fix confusion about parts required for float formatting

The documentation for flt2dec doesn't match up with the actual
implementation, so fix the documentation to align with reality.
Presumably due to the mismatch, the formatting code for floats in
std::fmt can use correspondingly shorter arrays in some places, so fix
those places up as well.

Fixes #41304.

diff --git a/src/libcore/fmt/float.rs b/src/libcore/fmt/float.rs
index 87def375b202b17e2e38c85cc62453e911b7992d..4825c2aa132640abc14c27cc5e2f7ce040ed3928 100644 (file)
--- a/src/libcore/fmt/float.rs
+++ b/src/libcore/fmt/float.rs
@@ -21,7 +21,7 @@ fn float_to_decimal_common_exact<T>(fmt: &mut Formatter, num: &T,
 {
     unsafe {
         let mut buf: [u8; 1024] = mem::uninitialized(); // enough for f32 and f64
-        let mut parts: [flt2dec::Part; 5] = mem::uninitialized();
+        let mut parts: [flt2dec::Part; 4] = mem::uninitialized();
         let formatted = flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact,
                                                     *num, sign, precision,
                                                     false, &mut buf, &mut parts);
@@ -39,7 +39,7 @@ fn float_to_decimal_common_shortest<T>(fmt: &mut Formatter,
     unsafe {
         // enough for f32 and f64
         let mut buf: [u8; flt2dec::MAX_SIG_DIGITS] = mem::uninitialized();
-        let mut parts: [flt2dec::Part; 5] = mem::uninitialized();
+        let mut parts: [flt2dec::Part; 4] = mem::uninitialized();
         let formatted = flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest,
                                                  *num, sign, 0, false, &mut buf, &mut parts);
         fmt.pad_formatted_parts(&formatted)
@@ -75,7 +75,7 @@ fn float_to_exponential_common_exact<T>(fmt: &mut Formatter, num: &T,
 {
     unsafe {
         let mut buf: [u8; 1024] = mem::uninitialized(); // enough for f32 and f64
-        let mut parts: [flt2dec::Part; 7] = mem::uninitialized();
+        let mut parts: [flt2dec::Part; 6] = mem::uninitialized();
         let formatted = flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact,
                                                   *num, sign, precision,
                                                   upper, &mut buf, &mut parts);
@@ -94,7 +94,7 @@ fn float_to_exponential_common_shortest<T>(fmt: &mut Formatter,
     unsafe {
         // enough for f32 and f64
         let mut buf: [u8; flt2dec::MAX_SIG_DIGITS] = mem::uninitialized();
-        let mut parts: [flt2dec::Part; 7] = mem::uninitialized();
+        let mut parts: [flt2dec::Part; 6] = mem::uninitialized();
         let formatted = flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest,
                                                      *num, sign, (0, 0), upper,
                                                      &mut buf, &mut parts);

diff --git a/src/libcore/num/flt2dec/mod.rs b/src/libcore/num/flt2dec/mod.rs
index 5123e42df61ca8e013943c5d2be7f1f561d57299..74b9e7bf37d5110a754d51a532d2eef5e9ea8d00 100644 (file)
--- a/src/libcore/num/flt2dec/mod.rs
+++ b/src/libcore/num/flt2dec/mod.rs
@@ -410,8 +410,8 @@ fn determine_sign(sign: Sign, decoded: &FullDecoded, negative: bool) -> &'static
 /// it will only print given digits and nothing else.
 ///
 /// The byte buffer should be at least `MAX_SIG_DIGITS` bytes long.
-/// There should be at least 5 parts available, due to the worst case like
-/// `[+][0.][0000][45][0000]` with `frac_digits = 10`.
+/// There should be at least 4 parts available, due to the worst case like
+/// `[+][0.][0000][2][0000]` with `frac_digits = 10`.
 pub fn to_shortest_str<'a, T, F>(mut format_shortest: F, v: T,
                                  sign: Sign, frac_digits: usize, _upper: bool,
                                  buf: &'a mut [u8], parts: &'a mut [Part<'a>]) -> Formatted<'a>
@@ -465,8 +465,8 @@ pub fn to_shortest_str<'a, T, F>(mut format_shortest: F, v: T,
 /// cannot be in this range, avoiding any confusion.
 ///
 /// The byte buffer should be at least `MAX_SIG_DIGITS` bytes long.
-/// There should be at least 7 parts available, due to the worst case like
-/// `[+][1][.][2345][e][-][67]`.
+/// There should be at least 6 parts available, due to the worst case like
+/// `[+][1][.][2345][e][-][6]`.
 pub fn to_shortest_exp_str<'a, T, F>(mut format_shortest: F, v: T,
                                      sign: Sign, dec_bounds: (i16, i16), upper: bool,
                                      buf: &'a mut [u8], parts: &'a mut [Part<'a>]) -> Formatted<'a>
@@ -544,8 +544,8 @@ fn estimate_max_buf_len(exp: i16) -> usize {
 /// The byte buffer should be at least `ndigits` bytes long unless `ndigits` is
 /// so large that only the fixed number of digits will be ever written.
 /// (The tipping point for `f64` is about 800, so 1000 bytes should be enough.)
-/// There should be at least 7 parts available, due to the worst case like
-/// `[+][1][.][2345][e][-][67]`.
+/// There should be at least 6 parts available, due to the worst case like
+/// `[+][1][.][2345][e][-][6]`.
 pub fn to_exact_exp_str<'a, T, F>(mut format_exact: F, v: T,
                                   sign: Sign, ndigits: usize, upper: bool,
                                   buf: &'a mut [u8], parts: &'a mut [Part<'a>]) -> Formatted<'a>
@@ -600,8 +600,8 @@ pub fn to_exact_exp_str<'a, T, F>(mut format_exact: F, v: T,
 /// The byte buffer should be enough for the output unless `frac_digits` is
 /// so large that only the fixed number of digits will be ever written.
 /// (The tipping point for `f64` is about 800, and 1000 bytes should be enough.)
-/// There should be at least 5 parts available, due to the worst case like
-/// `[+][0.][0000][45][0000]` with `frac_digits = 10`.
+/// There should be at least 4 parts available, due to the worst case like
+/// `[+][0.][0000][2][0000]` with `frac_digits = 10`.
 pub fn to_exact_fixed_str<'a, T, F>(mut format_exact: F, v: T,
                                     sign: Sign, frac_digits: usize, _upper: bool,
                                     buf: &'a mut [u8], parts: &'a mut [Part<'a>]) -> Formatted<'a>