[1] Updates for code review.

cpp/src/arrow/flight/client_header_internal.cc

@@ -26,6 +26,7 @@
 #include "arrow/util/make_unique.h"
 #include "arrow/util/string.h"
 #include "arrow/util/uri.h"
+#include "arrow/util/value_parsing.h"
 
 #ifdef _WIN32
 #define strcasecmp stricmp
@@ -57,6 +58,13 @@ bool CaseInsensitiveComparator::operator()(const std::string& lhs,
   return strcasecmp(lhs.c_str(), rhs.c_str()) < 0;
 }
 
+size_t CaseInsensitiveHash::operator()(const std::string& key) const {
+  std::string upper_string = key;
+  std::transform(upper_string.begin(), upper_string.end(), upper_string.begin(),
+                 ::toupper);
+  return std::hash<std::string>{}(upper_string);
+}
+
 Cookie Cookie::parse(const arrow::util::string_view& cookie_header_value) {
   // Parse the cookie string. If the cookie has an expiration, record it.
   // If the cookie has a max-age, calculate the current time + max_age and set that as
@@ -252,8 +260,7 @@ void CookieCache::UpdateCachedCookies(const CallHeaders& incoming_headers) {
 
     // Cache cookies regardless of whether or not they are expired. The server may have
     // explicitly sent a Set-Cookie to expire a cached cookie.
-    std::pair<std::map<std::string, Cookie, CaseInsensitiveComparator>::iterator, bool>
-        insertable = cookies.insert({cookie.GetName(), cookie});
+    auto insertable = cookies.insert({cookie.GetName(), cookie});
 
     // Force overwrite on insert collision.
     if (!insertable.second) {

cpp/src/arrow/flight/client_header_internal.h

@@ -23,7 +23,6 @@
 #include "arrow/flight/client_middleware.h"
 #include "arrow/result.h"
 #include "arrow/util/optional.h"
-#include "arrow/util/value_parsing.h"
 
 #ifdef GRPCPP_PP_INCLUDE
 #include <grpcpp/grpcpp.h>
@@ -34,15 +33,28 @@
 #include <grpc++/grpc++.h>
 #endif
 
+#include <chrono>
+#include <functional>
+#include <mutex>
+#include <string>
+#include <unordered_map>
+
 namespace arrow {
 namespace flight {
 namespace internal {
 
 /// \brief Case insensitive comparator for use by cookie caching map. Cookies are not
 /// case sensitive.
-struct ARROW_FLIGHT_EXPORT CaseInsensitiveComparator
-    : public std::binary_function<std::string, std::string, bool> {
-  bool operator()(const std::string& lhs, const std::string& rhs) const;
+class ARROW_FLIGHT_EXPORT CaseInsensitiveComparator {
+ public:
+  bool operator()(const std::string& t1, const std::string& t2) const;
+};
+
+/// \brief Case insensitive hasher for use by cookie caching map. Cookies are not
+/// case sensitive.
+class ARROW_FLIGHT_EXPORT CaseInsensitiveHash {
+ public:
+  size_t operator()(const std::string& key) const;
 };
 
 /// \brief Class to represent a cookie.
@@ -114,7 +126,8 @@ class ARROW_FLIGHT_EXPORT CookieCache {
 
   // Mutex must be used to protect cookie cache.
   std::mutex mutex_;
-  std::map<std::string, Cookie, CaseInsensitiveComparator> cookies;
+  std::unordered_map<std::string, Cookie, CaseInsensitiveHash, CaseInsensitiveComparator>
+      cookies;
 };
 
 /// \brief Add basic authentication header key value pair to context.