Add bxs_is_visible_char() to 'bxstring' module

src/bxstring.c

@@ -351,6 +351,25 @@ int bxs_is_empty(bxstr_t *pString)
 
 
 
+int bxs_is_visible_char(bxstr_t *pString, size_t idx)
+{
+    int result = 0;
+    if (pString != NULL) {
+        for (size_t i = 0; i <= idx && i < pString->num_chars_visible; i++) {
+            if (pString->visible_char[i] == idx) {
+                result = 1;
+                break;
+            }
+            else if (pString->visible_char[i] > idx) {
+                break;
+            }
+        }
+    }
+    return result;
+}
+
+
+
 int bxs_strcmp(bxstr_t *s1, bxstr_t *s2)
 {
     if (s1 == NULL) {

src/bxstring.h

@@ -156,6 +156,16 @@ char *bxs_to_output(bxstr_t *pString);
 int bxs_is_empty(bxstr_t *pString);
 
 
+/**
+ * Determine if the character at position `idx` in the given `pString` is a visible character. If `idx` is out of
+ * bounds, this function will return 0.
+ * @param pString the string to check (may be NULL, which means no visible characters)
+ * @param idx the index in `pString` of the character to check (zero-based)
+ * @return 1 for visible, 0 for not visible
+ */
+int bxs_is_visible_char(bxstr_t *pString, size_t idx);
+
+
 /**
  * Determine whether the given `pString` is a valid string under at least one condition. This will return `false` for
  * strings which should really never occur anywhere.

utest/bxstring_test.c

@@ -906,6 +906,32 @@ void test_bxs_is_empty_null(void **state)
 
 
 
+void test_bxs_is_visible_char(void **state)
+{
+    UNUSED(state);
+
+    uint32_t *ustr32 = u32_strconv_from_arg("\x1b[38;5;203mX\x1b[0m \x1b[38;5;203mY\x1b[0m", "ASCII");
+    assert_non_null(ustr32);
+    bxstr_t *input = bxs_from_unicode(ustr32);
+
+    assert_int_equal(0, bxs_is_visible_char(NULL, 4));
+    assert_int_equal(0, bxs_is_visible_char(input, 1000));
+    assert_int_equal(0, bxs_is_visible_char(input, 0));
+    assert_int_equal(0, bxs_is_visible_char(input, 1));
+    assert_int_equal(0, bxs_is_visible_char(input, 31));
+    assert_int_equal(0, bxs_is_visible_char(input, 32));
+    assert_int_equal(0, bxs_is_visible_char(input, 33));
+
+    assert_int_equal(1, bxs_is_visible_char(input, 11));
+    assert_int_equal(1, bxs_is_visible_char(input, 16));
+    assert_int_equal(1, bxs_is_visible_char(input, 28));
+
+    BFREE(ustr32);
+    bxs_free(input);
+}
+
+
+
 void test_bxs_strcmp(void **state)
 {
     UNUSED(state);

utest/bxstring_test.h

@@ -67,6 +67,8 @@ void test_bxs_to_output(void **state);
 
 void test_bxs_is_empty_null(void **state);
 
+void test_bxs_is_visible_char(void **state);
+
 void test_bxs_strcmp(void **state);
 
 void test_bxs_valid_anywhere_error(void **state);

utest/main.c

@@ -153,6 +153,7 @@ int main(void)
         cmocka_unit_test_setup(test_bxs_rtrim_empty, beforeTest),
         cmocka_unit_test_setup(test_bxs_to_output, beforeTest),
         cmocka_unit_test_setup(test_bxs_is_empty_null, beforeTest),
+        cmocka_unit_test_setup(test_bxs_is_visible_char, beforeTest),
         cmocka_unit_test_setup(test_bxs_strcmp, beforeTest),
         cmocka_unit_test_setup(test_bxs_valid_anywhere_error, beforeTest),
         cmocka_unit_test_setup(test_bxs_valid_in_filename_error, beforeTest),