Optimize deserializeMsgPack()

CHANGELOG.md

@@ -4,6 +4,7 @@ ArduinoJson: change log
 * Add `ARDUINOJSON_STRING_LENGTH_SIZE` to the namespace name
 * Add MsgPack bin8/bin16/bin32 support (PR #2078 by @Sanae6)
 * Make string support even more generic (PR #2084 by @d-a-v)
+* Optimize `deserializeMsgPack()`
 
 v7.0.4 (2024-03-12)
 ------

extras/tests/MsgPackDeserializer/deserializeVariant.cpp

@@ -228,12 +228,12 @@ TEST_CASE("deserializeMsgPack() under memory constaints") {
       checkError(0, "\x80", DeserializationError::Ok);
     }
     SECTION("{H:1}") {
-      checkError(0, "\x81\xA1H\x01", DeserializationError::NoMemory);
+      checkError(1, "\x81\xA1H\x01", DeserializationError::NoMemory);
-      checkError(3, "\x81\xA1H\x01", DeserializationError::Ok);
+      checkError(2, "\x81\xA1H\x01", DeserializationError::Ok);
     }
     SECTION("{H:1,W:2}") {
-      checkError(3, "\x82\xA1H\x01\xA1W\x02", DeserializationError::NoMemory);
+      checkError(2, "\x82\xA1H\x01\xA1W\x02", DeserializationError::NoMemory);
-      checkError(5, "\x82\xA1H\x01\xA1W\x02", DeserializationError::Ok);
+      checkError(3, "\x82\xA1H\x01\xA1W\x02", DeserializationError::Ok);
     }
   }
 
@@ -242,13 +242,13 @@ TEST_CASE("deserializeMsgPack() under memory constaints") {
       checkError(0, "\xDE\x00\x00", DeserializationError::Ok);
     }
     SECTION("{H:1}") {
-      checkError(2, "\xDE\x00\x01\xA1H\x01", DeserializationError::NoMemory);
+      checkError(1, "\xDE\x00\x01\xA1H\x01", DeserializationError::NoMemory);
-      checkError(3, "\xDE\x00\x01\xA1H\x01", DeserializationError::Ok);
+      checkError(2, "\xDE\x00\x01\xA1H\x01", DeserializationError::Ok);
     }
     SECTION("{H:1,W:2}") {
-      checkError(3, "\xDE\x00\x02\xA1H\x01\xA1W\x02",
+      checkError(2, "\xDE\x00\x02\xA1H\x01\xA1W\x02",
                  DeserializationError::NoMemory);
-      checkError(5, "\xDE\x00\x02\xA1H\x01\xA1W\x02", DeserializationError::Ok);
+      checkError(3, "\xDE\x00\x02\xA1H\x01\xA1W\x02", DeserializationError::Ok);
     }
   }
 
@@ -257,14 +257,14 @@ TEST_CASE("deserializeMsgPack() under memory constaints") {
       checkError(0, "\xDF\x00\x00\x00\x00", DeserializationError::Ok);
     }
     SECTION("{H:1}") {
-      checkError(2, "\xDF\x00\x00\x00\x01\xA1H\x01",
+      checkError(1, "\xDF\x00\x00\x00\x01\xA1H\x01",
                  DeserializationError::NoMemory);
-      checkError(3, "\xDF\x00\x00\x00\x01\xA1H\x01", DeserializationError::Ok);
+      checkError(2, "\xDF\x00\x00\x00\x01\xA1H\x01", DeserializationError::Ok);
     }
     SECTION("{H:1,W:2}") {
-      checkError(3, "\xDF\x00\x00\x00\x02\xA1H\x01\xA1W\x02",
+      checkError(2, "\xDF\x00\x00\x00\x02\xA1H\x01\xA1W\x02",
                  DeserializationError::NoMemory);
-      checkError(5, "\xDF\x00\x00\x00\x02\xA1H\x01\xA1W\x02",
+      checkError(3, "\xDF\x00\x00\x00\x02\xA1H\x01\xA1W\x02",
                  DeserializationError::Ok);
     }
   }

src/ArduinoJson/Memory/StringBuffer.hpp

@@ -0,0 +1,67 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2024, Benoit BLANCHON
+// MIT License
+
+#pragma once
+
+#include <ArduinoJson/Memory/ResourceManager.hpp>
+
+ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
+
+class StringBuffer {
+ public:
+  StringBuffer(ResourceManager* resources) : resources_(resources) {}
+
+  ~StringBuffer() {
+    if (node_)
+      resources_->destroyString(node_);
+  }
+
+  char* reserve(size_t capacity) {
+    if (node_ && capacity > node_->length) {
+      // existing buffer is too small, we need to reallocate
+      resources_->destroyString(node_);
+      node_ = nullptr;
+    }
+    if (!node_)
+      node_ = resources_->createString(capacity);
+    if (!node_)
+      return nullptr;
+    size_ = capacity;
+    node_->data[capacity] = 0;  // null-terminate the string
+    return node_->data;
+  }
+
+  StringNode* save() {
+    ARDUINOJSON_ASSERT(node_ != nullptr);
+    node_->data[size_] = 0;
+    auto node = resources_->getString(adaptString(node_->data, size_));
+    if (node) {
+      node->references++;
+      return node;
+    }
+
+    if (node_->length != size_) {
+      node = resources_->resizeString(node_, size_);
+      ARDUINOJSON_ASSERT(node != nullptr);  // realloc to smaller can't fail
+    } else {
+      node = node_;
+    }
+    node_ = nullptr;
+    resources_->saveString(node);
+    return node;
+  }
+
+  JsonString str() const {
+    ARDUINOJSON_ASSERT(node_ != nullptr);
+
+    return JsonString(node_->data, node_->length, JsonString::Copied);
+  }
+
+ private:
+  ResourceManager* resources_;
+  StringNode* node_ = nullptr;
+  size_t size_ = 0;
+};
+
+ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/MsgPack/MsgPackDeserializer.hpp

@@ -6,6 +6,7 @@
 
 #include <ArduinoJson/Deserialization/deserialize.hpp>
 #include <ArduinoJson/Memory/ResourceManager.hpp>
+#include <ArduinoJson/Memory/StringBuffer.hpp>
 #include <ArduinoJson/MsgPack/endianness.hpp>
 #include <ArduinoJson/MsgPack/ieee754.hpp>
 #include <ArduinoJson/Polyfills/type_traits.hpp>
@@ -19,7 +20,7 @@ class MsgPackDeserializer {
   MsgPackDeserializer(ResourceManager* resources, TReader reader)
       : resources_(resources),
         reader_(reader),
-        stringBuilder_(resources),
+        stringBuffer_(resources),
         foundSomething_(false) {}
 
   template <typename TFilter>
@@ -239,7 +240,7 @@ class MsgPackDeserializer {
     return DeserializationError::Ok;
   }
 
-  DeserializationError::Code readBytes(uint8_t* p, size_t n) {
+  DeserializationError::Code readBytes(void* p, size_t n) {
     if (reader_.readBytes(reinterpret_cast<char*>(p), n) == n)
       return DeserializationError::Ok;
     return DeserializationError::IncompleteInput;
@@ -247,7 +248,7 @@ class MsgPackDeserializer {
 
   template <typename T>
   DeserializationError::Code readBytes(T& value) {
-    return readBytes(reinterpret_cast<uint8_t*>(&value), sizeof(value));
+    return readBytes(&value, sizeof(value));
   }
 
   DeserializationError::Code skipBytes(size_t n) {
@@ -379,28 +380,16 @@ class MsgPackDeserializer {
     if (err)
       return err;
 
-    variant->setOwnedString(stringBuilder_.save());
+    variant->setOwnedString(stringBuffer_.save());
     return DeserializationError::Ok;
   }
 
   DeserializationError::Code readString(size_t n) {
-    DeserializationError::Code err;
+    char* p = stringBuffer_.reserve(n);
-
+    if (!p)
-    stringBuilder_.startString();
-    for (; n; --n) {
-      uint8_t c;
-
-      err = readBytes(c);
-      if (err)
-        return err;
-
-      stringBuilder_.append(static_cast<char>(c));
-    }
-
-    if (!stringBuilder_.isValid())
       return DeserializationError::NoMemory;
 
-    return DeserializationError::Ok;
+    return readBytes(p, n);
   }
 
   template <typename T>
@@ -422,7 +411,7 @@ class MsgPackDeserializer {
     if (err)
       return err;
 
-    variant->setBinary(stringBuilder_.save());
+    variant->setBinary(stringBuffer_.save());
     return DeserializationError::Ok;
   }
 
@@ -517,7 +506,7 @@ class MsgPackDeserializer {
       if (err)
         return err;
 
-      JsonString key = stringBuilder_.str();
+      JsonString key = stringBuffer_.str();
       TFilter memberFilter = filter[key.c_str()];
       VariantData* member;
 
@@ -525,7 +514,7 @@ class MsgPackDeserializer {
         ARDUINOJSON_ASSERT(object != 0);
 
         // Save key in memory pool.
-        auto savedKey = stringBuilder_.save();
+        auto savedKey = stringBuffer_.save();
 
         member = object->addMember(savedKey, resources_);
         if (!member)
@@ -582,7 +571,7 @@ class MsgPackDeserializer {
 
   ResourceManager* resources_;
   TReader reader_;
-  StringBuilder stringBuilder_;
+  StringBuffer stringBuffer_;
   bool foundSomething_;
 };