From 9300d7b80bb9dd7764efec1194f91c9ee6d595e2 Mon Sep 17 00:00:00 2001
From: Kefu Chai <kefu.chai@scylladb.com>
Date: Sat, 9 Mar 2024 21:08:12 +0800
Subject: [PATCH] utils/human_readable: add fmt::formatter for
 human_readable_value

before this change, we rely on the default-generated fmt::formatter created
from operator<<, but fmt v10 dropped the default-generated formatter.

in this change, we define formatters for `utils::human_readable_value`,
and drop its operator<<

Refs #13245

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
---
 utils/human_readable.cc | 17 +++++++++--------
 utils/human_readable.hh | 10 ++++++----
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/utils/human_readable.cc b/utils/human_readable.cc
index 76c10dbeb8..20eaddb5dd 100644
--- a/utils/human_readable.cc
+++ b/utils/human_readable.cc
@@ -13,14 +13,6 @@
 
 namespace utils {
 
-std::ostream& operator<<(std::ostream& os, const human_readable_value& val) {
-    os << val.value;
-    if (val.suffix) {
-        os << val.suffix;
-    }
-    return os;
-}
-
 static human_readable_value to_human_readable_value(uint64_t value, uint64_t step, uint64_t precision, const std::array<char, 5>& suffixes) {
     if (!value) {
         return {0, suffixes[0]};
@@ -48,3 +40,12 @@ human_readable_value to_hr_size(uint64_t size) {
 }
 
 } // namespace utils
+
+auto fmt::formatter<utils::human_readable_value>::format(const utils::human_readable_value& val, fmt::format_context& ctx) const
+        -> decltype(ctx.out()) {
+    auto out = fmt::format_to(ctx.out(), "{}", val.value);
+    if (val.suffix) {
+        out = fmt::format_to(out, "{}", val.suffix);
+    }
+    return out;
+}
diff --git a/utils/human_readable.hh b/utils/human_readable.hh
index 5494294d16..81c203b0b6 100644
--- a/utils/human_readable.hh
+++ b/utils/human_readable.hh
@@ -8,8 +8,8 @@
 
 #pragma once
 
-#include <cinttypes>
-#include <iosfwd>
+#include <cstdint>
+#include <fmt/core.h>
 
 namespace utils {
 
@@ -18,8 +18,6 @@ struct human_readable_value {
     char suffix; // 0 -> no suffix
 };
 
-std::ostream& operator<<(std::ostream& os, const human_readable_value& val);
-
 /// Convert a size to a human readable representation.
 ///
 /// The human-readable representation has at most 4 digits
@@ -38,3 +36,7 @@ std::ostream& operator<<(std::ostream& os, const human_readable_value& val);
 human_readable_value to_hr_size(uint64_t size);
 
 } // namespace utils
+
+template <> struct fmt::formatter<utils::human_readable_value> : fmt::formatter<std::string_view> {
+    auto format(const utils::human_readable_value&, fmt::format_context& ctx) const -> decltype(ctx.out());
+};