Bug 1660177 - Replace SpliceableJSONWriter::Splice(const char*) with better calls where possible - r=canaltinova

In most calls to `SpliceableJSONWriter::Splice(const char*)`:
- The data comes from a `ChunkedJSONWriteFunc` and is copied to a new buffer, which is then copied again through `Write()`. Instead we can copy the data directly from the `ChunkedJSONWriteFunc`; and this is a nice complement to `TakeAndSplice()` below.
- Or the length is already known, so we can pass it to a new `Splice(const char*, size_t)`, which forwards it to `Write(const char*, size_t)`, saving one `strlen` call.

Differential Revision: https://phabricator.services.mozilla.com/D87703

mozglue/baseprofiler/core/ProfileBufferEntry.cpp

@@ -205,9 +205,8 @@ UniqueJSONStrings::UniqueJSONStrings(const UniqueJSONStrings& aOther) {
       mStringHashToIndexMap.putNewInfallible(iter.get().key(),
                                              iter.get().value());
     }
-    UniquePtr<char[]> stringTableJSON =
+    mStringTableWriter.CopyAndSplice(
-        aOther.mStringTableWriter.ChunkedWriteFunc().CopyData();
+        aOther.mStringTableWriter.ChunkedWriteFunc());
-    mStringTableWriter.Splice(stringTableJSON.get());
   }
 }
 

mozglue/baseprofiler/core/platform.cpp

@@ -2927,7 +2927,7 @@ static void locked_profiler_save_profile_to_file(PSLockRef aLock,
       Vector<std::string> exitProfiles = ActivePS::MoveExitProfiles(aLock);
       for (auto& exitProfile : exitProfiles) {
         if (!exitProfile.empty()) {
-          w.Splice(exitProfile.c_str());
+          w.Splice(exitProfile.c_str(), exitProfile.length());
         }
       }
       w.EndArray();

mozglue/baseprofiler/public/BaseProfileJSONWriter.h

@@ -186,12 +186,26 @@ class SpliceableJSONWriter : public JSONWriter {
     mNeedComma[mDepth] = true;
   }
 
+  void Splice(const char* aStr, size_t aLen) {
+    Separator();
+    WriteFunc()->Write(aStr, aLen);
+    mNeedComma[mDepth] = true;
+  }
+
   // Splice the given JSON directly in, without quoting.
   void SplicedJSONProperty(const char* aMaybePropertyName,
                            const char* aJsonValue) {
     Scalar(aMaybePropertyName, aJsonValue);
   }
 
+  void CopyAndSplice(const ChunkedJSONWriteFunc& aFunc) {
+    Separator();
+    for (size_t i = 0; i < aFunc.mChunkList.length(); i++) {
+      WriteFunc()->Write(aFunc.mChunkList[i].get(), aFunc.mChunkLengths[i]);
+    }
+    mNeedComma[mDepth] = true;
+  }
+
   // Takes the chunks from aFunc and write them. If move is not possible
   // (e.g., using OStreamJSONWriteFunc), aFunc's chunks are copied and its
   // storage cleared.

tools/profiler/core/ProfileBufferEntry.cpp

@@ -217,9 +217,8 @@ UniqueJSONStrings::UniqueJSONStrings(const UniqueJSONStrings& aOther) {
       mStringHashToIndexMap.putNewInfallible(iter.get().key(),
                                              iter.get().value());
     }
-    UniquePtr<char[]> stringTableJSON =
+    mStringTableWriter.CopyAndSplice(
-        aOther.mStringTableWriter.ChunkedWriteFunc().CopyData();
+        aOther.mStringTableWriter.ChunkedWriteFunc());
-    mStringTableWriter.Splice(stringTableJSON.get());
   }
 }
 
@@ -357,7 +356,8 @@ UniqueStacks::LookupFramesForJITAddressFromBufferPos(void* aJITAddress,
       auto frameJSON =
           jitFrameInfoRange.mJITFrameToFrameJSONMap.lookup(jitFrameKey);
       MOZ_RELEASE_ASSERT(frameJSON, "Should have cached JSON for this frame");
-      mFrameTableWriter.Splice(frameJSON->value().get());
+      mFrameTableWriter.Splice(frameJSON->value().get(),
+                               frameJSON->value().Length());
       MOZ_RELEASE_ASSERT(mFrameToIndexMap.add(entry, frameKey, index));
     }
     MOZ_RELEASE_ASSERT(frameKeys.append(std::move(frameKey)));

tools/profiler/core/platform.cpp

@@ -4418,7 +4418,7 @@ static void locked_profiler_save_profile_to_file(
       Vector<nsCString> exitProfiles = ActivePS::MoveExitProfiles(aLock);
       for (auto& exitProfile : exitProfiles) {
         if (!exitProfile.IsEmpty()) {
-          w.Splice(exitProfile.get());
+          w.Splice(exitProfile.get(), exitProfile.Length());
         }
       }
       w.EndArray();

tools/profiler/gecko/nsProfiler.cpp

@@ -807,7 +807,8 @@ void nsProfiler::GatheredOOPProfile(const nsACString& aProfile) {
                      "Should always have a writer if mGathering is true");
 
   if (!aProfile.IsEmpty()) {
-    mWriter->Splice(PromiseFlatCString(aProfile).get());
+    // TODO: Remove PromiseFlatCString, see bug 1657033.
+    mWriter->Splice(PromiseFlatCString(aProfile).get(), aProfile.Length());
   }
 
   mPendingProfiles--;
@@ -890,7 +891,7 @@ RefPtr<nsProfiler::GatheringPromise> nsProfiler::StartGathering(
   Vector<nsCString> exitProfiles = profiler_move_exit_profiles();
   for (auto& exitProfile : exitProfiles) {
     if (!exitProfile.IsEmpty()) {
-      mWriter->Splice(exitProfile.get());
+      mWriter->Splice(exitProfile.get(), exitProfile.Length());
     }
   }