Add new -M/--max-columns option.

This permits setting the maximum line width with respect to the number
of bytes in a line. Omitted lines (whether part of a match, replacement
or context) are replaced with a message stating that the line was
elided.

Fixes #129

5 files changed, 121 insertions, 16 deletions

diff --git a/doc/rg.1.md b/doc/rg.1.md
index d8e498c0..8e8ca289 100644
--- a/doc/rg.1.md
+++ b/doc/rg.1.md
@@ -203,6 +203,10 @@ Project home page: https://github.com/BurntSushi/ripgrep
 -L, --follow
 : Follow symlinks.
 
+-M, --max-columns *NUM*
+: Don't print lines longer than this limit in bytes. Longer lines are omitted,
+  and only the number of matches in that line is printed.
+
 -m, --max-count *NUM*
 : Limit the number of matching lines per file searched to NUM.
 
diff --git a/src/app.rs b/src/app.rs
index c285ab03..21cf2410 100644
--- a/src/app.rs
+++ b/src/app.rs
@@ -169,6 +169,9 @@ fn app<F>(next_line_help: bool, doc: F) -> App<'static, 'static>
              .short("j").value_name("ARG").takes_value(true)
              .validator(validate_number))
         .arg(flag("vimgrep"))
+        .arg(flag("max-columns").short("M")
+             .value_name("NUM").takes_value(true)
+             .validator(validate_number))
         .arg(flag("type-add")
              .value_name("TYPE").takes_value(true)
              .multiple(true).number_of_values(1))
@@ -473,6 +476,11 @@ lazy_static! {
              "Show results with every match on its own line, including \
               line numbers and column numbers. With this option, a line with \
               more than one match will be printed more than once.");
+        doc!(h, "max-columns",
+             "Don't print lines longer than this limit in bytes.",
+             "Don't print lines longer than this limit in bytes. Longer lines \
+              are omitted, and only the number of matches in that line is \
+              printed.");
 
         doc!(h, "type-add",
              "Add a new glob for a file type.",
diff --git a/src/args.rs b/src/args.rs
index cc48b7ad..148ae8b7 100644
--- a/src/args.rs
+++ b/src/args.rs
@@ -56,6 +56,7 @@ pub struct Args {
     invert_match: bool,
     line_number: bool,
     line_per_match: bool,
+    max_columns: Option<usize>,
     max_count: Option<u64>,
     max_filesize: Option<u64>,
     maxdepth: Option<usize>,
@@ -156,7 +157,8 @@ impl Args {
             .line_per_match(self.line_per_match)
             .null(self.null)
             .path_separator(self.path_separator)
-            .with_filename(self.with_filename);
+            .with_filename(self.with_filename)
+            .max_columns(self.max_columns);
         if let Some(ref rep) = self.replace {
             p = p.replace(rep.clone());
         }
@@ -348,6 +350,7 @@ impl<'a> ArgMatches<'a> {
             invert_match: self.is_present("invert-match"),
             line_number: line_number,
             line_per_match: self.is_present("vimgrep"),
+            max_columns: try!(self.usize_of("max-columns")),
             max_count: try!(self.usize_of("max-count")).map(|max| max as u64),
             max_filesize: try!(self.max_filesize()),
             maxdepth: try!(self.usize_of("maxdepth")),
diff --git a/src/printer.rs b/src/printer.rs
index 8c04dd1a..809e0d75 100644
--- a/src/printer.rs
+++ b/src/printer.rs
@@ -3,12 +3,32 @@ use std::fmt;
 use std::path::Path;
 use std::str::FromStr;
 
-use regex::bytes::Regex;
+use regex::bytes::{Regex, Replacer, Captures};
 use termcolor::{Color, ColorSpec, ParseColorError, WriteColor};
 
 use pathutil::strip_prefix;
 use ignore::types::FileTypeDef;
 
+/// CountingReplacer implements the Replacer interface for Regex,
+/// and counts how often replacement is being performed.
+struct CountingReplacer<'r> {
+    replace: &'r [u8],
+    count: &'r mut usize,
+}
+
+impl<'r> CountingReplacer<'r> {
+    fn new(replace: &'r [u8], count: &'r mut usize) -> CountingReplacer<'r> {
+        CountingReplacer { replace: replace, count: count }
+    }
+}
+
+impl<'r> Replacer for CountingReplacer<'r> {
+    fn replace_append(&mut self, caps: &Captures, dst: &mut Vec<u8>) {
+        *self.count += 1;
+        caps.expand(self.replace, dst);
+    }
+}
+
 /// Printer encapsulates all output logic for searching.
 ///
 /// Note that we currently ignore all write errors. It's probably worthwhile
@@ -46,6 +66,8 @@ pub struct Printer<W> {
     colors: ColorSpecs,
     /// The separator to use for file paths. If empty, this is ignored.
     path_separator: Option<u8>,
+    /// Restrict lines to this many columns.
+    max_columns: Option<usize>
 }
 
 impl<W: WriteColor> Printer<W> {
@@ -65,6 +87,7 @@ impl<W: WriteColor> Printer<W> {
             with_filename: false,
             colors: ColorSpecs::default(),
             path_separator: None,
+            max_columns: None,
         }
     }
 
@@ -144,6 +167,12 @@ impl<W: WriteColor> Printer<W> {
         self
     }
 
+    /// Configure the max. number of columns used for printing matching lines.
+    pub fn max_columns(mut self, max_columns: Option<usize>) -> Printer<W> {
+        self.max_columns = max_columns;
+        self
+    }
+
     /// Returns true if and only if something has been printed.
     pub fn has_printed(&self) -> bool {
         self.has_printed
@@ -263,31 +292,57 @@ impl<W: WriteColor> Printer<W> {
             self.write(b":");
         }
         if self.replace.is_some() {
-            let line = re.replace_all(
-                &buf[start..end], &**self.replace.as_ref().unwrap());
+            let mut count = 0;
+            let line = {
+                let replacer = CountingReplacer::new(
+                    self.replace.as_ref().unwrap(), &mut count);
+                re.replace_all(&buf[start..end], replacer)
+            };
+            if self.max_columns.map_or(false, |m| line.len() > m) {
+                let _ = self.wtr.set_color(self.colors.matched());
+                let msg = format!(
+                    "[Omitted long line with {} replacements]", count);
+                self.write(msg.as_bytes());
+                let _ = self.wtr.reset();
+                self.write_eol();
+                return;
+            }
             self.write(&line);
+            if line.last() != Some(&self.eol) {
+                self.write_eol();
+            }
         } else {
             self.write_matched_line(re, &buf[start..end]);
-        }
-        if buf[start..end].last() != Some(&self.eol) {
-            self.write_eol();
+            // write_matched_line guarantees to write a newline.
         }
     }
 
     fn write_matched_line(&mut self, re: &Regex, buf: &[u8]) {
+        if self.max_columns.map_or(false, |m| buf.len() > m) {
+            let count = re.find_iter(buf).count();
+            let _ = self.wtr.set_color(self.colors.matched());
+            let msg = format!("[Omitted long line with {} matches]", count);
+            self.write(msg.as_bytes());
+            let _ = self.wtr.reset();
+            self.write_eol();
+            return;
+        }
         if !self.wtr.supports_color() || self.colors.matched().is_none() {
             self.write(buf);
-            return;
+        } else {
+            let mut last_written = 0;
+            for m in re.find_iter(buf) {
+                self.write(&buf[last_written..m.start()]);
+                let _ = self.wtr.set_color(self.colors.matched());
+                self.write(&buf[m.start()..m.end()]);
+                let _ = self.wtr.reset();
+                last_written = m.end();
+            }
+            self.write(&buf[last_written..]);
         }
-        let mut last_written = 0;
-        for m in re.find_iter(buf) {
-            self.write(&buf[last_written..m.start()]);
-            let _ = self.wtr.set_color(self.colors.matched());
-            self.write(&buf[m.start()..m.end()]);
-            let _ = self.wtr.reset();
-            last_written = m.end();
+        if buf.last() != Some(&self.eol) {
+            self.write_eol();
         }
-        self.write(&buf[last_written..]);
     }
 
     pub fn context<P: AsRef<Path>>(
@@ -312,6 +367,11 @@ impl<W: WriteColor> Printer<W> {
         if let Some(line_number) = line_number {
             self.line_number(line_number, b'-');
         }
+        if self.max_columns.map_or(false, |m| end - start > m) {
+            self.write(format!("[Omitted long context line]").as_bytes());
+            self.write_eol();
+            return;
+        }
         self.write(&buf[start..end]);
         if buf[start..end].last() != Some(&self.eol) {
             self.write_eol();
diff --git a/tests/tests.rs b/tests/tests.rs
index 9e216b52..9477f32e 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -1314,6 +1314,36 @@ clean!(feature_109_case_sensitive_part2, "test", ".",
     wd.assert_err(&mut cmd);
 });
 
+// See: https://github.com/BurntSushi/ripgrep/issues/129
+clean!(feature_129_matches, "test", ".", |wd: WorkDir, mut cmd: Command| {
+    wd.create("foo", "test\ntest abcdefghijklmnopqrstuvwxyz test");
+    cmd.arg("-M26");
+
+    let lines: String = wd.stdout(&mut cmd);
+    let expected = "foo:test\nfoo:[Omitted long line with 2 matches]\n";
+    assert_eq!(lines, expected);
+});
+
+// See: https://github.com/BurntSushi/ripgrep/issues/129
+clean!(feature_129_context, "test", ".", |wd: WorkDir, mut cmd: Command| {
+    wd.create("foo", "test\nabcdefghijklmnopqrstuvwxyz");
+    cmd.arg("-M20").arg("-C1");
+
+    let lines: String = wd.stdout(&mut cmd);
+    let expected = "foo:test\nfoo-[Omitted long context line]\n";
+    assert_eq!(lines, expected);
+});
+
+// See: https://github.com/BurntSushi/ripgrep/issues/129
+clean!(feature_129_replace, "test", ".", |wd: WorkDir, mut cmd: Command| {
+    wd.create("foo", "test\ntest abcdefghijklmnopqrstuvwxyz test");
+    cmd.arg("-M26").arg("-rfoo");
+
+    let lines: String = wd.stdout(&mut cmd);
+    let expected = "foo:foo\nfoo:[Omitted long line with 2 replacements]\n";
+    assert_eq!(lines, expected);
+});
+
 // See: https://github.com/BurntSushi/ripgrep/issues/159
 clean!(feature_159_works, "test", ".", |wd: WorkDir, mut cmd: Command| {
     wd.create("foo", "test\ntest");