From 67cc11ad6f5fb7b1e1948513292ef00edee34f5e Mon Sep 17 00:00:00 2001
From: Assaf Gordon <assafgordon@fb.com>
Date: Mon, 31 Jan 2022 15:35:29 -0800
Subject: [PATCH] add helper class for fmt>8.1

Summary:
This is a long-term solution instead of the 'quick fix' of D33661759 .
fmt version >=8.1 changed internal structures and does not automatically
format the 'DestructorContext' enum.
Add a helper class to format the enum to strings, based on the example
in https://fmt.dev/latest/api.html#udt .

NOTE:
This changes the debug output of the ItemRecords::validate() function
(the last two parameters in the two XLOGF calls).

Reviewed By: therealgymmy

Differential Revision: D33662085

fbshipit-source-id: 608b498c762ca95cc71cb1597831a5c2a5f2c575
---
 cachelib/cachebench/cache/ItemRecords.h | 26 +++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/cachelib/cachebench/cache/ItemRecords.h b/cachelib/cachebench/cache/ItemRecords.h
index 651972722..cc1cfe100 100644
--- a/cachelib/cachebench/cache/ItemRecords.h
+++ b/cachelib/cachebench/cache/ItemRecords.h
@@ -22,6 +22,32 @@
 #include "cachelib/allocator/Cache.h"
 #include "cachelib/cachebench/cache/CacheValue.h"
 
+using DestructorContext = facebook::cachelib::DestructorContext;
+/* From: https://fmt.dev/latest/api.html#udt */
+template <>
+struct fmt::formatter<DestructorContext> : formatter<string_view> {
+  // parse is inherited from formatter<string_view>.
+  template <typename FormatContext>
+  auto format(DestructorContext c, FormatContext& ctx) {
+    string_view name = "unknown";
+    switch (c) {
+    case DestructorContext::kEvictedFromRAM:
+      name = "kEvictedFromRAM";
+      break;
+    case DestructorContext::kEvictedFromNVM:
+      name = "kEvictedFromNVM";
+      break;
+    case DestructorContext::kRemovedFromRAM:
+      name = "kRemovedFromRAM";
+      break;
+    case DestructorContext::kRemovedFromNVM:
+      name = "kRemovedFromNVM";
+      break;
+    }
+    return formatter<string_view>::format(name, ctx);
+  }
+};
+
 namespace facebook::cachelib::cachebench {
 /*
  * ItemRecord and ItemRecords are used for DestructorCheck in cachebench.