Added BasicJsonDocument::shrinkToFit()

extras/tests/JsonDocument/CMakeLists.txt

@@ -12,6 +12,7 @@ add_executable(JsonDocumentTests
 	isNull.cpp
 	nesting.cpp
 	remove.cpp
+	shrinkToFit.cpp
 	size.cpp
 	StaticJsonDocument.cpp
 	subscript.cpp

extras/tests/JsonDocument/shrinkToFit.cpp

@@ -0,0 +1,151 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+#include <stdlib.h>  // malloc, free
+#include <string>
+
+using ARDUINOJSON_NAMESPACE::addPadding;
+
+class ArmoredAllocator {
+ public:
+  ArmoredAllocator() : _ptr(0), _size(0) {}
+
+  void* allocate(size_t size) {
+    _ptr = malloc(size);
+    _size = size;
+    return _ptr;
+  }
+
+  void deallocate(void* ptr) {
+    REQUIRE(ptr == _ptr);
+    free(ptr);
+    _ptr = 0;
+    _size = 0;
+  }
+
+  void* reallocate(void* ptr, size_t new_size) {
+    REQUIRE(ptr == _ptr);
+    // don't call realloc, instead alloc a new buffer and erase the old one
+    // this way we make sure we support relocation
+    void* new_ptr = malloc(new_size);
+    memcpy(new_ptr, _ptr, std::min(new_size, _size));
+    memset(_ptr, '#', _size);  // erase
+    free(_ptr);
+    _ptr = new_ptr;
+    return new_ptr;
+  }
+
+ private:
+  void* _ptr;
+  size_t _size;
+};
+
+typedef BasicJsonDocument<ArmoredAllocator> ShrinkToFitTestDocument;
+
+void testShrinkToFit(ShrinkToFitTestDocument& doc, std::string expected_json,
+                     size_t expected_size) {
+  doc.shrinkToFit();
+
+  REQUIRE(doc.capacity() == expected_size);
+  REQUIRE(doc.memoryUsage() == expected_size);
+
+  std::string json;
+  serializeJson(doc, json);
+  REQUIRE(json == expected_json);
+}
+
+TEST_CASE("BasicJsonDocument::shrinkToFit()") {
+  ShrinkToFitTestDocument doc(4096);
+
+  SECTION("null") {
+    testShrinkToFit(doc, "null", 0);
+  }
+
+  SECTION("empty object") {
+    deserializeJson(doc, "{}");
+    testShrinkToFit(doc, "{}", JSON_OBJECT_SIZE(0));
+  }
+
+  SECTION("empty array") {
+    deserializeJson(doc, "[]");
+    testShrinkToFit(doc, "[]", JSON_ARRAY_SIZE(0));
+  }
+
+  SECTION("linked string") {
+    doc.set("hello");
+    testShrinkToFit(doc, "\"hello\"", 0);
+  }
+
+  SECTION("owned string") {
+    doc.set(std::string("abcdefg"));
+    testShrinkToFit(doc, "\"abcdefg\"", 8);
+  }
+
+  SECTION("linked raw") {
+    doc.set(serialized("[{},123]"));
+    testShrinkToFit(doc, "[{},123]", 0);
+  }
+
+  SECTION("owned raw") {
+    doc.set(serialized(std::string("[{},123]")));
+    testShrinkToFit(doc, "[{},123]", 8);
+  }
+
+  SECTION("linked key") {
+    doc["key"] = 42;
+    testShrinkToFit(doc, "{\"key\":42}", JSON_OBJECT_SIZE(1));
+  }
+
+  SECTION("owned key") {
+    doc[std::string("abcdefg")] = 42;
+    testShrinkToFit(doc, "{\"abcdefg\":42}", JSON_OBJECT_SIZE(1) + 8);
+  }
+
+  SECTION("linked string in array") {
+    doc.add("hello");
+    testShrinkToFit(doc, "[\"hello\"]", JSON_ARRAY_SIZE(1));
+  }
+
+  SECTION("owned string in array") {
+    doc.add(std::string("abcdefg"));
+    testShrinkToFit(doc, "[\"abcdefg\"]", JSON_ARRAY_SIZE(1) + 8);
+  }
+
+  SECTION("linked string in object") {
+    doc["key"] = "hello";
+    testShrinkToFit(doc, "{\"key\":\"hello\"}", JSON_OBJECT_SIZE(1));
+  }
+
+  SECTION("owned string in object") {
+    doc["key"] = std::string("abcdefg");
+    testShrinkToFit(doc, "{\"key\":\"abcdefg\"}", JSON_ARRAY_SIZE(1) + 8);
+  }
+
+  SECTION("unaligned") {
+    doc.add(std::string("?"));  // two bytes in the string pool
+    REQUIRE(doc.memoryUsage() == JSON_OBJECT_SIZE(1) + 2);
+
+    doc.shrinkToFit();
+
+    // the new capacity should be padded to align the pointers
+    REQUIRE(doc.capacity() == JSON_OBJECT_SIZE(1) + sizeof(void*));
+    REQUIRE(doc.memoryUsage() == JSON_OBJECT_SIZE(1) + 2);
+    REQUIRE(doc[0] == "?");
+  }
+}
+
+TEST_CASE("DynamicJsonDocument::shrinkToFit()") {
+  DynamicJsonDocument doc(4096);
+
+  deserializeJson(doc, "{\"hello\":[\"world\"]");
+
+  doc.shrinkToFit();
+
+  std::string json;
+  serializeJson(doc, json);
+  REQUIRE(json == "{\"hello\":[\"world\"]}");
+}