[bug-diffutils] bug#20062: bug#20062: [PATCH] diff: add support for --color

[Giuseppe Scrivano]

Hi Paul,

I've attached the last version of the patch.  Is there anything left
that should be done?

Thanks,
Giuseppe

>From 8b39f7297c0137af62336ad79044271803b66299 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Sun, 8 Mar 2015 22:45:11 +0100
Subject: [PATCH] diff: add support for --color

* doc/diffutils.texi (diff Options): Add documentation for --color.
Copied from coreutils ls --color.
* src/context.c (pr_unidiff_hunk): Set the color context.
(print_context_header): Likewise.
(pr_context_hunk): Likewise.
* src/diff.h (enum colors_style): New enum to record when to use colors.
(colors_style): New variable to memorize the argument value.
(set_add_color_context): Add function definition.
(set_delete_color_context): Likewise.
(set_header_color_context): Likewise.
(set_line_numbers_color_context): Likewise.
(reset_color_context): Likewise.
* src/diff.c: : Define COLOR_OPTION.
(specify_colors_style): New function.
(longopts): Add --color.
(main): Handle --color argument.
(option_help_msgid): Add usage string for --color.
* src/normal.c (print_normal_hunk): Set the color context.
* src/side.c (print_1sdiff_line): Likewise.
* src/util.c (colors_enabled): New boolean variable.
(begin_output): Call check_color_output once the output file is
configured.
(colors_enabled): New boolean variable.
(check_color_output): New function.
(install_signal_handlers): Likewise.
(signal_handler): Likewise.
(set_add_color_context): Likewise.
(set_delete_color_context): Likewise.
(reset_color_context): Likewise.
(set_header_color_context): Likewise.
(set_line_numbers_color_context): Likewise.
---
 doc/diffutils.texi |  21 +++++++++
 src/context.c      |  51 ++++++++++++++++++----
 src/diff.c         |  27 +++++++++++-
 src/diff.h         |  21 +++++++++
 src/normal.c       |  18 ++++++--
 src/side.c         |  15 +++++++
 src/util.c         | 126 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 7 files changed, 265 insertions(+), 14 deletions(-)

diff --git a/doc/diffutils.texi b/doc/diffutils.texi
index 3e25807..dd5a1c6 100644
--- a/doc/diffutils.texi
+++ b/doc/diffutils.texi
@@ -3745,6 +3745,27 @@ Read and write data in binary mode.  @xref{Binary}.
 Use the context output format, showing three lines of context.
 @xref{Context Format}.
 
address@hidden --color address@hidden
address@hidden color, distinguishing different context
+Specify whether to use color for distinguishing different contexts,
+like header, added or removed lines.  @var{when} may be omitted, or
+one of:
address@hidden @bullet
address@hidden none
address@hidden none @r{color option}
+Do not use color at all.  This is the default when no --color option
+is present.
address@hidden auto
address@hidden auto @r{color option}
address@hidden terminal, using color iff
+Only use color if standard output is a terminal.
address@hidden always
address@hidden always @r{color option}
+Always use color.
address@hidden itemize
+Specifying @option{--color} and no @var{when} is equivalent to
address@hidden
+
 @item -C @var{lines}
 @itemx address@hidden@address@hidden
 Use the context output format, showing @var{lines} (an integer) lines of
diff --git a/src/context.c b/src/context.c
index e0f21c4..9b23d36 100644
--- a/src/context.c
+++ b/src/context.c
@@ -80,6 +80,7 @@ print_context_label (char const *mark,
 void
 print_context_header (struct file_data inf[], char const *const *names, bool 
unidiff)
 {
+  set_header_color_context ();
   if (unidiff)
     {
       print_context_label ("---", &inf[0], names[0], file_label[0]);
@@ -90,6 +91,7 @@ print_context_header (struct file_data inf[], char const 
*const *names, bool uni
       print_context_label ("***", &inf[0], names[0], file_label[0]);
       print_context_label ("---", &inf[1], names[1], file_label[1]);
     }
+  reset_color_context (false);
 }
 
 /* Print an edit script in context format.  */
@@ -215,6 +217,7 @@ pr_context_hunk (struct change *hunk)
 
       for (i = first0; i <= last0; i++)
        {
+          bool reset_context = false;
          /* Skip past changes that apply (in file 0)
             only to lines before line I.  */
 
@@ -225,12 +228,18 @@ pr_context_hunk (struct change *hunk)
 
          prefix = " ";
          if (next && next->line0 <= i)
-           /* The change NEXT covers this line.
-              If lines were inserted here in file 1, this is "changed".
-              Otherwise it is "deleted".  */
-           prefix = (next->inserted > 0 ? "!" : "-");
+            {
+              reset_context = true;
+              set_delete_color_context ();
+              /* The change NEXT covers this line.
+                 If lines were inserted here in file 1, this is "changed".
+                 Otherwise it is "deleted".  */
+              prefix = (next->inserted > 0 ? "!" : "-");
+            }
 
          print_1_line (prefix, &files[0].linbuf[i]);
+          if (reset_context)
+            reset_color_context (false);
        }
     }
 
@@ -244,6 +253,7 @@ pr_context_hunk (struct change *hunk)
 
       for (i = first1; i <= last1; i++)
        {
+          bool reset_context = false;
          /* Skip past changes that apply (in file 1)
             only to lines before line I.  */
 
@@ -254,12 +264,17 @@ pr_context_hunk (struct change *hunk)
 
          prefix = " ";
          if (next && next->line1 <= i)
-           /* The change NEXT covers this line.
-              If lines were deleted here in file 0, this is "changed".
-              Otherwise it is "inserted".  */
-           prefix = (next->deleted > 0 ? "!" : "+");
-
+            {
+              reset_context = true;
+              set_add_color_context ();
+              /* The change NEXT covers this line.
+                 If lines were deleted here in file 0, this is "changed".
+                 Otherwise it is "inserted".  */
+              prefix = (next->deleted > 0 ? "!" : "+");
+            }
          print_1_line (prefix, &files[1].linbuf[i]);
+          if (reset_context)
+            reset_color_context (false);
        }
     }
 }
@@ -330,11 +345,13 @@ pr_unidiff_hunk (struct change *hunk)
   begin_output ();
   out = outfile;
 
+  set_line_numbers_color_context ();
   fputs ("@@ -", out);
   print_unidiff_number_range (&files[0], first0, last0);
   fputs (" +", out);
   print_unidiff_number_range (&files[1], first1, last1);
   fputs (" @@", out);
+  reset_color_context (false);
 
   if (function)
     print_context_function (out, function);
@@ -360,9 +377,17 @@ pr_unidiff_hunk (struct change *hunk)
        }
       else
        {
+          bool reset_context = false;
+
          /* For each difference, first output the deleted part. */
 
          k = next->deleted;
+          if (k)
+            {
+              reset_context = true;
+              set_delete_color_context ();
+            }
+
          while (k--)
            {
              char const * const *line = &files[0].linbuf[i++];
@@ -375,9 +400,15 @@ pr_unidiff_hunk (struct change *hunk)
          /* Then output the inserted part. */
 
          k = next->inserted;
+          if (k)
+            {
+              reset_context = true;
+              set_add_color_context ();
+            }
          while (k--)
            {
              char const * const *line = &files[1].linbuf[j++];
+             set_add_color_context ();
              putc ('+', out);
              if (initial_tab && ! (suppress_blank_empty && **line == '\n'))
                putc ('\t', out);
@@ -386,6 +417,8 @@ pr_unidiff_hunk (struct change *hunk)
 
          /* We're done with this hunk, so on to the next! */
 
+          if (reset_context)
+            reset_color_context (false);
          next = next->link;
        }
     }
diff --git a/src/diff.c b/src/diff.c
index ff28377..be6e6e3 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -70,6 +70,7 @@ static void add_regexp (struct regexp_list *, char const *);
 static void summarize_regexp_list (struct regexp_list *);
 static void specify_style (enum output_style);
 static void specify_value (char const **, char const *, char const *);
+static void specify_colors_style (char const *);
 static void try_help (char const *, char const *) __attribute__((noreturn));
 static void check_stdout (void);
 static void usage (void);
@@ -136,7 +137,9 @@ enum
   UNCHANGED_GROUP_FORMAT_OPTION,
   OLD_GROUP_FORMAT_OPTION,
   NEW_GROUP_FORMAT_OPTION,
-  CHANGED_GROUP_FORMAT_OPTION
+  CHANGED_GROUP_FORMAT_OPTION,
+
+  COLOR_OPTION,
 };
 
 static char const group_format_option[][sizeof "--unchanged-group-format"] =
@@ -159,6 +162,7 @@ static struct option const longopts[] =
   {"binary", 0, 0, BINARY_OPTION},
   {"brief", 0, 0, 'q'},
   {"changed-group-format", 1, 0, CHANGED_GROUP_FORMAT_OPTION},
+  {"color", 2, 0, COLOR_OPTION},
   {"context", 2, 0, 'C'},
   {"ed", 0, 0, 'e'},
   {"exclude", 1, 0, 'x'},
@@ -627,6 +631,10 @@ main (int argc, char **argv)
          specify_value (&group_format[c], optarg, group_format_option[c]);
          break;
 
+       case COLOR_OPTION:
+         specify_colors_style (optarg);
+         break;
+
        default:
          try_help (NULL, NULL);
        }
@@ -940,6 +948,8 @@ static char const * const option_help_msgid[] = {
   N_("-d, --minimal            try hard to find a smaller set of changes"),
   N_("    --horizon-lines=NUM  keep NUM lines of the common prefix and 
suffix"),
   N_("    --speed-large-files  assume large files and many scattered small 
changes"),
+  N_("    --color[=WHEN]         colorize the output; WHEN can be 'never', 
'always',"),
+  N_("                             or 'auto' (the default)"),
   "",
   N_("    --help               display this help and exit"),
   N_("-v, --version            output version information and exit"),
@@ -1008,6 +1018,21 @@ specify_style (enum output_style style)
       output_style = style;
     }
 }
+
+/* Set the color mode.  */
+static void
+specify_colors_style (char const *value)
+{
+  if (value == NULL || STREQ (value, "auto"))
+    colors_style = AUTO;
+  else if (STREQ (value, "always"))
+    colors_style = ALWAYS;
+  else if (STREQ (value, "never"))
+    colors_style = NEVER;
+  else
+    try_help ("invalid color '%s'", value);
+}
+
 
 /* Set the last-modified time of *ST to be the current time.  */
 
diff --git a/src/diff.h b/src/diff.h
index 465e4bc..553bad1 100644
--- a/src/diff.h
+++ b/src/diff.h
@@ -38,6 +38,19 @@ enum changes
   /* Both deletes and inserts: a hunk containing both old and new lines.  */
   CHANGED
 };
+
+/* What kind of changes a hunk contains.  */
+enum colors_style
+{
+  /* Never output colors.  */
+  NEVER,
+
+  /* Output colors if the output is a terminal.  */
+  AUTO,
+
+  /* Always output colors.  */
+  ALWAYS,
+};
 
 /* Variables for command line options */
 
@@ -83,6 +96,9 @@ enum output_style
 
 XTERN enum output_style output_style;
 
+/* Define the current color context used to print a line.  */
+XTERN enum colors_style colors_style;
+
 /* Nonzero if output cannot be generated for identical files.  */
 XTERN bool no_diff_means_no_output;
 
@@ -390,3 +406,8 @@ extern void print_script (struct change *, struct change * 
(*) (struct change *)
 extern void setup_output (char const *, char const *, bool);
 extern void translate_range (struct file_data const *, lin, lin,
                              long int *, long int *);
+extern void set_header_color_context (void);
+extern void set_add_color_context (void);
+extern void set_delete_color_context (void);
+extern void reset_color_context (bool from_signal);
+extern void set_line_numbers_color_context (void);
diff --git a/src/normal.c b/src/normal.c
index 721fd1a..0ce01ee 100644
--- a/src/normal.c
+++ b/src/normal.c
@@ -49,21 +49,31 @@ print_normal_hunk (struct change *hunk)
   begin_output ();
 
   /* Print out the line number header for this hunk */
+  set_line_numbers_color_context ();
   print_number_range (',', &files[0], first0, last0);
   fputc (change_letter[changes], outfile);
   print_number_range (',', &files[1], first1, last1);
   fputc ('\n', outfile);
+  reset_color_context (false);
 
   /* Print the lines that the first file has.  */
   if (changes & OLD)
-    for (i = first0; i <= last0; i++)
-      print_1_line ("<", &files[0].linbuf[i]);
+    {
+      set_delete_color_context ();
+      for (i = first0; i <= last0; i++)
+        print_1_line ("<", &files[0].linbuf[i]);
+      reset_color_context (false);
+    }
 
   if (changes == CHANGED)
     fputs ("---\n", outfile);
 
   /* Print the lines that the second file has.  */
   if (changes & NEW)
-    for (i = first1; i <= last1; i++)
-      print_1_line (">", &files[1].linbuf[i]);
+    {
+      set_add_color_context ();
+      for (i = first1; i <= last1; i++)
+        print_1_line (">", &files[1].linbuf[i]);
+      reset_color_context (false);
+    }
 }
diff --git a/src/side.c b/src/side.c
index 155512c..8327d11 100644
--- a/src/side.c
+++ b/src/side.c
@@ -206,6 +206,18 @@ print_1sdiff_line (char const *const *left, char sep,
   size_t c2o = sdiff_column2_offset;
   size_t col = 0;
   bool put_newline = false;
+  bool color_to_reset = false;
+
+  if (sep == '<')
+    {
+      set_delete_color_context ();
+      color_to_reset = true;
+    }
+  else if (sep == '>')
+    {
+      set_add_color_context ();
+      color_to_reset = true;
+    }
 
   if (left)
     {
@@ -233,6 +245,9 @@ print_1sdiff_line (char const *const *left, char sep,
 
   if (put_newline)
     putc ('\n', out);
+
+  if (color_to_reset)
+    reset_color_context (false);
 }
 
 /* Print lines common to both files in side-by-side format.  */
diff --git a/src/util.c b/src/util.c
index 2d6d3fc..0f8f7a8 100644
--- a/src/util.c
+++ b/src/util.c
@@ -24,6 +24,7 @@
 #include <system-quote.h>
 #include <xalloc.h>
 #include "xvasprintf.h"
+#include <signal.h>
 
 char const pr_program[] = PR_PROGRAM;
 
@@ -143,6 +144,59 @@ print_message_queue (void)
     }
 }
 
+static void
+signal_handler (int sig)
+{
+  reset_color_context (true);
+
+  /* Restore the default handler, and report the signal again.  */
+  signal (sig, SIG_DFL);
+  raise (sig);
+}
+
+static void
+install_signal_handlers (void)
+{
+  int j;
+#if HAVE_SIGACTION
+  struct sigaction act;
+#endif
+  int const sig[] =
+    {
+      SIGTSTP,
+      SIGALRM, SIGHUP, SIGINT, SIGPIPE, SIGQUIT, SIGTERM,
+#ifdef SIGPOLL
+      SIGPOLL,
+#endif
+#ifdef SIGPROF
+      SIGPROF,
+#endif
+#ifdef SIGVTALRM
+      SIGVTALRM,
+#endif
+#ifdef SIGXCPU
+      SIGXCPU,
+#endif
+#ifdef SIGXFSZ
+      SIGXFSZ,
+#endif
+    };
+
+  for (j = 0; j < sizeof (sig) / sizeof (*sig); j++)
+    {
+#if HAVE_SIGACTION
+      sigaction (sig[j], NULL, &act);
+      if (act.sa_handler != SIG_IGN)
+        {
+          act.sa_handler = signal_handler;
+          sigaction (sig[j], &act, NULL);
+        }
+#else
+      signal (sig[j], signal_handler);
+#endif
+    }
+}
+
 /* Call before outputting the results of comparing files NAME0 and NAME1
    to set up OUTFILE, the stdio stream for the output to go to.
 
@@ -153,6 +207,24 @@ print_message_queue (void)
 static char const *current_name0;
 static char const *current_name1;
 static bool currently_recursive;
+static bool colors_enabled;
+static bool output_is_tty;
+
+static void
+check_color_output (bool is_pipe)
+{
+  if (! outfile)
+    return;
+
+  output_is_tty = (colors_style != NEVER && !is_pipe
+                   && isatty (fileno (outfile)));
+
+  colors_enabled = (colors_style == ALWAYS
+                    || (colors_style == AUTO && output_is_tty));
+
+  if (output_is_tty)
+    install_signal_handlers ();
+}
 
 void
 setup_output (char const *name0, char const *name1, bool recursive)
@@ -313,6 +385,7 @@ begin_output (void)
            outfile = fdopen (pipes[1], "w");
            if (!outfile)
              pfatal_with_name ("fdopen");
+           check_color_output (true);
          }
 #else
        char *command = system_quote_argv (SCI_SYSTEM, (char **) argv);
@@ -320,6 +393,7 @@ begin_output (void)
        outfile = popen (command, "w");
        if (!outfile)
          pfatal_with_name (command);
+       check_color_output (true);
        free (command);
 #endif
       }
@@ -330,6 +404,7 @@ begin_output (void)
       /* If -l was not specified, output the diff straight to 'stdout'.  */
 
       outfile = stdout;
+      check_color_output (false);
 
       /* If handling multiple files (because scanning a directory),
         print which files the following output is about.  */
@@ -717,6 +792,57 @@ output_1_line (char const *base, char const *limit, char 
const *flag_format,
     }
 }
 
+void
+set_header_color_context (void)
+{
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[1;39m");
+}
+
+void
+set_line_numbers_color_context (void)
+{
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[36m");
+}
+
+void
+set_add_color_context (void)
+{
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[32m");
+}
+
+void
+set_delete_color_context (void)
+{
+  if (colors_enabled)
+    fprintf (outfile, "\x1B[31m");
+}
+
+void
+reset_color_context (bool from_signal)
+{
+  static char const reset_sequence[] = "\x1b[0m";
+  if (! colors_enabled)
+    return;
+
+  if (! from_signal)
+    fputs (reset_sequence, outfile);
+  else
+    {
+      size_t written = 0;
+      while (written < sizeof reset_sequence - 1)
+        {
+          int ret = write (STDOUT_FILENO, reset_sequence + written,
+                           sizeof reset_sequence - 1 - written);
+          if (ret < 0)
+            return;
+          written += ret;
+        }
+    }
+}
+
 char const change_letter[] = { 0, 'd', 'a', 'c' };
 
 /* Translate an internal line number (an index into diff's table of lines)
-- 
2.1.0