diff --git a/include/tools/json_writer.hxx b/include/tools/json_writer.hxx
index 45df53c61c5f..72ed59edadc5 100644
--- a/include/tools/json_writer.hxx
+++ b/include/tools/json_writer.hxx
@@ -17,6 +17,7 @@
 
 #include <string>
 #include <string_view>
+#include <utility>
 
 /** Simple JSON encoder designed specifically for LibreOfficeKit purposes.
  *
@@ -73,7 +74,7 @@ public:
 
     /** Hands ownership of the underlying storage buffer to the caller,
      * after this no more document modifications may be written. */
-    char* extractData();
+    char* extractData() { return extractDataImpl().first; }
     OString extractAsOString();
     std::string extractAsStdString();
 
@@ -85,17 +86,9 @@ private:
     void endArray();
     void endStruct();
     void addCommaBeforeField();
-    void reallocBuffer(int noMoreBytesRequired);
     void writeEscapedOUString(const OUString& rPropVal);
-
-    // this part inline to speed up the fast path
-    inline void ensureSpace(int noMoreBytesRequired)
-    {
-        assert(mpBuffer && "already extracted data");
-        int currentUsed = mPos - mpBuffer;
-        if (currentUsed + noMoreBytesRequired >= mSpaceAllocated)
-            reallocBuffer(noMoreBytesRequired);
-    }
+    std::pair<char*, int> extractDataImpl();
+    void ensureSpace(int noMoreBytesRequired);
 };
 
 /**
diff --git a/tools/source/misc/json_writer.cxx b/tools/source/misc/json_writer.cxx
index 7024b580c7fd..d6e34179f930 100644
--- a/tools/source/misc/json_writer.cxx
+++ b/tools/source/misc/json_writer.cxx
@@ -388,18 +388,22 @@ void JsonWriter::addCommaBeforeField()
     }
 }
 
-void JsonWriter::reallocBuffer(int noMoreBytesRequired)
+void JsonWriter::ensureSpace(int noMoreBytesRequired)
 {
+    assert(mpBuffer && "already extracted data");
     int currentUsed = mPos - mpBuffer;
-    auto newSize = std::max<int>(mSpaceAllocated * 2, (currentUsed + noMoreBytesRequired) * 2);
-    mpBuffer = static_cast<char*>(realloc(mpBuffer, newSize));
-    mPos = mpBuffer + currentUsed;
-    mSpaceAllocated = newSize;
+    if (currentUsed + noMoreBytesRequired >= mSpaceAllocated)
+    {
+        auto newSize = (currentUsed + noMoreBytesRequired) * 2;
+        mpBuffer = static_cast<char*>(realloc(mpBuffer, newSize));
+        mPos = mpBuffer + currentUsed;
+        mSpaceAllocated = newSize;
+    }
 }
 
 /** Hands ownership of the underlying storage buffer to the caller,
   * after this no more document modifications may be written. */
-char* JsonWriter::extractData()
+std::pair<char*, int> JsonWriter::extractDataImpl()
 {
     assert(mStartNodeCount == 0 && "did not close all nodes");
     assert(mpBuffer && "data already extracted");
@@ -409,24 +413,23 @@ char* JsonWriter::extractData()
     ++mPos;
     // null-terminate
     *mPos = 0;
+    const int sz = mPos - mpBuffer;
     mPos = nullptr;
-    char* pRet = nullptr;
-    std::swap(pRet, mpBuffer);
-    return pRet;
+    return { std::exchange(mpBuffer, nullptr), sz };
 }
 
 OString JsonWriter::extractAsOString()
 {
-    char* pChar = extractData();
-    OString ret(pChar);
+    auto[pChar, sz] = extractDataImpl();
+    OString ret(pChar, sz);
     free(pChar);
     return ret;
 }
 
 std::string JsonWriter::extractAsStdString()
 {
-    char* pChar = extractData();
-    std::string ret(pChar);
+    auto[pChar, sz] = extractDataImpl();
+    std::string ret(pChar, sz);
     free(pChar);
     return ret;
 }