatted)
+    }
+}
+
+// Common code of floating point Debug and Display.
+fn float_to_decimal_common<T>(
+    fmt: &mut Formatter<'_>,
+    num: &T,
+    negative_zero: bool,
+    min_precision: usize,
+) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    let force_sign = fmt.sign_plus();
+    let sign = match (force_sign, negative_zero) {
+        (false, false) => flt2dec::Sign::Minus,
+        (false, true) => flt2dec::Sign::MinusRaw,
+        (true, false) => flt2dec::Sign::MinusPlus,
+        (true, true) => flt2dec::Sign::MinusPlusRaw,
+    };
+
+    if let Some(precision) = fmt.precision {
+        float_to_decimal_common_exact(fmt, num, sign, precision)
+    } else {
+        float_to_decimal_common_shortest(fmt, num, sign, min_precision)
+    }
+}
+
+// Don't inline this so callers don't use the stack space this function
+// requires unless they have to.
+#[inline(never)]
+fn float_to_exponential_common_exact<T>(
+    fmt: &mut Formatter<'_>,
+    num: &T,
+    sign: flt2dec::Sign,
+    precision: usize,
+    upper: bool,
+) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    // SAFETY: Possible undefined behavior, see FIXME(#53491)
+    unsafe {
+        let mut buf = MaybeUninit::<[u8; 1024]>::uninit(); // enough for f32 and f64
+        let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 6]>::uninit();
+        // FIXME(#53491)
+        let formatted = flt2dec::to_exact_exp_str(
+            flt2dec::strategy::grisu::format_exact,
+            *num,
+            sign,
+            precision,
+            upper,
+            buf.get_mut(),
+            parts.get_mut(),
+        );
+        fmt.pad_formatted_parts(&formatted)
+    }
+}
+
+// Don't inline this so callers that call both this and the above won't wind
+// up using the combined stack space of both functions in some cases.
+#[inline(never)]
+fn float_to_exponential_common_shortest<T>(
+    fmt: &mut Formatter<'_>,
+    num: &T,
+    sign: flt2dec::Sign,
+    upper: bool,
+) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    // SAFETY: Possible undefined behavior, see FIXME(#53491)
+    unsafe {
+        // enough for f32 and f64
+        let mut buf = MaybeUninit::<[u8; flt2dec::MAX_SIG_DIGITS]>::uninit();
+        let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 6]>::uninit();
+        // FIXME(#53491)
+        let formatted = flt2dec::to_shortest_exp_str(
+            flt2dec::strategy::grisu::format_shortest,
+            *num,
+            sign,
+            (0, 0),
+            upper,
+            buf.get_mut(),
+            parts.get_mut(),
+        );
+        fmt.pad_formatted_parts(&formatted)
+    }
+}
+
+// Common code of floating point LowerExp and UpperExp.
+fn float_to_exponential_common<T>(fmt: &mut Formatter<'_>, num: &T, upper: bool) -> Result
+where
+    T: flt2dec::DecodableFloat,
+{
+    let force_sign = fmt.sign_plus();
+    let sign = match force_sign {
+        false => flt2dec::Sign::Minus,
+        true => flt2dec::Sign::MinusPlus,
+    };
+
+    if let Some(precision) = fmt.precision {
+        // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
+        float_to_exponential_common_exact(fmt, num, sign, precision + 1, upper)
+    } else {
+        float_to_exponential_common_shortest(fmt, num, sign, upper)
+    }
+}
+
+macro_rules! floating {
+    ($ty:ident) => {
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl Debug for $ty {
+            fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+                float_to_decimal_common(fmt, self, true, 1)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl Display for $ty {
+            fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+                float_to_decimal_common(fmt, self, false, 0)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl LowerExp for $ty {
+            fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+                float_to_exponential_common(fmt, self, false)
+            }
+        }
+
+        #[stable(feature = "rust1", since = "1.0.0")]
+        impl UpperExp for $ty {
+            fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
+                float_to_exponential_common(fmt, self, true)
+            }
+        }
+    };
+}
+
+floating! { f32 }
+floating! { f64 }