make Range::size() constexpr

[folly.git] / folly / Range.h

diff --git a/folly/Range.h b/folly/Range.h
index d42fe54872cee5b29454a6f80c82bebfc6c89c97..4a06491684549db077af179fb49270e4223375f8 100644 (file)
--- a/folly/Range.h
+++ b/folly/Range.h
@@ -17,13 +17,13 @@
 // @author Mark Rabkin (mrabkin@fb.com)
 // @author Andrei Alexandrescu (andrei.alexandrescu@fb.com)
 
-#ifndef FOLLY_RANGE_H_
-#define FOLLY_RANGE_H_
+#pragma once
 
-#include <folly/Portability.h>
 #include <folly/FBString.h>
+#include <folly/Portability.h>
 #include <folly/SpookyHashV2.h>
 #include <folly/portability/Constexpr.h>
+#include <folly/portability/String.h>
 
 #include <algorithm>
 #include <boost/operators.hpp>
@@ -353,8 +353,13 @@ public:
     reset(str.data(), str.size());
   }
 
-  size_type size() const {
-    assert(b_ <= e_);
+  constexpr size_type size() const {
+    // It would be nice to assert(b_ <= e_) here.  This can be achieved even
+    // in a C++11 compatible constexpr function:
+    // http://ericniebler.com/2014/09/27/assert-and-constexpr-in-cxx11/
+    // Unfortunately current gcc versions have a bug causing it to reject
+    // this check in a constexpr function:
+    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71448
     return e_ - b_;
   }
   size_type walk_size() const {
@@ -1085,14 +1090,12 @@ inline size_t qfind(const Range<const char*>& haystack, const char& needle) {
   return pos == nullptr ? std::string::npos : pos - haystack.data();
 }
 
-#if FOLLY_HAVE_MEMRCHR
 template <>
 inline size_t rfind(const Range<const char*>& haystack, const char& needle) {
   auto pos = static_cast<const char*>(
     ::memrchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
 }
-#endif
 
 // specialization for ByteRange
 template <>
@@ -1103,7 +1106,6 @@ inline size_t qfind(const Range<const unsigned char*>& haystack,
   return pos == nullptr ? std::string::npos : pos - haystack.data();
 }
 
-#if FOLLY_HAVE_MEMRCHR
 template <>
 inline size_t rfind(const Range<const unsigned char*>& haystack,
                     const unsigned char& needle) {
@@ -1111,7 +1113,6 @@ inline size_t rfind(const Range<const unsigned char*>& haystack,
     ::memrchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
 }
-#endif
 
 template <class T>
 size_t qfind_first_of(const Range<T>& haystack,
@@ -1150,5 +1151,3 @@ struct hasher<folly::Range<T*>,
 #pragma GCC diagnostic pop
 
 FOLLY_ASSUME_FBVECTOR_COMPATIBLE_1(folly::Range);
-
-#endif // FOLLY_RANGE_H_