Expose util function to truncate first line

Move the local implementation from adb functions to the string util
functions.

app/src/adb.c

@@ -253,17 +253,6 @@ adb_execute_for_output(const char *serial, const char *const adb_cmd[],
     return r;
 }
 
-static size_t
-truncate_first_line(char *data, size_t len) {
-    data[len - 1] = '\0';
-    char *eol = strpbrk(data, "\r\n");
-    if (eol) {
-        *eol = '\0';
-        len = eol - data;
-    }
-    return len;
-}
-
 char *
 adb_get_serialno(void) {
     char buf[128];
@@ -275,6 +264,6 @@ adb_get_serialno(void) {
         return NULL;
     }
 
-    truncate_first_line(buf, r);
+    sc_str_truncate_first_line(buf, r);
     return strdup(buf);
 }

app/src/util/str.c

@@ -291,3 +291,14 @@ error:
     free(buf.s);
     return NULL;
 }
+
+size_t
+sc_str_truncate_first_line(char *data, size_t len) {
+    data[len - 1] = '\0';
+    char *eol = strpbrk(data, "\r\n");
+    if (eol) {
+        *eol = '\0';
+        len = eol - data;
+    }
+    return len;
+}

app/src/util/str.h

@@ -103,4 +103,15 @@ sc_str_from_wchars(const wchar_t *s);
 char *
 sc_str_wrap_lines(const char *input, unsigned columns, unsigned indent);
 
+/**
+ * Truncate the data after the first line
+ *
+ * An '\0' is always written at the end of the data, even if no newline
+ * character is encountered.
+ *
+ * Return the size of the resulting line.
+ */
+size_t
+sc_str_truncate_first_line(char *data, size_t len);
+
 #endif

app/tests/test_str.c

@@ -337,6 +337,14 @@ static void test_wrap_lines(void) {
     free(formatted);
 }
 
+static void test_truncate_first_line(void) {
+    char s[] = "hello\nworld\n!";
+    size_t len = sc_str_truncate_first_line(s, sizeof(s));
+
+    assert(len == 5);
+    assert(!strcmp("hello", s));
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -356,5 +364,6 @@ int main(int argc, char *argv[]) {
     test_parse_integer_with_suffix();
     test_strlist_contains();
     test_wrap_lines();
+    test_truncate_first_line();
     return 0;
 }