- optimize memory usage

src/libs/ice/ICEByteBuffer.cpp

@@ -497,12 +497,12 @@ size_t BufferReader::count() const
 }
 
 // -------------- BufferWriter ----------------------
-BufferWriter::BufferWriter(ByteBuffer &buffer)
-    :mData(buffer.mutableData()), mIndex(0)
+BufferWriter::BufferWriter(ByteBuffer &buffer, size_t startOffset)
+    :mBuffer(&buffer), mData(buffer.mutableData() + startOffset), mBase(startOffset), mIndex(0), mCapacity(0)
 {}
 
-BufferWriter::BufferWriter(void *output)
-    :mData(reinterpret_cast<uint8_t*>(output)), mIndex(0)
+BufferWriter::BufferWriter(void *output, size_t capacity)
+    :mBuffer(nullptr), mData(reinterpret_cast<uint8_t*>(output)), mBase(0), mIndex(0), mCapacity(capacity)
 {}
 
 
@@ -545,6 +545,30 @@ void BufferWriter::writeIp(const NetworkAddress& ip)
 
 void BufferWriter::writeBuffer(const void* dataPtr, size_t dataSize)
 {
+    if (dataSize == 0)
+        return;
+
+    if (mBuffer)
+    {
+        // Growable mode: ensure the backing buffer is large enough, then refresh
+        // the cached pointer in case resize() reallocated the storage.
+        size_t needed = mBase + mIndex + dataSize;
+        if (needed > mBuffer->size())
+            mBuffer->resize(needed);
+        mData = mBuffer->mutableData() + mBase;
+    }
+    else
+    {
+        // Bounded mode: never write past the caller-supplied capacity.
+        if (mIndex + dataSize > mCapacity)
+        {
+            assert(0 && "BufferWriter capacity exceeded");
+            dataSize = mIndex < mCapacity ? mCapacity - mIndex : 0;
+            if (dataSize == 0)
+                return;
+        }
+    }
+
     memmove(mData + mIndex, dataPtr, dataSize);
     mIndex += dataSize;
 }

src/libs/ice/ICEByteBuffer.h

@@ -172,12 +172,17 @@ namespace ice
   class BufferWriter
   {
   protected:
-    uint8_t* mData;
-    size_t mIndex;
+    ByteBuffer* mBuffer;  // Non-null => growable: writes resize this buffer to fit
+    uint8_t* mData;       // Cached write pointer (refreshed on growth in growable mode)
+    size_t mBase;         // Start offset within mBuffer (growable mode)
+    size_t mIndex;        // Bytes written since mBase
+    size_t mCapacity;     // Usable capacity from mData (raw/bounded mode)
 
   public:
-    BufferWriter(void* output);
-    BufferWriter(ByteBuffer& buffer);
+    // Bounded writer over caller-owned memory. Writes past 'capacity' are refused.
+    BufferWriter(void* output, size_t capacity);
+    // Growable writer: the backing buffer is resized as needed so writes never overflow.
+    BufferWriter(ByteBuffer& buffer, size_t startOffset = 0);
 
     void          writeUInt(uint32_t value);
     void          writeUShort(uint16_t value);

src/libs/ice/ICEStunMessage.cpp

@@ -216,8 +216,10 @@ void StunMessage::buildPacket(ByteBuffer& buffer, const std::string& password)
   for (size_t i=0; i<4; i++)
     bitstream.writeBit(bit(msgtype, 3-i));
   
-  // Enqueue 2 bytes of length - now it is zero
-  BufferWriter stream(buffer.mutableData() + bitstream.count() / 8);
+  // Enqueue 2 bytes of length - now it is zero.
+  // Growable writer starting right after the bits already emitted; it resizes
+  // 'buffer' as attributes are appended so an oversized message cannot overflow.
+  BufferWriter stream(buffer, bitstream.count() / 8);
   stream.writeUShort(0);
 
   // Enqueue magic cookie value