Add util function to remove trailing '\r'

Depending on the platform and adb versions, the lines output by adb
could end with "\r\r\n". This util function helps to remove all trailing
'\r'.

PR #2827 <https://github.com/Genymobile/scrcpy/pull/2827>

app/src/util/str.c

@@ -330,3 +330,14 @@ sc_str_index_of_column(const char *s, unsigned col, const char *seps) {
 
     return col == colidx ? (ssize_t) idx : -1;
 }
+
+size_t
+sc_str_remove_trailing_cr(char *s, size_t len) {
+    while (len) {
+        if (s[len - 1] != '\r') {
+            break;
+        }
+        s[--len] = '\0';
+    }
+    return len;
+}

app/src/util/str.h

@@ -134,4 +134,15 @@ sc_str_truncate(char *data, size_t len, const char *endchars);
 ssize_t
 sc_str_index_of_column(const char *s, unsigned col, const char *seps);
 
+/**
+ * Remove all `\r` at the end of the line
+ *
+ * The line length is provided by `len` (this avoids a call to `strlen()` when
+ * the caller already knows the length).
+ *
+ * Return the new length.
+ */
+size_t
+sc_str_remove_trailing_cr(char *s, size_t len);
+
 #endif

app/tests/test_str.c

@@ -384,6 +384,20 @@ static void test_index_of_column(void) {
     assert(sc_str_index_of_column("  a bc  d", 1, " ") == 2);
 }
 
+static void test_remove_trailing_cr() {
+    char s[] = "abc\r";
+    sc_str_remove_trailing_cr(s, sizeof(s) - 1);
+    assert(!strcmp(s, "abc"));
+
+    char s2[] = "def\r\r\r\r";
+    sc_str_remove_trailing_cr(s2, sizeof(s2) - 1);
+    assert(!strcmp(s2, "def"));
+
+    char s3[] = "adb\rdef\r";
+    sc_str_remove_trailing_cr(s3, sizeof(s3) - 1);
+    assert(!strcmp(s3, "adb\rdef"));
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -405,5 +419,6 @@ int main(int argc, char *argv[]) {
     test_wrap_lines();
     test_truncate();
     test_index_of_column();
+    test_remove_trailing_cr();
     return 0;
 }