printf: support precision for integers

src/uucore/src/lib/features/format/num_format.rs

@@ -63,6 +63,7 @@ pub enum NumberAlignment {
 
 pub struct SignedInt {
     pub width: usize,
+    pub precision: usize,
     pub positive_sign: PositiveSign,
     pub alignment: NumberAlignment,
 }
@@ -79,16 +80,19 @@ impl Formatter for SignedInt {
             }?;
         }
 
+        let s = format!("{:0width$}", x, width = self.precision);
+
         match self.alignment {
-            NumberAlignment::Left => write!(writer, "{x:<width$}", width = self.width),
+            NumberAlignment::Left => write!(writer, "{s:<width$}", width = self.width),
-            NumberAlignment::RightSpace => write!(writer, "{x:>width$}", width = self.width),
+            NumberAlignment::RightSpace => write!(writer, "{s:>width$}", width = self.width),
-            NumberAlignment::RightZero => write!(writer, "{x:0>width$}", width = self.width),
+            NumberAlignment::RightZero => write!(writer, "{s:0>width$}", width = self.width),
         }
     }
 
     fn try_from_spec(s: Spec) -> Result<Self, FormatError> {
         let Spec::SignedInt {
             width,
+            precision,
             positive_sign,
             alignment,
         } = s
@@ -102,8 +106,15 @@ impl Formatter for SignedInt {
             Some(CanAsterisk::Asterisk) => return Err(FormatError::SpecError),
         };
 
+        let precision = match precision {
+            Some(CanAsterisk::Fixed(x)) => x,
+            None => 0,
+            Some(CanAsterisk::Asterisk) => return Err(FormatError::SpecError),
+        };
+
         Ok(Self {
             width,
+            precision,
             positive_sign,
             alignment,
         })
@@ -113,6 +124,7 @@ impl Formatter for SignedInt {
 pub struct UnsignedInt {
     pub variant: UnsignedIntVariant,
     pub width: usize,
+    pub precision: usize,
     pub alignment: NumberAlignment,
 }
 
@@ -120,7 +132,7 @@ impl Formatter for UnsignedInt {
     type Input = u64;
 
     fn fmt(&self, mut writer: impl Write, x: Self::Input) -> std::io::Result<()> {
-        let s = match self.variant {
+        let mut s = match self.variant {
             UnsignedIntVariant::Decimal => format!("{x}"),
             UnsignedIntVariant::Octal(Prefix::No) => format!("{x:o}"),
             UnsignedIntVariant::Octal(Prefix::Yes) => format!("{x:#o}"),
@@ -138,6 +150,10 @@ impl Formatter for UnsignedInt {
             }
         };
 
+        if self.precision > s.len() {
+            s = format!("{:0width$}", s, width = self.precision)
+        }
+
         match self.alignment {
             NumberAlignment::Left => write!(writer, "{s:<width$}", width = self.width),
             NumberAlignment::RightSpace => write!(writer, "{s:>width$}", width = self.width),
@@ -149,6 +165,7 @@ impl Formatter for UnsignedInt {
         let Spec::UnsignedInt {
             variant,
             width,
+            precision,
             alignment,
         } = s
         else {
@@ -161,8 +178,15 @@ impl Formatter for UnsignedInt {
             Some(CanAsterisk::Asterisk) => return Err(FormatError::SpecError),
         };
 
+        let precision = match precision {
+            Some(CanAsterisk::Fixed(x)) => x,
+            None => 0,
+            Some(CanAsterisk::Asterisk) => return Err(FormatError::SpecError),
+        };
+
         Ok(Self {
             width,
+            precision,
             variant,
             alignment,
         })

src/uucore/src/lib/features/format/spec.rs

@@ -22,12 +22,14 @@ pub enum Spec {
     },
     SignedInt {
         width: Option<CanAsterisk<usize>>,
+        precision: Option<CanAsterisk<usize>>,
         positive_sign: PositiveSign,
         alignment: NumberAlignment,
     },
     UnsignedInt {
         variant: UnsignedIntVariant,
         width: Option<CanAsterisk<usize>>,
+        precision: Option<CanAsterisk<usize>>,
         alignment: NumberAlignment,
     },
     Float {
@@ -167,6 +169,7 @@ impl Spec {
             },
             b'd' | b'i' => Spec::SignedInt {
                 width,
+                precision,
                 alignment: match (minus, zero) {
                     (true, _) => NumberAlignment::Left,
                     (false, true) => NumberAlignment::RightZero,
@@ -197,6 +200,7 @@ impl Spec {
                 };
                 Spec::UnsignedInt {
                     variant,
+                    precision,
                     width,
                     alignment,
                 }
@@ -282,10 +286,12 @@ impl Spec {
             }
             &Spec::SignedInt {
                 width,
+                precision,
                 positive_sign,
                 alignment,
             } => {
                 let width = resolve_asterisk(width, &mut args)?.unwrap_or(0);
+                let precision = resolve_asterisk(precision, &mut args)?.unwrap_or(0);
 
                 let arg = next_arg(&mut args)?;
                 let Some(i) = arg.get_i64() else {
@@ -294,6 +300,7 @@ impl Spec {
 
                 num_format::SignedInt {
                     width,
+                    precision,
                     positive_sign,
                     alignment,
                 }
@@ -303,9 +310,11 @@ impl Spec {
             &Spec::UnsignedInt {
                 variant,
                 width,
+                precision,
                 alignment,
             } => {
                 let width = resolve_asterisk(width, &mut args)?.unwrap_or(0);
+                let precision = resolve_asterisk(precision, &mut args)?.unwrap_or(0);
 
                 let arg = next_arg(args)?;
                 let Some(i) = arg.get_u64() else {
@@ -314,6 +323,7 @@ impl Spec {
 
                 num_format::UnsignedInt {
                     variant,
+                    precision,
                     width,
                     alignment,
                 }