patch/format_startcount.diff

---
 util.c |   30 +++++++++++++++++++++++++++---
 util.h |    2 ++
 2 files changed, 29 insertions(+), 3 deletions(-)

Index: b/util.c
===================================================================
--- a/util.c
+++ b/util.c
@@ -466,10 +466,9 @@ remove_prefix (char *p, size_t prefixlen
     continue;
 }
 
-char *
-format_linenum (char numbuf[LINENUM_LENGTH_BOUND + 1], LINENUM n)
+static char *
+__format_linenum (char *p, LINENUM n)
 {
-  char *p = numbuf + LINENUM_LENGTH_BOUND;
   *p = '\0';
 
   if (n < 0)
@@ -490,6 +489,31 @@ format_linenum (char numbuf[LINENUM_LENG
   return p;
 }
 
+char *
+format_linenum (char numbuf[LINENUM_LENGTH_BOUND + 1], LINENUM n)
+{
+    return __format_linenum(numbuf + LINENUM_LENGTH_BOUND, n);
+}
+
+char *
+format_startcount (char rangebuf[LINERANGE_LENGTH_BOUND + 1],
+		   LINENUM first, LINENUM lines)
+{
+    char *p = rangebuf + LINERANGE_LENGTH_BOUND;
+
+    if (lines == 1)
+      rangebuf = __format_linenum (p, first);
+    else
+      {
+	if (lines == 0 && first == 1)
+	    first = 0;  /* what diff produces ... */
+	p = __format_linenum(p, lines);
+	rangebuf = __format_linenum(--p, first);
+	*p = ',';
+      }
+    return rangebuf;
+}
+
 #if !HAVE_VPRINTF
 #define vfprintf my_vfprintf
 static int
Index: b/util.h
===================================================================
--- a/util.h
+++ b/util.h
@@ -25,6 +25,7 @@
 /* An upper bound on the print length of a signed decimal line number.
    Add one for the sign.  */
 #define LINENUM_LENGTH_BOUND (sizeof (LINENUM) * CHAR_BIT / 3 + 1)
+#define LINERANGE_LENGTH_BOUND (LINENUM_LENGTH_BOUND * 2 + 1)
 
 XTERN enum backup_type backup_type;
 
@@ -45,6 +46,7 @@ bool version_get (char const *, char con
 int create_file (char const *, int, mode_t);
 int systemic (char const *);
 char *format_linenum (char[LINENUM_LENGTH_BOUND + 1], LINENUM);
+char *format_startcount (char[LINERANGE_LENGTH_BOUND + 1], LINENUM, LINENUM);
 void Fseek (FILE *, file_offset, int);
 void copy_file (char const *, char const *, int, mode_t);
 void exit_with_signal (int) __attribute__ ((noreturn));