printf - Update %g formatting to match GNU

src/uucore/src/lib/features/tokenize/num_format/formatters/decf.rs

@@ -5,21 +5,88 @@ use super::super::format_field::FormatField;
 use super::super::formatter::{FormatPrimitive, Formatter, InitialPrefix};
 use super::float_common::{get_primitive_dec, primitive_to_str_common, FloatAnalysis};
 
-fn get_len_fmt_primitive(fmt: &FormatPrimitive) -> usize {
-    let mut len = 0;
-    if let Some(ref s) = fmt.prefix {
-        len += s.len();
+const SIGNIFICANT_FIGURES: usize = 6;
+
+fn round_to_significance(input: &str, significant_figures: usize) -> u32 {
+    if significant_figures < input.len() {
+        let digits = &input[..significant_figures + 1];
+        let float_representation = digits.parse::<f32>().unwrap();
+        (float_representation / 10.0).round() as u32
+    } else {
+        input.parse::<u32>().unwrap_or(0)
     }
-    if let Some(ref s) = fmt.pre_decimal {
-        len += s.len();
+}
+
+fn round(mut format: FormatPrimitive) -> FormatPrimitive {
+    let mut significant_figures = SIGNIFICANT_FIGURES;
+
+    if format.pre_decimal.is_some() {
+        let input = format.pre_decimal.as_ref().unwrap();
+        let rounded = round_to_significance(input, significant_figures);
+        let mut rounded_str = rounded.to_string();
+        significant_figures -= rounded_str.len();
+
+        if significant_figures == 0 {
+            if let Some(digits) = &format.post_decimal {
+                if digits.chars().next().unwrap_or('0') >= '5' {
+                    let rounded = rounded + 1;
+                    rounded_str = rounded.to_string();
                 }
-    if let Some(ref s) = fmt.post_decimal {
-        len += s.len();
             }
-    if let Some(ref s) = fmt.suffix {
-        len += s.len();
         }
-    len
+        format.pre_decimal = Some(rounded_str);
+    }
+
+    if significant_figures == 0 {
+        format.post_decimal = Some(String::new());
+    } else if let Some(input) = format.post_decimal {
+        let leading_zeroes = input.len() - input.trim_start_matches('0').len();
+
+        let rounded_str = if leading_zeroes <= significant_figures {
+            let mut post_decimal = String::with_capacity(significant_figures);
+            for _ in 0..leading_zeroes {
+                post_decimal.push('0');
+            }
+
+            significant_figures -= leading_zeroes;
+            let rounded = round_to_significance(&input[leading_zeroes..], significant_figures);
+            post_decimal.push_str(&rounded.to_string());
+            post_decimal
+        } else {
+            input[..significant_figures].to_string()
+        };
+        format.post_decimal = Some(rounded_str);
+    }
+    format
+}
+
+fn truncate(mut format: FormatPrimitive) -> FormatPrimitive {
+    if let Some(ref post_dec) = format.post_decimal {
+        let trimmed = post_dec.trim_end_matches('0');
+
+        if trimmed.is_empty() {
+            format.post_decimal = Some("".into());
+            if format.suffix == Some("e+00".into()) {
+                format.suffix = Some("".into());
+            }
+        } else if trimmed.len() != post_dec.len() {
+            format.post_decimal = Some(trimmed.to_owned());
+        }
+    }
+    format
+}
+
+fn is_float_magnitude(suffix: &Option<String>) -> bool {
+    match suffix {
+        Some(exponent) => {
+            if exponent.chars().nth(1) == Some('-') {
+                exponent < &"e-05".into()
+            } else {
+                exponent < &"e+06".into()
+            }
+        }
+        None => true,
+    }
 }
 
 pub struct Decf;
@@ -46,34 +113,26 @@ impl Formatter for Decf {
             None,
             false,
         );
-        let mut f_sci = get_primitive_dec(
+        let mut f_dec = get_primitive_dec(
             initial_prefix,
             &str_in[initial_prefix.offset..],
             &analysis,
             second_field as usize,
             Some(*field.field_char == 'G'),
         );
-        // strip trailing zeroes
-        if let Some(ref post_dec) = f_sci.post_decimal {
-            let trimmed = post_dec.trim_end_matches('0');
-            if trimmed.len() != post_dec.len() {
-                f_sci.post_decimal = Some(trimmed.to_owned());
-            }
-        }
-        let f_fl = get_primitive_dec(
+
+        if is_float_magnitude(&f_dec.suffix) {
+            f_dec = get_primitive_dec(
                 initial_prefix,
                 &str_in[initial_prefix.offset..],
                 &analysis,
                 second_field as usize,
                 None,
             );
-        Some(
-            if get_len_fmt_primitive(&f_fl) >= get_len_fmt_primitive(&f_sci) {
-                f_sci
-            } else {
-                f_fl
-            },
-        )
+        }
+
+        f_dec = truncate(round(f_dec));
+        Some(f_dec)
     }
     fn primitive_to_str(&self, prim: &FormatPrimitive, field: FormatField) -> String {
         primitive_to_str_common(prim, &field)

tests/by-util/test_printf.rs

@@ -289,7 +289,7 @@ fn sub_num_dec_trunc() {
     new_ucmd!()
         .args(&["pi is ~ %g", "3.1415926535"])
         .succeeds()
-        .stdout_only("pi is ~ 3.141593");
+        .stdout_only("pi is ~ 3.14159");
 }
 
 #[cfg_attr(not(feature = "test_unimplemented"), ignore)]
@@ -469,3 +469,67 @@ fn sub_float_leading_zeroes() {
         .succeeds()
         .stdout_only("001.000000");
 }
+
+#[test]
+fn sub_general_float() {
+    new_ucmd!()
+        .args(&["%g", "1.1"])
+        .succeeds()
+        .stdout_only("1.1");
+}
+
+#[test]
+fn sub_general_truncate_to_integer() {
+    new_ucmd!()
+        .args(&["%g", "1.0"])
+        .succeeds()
+        .stdout_only("1");
+}
+
+#[test]
+fn sub_general_prefix_with_spaces() {
+    new_ucmd!()
+        .args(&["%5g", "1.1"])
+        .succeeds()
+        .stdout_only("  1.1");
+}
+
+#[test]
+fn sub_general_large_integer() {
+    new_ucmd!()
+        .args(&["%g", "1000000"])
+        .succeeds()
+        .stdout_only("1e+06");
+}
+
+#[test]
+fn sub_general_round_scientific_notation() {
+    new_ucmd!()
+        .args(&["%g", "123456789"])
+        .succeeds()
+        .stdout_only("1.23457e+08");
+}
+
+#[test]
+fn sub_general_scientific_leading_zeroes() {
+    new_ucmd!()
+        .args(&["%g", "1000010"])
+        .succeeds()
+        .stdout_only("1.00001e+06");
+}
+
+#[test]
+fn sub_general_round_float() {
+    new_ucmd!()
+        .args(&["%g", "12345.6789"])
+        .succeeds()
+        .stdout_only("12345.7");
+}
+
+#[test]
+fn sub_general_round_float_to_integer() {
+    new_ucmd!()
+        .args(&["%g", "123456.7"])
+        .succeeds()
+        .stdout_only("123457");
+}