Implement rev (#56)

* Implement `rev`

* Use uucore facility for error reporting

Cargo.lock

@@ -644,6 +644,7 @@ dependencies = [
  "uu_ctrlaltdel",
  "uu_lscpu",
  "uu_mountpoint",
+ "uu_rev",
  "uucore",
  "xattr",
 ]
@@ -674,6 +675,14 @@ dependencies = [
  "uucore",
 ]
 
+[[package]]
+name = "uu_rev"
+version = "0.0.1"
+dependencies = [
+ "clap",
+ "uucore",
+]
+
 [[package]]
 name = "uucore"
 version = "0.0.27"

Cargo.toml

@@ -28,6 +28,7 @@ feat_common_core = [
   "mountpoint",
   "lscpu",
   "ctrlaltdel",
+  "rev",
 ]
 
 [workspace.dependencies]
@@ -58,6 +59,7 @@ textwrap = { workspace = true }
 lscpu = { optional = true, version = "0.0.1", package = "uu_lscpu", path = "src/uu/lscpu" }
 mountpoint = { optional = true, version = "0.0.1", package = "uu_mountpoint", path = "src/uu/mountpoint" }
 ctrlaltdel = { optional = true, version = "0.0.1", package = "uu_ctrlaltdel", path = "src/uu/ctrlaltdel" }
+rev = { optional = true, version = "0.0.1", package = "uu_rev", path = "src/uu/rev" }
 
 [dev-dependencies]
 pretty_assertions = "1"

src/uu/rev/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "uu_rev"
+version = "0.0.1"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+uucore = { workspace = true }
+clap = { workspace = true }
+
+[lib]
+path = "src/rev.rs"
+
+[[bin]]
+name = "rev"
+path = "src/main.rs"

src/uu/rev/rev.md

@@ -0,0 +1,7 @@
+# rev
+
+```
+rev [options] [file ...]
+```
+
+Reverse lines characterwise.

src/uu/rev/src/main.rs

@@ -0,0 +1 @@
+uucore::bin!(uu_rev);

src/uu/rev/src/rev.rs

@@ -0,0 +1,81 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use clap::{crate_version, Command};
+use clap::{Arg, ArgAction};
+use std::env;
+use std::io::{BufRead, BufReader, Read, Write};
+use uucore::{error::UResult, format_usage, help_about, help_usage};
+
+const ABOUT: &str = help_about!("rev.md");
+const USAGE: &str = help_usage!("rev.md");
+
+#[uucore::main]
+pub fn uumain(args: impl uucore::Args) -> UResult<()> {
+    let matches: clap::ArgMatches = uu_app().try_get_matches_from(args)?;
+    let files = matches.get_many::<String>("file");
+
+    match files {
+        Some(files) => {
+            for path in files {
+                let file = match std::fs::File::open(path) {
+                    Ok(val) => val,
+                    Err(err) => {
+                        uucore::error::set_exit_code(1);
+                        uucore::show_error!("cannot open {}: {}", path, err);
+                        continue;
+                    }
+                };
+                if let Err(err) = rev_stream(file) {
+                    uucore::error::set_exit_code(1);
+                    uucore::show_error!("cannot read {}: {}", path, err);
+                }
+            }
+        }
+        None => {
+            let stdin = std::io::stdin().lock();
+            let _ = rev_stream(stdin);
+        }
+    }
+
+    Ok(())
+}
+
+fn rev_stream(stream: impl Read) -> std::io::Result<()> {
+    let mut stdout = std::io::stdout().lock();
+    let mut stream = BufReader::new(stream);
+    let mut buf = Vec::with_capacity(4096);
+    loop {
+        buf.clear();
+        stream.read_until(b'\n', &mut buf)?;
+        if buf.last().copied() != Some(b'\n') {
+            buf.reverse();
+            stdout.write_all(&buf)?;
+            break;
+        } else {
+            buf.pop();
+            buf.reverse();
+            buf.push(b'\n');
+            stdout.write_all(&buf)?;
+        }
+    }
+    Ok(())
+}
+
+pub fn uu_app() -> Command {
+    Command::new(uucore::util_name())
+        .version(crate_version!())
+        .about(ABOUT)
+        .override_usage(format_usage(USAGE))
+        .infer_long_args(true)
+        .arg(
+            Arg::new("file")
+                .value_name("FILE")
+                .help("Paths of files to reverse")
+                .index(1)
+                .action(ArgAction::Set)
+                .num_args(1..),
+        )
+}

tests/by-util/test_rev.rs

@@ -0,0 +1,12 @@
+// This file is part of the uutils util-linux package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+// spell-checker:ignore (words) symdir somefakedir
+
+use crate::common::util::TestScenario;
+
+#[test]
+fn test_invalid_arg() {
+    new_ucmd!().arg("--definitely-invalid").fails().code_is(1);
+}

tests/tests.rs

@@ -16,3 +16,7 @@ mod test_mountpoint;
 #[cfg(feature = "ctrlaltdel")]
 #[path = "by-util/test_ctrlaltdel.rs"]
 mod test_ctrlaltdel;
+
+#[cfg(feature = "rev")]
+#[path = "by-util/test_rev.rs"]
+mod test_rev;