paste: implement "-z" flag

Fixes #3637

src/uu/paste/src/paste.rs

@@ -8,6 +8,7 @@
 // spell-checker:ignore (ToDO) delim
 
 use clap::{crate_version, Arg, Command};
+use std::fmt::Display;
 use std::fs::File;
 use std::io::{stdin, stdout, BufRead, BufReader, Read, Write};
 use std::path::Path;
@@ -20,16 +21,34 @@ mod options {
     pub const DELIMITER: &str = "delimiters";
     pub const SERIAL: &str = "serial";
     pub const FILE: &str = "file";
+    pub const ZERO_TERMINATED: &str = "zero-terminated";
+}
+
+#[repr(u8)]
+#[derive(Clone, Copy)]
+enum LineEnding {
+    Newline = b'\n',
+    Nul = 0,
+}
+
+impl Display for LineEnding {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::Newline => writeln!(f),
+            Self::Nul => write!(f, "\0"),
+        }
+    }
 }
 
 // Wraps BufReader and stdin
-fn read_line<R: Read>(
+fn read_until<R: Read>(
     reader: Option<&mut BufReader<R>>,
-    buf: &mut String,
+    byte: u8,
+    buf: &mut Vec<u8>,
 ) -> std::io::Result<usize> {
     match reader {
-        Some(reader) => reader.read_line(buf),
-        None => stdin().read_line(buf),
+        Some(reader) => reader.read_until(byte, buf),
+        None => stdin().lock().read_until(byte, buf),
     }
 }
 
@@ -44,7 +63,13 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         .unwrap()
         .map(|s| s.to_owned())
         .collect();
-    paste(files, serial, delimiters)
+    let line_ending = if matches.is_present(options::ZERO_TERMINATED) {
+        LineEnding::Nul
+    } else {
+        LineEnding::Newline
+    };
+
+    paste(files, serial, delimiters, line_ending)
 }
 
 pub fn uu_app<'a>() -> Command<'a> {
@@ -74,9 +99,20 @@ pub fn uu_app<'a>() -> Command<'a> {
                 .default_value("-")
                 .value_hint(clap::ValueHint::FilePath),
         )
+        .arg(
+            Arg::new(options::ZERO_TERMINATED)
+                .long(options::ZERO_TERMINATED)
+                .short('z')
+                .help("line delimiter is NUL, not newline"),
+        )
 }
 
-fn paste(filenames: Vec<String>, serial: bool, delimiters: &str) -> UResult<()> {
+fn paste(
+    filenames: Vec<String>,
+    serial: bool,
+    delimiters: &str,
+    line_ending: LineEnding,
+) -> UResult<()> {
     let mut files = Vec::with_capacity(filenames.len());
     for name in filenames {
         let file = if name == "-" {
@@ -91,28 +127,44 @@ fn paste(filenames: Vec<String>, serial: bool, delimiters: &str) -> UResult<()>
 
     let delimiters: Vec<char> = unescape(delimiters).chars().collect();
     let mut delim_count = 0;
+    let mut delim_length = 1;
     let stdout = stdout();
     let mut stdout = stdout.lock();
 
-    let mut output = String::new();
+    let mut output = Vec::new();
     if serial {
         for file in &mut files {
             output.clear();
             loop {
-                match read_line(file.as_mut(), &mut output) {
+                match read_until(file.as_mut(), line_ending as u8, &mut output) {
                     Ok(0) => break,
                     Ok(_) => {
-                        if output.ends_with('\n') {
+                        if output.ends_with(&[line_ending as u8]) {
                             output.pop();
                         }
-                        output.push(delimiters[delim_count % delimiters.len()]);
+                        // a buffer of length four is large enough to encode any char
+                        let mut buffer = [0; 4];
+                        let ch =
+                            delimiters[delim_count % delimiters.len()].encode_utf8(&mut buffer);
+                        delim_length = ch.len();
+
+                        for byte in buffer.iter().take(delim_length) {
+                            output.push(*byte);
+                        }
                     }
                     Err(e) => return Err(e.map_err_context(String::new)),
                 }
                 delim_count += 1;
             }
-            output.pop();
-            writeln!(stdout, "{}", output)?;
+            // remove final delimiter
+            output.truncate(output.len() - delim_length);
+
+            write!(
+                stdout,
+                "{}{}",
+                String::from_utf8_lossy(&output),
+                line_ending
+            )?;
         }
     } else {
         let mut eof = vec![false; files.len()];
@@ -123,28 +175,42 @@ fn paste(filenames: Vec<String>, serial: bool, delimiters: &str) -> UResult<()>
                 if eof[i] {
                     eof_count += 1;
                 } else {
-                    match read_line(file.as_mut(), &mut output) {
+                    match read_until(file.as_mut(), line_ending as u8, &mut output) {
                         Ok(0) => {
                             eof[i] = true;
                             eof_count += 1;
                         }
                         Ok(_) => {
-                            if output.ends_with('\n') {
+                            if output.ends_with(&[line_ending as u8]) {
                                 output.pop();
                             }
                         }
                         Err(e) => return Err(e.map_err_context(String::new)),
                     }
                 }
-                output.push(delimiters[delim_count % delimiters.len()]);
+                // a buffer of length four is large enough to encode any char
+                let mut buffer = [0; 4];
+                let ch = delimiters[delim_count % delimiters.len()].encode_utf8(&mut buffer);
+                delim_length = ch.len();
+
+                for byte in buffer.iter().take(delim_length) {
+                    output.push(*byte);
+                }
+
                 delim_count += 1;
             }
             if files.len() == eof_count {
                 break;
             }
             // Remove final delimiter
-            output.pop();
-            writeln!(stdout, "{}", output)?;
+            output.truncate(output.len() - delim_length);
+
+            write!(
+                stdout,
+                "{}{}",
+                String::from_utf8_lossy(&output),
+                line_ending
+            )?;
             delim_count = 0;
         }
     }

tests/by-util/test_paste.rs

@@ -33,6 +33,30 @@ static EXAMPLE_DATA: &[TestData] = &[
         ins: &["a\n", "b\n"],
         out: "a\tb\n",
     },
+    TestData {
+        name: "zno-nl-1",
+        args: &["-z"],
+        ins: &["a", "b"],
+        out: "a\tb\0",
+    },
+    TestData {
+        name: "zno-nl-2",
+        args: &["-z"],
+        ins: &["a\0", "b"],
+        out: "a\tb\0",
+    },
+    TestData {
+        name: "zno-nl-3",
+        args: &["-z"],
+        ins: &["a", "b\0"],
+        out: "a\tb\0",
+    },
+    TestData {
+        name: "zno-nl-4",
+        args: &["-z"],
+        ins: &["a\0", "b\0"],
+        out: "a\tb\0",
+    },
     // Same as above, but with a two lines in each input file and the
     // addition of the -d option to make SPACE be the output
     // delimiter.
@@ -60,6 +84,30 @@ static EXAMPLE_DATA: &[TestData] = &[
         ins: &["1\na\n", "2\nb\n"],
         out: "1 2\na b\n",
     },
+    TestData {
+        name: "zno-nla1",
+        args: &["-zd", " "],
+        ins: &["1\0a", "2\0b"],
+        out: "1 2\0a b\0",
+    },
+    TestData {
+        name: "zno-nla2",
+        args: &["-zd", " "],
+        ins: &["1\0a\0", "2\0b"],
+        out: "1 2\0a b\0",
+    },
+    TestData {
+        name: "zno-nla3",
+        args: &["-zd", " "],
+        ins: &["1\0a", "2\0b\0"],
+        out: "1 2\0a b\0",
+    },
+    TestData {
+        name: "zno-nla4",
+        args: &["-zd", " "],
+        ins: &["1\0a\0", "2\0b\0"],
+        out: "1 2\0a b\0",
+    },
     TestData {
         name: "multibyte-delim",
         args: &["-d", "💣"],