str_uniq() function added.

README.md

@@ -211,6 +211,11 @@ provided (see `str.h` file).
 Binary search for the given key. The input array must be sorted using `str_order_asc`.
 Returns a pointer to the string matching the key, or NULL.
 
+`size_t str_uniq(str* const array, const size_t count)`<br>
+Retain only the unique strings in the given array. Returns the number of strings.
+After the call, the strings in the array are sorted, so the array is suitable for
+binary search using `str_search()` function.
+
 #### Memory allocation
 By default the library uses `malloc(3)` for memory allocations, and calls `abort(3)`
 if the allocation fails. This behaviour can be changed by hash-defining `STR_EXT_ALLOC`

str.c

@@ -328,6 +328,36 @@ void str_sort(const str_cmp_func cmp, str* const array, const size_t count)
 		qsort(array, count, sizeof(array[0]), cmp);
 }
 
+// retain unique strings only
+size_t str_uniq(str* const array, const size_t count)
+{
+	if(!array || count == 0)
+		return 0;
+
+	if(count == 1)
+		return 1;
+
+	// O(n * log n), but without memory allocation
+	str_sort(str_order_asc, array, count);
+
+	str* p = array;
+	const str* const end = array + count;
+
+	for(str* s = array + 1; ; ++s)
+	{
+		while(s < end && str_eq(*p, *s))
+			str_clear(s++);
+
+		if(s == end)
+			break;
+
+		if(++p < s)
+			*p = str_move(s);
+	}
+
+	return p + 1 - array;
+}
+
 // searching
 const str* str_search(const str key, const str* const array, const size_t count)
 {

str.h

@@ -179,6 +179,9 @@ int str_order_desc_ci(const void* const s1, const void* const s2);
 // sort array of strings
 void str_sort(const str_cmp_func cmp, str* const array, const size_t count);
 
+// retain unique strings only
+size_t str_uniq(str* const array, const size_t count);
+
 // searching
 const str* str_search(const str key, const str* const array, const size_t count);
 

str_test.c

@@ -283,6 +283,8 @@ void test_sort(void)
 	assert(str_eq(src[1], str_lit("z")));
 	assert(str_eq(src[2], str_lit("bbb")));
 	assert(str_eq(src[3], str_lit("aaa")));
+
+	passed;
 }
 
 static
@@ -303,6 +305,8 @@ void test_sort_ci(void)
 	assert(str_eq_ci(src[1], str_lit("zzz")));
 	assert(str_eq_ci(src[2], str_lit("aaa")));
 	assert(str_eq_ci(src[3], str_lit("aaa")));
+
+	passed;
 }
 
 static
@@ -318,6 +322,40 @@ void test_search(void)
 	assert(str_search(src[2], src, count) == &src[2]);
 	assert(str_search(src[3], src, count) == &src[3]);
 	assert(str_search(str_lit("xxx"), src, count) == NULL);
+
+	passed;
+}
+
+static
+void test_uniq(void)
+{
+	str src[10] = { 0 };
+
+	str* p = src;
+
+	str_dup(p++, str_lit("zzz"));
+	str_dup(p++, str_lit("zzz"));
+	str_dup(p++, str_lit("aaa"));
+	str_dup(p++, str_lit("bbb"));
+	str_dup(p++, str_lit("aaa"));
+	str_dup(p++, str_lit("bbb"));
+	str_dup(p++, str_lit("bbb"));
+	str_dup(p++, str_lit("bbb"));
+	str_dup(p++, str_lit("aaa"));
+	str_dup(p++, str_lit("zzz"));
+
+	const size_t count = str_uniq(src, p - src);
+
+	assert(count == 3);
+	assert(str_eq(src[0], str_lit("aaa")));
+	assert(str_eq(src[1], str_lit("bbb")));
+	assert(str_eq(src[2], str_lit("zzz")));
+
+	// clean-up
+	for(size_t i = 0; i < count; ++i)
+		str_free(src[i]);
+
+	passed;
 }
 
 int main(void)
@@ -338,6 +376,7 @@ int main(void)
 	test_sort();
 	test_sort_ci();
 	test_search();
+	test_uniq();
 
 	return puts("OK.") < 0;
 }