NVMeCache: make the return of getCache() const

Returing a const std::span now to privent the receiver from overwriting
the cache value.

Tested: N/A
Google-Bug-Id: 348660385
Signed-off-by: Hao Jiang <jianghao@google.com>
Change-Id: I28211a41e4232ec9ded98bd2c89a25e3592a4f8a

src/NVMeCache.hpp

diff --git a/src/NVMeCache.hpp b/src/NVMeCache.hpp
index e0dce89..ba20773 100644
--- a/src/NVMeCache.hpp
+++ b/src/NVMeCache.hpp
@@ -89,7 +89,8 @@
     virtual constexpr std::string_view getIdentifier() const noexcept = 0;
     virtual bool isCacheValid() const noexcept = 0;
     virtual std::tuple<std::chrono::time_point<ClockType>,
-                       std::chrono::time_point<ClockType>, std::span<uint8_t>>
+                       std::chrono::time_point<ClockType>,
+                       std::span<const uint8_t>>
         getCache() const noexcept = 0;
 };
 

src/NVMeCacheImpl.hpp

diff --git a/src/NVMeCacheImpl.hpp b/src/NVMeCacheImpl.hpp
index 262c4c4..824205f 100644
--- a/src/NVMeCacheImpl.hpp
+++ b/src/NVMeCacheImpl.hpp
@@ -50,7 +50,7 @@
         return cacheValid;
     }
     std::tuple<std::chrono::time_point<ClockType>,
-               std::chrono::time_point<ClockType>, std::span<uint8_t>>
+               std::chrono::time_point<ClockType>, std::span<const uint8_t>>
         getCache() const noexcept override
     {
         return {};

src/NVMeMetricStore.cpp

diff --git a/src/NVMeMetricStore.cpp b/src/NVMeMetricStore.cpp
index c99ad6b..03bb21c 100644
--- a/src/NVMeMetricStore.cpp
+++ b/src/NVMeMetricStore.cpp
@@ -3,8 +3,9 @@
 #include <xyz/openbmc_project/Common/File/error.hpp>
 #include <xyz/openbmc_project/Common/error.hpp>
 
-sdbusplus::message::unix_fd MetricStore::writeToFd(std::span<uint8_t> header,
-                                                   std::span<uint8_t> data)
+sdbusplus::message::unix_fd
+    MetricStore::writeToFd(std::span<const uint8_t> header,
+                           std::span<const uint8_t> data)
 {
     std::array<int, 2> pipe{};
     if (::pipe(pipe.data()) < 0)

src/NVMeMetricStore.hpp

diff --git a/src/NVMeMetricStore.hpp b/src/NVMeMetricStore.hpp
index 6871b01..f88b4d5 100644
--- a/src/NVMeMetricStore.hpp
+++ b/src/NVMeMetricStore.hpp
@@ -82,8 +82,8 @@
      *
      * @return sdbusplus::message::unix_fd: Returns the read end of the pipe
      */
-    sdbusplus::message::unix_fd writeToFd(std::span<uint8_t> header,
-                                          std::span<uint8_t> data);
+    sdbusplus::message::unix_fd writeToFd(std::span<const uint8_t> header,
+                                          std::span<const uint8_t> data);
 
     /**
      * @brief Gets Metric using a unique metric name. Metric must be registered

tests/test_nvme_cache.cpp

diff --git a/tests/test_nvme_cache.cpp b/tests/test_nvme_cache.cpp
index fdcc189..a56619e 100644
--- a/tests/test_nvme_cache.cpp
+++ b/tests/test_nvme_cache.cpp
@@ -51,10 +51,10 @@
 
     MOCK_METHOD(bool, isCacheValid, (), (const, noexcept, override));
 
-    MOCK_METHOD(
-        (std::tuple<std::chrono::time_point<ClockType>,
-                    std::chrono::time_point<ClockType>, std::span<uint8_t>>),
-        getCache, (), (const, noexcept, override));
+    MOCK_METHOD((std::tuple<std::chrono::time_point<ClockType>,
+                            std::chrono::time_point<ClockType>,
+                            std::span<const uint8_t>>),
+                getCache, (), (const, noexcept, override));
 };
 
 /**