Add processor() method to UNameAPI trait (#96)

* Add processor() method to UNameAPI trait

Implements processor type mapping to provide GNU coreutils-compatible
processor information, addressing uutils/coreutils#8659.

Changes:
- Add processor() method to UNameAPI trait with comprehensive docs
- Implement map_processor() helper in lib_impl for arch-to-processor mapping
- Add processor field and implementation to all platform modules (Unix, Windows, unknown)
- Include platform-specific tests verifying correct processor mappings
- Update example code to demonstrate processor() usage
- Add workspace declaration to Cargo.toml to prevent parent workspace inheritance

Processor mapping behavior:
- macOS: arm64 → arm
- Linux: aarch64 → aarch64 (passthrough)
- x86_64/amd64 → x86_64
- i386/i486/i586/i686 → i686
- ARMv6/v7/v8 variants → arm
- Unknown architectures pass through unchanged (better than "unknown")

This provides the foundation for uutils/coreutils to migrate from its
local processor mapping implementation, consolidating platform knowledge
in the appropriate abstraction layer.

Ref: uutils/coreutils#8659

* docs: update README to include processor() method

Add processor() to example code and expected output as requested by @sylvestre

* docs: clarify processor() vs machine() difference and add comprehensive tests

Address review feedback:
- Remove incomplete archive.is placeholder
- Add detailed documentation explaining how processor() differs from machine()
- Include comparison table showing platform-specific behavior
- Add comprehensive unit test for map_processor() covering all branches
- Improves test coverage from 66.66% to 100% in lib_impl.rs

README.md

@@ -29,6 +29,7 @@ fn main() {
     println!("{}", info.release().to_string_lossy());
     println!("{}", info.version().to_string_lossy());
     println!("{}", info.machine().to_string_lossy());
+    println!("{}", info.processor().to_string_lossy());
     println!("{}", info.osname().to_string_lossy());
 }
 ```
@@ -41,6 +42,7 @@ hostname
 5.10.0-8-amd64
 #1 SMP Debian 5.10.46-4 (2021-08-03)
 x86_64
+x86_64
 GNU/Linux
 ```
 

examples/ex.rs

@@ -14,5 +14,6 @@ fn main() {
     println!("{}", info.release().to_string_lossy());
     println!("{}", info.version().to_string_lossy());
     println!("{}", info.machine().to_string_lossy());
+    println!("{}", info.processor().to_string_lossy());
     println!("{}", info.osname().to_string_lossy());
 }

src/lib.rs

@@ -103,6 +103,14 @@ pub trait UNameAPI {
     /// The name of the current system's hardware.
     fn machine(&self) -> &OsStr;
 
+    /// The processor type (architecture) of the current system.
+    ///
+    /// Maps machine architecture strings to GNU coreutils-compatible processor types.
+    /// For example, "arm64" may map to "arm", "x86_64" to "x86_64", etc.
+    /// This provides more semantically meaningful processor information than the
+    /// raw machine string in some contexts.
+    fn processor(&self) -> &OsStr;
+
     /// The name of the current OS.
     fn osname(&self) -> &OsStr;
 }

src/lib_impl.rs

@@ -1,5 +1,7 @@
 // "plumbing" setup and connections for `lib.rs`
 
+// spell-checker:ignore (jargon) armv
+
 #![warn(unused_results)] // enable warnings for unused results
 
 #[cfg(target_os = "windows")]
@@ -23,6 +25,45 @@ type PathStr = Path;
 #[cfg(target_os = "windows")]
 type PathString = PathBuf;
 
+//=== platform-specific functions
+
+// map_processor
+/// *Returns* processor type mapped from machine architecture string.
+///
+/// Provides GNU coreutils-compatible processor type mappings from machine architecture strings.
+/// This function normalizes architecture names to match the output of GNU coreutils' `uname -p`.
+///
+/// # Difference from `machine()`
+///
+/// While [`UNameAPI::machine()`] returns the raw architecture string from the OS (e.g., "arm64" on macOS),
+/// `processor()` provides a normalized, cross-platform compatible representation:
+///
+/// | Platform | machine() | processor() | Reason |
+/// |----------|-----------|-------------|--------|
+/// | macOS ARM | "arm64" | "arm" | GNU coreutils compatibility |
+/// | Linux ARM64 | "aarch64" | "aarch64" | Preserve Linux convention |
+/// | Windows x86 | "i386"-"i686" | "i686" | Normalize to common name |
+///
+/// # Architecture Mappings
+///
+/// * macOS uses "arm64" for ARM-based Macs → maps to "arm"
+/// * Linux uses "aarch64" for ARM64 → passes through as "aarch64"
+/// * Various i386/i486/i586/i686 variants → normalized to "i686"
+/// * ARMv6/v7/v8 variants → mapped to "arm"
+/// * Unknown architectures pass through unchanged (better than returning "unknown")
+///
+/// ref: <https://github.com/uutils/coreutils/issues/8659>
+pub(crate) fn map_processor(machine: &str) -> String {
+    match machine {
+        "arm64" => "arm".to_string(),
+        "aarch64" => "aarch64".to_string(),
+        "x86_64" | "amd64" => "x86_64".to_string(),
+        "i386" | "i486" | "i586" | "i686" => "i686".to_string(),
+        "armv7l" | "armv6l" | "armv8l" => "arm".to_string(),
+        _ => machine.to_string(),
+    }
+}
+
 //=== platform-specific const
 
 // HOST_OS_NAME * ref: [`uname` info](https://en.wikipedia.org/wiki/Uname)
@@ -73,3 +114,28 @@ mod target;
 mod target;
 
 pub use target::*;
+
+//=== Tests
+
+#[test]
+fn test_map_processor_mappings() {
+    // ARM variants
+    assert_eq!(map_processor("arm64"), "arm");
+    assert_eq!(map_processor("aarch64"), "aarch64");
+    assert_eq!(map_processor("armv6l"), "arm");
+    assert_eq!(map_processor("armv7l"), "arm");
+    assert_eq!(map_processor("armv8l"), "arm");
+
+    // x86 variants
+    assert_eq!(map_processor("x86_64"), "x86_64");
+    assert_eq!(map_processor("amd64"), "x86_64");
+    assert_eq!(map_processor("i386"), "i686");
+    assert_eq!(map_processor("i486"), "i686");
+    assert_eq!(map_processor("i586"), "i686");
+    assert_eq!(map_processor("i686"), "i686");
+
+    // Unknown/passthrough architectures
+    assert_eq!(map_processor("riscv64"), "riscv64");
+    assert_eq!(map_processor("powerpc64"), "powerpc64");
+    assert_eq!(map_processor("unknown"), "unknown");
+}

src/platform/unix.rs

@@ -40,6 +40,7 @@ pub struct PlatformInfo {
     release: OsString,
     version: OsString,
     machine: OsString,
+    processor: OsString,
     osname: OsString,
 }
 
@@ -47,13 +48,16 @@ impl PlatformInfoAPI for PlatformInfo {
     // * note: this function *should* never fail
     fn new() -> Result<Self, PlatformInfoError> {
         let utsname = UTSName(utsname()?);
+        let machine = oss_from_cstr(&utsname.0.machine);
+        let processor = OsString::from(crate::lib_impl::map_processor(&machine.to_string_lossy()));
         Ok(Self {
             utsname,
             sysname: oss_from_cstr(&utsname.0.sysname),
             nodename: oss_from_cstr(&utsname.0.nodename),
             release: oss_from_cstr(&utsname.0.release),
             version: oss_from_cstr(&utsname.0.version),
-            machine: oss_from_cstr(&utsname.0.machine),
+            machine,
+            processor,
             osname: OsString::from(crate::lib_impl::HOST_OS_NAME),
         })
     }
@@ -80,6 +84,10 @@ impl UNameAPI for PlatformInfo {
         &self.machine
     }
 
+    fn processor(&self) -> &OsStr {
+        &self.processor
+    }
+
     fn osname(&self) -> &OsStr {
         &self.osname
     }
@@ -222,6 +230,28 @@ fn test_osname() {
     assert!(osname.starts_with(crate::lib_impl::HOST_OS_NAME));
 }
 
+#[test]
+fn test_processor() {
+    let info = PlatformInfo::new().unwrap();
+    let processor = info.processor().to_string_lossy();
+
+    // Processor should not be empty
+    assert!(!processor.is_empty());
+
+    // On common platforms, verify expected mappings
+    #[cfg(all(target_arch = "aarch64", target_os = "macos"))]
+    assert_eq!(processor, "arm", "macOS arm64 should map to 'arm'");
+
+    #[cfg(all(target_arch = "aarch64", target_os = "linux"))]
+    assert_eq!(processor, "aarch64", "Linux aarch64 should pass through");
+
+    #[cfg(target_arch = "x86_64")]
+    assert_eq!(processor, "x86_64", "x86_64 should pass through");
+
+    #[cfg(target_arch = "x86")]
+    assert_eq!(processor, "i686", "x86 variants should normalize to i686");
+}
+
 #[test]
 fn structure_clone() {
     let info = PlatformInfo::new().unwrap();

src/platform/unknown.rs

@@ -51,6 +51,10 @@ impl UNameAPI for PlatformInfo {
         &self.unknown
     }
 
+    fn processor(&self) -> &OsStr {
+        &self.unknown
+    }
+
     fn osname(&self) -> &OsStr {
         &self.unknown
     }
@@ -65,6 +69,7 @@ fn test_unknown() {
     assert_eq!(platform_info.release().to_string_lossy(), "unknown");
     assert_eq!(platform_info.version().to_string_lossy(), "unknown");
     assert_eq!(platform_info.machine().to_string_lossy(), "unknown");
+    assert_eq!(platform_info.processor().to_string_lossy(), "unknown");
     assert_eq!(platform_info.osname().to_string_lossy(), "unknown");
 }
 

src/platform/windows.rs

@@ -69,6 +69,7 @@ pub struct PlatformInfo {
     release: OsString,
     version: OsString,
     machine: OsString,
+    processor: OsString,
     osname: OsString,
 }
 
@@ -84,6 +85,7 @@ impl PlatformInfoAPI for PlatformInfo {
         let release = version_info.release.clone();
         let version = version_info.version.clone();
         let machine = determine_machine(&system_info);
+        let processor = OsString::from(crate::lib_impl::map_processor(&machine.to_string_lossy()));
         let osname = determine_osname(&version_info);
 
         Ok(Self {
@@ -96,6 +98,7 @@ impl PlatformInfoAPI for PlatformInfo {
             release,
             version,
             machine,
+            processor,
             osname,
         })
     }
@@ -122,6 +125,10 @@ impl UNameAPI for PlatformInfo {
         &self.machine
     }
 
+    fn processor(&self) -> &OsStr {
+        &self.processor
+    }
+
     fn osname(&self) -> &OsStr {
         &self.osname
     }
@@ -746,6 +753,30 @@ fn test_known_winos_names() {
     );
 }
 
+#[test]
+fn test_processor() {
+    let info = PlatformInfo::new().unwrap();
+    let processor = info.processor().to_string_lossy();
+
+    // Processor should not be empty
+    assert!(!processor.is_empty());
+
+    // On common Windows platforms, verify expected mappings
+    #[cfg(target_arch = "x86_64")]
+    assert_eq!(processor, "x86_64", "Windows x86_64 should pass through");
+
+    #[cfg(target_arch = "x86")]
+    assert_eq!(processor, "i686", "Windows x86 should normalize to i686");
+
+    #[cfg(target_arch = "aarch64")]
+    assert_eq!(
+        processor, "aarch64",
+        "Windows ARM64 should pass through as aarch64"
+    );
+
+    println!("Windows processor=[{}]'{}'", processor.len(), processor);
+}
+
 #[test]
 fn structure_clone() {
     let info = PlatformInfo::new().unwrap();