An intro to the upgrade mutex in the Synchronized docs

[folly.git] / folly / Range.h

diff --git a/folly/Range.h b/folly/Range.h
index 4a06491684549db077af179fb49270e4223375f8..0b63f45770efa5f29ec579b48d23c86d37bdd962 100644 (file)
--- a/folly/Range.h
+++ b/folly/Range.h
@@ -1085,6 +1085,10 @@ size_t rfind(const Range<T>& haystack,
 // specialization for StringPiece
 template <>
 inline size_t qfind(const Range<const char*>& haystack, const char& needle) {
+  // memchr expects a not-null pointer, early return if the range is empty.
+  if (haystack.empty()) {
+    return std::string::npos;
+  }
   auto pos = static_cast<const char*>(
     ::memchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
@@ -1092,6 +1096,10 @@ inline size_t qfind(const Range<const char*>& haystack, const char& needle) {
 
 template <>
 inline size_t rfind(const Range<const char*>& haystack, const char& needle) {
+  // memchr expects a not-null pointer, early return if the range is empty.
+  if (haystack.empty()) {
+    return std::string::npos;
+  }
   auto pos = static_cast<const char*>(
     ::memrchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
@@ -1101,6 +1109,10 @@ inline size_t rfind(const Range<const char*>& haystack, const char& needle) {
 template <>
 inline size_t qfind(const Range<const unsigned char*>& haystack,
                     const unsigned char& needle) {
+  // memchr expects a not-null pointer, early return if the range is empty.
+  if (haystack.empty()) {
+    return std::string::npos;
+  }
   auto pos = static_cast<const unsigned char*>(
     ::memchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
@@ -1109,6 +1121,10 @@ inline size_t qfind(const Range<const unsigned char*>& haystack,
 template <>
 inline size_t rfind(const Range<const unsigned char*>& haystack,
                     const unsigned char& needle) {
+  // memchr expects a not-null pointer, early return if the range is empty.
+  if (haystack.empty()) {
+    return std::string::npos;
+  }
   auto pos = static_cast<const unsigned char*>(
     ::memrchr(haystack.data(), needle, haystack.size()));
   return pos == nullptr ? std::string::npos : pos - haystack.data();
@@ -1146,6 +1162,14 @@ struct hasher<folly::Range<T*>,
   }
 };
 
+/**
+ * Ubiquitous helper template for knowing what's a string
+ */
+template <class T> struct IsSomeString {
+  enum { value = std::is_same<T, std::string>::value
+         || std::is_same<T, fbstring>::value };
+};
+
 }  // !namespace folly
 
 #pragma GCC diagnostic pop