Merge pull request #4696 from jeddenlea/wc

wc: streaming --files0-from and other improvements

Cargo.lock

@@ -3350,6 +3350,7 @@ dependencies = [
  "clap",
  "libc",
  "nix",
+ "thiserror",
  "unicode-width",
  "uucore",
 ]

src/uu/wc/Cargo.toml

@@ -18,6 +18,7 @@ path = "src/wc.rs"
 clap = { workspace=true }
 uucore = { workspace=true, features=["pipes"] }
 bytecount = { workspace=true }
+thiserror = { workspace=true }
 unicode-width = { workspace=true }
 
 [target.'cfg(unix)'.dependencies]

src/uu/wc/src/countable.rs

@@ -28,6 +28,7 @@ impl WordCountable for StdinLock<'_> {
         self
     }
 }
+
 impl WordCountable for File {
     type Buffered = BufReader<Self>;
 

src/uu/wc/src/wc.rs

@@ -5,59 +5,79 @@
 //  * For the full copyright and license information, please view the LICENSE
 //  * file that was distributed with this source code.
 
-// cSpell:ignore wc wc's
+// cSpell:ignore ilog wc wc's
 
 mod count_fast;
 mod countable;
 mod utf8;
 mod word_count;
-use clap::builder::ValueParser;
-use count_fast::{count_bytes_chars_and_lines_fast, count_bytes_fast};
-use countable::WordCountable;
+
+use std::{
+    borrow::{Borrow, Cow},
+    cmp::max,
+    ffi::OsString,
+    fs::{self, File},
+    io::{self, Write},
+    iter,
+    path::{Path, PathBuf},
+};
+
+use clap::{builder::ValueParser, crate_version, Arg, ArgAction, ArgMatches, Command};
+use thiserror::Error;
 use unicode_width::UnicodeWidthChar;
 use utf8::{BufReadDecoder, BufReadDecoderError};
-use uucore::{format_usage, help_about, help_usage, show};
-use word_count::{TitledWordCount, WordCount};
 
-use clap::{crate_version, Arg, ArgAction, ArgMatches, Command};
+use uucore::{
+    error::{FromIo, UError, UResult},
+    format_usage, help_about, help_usage,
+    quoting_style::{escape_name, QuotingStyle},
+    show,
+};
 
-use std::cmp::max;
-use std::error::Error;
-use std::ffi::{OsStr, OsString};
-use std::fmt::Display;
-use std::fs::{self, File};
-use std::io::{self, Read, Write};
-use std::path::PathBuf;
-
-use uucore::error::{UError, UResult, USimpleError};
-use uucore::quoting_style::{escape_name, QuotingStyle};
+use crate::{
+    count_fast::{count_bytes_chars_and_lines_fast, count_bytes_fast},
+    countable::WordCountable,
+    word_count::WordCount,
+};
 
 /// The minimum character width for formatting counts when reading from stdin.
 const MINIMUM_WIDTH: usize = 7;
 
-struct Settings {
+struct Settings<'a> {
     show_bytes: bool,
     show_chars: bool,
     show_lines: bool,
     show_words: bool,
     show_max_line_length: bool,
-    files0_from_stdin_mode: bool,
-    title_quoting_style: QuotingStyle,
+    files0_from: Option<Input<'a>>,
     total_when: TotalWhen,
 }
 
-impl Settings {
-    fn new(matches: &ArgMatches) -> Self {
-        let title_quoting_style = QuotingStyle::Shell {
-            escape: true,
-            always_quote: false,
-            show_control: false,
-        };
+impl Default for Settings<'_> {
+    fn default() -> Self {
+        // Defaults if none of -c, -m, -l, -w, nor -L are specified.
+        Self {
+            show_bytes: true,
+            show_chars: false,
+            show_lines: true,
+            show_words: true,
+            show_max_line_length: false,
+            files0_from: None,
+            total_when: TotalWhen::default(),
+        }
+    }
+}
 
-        let files0_from_stdin_mode = match matches.get_one::<String>(options::FILES0_FROM) {
-            Some(files_0_from) => files_0_from == STDIN_REPR,
-            None => false,
-        };
+impl<'a> Settings<'a> {
+    fn new(matches: &'a ArgMatches) -> Self {
+        let files0_from = matches
+            .get_one::<OsString>(options::FILES0_FROM)
+            .map(Into::into);
+
+        let total_when = matches
+            .get_one::<String>(options::TOTAL)
+            .map(Into::into)
+            .unwrap_or_default();
 
         let settings = Self {
             show_bytes: matches.get_flag(options::BYTES),
@@ -65,47 +85,39 @@ impl Settings {
             show_lines: matches.get_flag(options::LINES),
             show_words: matches.get_flag(options::WORDS),
             show_max_line_length: matches.get_flag(options::MAX_LINE_LENGTH),
-            files0_from_stdin_mode,
-            title_quoting_style,
-            total_when: matches.get_one::<String>(options::TOTAL).unwrap().into(),
+            files0_from,
+            total_when,
         };
 
-        if settings.show_bytes
-            || settings.show_chars
-            || settings.show_lines
-            || settings.show_words
-            || settings.show_max_line_length
-        {
-            return settings;
-        }
-
-        Self {
-            show_bytes: true,
-            show_chars: false,
-            show_lines: true,
-            show_words: true,
-            show_max_line_length: false,
-            files0_from_stdin_mode,
-            title_quoting_style: settings.title_quoting_style,
-            total_when: settings.total_when,
+        if settings.number_enabled() > 0 {
+            settings
+        } else {
+            Self {
+                files0_from: settings.files0_from,
+                total_when,
+                ..Default::default()
+            }
         }
     }
 
     fn number_enabled(&self) -> u32 {
-        let mut result = 0;
-        result += self.show_bytes as u32;
-        result += self.show_chars as u32;
-        result += self.show_lines as u32;
-        result += self.show_max_line_length as u32;
-        result += self.show_words as u32;
-        result
+        [
+            self.show_bytes,
+            self.show_chars,
+            self.show_lines,
+            self.show_max_line_length,
+            self.show_words,
+        ]
+        .into_iter()
+        .map(Into::<u32>::into)
+        .sum()
     }
 }
 
 const ABOUT: &str = help_about!("wc.md");
 const USAGE: &str = help_usage!("wc.md");
 
-pub mod options {
+mod options {
     pub static BYTES: &str = "bytes";
     pub static CHAR: &str = "chars";
     pub static FILES0_FROM: &str = "files0-from";
@@ -114,68 +126,202 @@ pub mod options {
     pub static TOTAL: &str = "total";
     pub static WORDS: &str = "words";
 }
-
 static ARG_FILES: &str = "files";
 static STDIN_REPR: &str = "-";
 
-enum StdinKind {
-    /// Stdin specified on command-line with "-".
-    Explicit,
+static QS_ESCAPE: &QuotingStyle = &QuotingStyle::Shell {
+    escape: true,
+    always_quote: false,
+    show_control: false,
+};
+static QS_QUOTE_ESCAPE: &QuotingStyle = &QuotingStyle::Shell {
+    escape: true,
+    always_quote: true,
+    show_control: false,
+};
 
-    /// Stdin implicitly specified on command-line by not passing any positional argument.
+/// Supported inputs.
+#[derive(Debug)]
+enum Inputs<'a> {
+    /// Default Standard input, i.e. no arguments.
+    Stdin,
+    /// Files; "-" means stdin, possibly multiple times!
+    Paths(Vec<Input<'a>>),
+    /// --files0-from; "-" means stdin.
+    Files0From(Input<'a>),
+}
+
+impl<'a> Inputs<'a> {
+    fn new(matches: &'a ArgMatches) -> UResult<Self> {
+        let arg_files = matches.get_many::<OsString>(ARG_FILES);
+        let files0_from = matches.get_one::<OsString>(options::FILES0_FROM);
+
+        match (arg_files, files0_from) {
+            (None, None) => Ok(Self::Stdin),
+            (Some(files), None) => Ok(Self::Paths(files.map(Into::into).collect())),
+            (None, Some(path)) => {
+                // If path is a file, and the file isn't too large, we'll load it ahead
+                // of time. Every path within the file will have its length checked to
+                // hopefully better align the output columns.
+                let input = Input::from(path);
+                match input.try_as_files0()? {
+                    Some(paths) => Ok(Self::Paths(paths)),
+                    None => Ok(Self::Files0From(input)),
+                }
+            }
+            (Some(_), Some(_)) => Err(WcError::FilesDisabled.into()),
+        }
+    }
+
+    // Creates an iterator which yields values borrowed from the command line arguments.
+    // Returns an error if the file specified in --files0-from cannot be opened.
+    fn try_iter(
+        &'a self,
+        settings: &'a Settings<'a>,
+    ) -> UResult<impl Iterator<Item = InputIterItem<'a>>> {
+        let base: Box<dyn Iterator<Item = _>> = match self {
+            Self::Stdin => Box::new(iter::once(Ok(Input::Stdin(StdinKind::Implicit)))),
+            Self::Paths(inputs) => Box::new(inputs.iter().map(|i| Ok(i.as_borrowed()))),
+            Self::Files0From(input) => match input {
+                Input::Path(path) => Box::new(files0_iter_file(path)?),
+                Input::Stdin(_) => Box::new(files0_iter_stdin()),
+            },
+        };
+
+        // The 1-based index of each yielded item must be tracked for error reporting.
+        let mut with_idx = base.enumerate().map(|(i, v)| (i + 1, v));
+        let files0_from_path = settings.files0_from.as_ref().map(|p| p.as_borrowed());
+
+        let iter = iter::from_fn(move || {
+            let (idx, next) = with_idx.next()?;
+            match next {
+                // filter zero length file names...
+                Ok(Input::Path(p)) if p.as_os_str().is_empty() => Some(Err({
+                    let maybe_ctx = files0_from_path.as_ref().map(|p| (p, idx));
+                    WcError::zero_len(maybe_ctx).into()
+                })),
+                _ => Some(next),
+            }
+        });
+        Ok(iter)
+    }
+}
+
+#[derive(Clone, Copy, Debug)]
+enum StdinKind {
+    /// Specified on command-line with "-" (STDIN_REPR)
+    Explicit,
+    /// Implied by the lack of any arguments
     Implicit,
 }
 
-/// Supported inputs.
-enum Input {
-    /// A regular file.
-    Path(PathBuf),
-
-    /// Standard input.
+/// Represents a single input, either to be counted or processed for other files names via
+/// --files0-from.
+#[derive(Debug)]
+enum Input<'a> {
+    Path(Cow<'a, Path>),
     Stdin(StdinKind),
 }
 
-impl From<&OsStr> for Input {
-    fn from(input: &OsStr) -> Self {
-        if input == STDIN_REPR {
+impl From<PathBuf> for Input<'_> {
+    fn from(p: PathBuf) -> Self {
+        if p.as_os_str() == STDIN_REPR {
             Self::Stdin(StdinKind::Explicit)
         } else {
-            Self::Path(input.into())
+            Self::Path(Cow::Owned(p))
         }
     }
 }
 
-impl Input {
-    /// Converts input to title that appears in stats.
-    fn to_title(&self, quoting_style: &QuotingStyle) -> Option<String> {
+impl<'a, T: AsRef<Path> + ?Sized> From<&'a T> for Input<'a> {
+    fn from(p: &'a T) -> Self {
+        let p = p.as_ref();
+        if p.as_os_str() == STDIN_REPR {
+            Self::Stdin(StdinKind::Explicit)
+        } else {
+            Self::Path(Cow::Borrowed(p))
+        }
+    }
+}
+
+impl<'a> Input<'a> {
+    /// Translates Path(Cow::Owned(_)) to Path(Cow::Borrowed(_)).
+    fn as_borrowed(&'a self) -> Self {
         match self {
-            Self::Path(path) => Some(escape_name(&path.clone().into_os_string(), quoting_style)),
-            Self::Stdin(StdinKind::Explicit) => {
-                Some(escape_name(OsStr::new(STDIN_REPR), quoting_style))
-            }
+            Self::Path(p) => Self::Path(Cow::Borrowed(p.borrow())),
+            Self::Stdin(k) => Self::Stdin(*k),
+        }
+    }
+
+    /// Converts input to title that appears in stats.
+    fn to_title(&self) -> Option<Cow<str>> {
+        match self {
+            Self::Path(path) => Some(match path.to_str() {
+                Some(s) if !s.contains('\n') => Cow::Borrowed(s),
+                _ => Cow::Owned(escape_name(path.as_os_str(), QS_ESCAPE)),
+            }),
+            Self::Stdin(StdinKind::Explicit) => Some(Cow::Borrowed(STDIN_REPR)),
             Self::Stdin(StdinKind::Implicit) => None,
         }
     }
 
-    fn path_display(&self, quoting_style: &QuotingStyle) -> String {
+    /// Converts input into the form that appears in errors.
+    fn path_display(&self) -> String {
         match self {
-            Self::Path(path) => escape_name(&path.clone().into_os_string(), quoting_style),
-            Self::Stdin(_) => escape_name(OsStr::new("standard input"), quoting_style),
+            Self::Path(path) => escape_name(path.as_os_str(), QS_ESCAPE),
+            Self::Stdin(_) => String::from("standard input"),
+        }
+    }
+
+    /// When given --files0-from, we may be given a path or stdin. Either may be a stream or
+    /// a regular file. If given a file less than 10 MiB, it will be consumed and turned into
+    /// a Vec of Input::Paths which can be scanned to determine the widths of the columns that
+    /// will ultimately be printed.
+    fn try_as_files0(&self) -> UResult<Option<Vec<Input<'static>>>> {
+        match self {
+            Self::Path(path) => match fs::metadata(path) {
+                Ok(meta) if meta.is_file() && meta.len() <= (10 << 20) => Ok(Some(
+                    files0_iter_file(path)?.collect::<Result<Vec<_>, _>>()?,
+                )),
+                _ => Ok(None),
+            },
+            Self::Stdin(_) if is_stdin_small_file() => {
+                Ok(Some(files0_iter_stdin().collect::<Result<Vec<_>, _>>()?))
+            }
+            Self::Stdin(_) => Ok(None),
         }
     }
 }
 
+#[cfg(unix)]
+fn is_stdin_small_file() -> bool {
+    use std::os::unix::io::{AsRawFd, FromRawFd};
+    // Safety: we'll rely on Rust to give us a valid RawFd for stdin with which we can attempt to
+    // open a File, but only for the sake of fetching .metadata().  ManuallyDrop will ensure we
+    // don't do anything else to the FD if anything unexpected happens.
+    let f = std::mem::ManuallyDrop::new(unsafe { File::from_raw_fd(io::stdin().as_raw_fd()) });
+    matches!(f.metadata(), Ok(meta) if meta.is_file() && meta.len() <= (10 << 20))
+}
+
+#[cfg(not(unix))]
+// Windows presents a piped stdin as a "normal file" with a length equal to however many bytes
+// have been buffered at the time it's checked. To be safe, we must never assume it's a file.
+fn is_stdin_small_file() -> bool {
+    false
+}
+
 /// When to show the "total" line
-#[derive(PartialEq)]
+#[derive(Clone, Copy, Default, PartialEq)]
 enum TotalWhen {
+    #[default]
     Auto,
     Always,
     Only,
     Never,
 }
 
-impl From<&String> for TotalWhen {
-    fn from(s: &String) -> Self {
+impl<T: AsRef<str>> From<T> for TotalWhen {
+    fn from(s: T) -> Self {
         match s.as_ref() {
             "auto" => Self::Auto,
             "always" => Self::Always,
@@ -196,33 +342,36 @@ impl TotalWhen {
     }
 }
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 enum WcError {
-    FilesDisabled(String),
-    StdinReprNotAllowed(String),
+    #[error("file operands cannot be combined with --files0-from")]
+    FilesDisabled,
+    #[error("when reading file names from stdin, no file name of '-' allowed")]
+    StdinReprNotAllowed,
+    #[error("invalid zero-length file name")]
+    ZeroLengthFileName,
+    #[error("{path}:{idx}: invalid zero-length file name")]
+    ZeroLengthFileNameCtx { path: Cow<'static, str>, idx: usize },
+}
+
+impl WcError {
+    fn zero_len(ctx: Option<(&Input, usize)>) -> Self {
+        match ctx {
+            Some((input, idx)) => {
+                let path = match input {
+                    Input::Stdin(_) => STDIN_REPR.into(),
+                    Input::Path(path) => escape_name(path.as_os_str(), QS_ESCAPE).into(),
+                };
+                Self::ZeroLengthFileNameCtx { path, idx }
+            }
+            None => Self::ZeroLengthFileName,
+        }
+    }
 }
 
 impl UError for WcError {
-    fn code(&self) -> i32 {
-        match self {
-            Self::FilesDisabled(_) | Self::StdinReprNotAllowed(_) => 1,
-        }
-    }
-
     fn usage(&self) -> bool {
-        matches!(self, Self::FilesDisabled(_))
-    }
-}
-
-impl Error for WcError {}
-
-impl Display for WcError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            Self::FilesDisabled(message) | Self::StdinReprNotAllowed(message) => {
-                write!(f, "{message}")
-            }
-        }
+        matches!(self, Self::FilesDisabled)
     }
 }
 
@@ -230,9 +379,8 @@ impl Display for WcError {
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uu_app().try_get_matches_from(args)?;
 
-    let inputs = inputs(&matches)?;
-
     let settings = Settings::new(&matches);
+    let inputs = Inputs::new(&matches)?;
 
     wc(&inputs, &settings)
 }
@@ -261,11 +409,12 @@ pub fn uu_app() -> Command {
             Arg::new(options::FILES0_FROM)
                 .long(options::FILES0_FROM)
                 .value_name("F")
-                .help(
-                    "read input from the files specified by
-    NUL-terminated names in file F;
-    If F is - then read names from standard input",
-                )
+                .help(concat!(
+                    "read input from the files specified by\n",
+                    "  NUL-terminated names in file F;\n",
+                    "  If F is - then read names from standard input"
+                ))
+                .value_parser(ValueParser::os_string())
                 .value_hint(clap::ValueHint::FilePath),
         )
         .arg(
@@ -286,10 +435,12 @@ pub fn uu_app() -> Command {
             Arg::new(options::TOTAL)
                 .long(options::TOTAL)
                 .value_parser(["auto", "always", "only", "never"])
-                .default_value("auto")
-                .hide_default_value(true)
                 .value_name("WHEN")
-                .help("when to print a line with total counts"),
+                .hide_possible_values(true)
+                .help(concat!(
+                    "when to print a line with total counts;\n",
+                    "  WHEN can be: auto, always, only, never"
+                )),
         )
         .arg(
             Arg::new(options::WORDS)
@@ -306,47 +457,6 @@ pub fn uu_app() -> Command {
         )
 }
 
-fn inputs(matches: &ArgMatches) -> UResult<Vec<Input>> {
-    match matches.get_many::<OsString>(ARG_FILES) {
-        Some(os_values) => {
-            if matches.contains_id(options::FILES0_FROM) {
-                return Err(WcError::FilesDisabled(
-                    "file operands cannot be combined with --files0-from".into(),
-                )
-                .into());
-            }
-
-            Ok(os_values.map(|s| Input::from(s.as_os_str())).collect())
-        }
-        None => match matches.get_one::<String>(options::FILES0_FROM) {
-            Some(files_0_from) => create_paths_from_files0(files_0_from),
-            None => Ok(vec![Input::Stdin(StdinKind::Implicit)]),
-        },
-    }
-}
-
-fn create_paths_from_files0(files_0_from: &str) -> UResult<Vec<Input>> {
-    let mut paths = String::new();
-    let read_from_stdin = files_0_from == STDIN_REPR;
-
-    if read_from_stdin {
-        io::stdin().lock().read_to_string(&mut paths)?;
-    } else {
-        File::open(files_0_from)?.read_to_string(&mut paths)?;
-    }
-
-    let paths: Vec<&str> = paths.split_terminator('\0').collect();
-
-    if read_from_stdin && paths.contains(&STDIN_REPR) {
-        return Err(WcError::StdinReprNotAllowed(
-            "when reading file names from stdin, no file name of '-' allowed".into(),
-        )
-        .into());
-    }
-
-    Ok(paths.iter().map(OsStr::new).map(Input::from).collect())
-}
-
 fn word_count_from_reader<T: WordCountable>(
     mut reader: T,
     settings: &Settings,
@@ -528,182 +638,250 @@ enum CountResult {
     Failure(io::Error),
 }
 
-/// If we fail opening a file we only show the error. If we fail reading it
-/// we show a count for what we managed to read.
+/// If we fail opening a file, we only show the error. If we fail reading the
+/// file, we show a count for what we managed to read.
 ///
-/// Therefore the reading implementations always return a total and sometimes
+/// Therefore, the reading implementations always return a total and sometimes
 /// return an error: (WordCount, Option<io::Error>).
-fn word_count_from_input(input: &Input, settings: &Settings) -> CountResult {
-    match input {
-        Input::Stdin(_) => {
-            let stdin = io::stdin();
-            let stdin_lock = stdin.lock();
-            let count = word_count_from_reader(stdin_lock, settings);
-            match count {
-                (total, Some(error)) => CountResult::Interrupted(total, error),
-                (total, None) => CountResult::Success(total),
-            }
-        }
+fn word_count_from_input(input: &Input<'_>, settings: &Settings) -> CountResult {
+    let (total, maybe_err) = match input {
+        Input::Stdin(_) => word_count_from_reader(io::stdin().lock(), settings),
         Input::Path(path) => match File::open(path) {
-            Err(error) => CountResult::Failure(error),
-            Ok(file) => match word_count_from_reader(file, settings) {
-                (total, Some(error)) => CountResult::Interrupted(total, error),
-                (total, None) => CountResult::Success(total),
-            },
+            Ok(f) => word_count_from_reader(f, settings),
+            Err(err) => return CountResult::Failure(err),
         },
+    };
+    match maybe_err {
+        None => CountResult::Success(total),
+        Some(err) => CountResult::Interrupted(total, err),
     }
 }
 
 /// Compute the number of digits needed to represent all counts in all inputs.
 ///
-/// `inputs` may include zero or more [`Input::Stdin`] entries, each of
-/// which represents reading from `stdin`. The presence of any such
-/// entry causes this function to return a width that is at least
-/// [`MINIMUM_WIDTH`].
+/// For [`Inputs::Stdin`], [`MINIMUM_WIDTH`] is returned, unless there is only one counter number
+/// to be printed, in which case 1 is returned.
 ///
-/// If `input` is empty, or if only one number needs to be printed (for just
-/// one file) then this function is optimized to return 1 without making any
-/// calls to get file metadata.
+/// For [`Inputs::Files0From`], [`MINIMUM_WIDTH`] is returned.
 ///
-/// If file metadata could not be read from any of the [`Input::Path`] input,
-/// that input does not affect number width computation
+/// An [`Inputs::Paths`] may include zero or more "-" entries, each of which represents reading
+/// from `stdin`. The presence of any such entry causes this function to return a width that is at
+/// least [`MINIMUM_WIDTH`].
 ///
-/// Otherwise, the file sizes in the file metadata are summed and the number of
-/// digits in that total size is returned as the number width
+/// If an [`Inputs::Paths`] contains only one path and only one number needs to be printed then
+/// this function is optimized to return 1 without making any calls to get file metadata.
 ///
-/// To mirror GNU wc's behavior a special case is added. If --files0-from is
-/// used and input is read from stdin and there is only one calculation enabled
-/// columns will not be aligned. This is not exactly GNU wc's behavior, but it
-/// is close enough to pass the GNU test suite.
-fn compute_number_width(inputs: &[Input], settings: &Settings) -> usize {
-    if inputs.is_empty()
-        || (inputs.len() == 1 && settings.number_enabled() == 1)
-        || (settings.files0_from_stdin_mode && settings.number_enabled() == 1)
-    {
-        return 1;
-    }
-
-    let mut minimum_width = 1;
-    let mut total = 0;
-
-    for input in inputs {
-        match input {
-            Input::Stdin(_) => {
-                minimum_width = MINIMUM_WIDTH;
+/// If file metadata could not be read from any of the [`Input::Path`] input, that input does not
+/// affect number width computation.  Otherwise, the file sizes from the files' metadata are summed
+/// and the number of digits in that total size is returned.
+fn compute_number_width(inputs: &Inputs, settings: &Settings) -> usize {
+    match inputs {
+        Inputs::Stdin if settings.number_enabled() == 1 => 1,
+        Inputs::Stdin => MINIMUM_WIDTH,
+        Inputs::Files0From(_) => 1,
+        Inputs::Paths(inputs) => {
+            if settings.number_enabled() == 1 && inputs.len() == 1 {
+                return 1;
             }
-            Input::Path(path) => {
-                if let Ok(meta) = fs::metadata(path) {
-                    if meta.is_file() {
-                        total += meta.len();
-                    } else {
-                        minimum_width = MINIMUM_WIDTH;
+
+            let mut minimum_width = 1;
+            let mut total: u64 = 0;
+            for input in inputs.iter() {
+                match input {
+                    Input::Stdin(_) => minimum_width = MINIMUM_WIDTH,
+                    Input::Path(path) => {
+                        if let Ok(meta) = fs::metadata(path) {
+                            if meta.is_file() {
+                                total += meta.len();
+                            } else {
+                                minimum_width = MINIMUM_WIDTH;
+                            }
+                        }
                     }
                 }
             }
+
+            if total == 0 {
+                minimum_width
+            } else {
+                let total_width = (1 + ilog10_u64(total))
+                    .try_into()
+                    .expect("ilog of a u64 should fit into a usize");
+                max(total_width, minimum_width)
+            }
         }
     }
-
-    max(minimum_width, total.to_string().len())
 }
 
-fn wc(inputs: &[Input], settings: &Settings) -> UResult<()> {
+type InputIterItem<'a> = Result<Input<'a>, Box<dyn UError>>;
+
+/// To be used with `--files0-from=-`, this applies a filter on the results of files0_iter to
+/// translate '-' into the appropriate error.
+fn files0_iter_stdin<'a>() -> impl Iterator<Item = InputIterItem<'a>> {
+    files0_iter(io::stdin().lock(), STDIN_REPR.into()).map(|i| match i {
+        Ok(Input::Stdin(_)) => Err(WcError::StdinReprNotAllowed.into()),
+        _ => i,
+    })
+}
+
+fn files0_iter_file<'a>(path: &Path) -> UResult<impl Iterator<Item = InputIterItem<'a>>> {
+    match File::open(path) {
+        Ok(f) => Ok(files0_iter(f, path.into())),
+        Err(e) => Err(e.map_err_context(|| {
+            format!(
+                "cannot open {} for reading",
+                escape_name(path.as_os_str(), QS_QUOTE_ESCAPE)
+            )
+        })),
+    }
+}
+
+fn files0_iter<'a>(
+    r: impl io::Read + 'static,
+    err_path: OsString,
+) -> impl Iterator<Item = InputIterItem<'a>> {
+    use std::io::BufRead;
+    let mut i = Some(
+        io::BufReader::new(r)
+            .split(b'\0')
+            .map(move |res| match res {
+                Ok(p) if p == STDIN_REPR.as_bytes() => Ok(Input::Stdin(StdinKind::Explicit)),
+                Ok(p) => {
+                    // On Unix systems, OsStrings are just strings of bytes, not necessarily UTF-8.
+                    #[cfg(unix)]
+                    {
+                        use std::os::unix::ffi::OsStringExt;
+                        Ok(Input::Path(PathBuf::from(OsString::from_vec(p)).into()))
+                    }
+
+                    // ...Windows does not, we must go through Strings.
+                    #[cfg(not(unix))]
+                    {
+                        let s = String::from_utf8(p)
+                            .map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
+                        Ok(Input::Path(PathBuf::from(s).into()))
+                    }
+                }
+                Err(e) => Err(e.map_err_context(|| {
+                    format!("{}: read error", escape_name(&err_path, QS_ESCAPE))
+                }) as Box<dyn UError>),
+            }),
+    );
+    // Loop until there is an error; yield that error and then nothing else.
+    std::iter::from_fn(move || {
+        let next = i.as_mut().and_then(Iterator::next);
+        if matches!(next, Some(Err(_)) | None) {
+            i = None;
+        }
+        next
+    })
+}
+
+fn wc(inputs: &Inputs, settings: &Settings) -> UResult<()> {
     let mut total_word_count = WordCount::default();
+    let mut num_inputs: usize = 0;
 
-    let (number_width, are_stats_visible, total_row_title) =
-        if settings.total_when == TotalWhen::Only {
-            (1, false, None)
-        } else {
-            let number_width = compute_number_width(inputs, settings);
-            let title = Some(String::from("total"));
+    let (number_width, are_stats_visible) = match settings.total_when {
+        TotalWhen::Only => (1, false),
+        _ => (compute_number_width(inputs, settings), true),
+    };
 
-            (number_width, true, title)
+    for maybe_input in inputs.try_iter(settings)? {
+        num_inputs += 1;
+
+        let input = match maybe_input {
+            Ok(input) => input,
+            Err(err) => {
+                show!(err);
+                continue;
+            }
         };
 
-    let is_total_row_visible = settings.total_when.is_total_row_visible(inputs.len());
-
-    for input in inputs {
-        let word_count = match word_count_from_input(input, settings) {
+        let word_count = match word_count_from_input(&input, settings) {
             CountResult::Success(word_count) => word_count,
-            CountResult::Interrupted(word_count, error) => {
-                show!(USimpleError::new(
-                    1,
-                    format!(
-                        "{}: {}",
-                        input.path_display(&settings.title_quoting_style),
-                        error
-                    )
-                ));
+            CountResult::Interrupted(word_count, err) => {
+                show!(err.map_err_context(|| input.path_display()));
                 word_count
             }
-            CountResult::Failure(error) => {
-                show!(USimpleError::new(
-                    1,
-                    format!(
-                        "{}: {}",
-                        input.path_display(&settings.title_quoting_style),
-                        error
-                    )
-                ));
+            CountResult::Failure(err) => {
+                show!(err.map_err_context(|| input.path_display()));
                 continue;
             }
         };
         total_word_count += word_count;
-        let result = word_count.with_title(input.to_title(&settings.title_quoting_style));
-
         if are_stats_visible {
-            if let Err(err) = print_stats(settings, &result, number_width) {
-                show!(USimpleError::new(
-                    1,
-                    format!(
-                        "failed to print result for {}: {}",
-                        &result.title.unwrap_or_else(|| String::from("<stdin>")),
-                        err,
-                    ),
-                ));
+            let maybe_title = input.to_title();
+            let maybe_title_str = maybe_title.as_deref();
+            if let Err(err) = print_stats(settings, &word_count, maybe_title_str, number_width) {
+                let title = maybe_title_str.unwrap_or("<stdin>");
+                show!(err.map_err_context(|| format!("failed to print result for {title}")));
             }
         }
     }
 
-    if is_total_row_visible {
-        let total_result = total_word_count.with_title(total_row_title);
-        if let Err(err) = print_stats(settings, &total_result, number_width) {
-            show!(USimpleError::new(
-                1,
-                format!("failed to print total: {err}")
-            ));
+    if settings.total_when.is_total_row_visible(num_inputs) {
+        let title = are_stats_visible.then_some("total");
+        if let Err(err) = print_stats(settings, &total_word_count, title, number_width) {
+            show!(err.map_err_context(|| "failed to print total".into()));
         }
     }
 
-    // Although this appears to be returning `Ok`, the exit code may
-    // have been set to a non-zero value by a call to `show!()` above.
+    // Although this appears to be returning `Ok`, the exit code may have been set to a non-zero
+    // value by a call to `record_error!()` above.
     Ok(())
 }
 
 fn print_stats(
     settings: &Settings,
-    result: &TitledWordCount,
+    result: &WordCount,
+    title: Option<&str>,
     number_width: usize,
 ) -> io::Result<()> {
-    let mut columns = Vec::new();
+    let mut stdout = io::stdout().lock();
 
-    if settings.show_lines {
-        columns.push(format!("{:1$}", result.count.lines, number_width));
-    }
-    if settings.show_words {
-        columns.push(format!("{:1$}", result.count.words, number_width));
-    }
-    if settings.show_chars {
-        columns.push(format!("{:1$}", result.count.chars, number_width));
-    }
-    if settings.show_bytes {
-        columns.push(format!("{:1$}", result.count.bytes, number_width));
-    }
-    if settings.show_max_line_length {
-        columns.push(format!("{:1$}", result.count.max_line_length, number_width));
-    }
-    if let Some(title) = &result.title {
-        columns.push(title.clone());
+    let maybe_cols = [
+        (settings.show_lines, result.lines),
+        (settings.show_words, result.words),
+        (settings.show_chars, result.chars),
+        (settings.show_bytes, result.bytes),
+        (settings.show_max_line_length, result.max_line_length),
+    ];
+
+    let mut space = "";
+    for (_, num) in maybe_cols.iter().filter(|(show, _)| *show) {
+        write!(stdout, "{space}{num:number_width$}")?;
+        space = " ";
     }
 
-    writeln!(io::stdout().lock(), "{}", columns.join(" "))
+    if let Some(title) = title {
+        writeln!(stdout, "{space}{title}")
+    } else {
+        writeln!(stdout)
+    }
+}
+
+// TODO: remove and just use usize::ilog10 once the MSRV is >= 1.67.
+fn ilog10_u64(mut u: u64) -> u32 {
+    if u == 0 {
+        panic!("cannot compute log of 0")
+    }
+    let mut log = 0;
+    if u >= 10_000_000_000 {
+        log += 10;
+        u /= 10_000_000_000;
+    }
+    if u >= 100_000 {
+        log += 5;
+        u /= 100_000;
+    }
+    // Rust's standard library in versions >= 1.67 does something even more clever than this, but
+    // this should work just fine for the time being.
+    log + match u {
+        1..=9 => 0,
+        10..=99 => 1,
+        100..=999 => 2,
+        1000..=9999 => 3,
+        10000..=99999 => 4,
+        _ => unreachable!(),
+    }
 }

src/uu/wc/src/word_count.rs

@@ -29,19 +29,3 @@ impl AddAssign for WordCount {
         *self = *self + other;
     }
 }
-
-impl WordCount {
-    pub fn with_title(self, title: Option<String>) -> TitledWordCount {
-        TitledWordCount { title, count: self }
-    }
-}
-
-/// This struct supplements the actual word count with an optional title that is
-/// displayed to the user at the end of the program.
-/// The reason we don't simply include title in the `WordCount` struct is that
-/// it would result in unnecessary copying of `String`.
-#[derive(Debug, Default, Clone)]
-pub struct TitledWordCount {
-    pub title: Option<String>,
-    pub count: WordCount,
-}

tests/by-util/test_wc.rs

@@ -268,12 +268,16 @@ fn test_multiple_default() {
             "lorem_ipsum.txt",
             "moby_dick.txt",
             "alice_in_wonderland.txt",
+            "alice in wonderland.txt",
         ])
         .run()
-        .stdout_is(
-            "  13  109  772 lorem_ipsum.txt\n  18  204 1115 moby_dick.txt\n   5   57  302 \
-             alice_in_wonderland.txt\n  36  370 2189 total\n",
-        );
+        .stdout_is(concat!(
+            "  13  109  772 lorem_ipsum.txt\n",
+            "  18  204 1115 moby_dick.txt\n",
+            "   5   57  302 alice_in_wonderland.txt\n",
+            "   5   57  302 alice in wonderland.txt\n",
+            "  41  427 2491 total\n",
+        ));
 }
 
 /// Test for an empty file.
@@ -352,17 +356,24 @@ fn test_file_bytes_dictate_width() {
     new_ucmd!()
         .args(&["-lwc", "alice_in_wonderland.txt", "lorem_ipsum.txt"])
         .run()
-        .stdout_is(
-            "   5   57  302 alice_in_wonderland.txt\n  13  109  772 \
-                    lorem_ipsum.txt\n  18  166 1074 total\n",
-        );
+        .stdout_is(concat!(
+            "   5   57  302 alice_in_wonderland.txt\n",
+            "  13  109  772 lorem_ipsum.txt\n",
+            "  18  166 1074 total\n",
+        ));
 
     // . is a directory, so minimum_width should get set to 7
     #[cfg(not(windows))]
-    const STDOUT: &str = "      0       0       0 emptyfile.txt\n      0       0       0 \
-                          .\n      0       0       0 total\n";
+    const STDOUT: &str = concat!(
+        "      0       0       0 emptyfile.txt\n",
+        "      0       0       0 .\n",
+        "      0       0       0 total\n",
+    );
     #[cfg(windows)]
-    const STDOUT: &str = "      0       0       0 emptyfile.txt\n      0       0       0 total\n";
+    const STDOUT: &str = concat!(
+        "      0       0       0 emptyfile.txt\n",
+        "      0       0       0 total\n",
+    );
     new_ucmd!()
         .args(&["-lwc", "emptyfile.txt", "."])
         .run()
@@ -375,7 +386,7 @@ fn test_read_from_directory_error() {
     #[cfg(not(windows))]
     const STDERR: &str = ".: Is a directory";
     #[cfg(windows)]
-    const STDERR: &str = ".: Access is denied";
+    const STDERR: &str = ".: Permission denied";
 
     #[cfg(not(windows))]
     const STDOUT: &str = "      0       0       0 .\n";
@@ -392,15 +403,10 @@ fn test_read_from_directory_error() {
 /// Test that getting counts from nonexistent file is an error.
 #[test]
 fn test_read_from_nonexistent_file() {
-    #[cfg(not(windows))]
-    const MSG: &str = "bogusfile: No such file or directory";
-    #[cfg(windows)]
-    const MSG: &str = "bogusfile: The system cannot find the file specified";
     new_ucmd!()
         .args(&["bogusfile"])
         .fails()
-        .stderr_contains(MSG)
-        .stdout_is("");
+        .stderr_only("wc: bogusfile: No such file or directory\n");
 }
 
 #[test]
@@ -424,13 +430,30 @@ fn test_files0_disabled_files_argument() {
 
 #[test]
 fn test_files0_from() {
+    // file
     new_ucmd!()
         .args(&["--files0-from=files0_list.txt"])
         .run()
-        .stdout_is(
-            "  13  109  772 lorem_ipsum.txt\n  18  204 1115 moby_dick.txt\n   5   57  302 \
-             alice_in_wonderland.txt\n  36  370 2189 total\n",
-        );
+        .success()
+        .stdout_is(concat!(
+            "  13  109  772 lorem_ipsum.txt\n",
+            "  18  204 1115 moby_dick.txt\n",
+            "   5   57  302 alice_in_wonderland.txt\n",
+            "  36  370 2189 total\n",
+        ));
+
+    // stream
+    new_ucmd!()
+        .args(&["--files0-from=-"])
+        .pipe_in_fixture("files0_list.txt")
+        .run()
+        .success()
+        .stdout_is(concat!(
+            "13 109 772 lorem_ipsum.txt\n",
+            "18 204 1115 moby_dick.txt\n",
+            "5 57 302 alice_in_wonderland.txt\n",
+            "36 370 2189 total\n",
+        ));
 }
 
 #[test]
@@ -439,7 +462,7 @@ fn test_files0_from_with_stdin() {
         .args(&["--files0-from=-"])
         .pipe_in("lorem_ipsum.txt")
         .run()
-        .stdout_is(" 13 109 772 lorem_ipsum.txt\n");
+        .stdout_is("13 109 772 lorem_ipsum.txt\n");
 }
 
 #[test]
@@ -448,10 +471,12 @@ fn test_files0_from_with_stdin_in_file() {
         .args(&["--files0-from=files0_list_with_stdin.txt"])
         .pipe_in_fixture("alice_in_wonderland.txt")
         .run()
-        .stdout_is(
-            "     13     109     772 lorem_ipsum.txt\n     18     204    1115 moby_dick.txt\n      5      57     302 \
-             -\n     36     370    2189 total\n",
-        );
+        .stdout_is(concat!(
+            "     13     109     772 lorem_ipsum.txt\n",
+            "     18     204    1115 moby_dick.txt\n",
+            "      5      57     302 -\n", // alice_in_wonderland.txt
+            "     36     370    2189 total\n",
+        ));
 }
 
 #[test]
@@ -530,3 +555,152 @@ fn test_total_only() {
         .run()
         .stdout_is("31 313 1887\n");
 }
+
+#[test]
+fn test_zero_length_files() {
+    // A trailing zero is ignored, but otherwise empty file names are an error...
+    const LIST: &str = "\0moby_dick.txt\0\0alice_in_wonderland.txt\0\0lorem_ipsum.txt\0";
+
+    // Try with and without the last \0
+    for l in [LIST.len(), LIST.len() - 1] {
+        new_ucmd!()
+            .args(&["--files0-from=-"])
+            .pipe_in(&LIST[..l])
+            .run()
+            .failure()
+            .stdout_is(concat!(
+                "18 204 1115 moby_dick.txt\n",
+                "5 57 302 alice_in_wonderland.txt\n",
+                "13 109 772 lorem_ipsum.txt\n",
+                "36 370 2189 total\n",
+            ))
+            .stderr_is(concat!(
+                "wc: -:1: invalid zero-length file name\n",
+                "wc: -:3: invalid zero-length file name\n",
+                "wc: -:5: invalid zero-length file name\n",
+            ));
+    }
+
+    // But, just as important, a zero-length file name may still be at the end...
+    new_ucmd!()
+        .args(&["--files0-from=-"])
+        .pipe_in(
+            LIST.as_bytes()
+                .iter()
+                .chain(b"\0")
+                .copied()
+                .collect::<Vec<_>>(),
+        )
+        .run()
+        .failure()
+        .stdout_is(concat!(
+            "18 204 1115 moby_dick.txt\n",
+            "5 57 302 alice_in_wonderland.txt\n",
+            "13 109 772 lorem_ipsum.txt\n",
+            "36 370 2189 total\n",
+        ))
+        .stderr_is(concat!(
+            "wc: -:1: invalid zero-length file name\n",
+            "wc: -:3: invalid zero-length file name\n",
+            "wc: -:5: invalid zero-length file name\n",
+            "wc: -:7: invalid zero-length file name\n",
+        ));
+}
+
+#[test]
+fn test_files0_errors_quoting() {
+    new_ucmd!()
+        .args(&["--files0-from=files0 with nonexistent.txt"])
+        .run()
+        .failure()
+        .stderr_is(concat!(
+            "wc: this_file_does_not_exist.txt: No such file or directory\n",
+            "wc: 'files0 with nonexistent.txt':2: invalid zero-length file name\n",
+            "wc: 'this file does not exist.txt': No such file or directory\n",
+            "wc: \"this files doesn't exist either.txt\": No such file or directory\n",
+        ))
+        .stdout_is("0 0 0 total\n");
+}
+
+#[test]
+fn test_files0_progressive_stream() {
+    use std::process::Stdio;
+    // You should be able to run wc and have a back-and-forth exchange with wc...
+    let mut child = new_ucmd!()
+        .args(&["--files0-from=-"])
+        .set_stdin(Stdio::piped())
+        .set_stdout(Stdio::piped())
+        .set_stderr(Stdio::piped())
+        .run_no_wait();
+
+    macro_rules! chk {
+        ($fn:ident, $exp:literal) => {
+            assert_eq!(child.$fn($exp.len()), $exp.as_bytes());
+        };
+    }
+
+    // File in, count out...
+    child.write_in("moby_dick.txt\0");
+    chk!(stdout_exact_bytes, "18 204 1115 moby_dick.txt\n");
+    child.write_in("lorem_ipsum.txt\0");
+    chk!(stdout_exact_bytes, "13 109 772 lorem_ipsum.txt\n");
+
+    // Introduce an error!
+    child.write_in("\0");
+    chk!(
+        stderr_exact_bytes,
+        "wc: -:3: invalid zero-length file name\n"
+    );
+
+    // wc is quick to forgive, let's move on...
+    child.write_in("alice_in_wonderland.txt\0");
+    chk!(stdout_exact_bytes, "5 57 302 alice_in_wonderland.txt\n");
+
+    // Fin.
+    child
+        .wait()
+        .expect("wc should finish")
+        .failure()
+        .stdout_only("36 370 2189 total\n");
+}
+
+#[test]
+fn files0_from_dir() {
+    // On Unix, `read(open("."))` fails. On Windows, `open(".")` fails. Thus, the errors happen in
+    // different contexts.
+    #[cfg(not(windows))]
+    macro_rules! dir_err {
+        ($p:literal) => {
+            concat!("wc: ", $p, ": read error: Is a directory\n")
+        };
+    }
+    #[cfg(windows)]
+    macro_rules! dir_err {
+        ($p:literal) => {
+            concat!("wc: cannot open ", $p, " for reading: Permission denied\n")
+        };
+    }
+
+    new_ucmd!()
+        .args(&["--files0-from=dir with spaces"])
+        .fails()
+        .stderr_only(dir_err!("'dir with spaces'"));
+
+    // Those contexts have different rules about quoting in errors...
+    #[cfg(windows)]
+    const DOT_ERR: &str = dir_err!("'.'");
+    #[cfg(not(windows))]
+    const DOT_ERR: &str = dir_err!(".");
+    new_ucmd!()
+        .args(&["--files0-from=."])
+        .fails()
+        .stderr_only(DOT_ERR);
+
+    // That also means you cannot `< . wc --files0-from=-` on Windows.
+    #[cfg(not(windows))]
+    new_ucmd!()
+        .args(&["--files0-from=-"])
+        .set_stdin(std::fs::File::open(".").unwrap())
+        .fails()
+        .stderr_only(dir_err!("-"));
+}

tests/fixtures/wc/alice in wonderland.txt

@@ -0,0 +1,5 @@
+Alice was beginning to get very tired of sitting by
+her sister on the bank, and of having nothing to do: once or twice
+she had peeped into the book her sister was reading, but it had no
+pictures or conversations in it, "and what is the use of a book,"
+thought Alice "without pictures or conversation?"

tests/fixtures/wc/files0 with nonexistent.txt

@@ -0,0 +1 @@
+this_file_does_not_exist.txtthis file does not exist.txtthis files doesn't exist either.txt