lslocks: Print output in a table format similar to the original

src/uu/lslocks/lslocks.md

@@ -0,0 +1,7 @@
+# lslocks
+
+```
+lslocks [OPTION]...
+```
+
+lists system locks

src/uu/lslocks/src/lslocks.rs

@@ -3,18 +3,18 @@
 // For the full copyright and license information, please view the LICENSE
 // file that was distributed with this source code.
 
-use std::{fs, str::FromStr};
+use std::{fmt, fs, str::FromStr};
 
 use clap::{crate_version, Command};
-use uucore::error::UResult;
+use uucore::{error::UResult, format_usage, help_about, help_usage};
 
 // See https://www.man7.org/linux/man-pages/man5/proc_locks.5.html for details on each field's meaning
 #[derive(Debug)]
 struct Lock {
-    ord: usize,
+    _ord: usize,
     lock_type: LockType,
-    strictness: Strictness,
-    variant: Variant,
+    mandatory: bool,
+    mode: LockMode,
     pid: Option<usize>, // This value is -1 for OFD locks, hence the Option
     major_minor: String,
     inode: usize,
@@ -22,6 +22,39 @@ struct Lock {
     end_offset: Option<usize>, // None = lock does not have an explicit end offset and applies until the end of the file
 }
 
+impl Lock {
+    fn get_value(&self, col: &Column) -> String {
+        match col {
+            Column::Command => resolve_command(self).unwrap_or("<unknown>".to_string()),
+            Column::Pid => self
+                .pid
+                .map(|pid| pid.to_string())
+                .unwrap_or("-".to_string()),
+            Column::Type => self.lock_type.to_string(),
+            Column::Size => todo!(),
+            Column::Inode => self.inode.to_string(),
+            Column::MajMin => self.major_minor.clone(),
+            Column::Mode => self.mode.to_string(),
+            Column::Mandatory => {
+                if self.mandatory {
+                    "1".to_string()
+                } else {
+                    "0".to_string()
+                }
+            }
+            Column::Start => self.start_offset.to_string(),
+            // TODO: In the case of EOF end_offset, we should actually resolve the actual file size and display that as the end offset
+            Column::End => self
+                .end_offset
+                .map(|offset| offset.to_string())
+                .unwrap_or("EOF".to_string()),
+            Column::Path => todo!(), // TODO: Resolve filepath of the lock target
+            Column::Blocker => todo!(), // TODO: Check if lock is blocker (and by what)
+            Column::Holders => todo!(), // TODO: Resolve all holders of the lock (this would also let us display a process/PID for OFD locks)
+        }
+    }
+}
+
 impl FromStr for Lock {
     type Err = ();
     fn from_str(input: &str) -> Result<Self, Self::Err> {
@@ -38,13 +71,17 @@ impl FromStr for Lock {
             .next()
             .and_then(|part| LockType::from_str(part).ok())
             .unwrap();
-        let strictness = parts
+        let mandatory = parts
             .next()
-            .and_then(|part| Strictness::from_str(part).ok())
+            .map(|part| match part {
+                "MANDATORY" => true,
+                "ADVISORY" => false,
+                _ => panic!("Unrecognized value in lock line: {}", part),
+            })
             .unwrap();
-        let variant = parts
+        let mode = parts
             .next()
-            .and_then(|part| Variant::from_str(part).ok())
+            .and_then(|part| LockMode::from_str(part).ok())
             .unwrap();
         let pid: Option<usize> = parts.next().and_then(|pid_str| match pid_str {
             "-1" => None,
@@ -69,10 +106,10 @@ impl FromStr for Lock {
         });
 
         Ok(Self {
-            ord,
+            _ord: ord,
             lock_type,
-            strictness,
-            variant,
+            mandatory,
+            mode,
             pid,
             major_minor,
             inode,
@@ -83,6 +120,7 @@ impl FromStr for Lock {
 }
 
 #[derive(Debug, PartialEq, Eq)]
+#[allow(clippy::upper_case_acronyms)]
 enum LockType {
     FLOCK,  // BSD file lock
     OFDLCK, // Open file descriptor
@@ -101,30 +139,23 @@ impl FromStr for LockType {
     }
 }
 
-#[derive(Debug)]
-enum Strictness {
-    Advisory,
-    Mandatory,
-}
-
-impl FromStr for Strictness {
-    type Err = ();
-    fn from_str(input: &str) -> Result<Self, Self::Err> {
-        match input {
-            "ADVISORY" => Ok(Self::Advisory),
-            "MANDATORY" => Ok(Self::Mandatory),
-            _ => Err(()),
+impl fmt::Display for LockType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            LockType::FLOCK => write!(f, "FLOCK"),
+            LockType::OFDLCK => write!(f, "OFDLCK"),
+            LockType::POSIX => write!(f, "POSIX"),
         }
     }
 }
 
 #[derive(Debug)]
-enum Variant {
+enum LockMode {
     Read,
     Write,
 }
 
-impl FromStr for Variant {
+impl FromStr for LockMode {
     type Err = ();
     fn from_str(input: &str) -> Result<Self, Self::Err> {
         match input {
@@ -135,8 +166,122 @@ impl FromStr for Variant {
     }
 }
 
+impl fmt::Display for LockMode {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            LockMode::Write => write!(f, "WRITE"),
+            LockMode::Read => write!(f, "READ"),
+        }
+    }
+}
+
+// All of the columns that need to be supported in the final version
+#[derive(Clone)]
+#[allow(dead_code)]
+enum Column {
+    Command,
+    Pid,
+    Type,
+    Size,
+    Inode,
+    MajMin,
+    Mode,
+    Mandatory,
+    Start,
+    End,
+    Path,
+    Blocker,
+    Holders,
+}
+
+impl Column {
+    fn header_text(&self) -> &'static str {
+        match self {
+            Self::Command => "COMMAND",
+            Self::Pid => "PID",
+            Self::Type => "TYPE",
+            Self::Size => "SIZE",
+            Self::Inode => "INODE",
+            Self::MajMin => "MAJ:MIN",
+            Self::Mode => "MODE",
+            Self::Mandatory => "M",
+            Self::Start => "START",
+            Self::End => "END",
+            Self::Path => "PATH",
+            Self::Blocker => "BLOCKER",
+            Self::Holders => "HOLDERS",
+        }
+    }
+}
+
+fn resolve_command(lock: &Lock) -> Option<String> {
+    if let Some(pid) = lock.pid {
+        return fs::read_to_string(format!("/proc/{}/comm", pid))
+            .map(|content| content.trim().to_string())
+            .ok();
+    }
+
+    // File descriptor locks don't have a real notion of an "owner process", since it can be shared by multiple processes.
+    // The original `lslocks` goes through `/proc/<pid>/fdinfo/*` to find *any* of the processes that reference the same device/inode combo from the lock
+    // We don't implement this behaviour yet, and just show "unknown" for the locks which don't have a clear owner
+    None
+}
+
+const DEFAULT_COLS: &[Column] = &[
+    Column::Command,
+    Column::Pid,
+    Column::Type,
+    //TODO: Implement Column::Size here
+    Column::Mode,
+    Column::Mandatory,
+    Column::Start,
+    Column::End,
+    //TODO: Implements Column::Path here
+];
+
+struct OutputOptions {
+    cols: Vec<Column>,
+}
+
+fn print_output(locks: Vec<Lock>, output_opts: OutputOptions) {
+    let mut column_widths: Vec<_> = output_opts
+        .cols
+        .iter()
+        .map(|col| col.header_text().len())
+        .collect();
+
+    for lock in &locks {
+        for (i, col) in output_opts.cols.iter().enumerate() {
+            column_widths[i] = column_widths[i].max(lock.get_value(col).len());
+        }
+    }
+
+    let headers: Vec<_> = output_opts
+        .cols
+        .iter()
+        .enumerate()
+        .map(|(i, col)| format!("{:<width$}", col.header_text(), width = column_widths[i]))
+        .collect();
+
+    println!("{}", headers.join(" "));
+
+    for lock in &locks {
+        let values: Vec<_> = output_opts
+            .cols
+            .iter()
+            .enumerate()
+            .map(|(i, col)| format!("{:<width$}", lock.get_value(col), width = column_widths[i]))
+            .collect();
+        println!("{}", values.join(" "));
+    }
+}
+
 #[uucore::main]
 pub fn uumain(_args: impl uucore::Args) -> UResult<()> {
+    let output_opts = OutputOptions {
+        cols: Vec::from(DEFAULT_COLS),
+    };
+
     let locks: Vec<_> = match fs::read_to_string("/proc/locks") {
         Ok(content) => content
             .lines()
@@ -145,16 +290,17 @@ pub fn uumain(_args: impl uucore::Args) -> UResult<()> {
         Err(e) => panic!("Could not read /proc/locks: {}", e),
     };
 
-    for lock in locks {
-        println!("{:?}", lock);
-    }
+    print_output(locks, output_opts);
     Ok(())
 }
 
+const ABOUT: &str = help_about!("lslocks.md");
+const USAGE: &str = help_usage!("lslocks.md");
+
 pub fn uu_app() -> Command {
     Command::new(uucore::util_name())
         .version(crate_version!())
-        //.about(ABOUT)
-        //.override_usage(format_usage(USAGE))
+        .about(ABOUT)
+        .override_usage(format_usage(USAGE))
         .infer_long_args(true)
 }