Just use stack allocations in parsing by default.

src/discord-rpc.cpp

@@ -82,18 +82,40 @@ extern "C" void Discord_UpdateConnection()
     }
     else {
         // reads
-        JsonDocument message;
-        while (Connection->Read(message)) {
+
+        // json parser will use this buffer first, then allocate more if needed; I seriously doubt we send any messages that would use all of this, though.
+        char parseBuffer[32 * 1024];
+        for (;;) {
+            PoolAllocator pa(parseBuffer, sizeof(parseBuffer));
+            StackAllocator sa;
+            JsonDocument message(rapidjson::kObjectType, &pa, sizeof(sa.fixedBuffer_), &sa);
+
+            if (!Connection->Read(message)) {
+                break;
+            }
+
+            const char* evtName = nullptr;
+            auto evt = message.FindMember("evt");
+            if (evt != message.MemberEnd() && evt->value.IsString()) {
+                evtName = evt->value.GetString();
+            }
+
             auto nonce = message.FindMember("nonce");
             if (nonce != message.MemberEnd() && nonce->value.IsString()) {
                 // in responses only -- should use to match up response when needed.
-                //auto cmd = message.FindMember("cmd"); needed?
+
+                if (evtName && strcmp(evtName, "ERROR") == 0) {
+                    auto data = message.FindMember("data");
+                    LastErrorCode = data->value["code"].GetInt();
+                    StringCopy(LastErrorMessage, data->value["message"].GetString());
+                    GotErrorMessage.store(true);
+                }
             }
             else {
                 // should have evt == name of event, optional data
-                auto evt = message.FindMember("evt");
-                if (evt != message.MemberEnd() && evt->value.IsString()) {
-                    const char* evtName = evt->value.GetString();
+                if (evtName == nullptr) {
+                    continue;
+                }
 
                 // todo ug
                 if (strcmp(evtName, "PRESENCE_REQUESTED") == 0) {
@@ -113,7 +135,6 @@ extern "C" void Discord_UpdateConnection()
                 }
             }
         }
-        }
 
         // writes
         while (SendQueuePendingSends.load()) {

src/rpc_connection.cpp

@@ -34,7 +34,10 @@ void RpcConnection::Open()
     }
 
     if (state == State::SentHandshake) {
-        JsonDocument message;
+        char parseBuffer[32 * 1024];
+        PoolAllocator pa(parseBuffer, sizeof(parseBuffer));
+        StackAllocator sa;
+        JsonDocument message(rapidjson::kObjectType, &pa, sizeof(sa.fixedBuffer_), &sa);
         if (Read(message)) {
             auto cmd = message.FindMember("cmd");
             if (cmd == message.MemberEnd() || !cmd->value.IsString()) {

src/serialization.cpp

@@ -2,6 +2,8 @@
 #include "connection.h"
 #include "discord-rpc.h"
 
+MallocAllocator MallocAllocatorInst;
+
 // it's ever so slightly faster to not have to strlen the key
 template<typename T>
 void WriteKey(JsonWriter& w, T& k) {
@@ -46,7 +48,7 @@ void JsonWriteCommandEnd(JsonWriter& writer)
 size_t JsonWriteRichPresenceObj(char* dest, size_t maxLen, int nonce, int pid, const DiscordRichPresence* presence)
 {
     DirectStringBuffer sb(dest, maxLen);
-    WriterAllocator wa;
+    StackAllocator wa;
     JsonWriter writer(sb, &wa, WriterNestingLevels);
 
     JsonWriteCommandStart(writer, nonce, "SET_ACTIVITY");
@@ -132,7 +134,7 @@ size_t JsonWriteRichPresenceObj(char* dest, size_t maxLen, int nonce, int pid, c
 size_t JsonWriteHandshakeObj(char* dest, size_t maxLen, int version, const char* applicationId)
 {
     DirectStringBuffer sb(dest, maxLen);
-    WriterAllocator wa;
+    StackAllocator wa;
     JsonWriter writer(sb, &wa, WriterNestingLevels);
 
     writer.StartObject();
@@ -148,7 +150,7 @@ size_t JsonWriteHandshakeObj(char* dest, size_t maxLen, int version, const char*
 size_t JsonWriteSubscribeCommand(char* dest, size_t maxLen, int nonce, const char* evtName)
 {
     DirectStringBuffer sb(dest, maxLen);
-    WriterAllocator wa;
+    StackAllocator wa;
     JsonWriter writer(sb, &wa, WriterNestingLevels);
 
     writer.StartObject();

src/serialization.h

@@ -63,7 +63,7 @@ public:
     static void Free(void* ptr) { /* shrug */ }
 };
 
-template<int Size>
+template<size_t Size>
 class FixedLinearAllocator : public LinearAllocator {
 public:
     char fixedBuffer_[Size];
@@ -98,9 +98,12 @@ public:
     }
 };
 
+using MallocAllocator = rapidjson::CrtAllocator;
+extern MallocAllocator MallocAllocatorInst;
+using PoolAllocator = rapidjson::MemoryPoolAllocator<MallocAllocator>;
 using UTF8 = rapidjson::UTF8<char>;
 // Writer appears to need about 16 bytes per nested object level (with 64bit size_t)
-using WriterAllocator = FixedLinearAllocator<2048>;
+using StackAllocator = FixedLinearAllocator<2048>;
 constexpr size_t WriterNestingLevels = 2048 / (2 * sizeof(size_t));
-using JsonWriter = rapidjson::Writer<DirectStringBuffer, UTF8, UTF8, WriterAllocator, rapidjson::kWriteNoFlags>;
-using JsonDocument = rapidjson::GenericDocument<UTF8>;
+using JsonWriter = rapidjson::Writer<DirectStringBuffer, UTF8, UTF8, StackAllocator, rapidjson::kWriteNoFlags>;
+using JsonDocument = rapidjson::GenericDocument<UTF8, PoolAllocator, FixedLinearAllocator<2048>>;