Add android::base::Readlink.
Bug: http://b/30988271
Change-Id: Ib844d7c9e33465dabf7aee5e24dc3d1d8d799abd
diff --git a/file.cpp b/file.cpp
index 4e7ac82..3963081 100644
--- a/file.cpp
+++ b/file.cpp
@@ -20,8 +20,10 @@
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
+#include <unistd.h>
#include <string>
+#include <vector>
#include "android-base/macros.h" // For TEMP_FAILURE_RETRY on Darwin.
#include "android-base/logging.h"
@@ -171,5 +173,29 @@
return true;
}
+#if !defined(_WIN32)
+bool Readlink(const std::string& path, std::string* result) {
+ result->clear();
+
+ // Most Linux file systems (ext2 and ext4, say) limit symbolic links to
+ // 4095 bytes. Since we'll copy out into the string anyway, it doesn't
+ // waste memory to just start there. We add 1 so that we can recognize
+ // whether it actually fit (rather than being truncated to 4095).
+ std::vector<char> buf(4095 + 1);
+ while (true) {
+ ssize_t size = readlink(path.c_str(), &buf[0], buf.size());
+ // Unrecoverable error?
+ if (size == -1) return false;
+ // It fit! (If size == buf.size(), it may have been truncated.)
+ if (static_cast<size_t>(size) < buf.size()) {
+ result->assign(&buf[0], size);
+ return true;
+ }
+ // Double our buffer and try again.
+ buf.resize(buf.size() * 2);
+ }
+}
+#endif
+
} // namespace base
} // namespace android