From 7aee1bc71c08f2c5b69243cb1ca792c8e7615faa Mon Sep 17 00:00:00 2001
From: Ben Pfaff <blp@cs.stanford.edu>
Date: Sat, 9 Jan 2021 11:24:22 -0800
Subject: [PATCH] string-array: New function string_array_uniq().

---
 src/libpspp/string-array.c | 19 +++++++++++++++++++
 src/libpspp/string-array.h |  1 +
 2 files changed, 20 insertions(+)

diff --git a/src/libpspp/string-array.c b/src/libpspp/string-array.c
index a22ade6e10..d4badf4638 100644
--- a/src/libpspp/string-array.c
+++ b/src/libpspp/string-array.c
@@ -234,6 +234,25 @@ string_array_sort (struct string_array *sa)
   qsort (sa->strings, sa->n, sizeof *sa->strings, compare_strings);
 }
 
+/* Removes all but one of any series of adjacent duplicate strings in SA. */
+void
+string_array_uniq (struct string_array *sa)
+{
+  if (!sa->n)
+    return;
+
+  size_t n = 1;
+  for (size_t i = 1; i < sa->n; i++)
+    {
+      char *s = sa->strings[i];
+      if (strcmp (sa->strings[n - 1], s))
+        sa->strings[n++] = s;
+      else
+        free (s);
+    }
+  sa->n = n;
+}
+
 /* Divides STRING into tokens at DELIMITERS and adds each token to SA. */
 void
 string_array_parse (struct string_array *sa, struct substring string,
diff --git a/src/libpspp/string-array.h b/src/libpspp/string-array.h
index ecad3326b6..353ddf5018 100644
--- a/src/libpspp/string-array.h
+++ b/src/libpspp/string-array.h
@@ -61,6 +61,7 @@ void string_array_terminate_null (struct string_array *);
 void string_array_shrink (struct string_array *);
 
 void string_array_sort (struct string_array *);
+void string_array_uniq (struct string_array *);
 
 void string_array_parse (struct string_array *, struct substring string,
                          struct substring delimiters);
-- 
2.30.2