basic/utf8: add ascii_is_valid_n()

src/basic/utf8.c

@@ -247,6 +247,9 @@ char *utf8_escape_non_printable(const char *str) {
 char *ascii_is_valid(const char *str) {
         const char *p;
 
+        /* Check whether the string consists of valid ASCII bytes,
+         * i.e values between 0 and 127, inclusive. */
+
         assert(str);
 
         for (p = str; *p; p++)
@@ -256,6 +259,21 @@ char *ascii_is_valid(const char *str) {
         return (char*) str;
 }
 
+char *ascii_is_valid_n(const char *str, size_t len) {
+        size_t i;
+
+        /* Very similar to ascii_is_valid(), but checks exactly len
+         * bytes and rejects any NULs in that range. */
+
+        assert(str);
+
+        for (i = 0; i < len; i++)
+                if ((unsigned char) str[i] >= 128 || str[i] == 0)
+                        return NULL;
+
+        return (char*) str;
+}
+
 /**
  * utf8_encode_unichar() - Encode single UCS-4 character as UTF-8
  * @out_utf8: output buffer of at least 4 bytes or NULL

src/basic/utf8.h

@@ -22,6 +22,7 @@ bool unichar_is_valid(char32_t c);
 
 const char *utf8_is_valid(const char *s) _pure_;
 char *ascii_is_valid(const char *s) _pure_;
+char *ascii_is_valid_n(const char *str, size_t len);
 
 bool utf8_is_printable_newline(const char* str, size_t length, bool newline) _pure_;
 #define utf8_is_printable(str, length) utf8_is_printable_newline(str, length, true)

src/test/test-utf8.c

@@ -24,11 +24,21 @@ static void test_utf8_is_valid(void) {
 }
 
 static void test_ascii_is_valid(void) {
-        assert_se(ascii_is_valid("alsdjf\t\vbarr\nba z"));
+        assert_se( ascii_is_valid("alsdjf\t\vbarr\nba z"));
         assert_se(!ascii_is_valid("\342\204\242"));
         assert_se(!ascii_is_valid("\341\204"));
 }
 
+static void test_ascii_is_valid_n(void) {
+        assert_se( ascii_is_valid_n("alsdjf\t\vbarr\nba z", 17));
+        assert_se( ascii_is_valid_n("alsdjf\t\vbarr\nba z", 16));
+        assert_se(!ascii_is_valid_n("alsdjf\t\vbarr\nba z", 18));
+        assert_se(!ascii_is_valid_n("\342\204\242", 3));
+        assert_se(!ascii_is_valid_n("\342\204\242", 2));
+        assert_se(!ascii_is_valid_n("\342\204\242", 1));
+        assert_se( ascii_is_valid_n("\342\204\242", 0));
+}
+
 static void test_utf8_encoded_valid_unichar(void) {
         assert_se(utf8_encoded_valid_unichar("\342\204\242") == 3);
         assert_se(utf8_encoded_valid_unichar("\302\256") == 2);
@@ -115,6 +125,7 @@ int main(int argc, char *argv[]) {
         test_utf8_is_valid();
         test_utf8_is_printable();
         test_ascii_is_valid();
+        test_ascii_is_valid_n();
         test_utf8_encoded_valid_unichar();
         test_utf8_escaping();
         test_utf8_escaping_printable();