deploy: 4155e2938f

examples/basic_json_document__memory_usage.cpp

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+#include <iostream>
+#include <string>
+#include <nlohmann/json_view.hpp>
+
+using json_document = nlohmann::json_document;
+
+int main()
+{
+    std::cout << std::boolalpha;
+
+    // long enough that copying it needs a real (heap) allocation, so the
+    // comparison below does not depend on the standard library's small
+    // string optimization threshold
+    const std::string text = std::string(200, ' ') + "[1, 2, 3, 4, 5]";
+
+    // memory_usage() is not portable across platforms/allocators/compilers, so
+    // compare it relatively instead of printing the raw byte count
+    json_document borrowed = json_document::parse(text);
+    json_document owned = json_document::parse_copy(text);
+
+    // the owned document additionally stores its own copy of the source text
+    std::cout << (owned.memory_usage() > borrowed.memory_usage()) << '\n';
+
+    // a document with more values needs a larger index
+    json_document small = json_document::parse(std::string("[1]"));
+    json_document large = json_document::parse(std::string("[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]"));
+    std::cout << (large.memory_usage() > small.memory_usage()) << '\n';
+}