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-rw-r--r--src/include/refstring.h127
1 files changed, 127 insertions, 0 deletions
diff --git a/src/include/refstring.h b/src/include/refstring.h
new file mode 100644
index 000000000000..f0d5b4456da5
--- /dev/null
+++ b/src/include/refstring.h
@@ -0,0 +1,127 @@
+//===------------------------ __refstring ---------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_REFSTRING_H
+#define _LIBCPP_REFSTRING_H
+
+#include <__config>
+#include <stdexcept>
+#include <cstddef>
+#include <cstring>
+#ifdef __APPLE__
+#include <dlfcn.h>
+#include <mach-o/dyld.h>
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __refstring_imp { namespace {
+typedef int count_t;
+
+struct _Rep_base {
+ std::size_t len;
+ std::size_t cap;
+ count_t count;
+};
+
+inline _Rep_base* rep_from_data(const char *data_) noexcept {
+ char *data = const_cast<char *>(data_);
+ return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base));
+}
+
+inline char * data_from_rep(_Rep_base *rep) noexcept {
+ char *data = reinterpret_cast<char *>(rep);
+ return data + sizeof(*rep);
+}
+
+#if defined(__APPLE__)
+inline
+const char* compute_gcc_empty_string_storage() _NOEXCEPT
+{
+ void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD);
+ if (handle == nullptr)
+ return nullptr;
+ void* sym = dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE");
+ if (sym == nullptr)
+ return nullptr;
+ return data_from_rep(reinterpret_cast<_Rep_base *>(sym));
+}
+
+inline
+const char*
+get_gcc_empty_string_storage() _NOEXCEPT
+{
+ static const char* p = compute_gcc_empty_string_storage();
+ return p;
+}
+#endif
+
+}} // namespace __refstring_imp
+
+using namespace __refstring_imp;
+
+inline
+__libcpp_refstring::__libcpp_refstring(const char* msg) {
+ std::size_t len = strlen(msg);
+ _Rep_base* rep = static_cast<_Rep_base *>(::operator new(sizeof(*rep) + len + 1));
+ rep->len = len;
+ rep->cap = len;
+ rep->count = 0;
+ char *data = data_from_rep(rep);
+ std::memcpy(data, msg, len + 1);
+ __imp_ = data;
+}
+
+inline
+__libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) _NOEXCEPT
+ : __imp_(s.__imp_)
+{
+ if (__uses_refcount())
+ __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+}
+
+inline
+__libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _NOEXCEPT {
+ bool adjust_old_count = __uses_refcount();
+ struct _Rep_base *old_rep = rep_from_data(__imp_);
+ __imp_ = s.__imp_;
+ if (__uses_refcount())
+ __sync_add_and_fetch(&rep_from_data(__imp_)->count, 1);
+ if (adjust_old_count)
+ {
+ if (__sync_add_and_fetch(&old_rep->count, count_t(-1)) < 0)
+ {
+ ::operator delete(old_rep);
+ }
+ }
+ return *this;
+}
+
+inline
+__libcpp_refstring::~__libcpp_refstring() {
+ if (__uses_refcount()) {
+ _Rep_base* rep = rep_from_data(__imp_);
+ if (__sync_add_and_fetch(&rep->count, count_t(-1)) < 0) {
+ ::operator delete(rep);
+ }
+ }
+}
+
+inline
+bool __libcpp_refstring::__uses_refcount() const {
+#ifdef __APPLE__
+ return __imp_ != get_gcc_empty_string_storage();
+#else
+ return true;
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif //_LIBCPP_REFSTRING_H