[PATCH 09/26] strvec: introduce new `strvec_splice()` function

[Patrick Steinhardt <ps@pks.im>]

Introduce a new `strvec_splice()` function that can replace a range of
strings in the vector with another array of strings. This function will
be used in subsequent commits.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 strvec.c              | 19 +++++++++++++
 strvec.h              |  9 ++++++
 t/unit-tests/strvec.c | 65 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 93 insertions(+)

diff --git a/strvec.c b/strvec.c
index f712070f574..81075c50cca 100644
--- a/strvec.c
+++ b/strvec.c
@@ -56,6 +56,25 @@ void strvec_pushv(struct strvec *array, const char **items)
 		strvec_push(array, *items);
 }
 
+void strvec_splice(struct strvec *array, size_t pos, size_t len,
+		   const char **replacement, size_t replacement_len)
+{
+	if (pos + len > array->alloc)
+		BUG("range outside of array boundary");
+	if (replacement_len > len)
+		ALLOC_GROW(array->v, array->nr + (replacement_len - len) + 1,
+			   array->alloc);
+	for (size_t i = 0; i < len; i++)
+		free((char *)array->v[pos + i]);
+	if (replacement_len != len) {
+		memmove(array->v + pos + replacement_len, array->v + pos + len,
+			(array->nr - pos - len + 1) * sizeof(char *));
+		array->nr += (replacement_len - len);
+	}
+	for (size_t i = 0; i < replacement_len; i++)
+		array->v[pos + i] = xstrdup(replacement[i]);
+}
+
 const char *strvec_replace(struct strvec *array, size_t idx, const char *replacement)
 {
 	char *to_free;
diff --git a/strvec.h b/strvec.h
index 4b73c1f092e..4e61cc93369 100644
--- a/strvec.h
+++ b/strvec.h
@@ -67,6 +67,15 @@ void strvec_pushl(struct strvec *, ...);
 /* Push a null-terminated array of strings onto the end of the array. */
 void strvec_pushv(struct strvec *, const char **);
 
+/*
+ * Replace `len` values starting at `pos` with the provided replacement
+ * strings. If `len` is zero this is effectively an insert at the given `pos`.
+ * If `replacement_len` is zero this is effectively a delete of `len` items
+ * starting at `pos`.
+ */
+void strvec_splice(struct strvec *array, size_t pos, size_t len,
+		   const char **replacement, size_t replacement_len);
+
 /**
  * Replace the value at the given index with a new value. The index must be
  * valid. Returns a pointer to the inserted value.
diff --git a/t/unit-tests/strvec.c b/t/unit-tests/strvec.c
index bf4c0cb172e..855b6023371 100644
--- a/t/unit-tests/strvec.c
+++ b/t/unit-tests/strvec.c
@@ -88,6 +88,71 @@ void test_strvec__pushv(void)
 	strvec_clear(&vec);
 }
 
+void test_strvec__splice_with_same_size_replacement(void)
+{
+	struct strvec vec = STRVEC_INIT;
+	const char *replacement[] = { "1" };
+
+	strvec_pushl(&vec, "foo", "bar", "baz", NULL);
+	strvec_splice(&vec, 1, 1, replacement, ARRAY_SIZE(replacement));
+	check_strvec(&vec, "foo", "1", "baz", NULL);
+	strvec_clear(&vec);
+}
+
+void test_strvec__splice_with_smaller_replacement(void)
+{
+	struct strvec vec = STRVEC_INIT;
+	const char *replacement[] = { "1" };
+
+	strvec_pushl(&vec, "foo", "bar", "baz", NULL);
+	strvec_splice(&vec, 1, 2, replacement, ARRAY_SIZE(replacement));
+	check_strvec(&vec, "foo", "1", NULL);
+	strvec_clear(&vec);
+}
+
+void test_strvec__splice_with_bigger_replacement(void)
+{
+	struct strvec vec = STRVEC_INIT;
+	const char *replacement[] = { "1", "2", "3" };
+
+	strvec_pushl(&vec, "foo", "bar", "baz", NULL);
+	strvec_splice(&vec, 0, 2, replacement, ARRAY_SIZE(replacement));
+	check_strvec(&vec, "1", "2", "3", "baz", NULL);
+	strvec_clear(&vec);
+}
+
+void test_strvec__splice_with_empty_replacement(void)
+{
+	struct strvec vec = STRVEC_INIT;
+
+	strvec_pushl(&vec, "foo", "bar", "baz", NULL);
+	strvec_splice(&vec, 0, 2, NULL, 0);
+	check_strvec(&vec, "baz", NULL);
+	strvec_clear(&vec);
+}
+
+void test_strvec__splice_with_empty_original(void)
+{
+	struct strvec vec = STRVEC_INIT;
+	const char *replacement[] = { "1", "2" };
+
+	strvec_pushl(&vec, "foo", "bar", "baz", NULL);
+	strvec_splice(&vec, 1, 0, replacement, ARRAY_SIZE(replacement));
+	check_strvec(&vec, "foo", "1", "2", "bar", "baz", NULL);
+	strvec_clear(&vec);
+}
+
+void test_strvec__splice_at_tail(void)
+{
+	struct strvec vec = STRVEC_INIT;
+	const char *replacement[] = { "1", "2" };
+
+	strvec_pushl(&vec, "foo", "bar", NULL);
+	strvec_splice(&vec, 2, 0, replacement, ARRAY_SIZE(replacement));
+	check_strvec(&vec, "foo", "bar", "1", "2", NULL);
+	strvec_clear(&vec);
+}
+
 void test_strvec__replace_at_head(void)
 {
 	struct strvec vec = STRVEC_INIT;
-- 
2.47.0.229.g8f8d6eee53.dirty