Add function rcutils_string_array_cmp

include/rcutils/types/string_array.h

@@ -110,6 +110,27 @@ RCUTILS_WARN_UNUSED
 rcutils_ret_t
 rcutils_string_array_fini(rcutils_string_array_t * string_array);
 
+/// Compare two string arrays.
+/**
+ * The two string arrays are compared according to lexographical order.
+ *
+ * \param[in] sa0 The first string array.
+ * \param[in] sa1 The second string array.
+ * \param[out] res Negative value if `lhs` appears before `rhs` in lexographical order.
+ *   Zero if `lhs` and `rhs` are equal.
+ *   Positive value if `lhs` appears after `rhs in lexographical order.
+ * \return `RCUTILS_RET_OK` if successful, or
+ * \return `RCUTILS_RET_INVALID_ARGUMENT` if there is an invalid arguments, or
+ * \return `RCUTILS_RET_ERROR` if an unknown error occurs.
+ */
+RCUTILS_PUBLIC
+RCUTILS_WARN_UNUSED
+rcutils_ret_t
+rcutils_string_array_cmp(
+  const rcutils_string_array_t * lhs,
+  const rcutils_string_array_t * rhs,
+  int * res);
+
 #ifdef __cplusplus
 }
 #endif

src/string_array.c

@@ -18,6 +18,7 @@ extern "C"
 #endif
 
 #include <stdlib.h>
+#include <string.h>
 
 #include "rcutils/allocator.h"
 #include "rcutils/error_handling.h"
@@ -87,6 +88,53 @@ rcutils_string_array_fini(rcutils_string_array_t * string_array)
   return RCUTILS_RET_OK;
 }
 
+rcutils_ret_t
+rcutils_string_array_cmp(
+  const rcutils_string_array_t * lhs,
+  const rcutils_string_array_t * rhs,
+  int * res)
+{
+  if (NULL == lhs || NULL == rhs) {
+    RCUTILS_SET_ERROR_MSG("string_array is null");
+    return RCUTILS_RET_INVALID_ARGUMENT;
+  }
+  if (NULL == lhs->data || NULL == rhs->data) {
+    RCUTILS_SET_ERROR_MSG("string_array data is null");
+    return RCUTILS_RET_INVALID_ARGUMENT;
+  }
+  if (NULL == res) {
+    RCUTILS_SET_ERROR_MSG("res argument is null");
+    return RCUTILS_RET_INVALID_ARGUMENT;
+  }
+
+  size_t smallest_size = lhs->size;
+  if (rhs->size < smallest_size) {
+    smallest_size = rhs->size;
+  }
+
+  for (size_t i = 0; i < smallest_size; ++i) {
+    if (NULL == lhs->data[i] || NULL == rhs->data[i]) {
+      RCUTILS_SET_ERROR_MSG("string_array element is null");
+      return RCUTILS_RET_ERROR;
+    }
+    // Loop until we find a pair of strings that are not equal
+    int strcmp_res = strcmp(lhs->data[i], rhs->data[i]);
+    if (0 != strcmp_res) {
+      *res = strcmp_res;
+      return RCUTILS_RET_OK;
+    }
+  }
+
+  // If all strings equal, compare array sizes
+  *res = 0;
+  if (lhs->size < rhs->size) {
+    *res = -1;
+  } else if (lhs->size > rhs->size) {
+    *res = 1;
+  }
+  return RCUTILS_RET_OK;
+}
+
 #ifdef __cplusplus
 }
 #endif

test/test_string_array.cpp

@@ -46,3 +46,75 @@ TEST(test_string_array, boot_string_array) {
   ret = rcutils_string_array_fini(&sa2);
   ASSERT_EQ(RCUTILS_RET_OK, ret);
 }
+
+TEST(test_string_array, string_array_cmp) {
+  auto allocator = rcutils_get_default_allocator();
+  rcutils_ret_t ret = RCUTILS_RET_OK;
+  int res = 0;
+
+  // Initialize some string arrays
+  rcutils_string_array_t sa0 = rcutils_get_zero_initialized_string_array();
+  ret = rcutils_string_array_init(&sa0, 3, &allocator);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  sa0.data[0] = strdup("foo");
+  sa0.data[1] = strdup("bar");
+  sa0.data[2] = strdup("baz");
+
+  rcutils_string_array_t sa1 = rcutils_get_zero_initialized_string_array();
+  ret = rcutils_string_array_init(&sa1, 3, &allocator);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  sa1.data[0] = strdup("foo");
+  sa1.data[1] = strdup("bar");
+  sa1.data[2] = strdup("baz");
+
+  rcutils_string_array_t sa2 = rcutils_get_zero_initialized_string_array();
+  ret = rcutils_string_array_init(&sa2, 3, &allocator);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  sa2.data[0] = strdup("foo");
+  sa2.data[1] = strdup("baz");
+  sa2.data[2] = strdup("bar");
+
+  rcutils_string_array_t sa3 = rcutils_get_zero_initialized_string_array();
+  ret = rcutils_string_array_init(&sa3, 2, &allocator);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  sa3.data[0] = strdup("foo");
+  sa3.data[1] = strdup("bar");
+
+  rcutils_string_array_t incomplete_string_array = rcutils_get_zero_initialized_string_array();
+  ret = rcutils_string_array_init(&incomplete_string_array, 3, &allocator);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+
+  // Test failure cases
+  EXPECT_EQ(RCUTILS_RET_INVALID_ARGUMENT, rcutils_string_array_cmp(NULL, &sa0, &res));
+  EXPECT_EQ(RCUTILS_RET_INVALID_ARGUMENT, rcutils_string_array_cmp(&sa0, NULL, &res));
+  EXPECT_EQ(RCUTILS_RET_INVALID_ARGUMENT, rcutils_string_array_cmp(&sa0, &sa1, NULL));
+  EXPECT_EQ(RCUTILS_RET_ERROR, rcutils_string_array_cmp(&sa0, &incomplete_string_array, &res));
+
+  // Test success cases
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa0, &sa1, &res));
+  EXPECT_EQ(res, 0);
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa1, &sa0, &res));
+  EXPECT_EQ(res, 0);
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa0, &sa2, &res));
+  EXPECT_LT(res, 0);
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa2, &sa0, &res));
+  EXPECT_GT(res, 0);
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa0, &sa3, &res));
+  EXPECT_GT(res, 0);
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa3, &sa0, &res));
+  EXPECT_LT(res, 0);
+  // Test transitivity
+  EXPECT_EQ(RCUTILS_RET_OK, rcutils_string_array_cmp(&sa3, &sa2, &res));
+  EXPECT_LT(res, 0);
+
+  ret = rcutils_string_array_fini(&sa0);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  ret = rcutils_string_array_fini(&sa1);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  ret = rcutils_string_array_fini(&sa2);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  ret = rcutils_string_array_fini(&sa3);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+  ret = rcutils_string_array_fini(&incomplete_string_array);
+  ASSERT_EQ(RCUTILS_RET_OK, ret);
+}