+static StringRef getDirnameCharSep(StringRef path, const char *Sep) {
+ assert(Sep[0] != '\0' && Sep[1] == '\0' &&
+ "Sep must be a 1-character string literal.");
+ if (path.empty())
+ return ".";
+
+ // If the path is all slashes, return a single slash.
+ // Otherwise, remove all trailing slashes.
+
+ signed pos = static_cast<signed>(path.size()) - 1;
+
+ while (pos >= 0 && path[pos] == Sep[0])
+ --pos;
+
+ if (pos < 0)
+ return path[0] == Sep[0] ? Sep : ".";
+
+ // Any slashes left?
+ signed i = 0;
+
+ while (i < pos && path[i] != Sep[0])
+ ++i;
+
+ if (i == pos) // No slashes? Return "."
+ return ".";
+
+ // There is at least one slash left. Remove all trailing non-slashes.
+ while (pos >= 0 && path[pos] != Sep[0])
+ --pos;
+
+ // Remove any trailing slashes.
+ while (pos >= 0 && path[pos] == Sep[0])
+ --pos;
+
+ if (pos < 0)
+ return path[0] == Sep[0] ? Sep : ".";
+
+ return path.substr(0, pos+1);
+}
+