[GitHub] [thrift] emmenlau commented on a change in pull request #2030: THRIFT-5114: Simplified reallocation of TMemoryBuffer

[GitBox <gi...@apache.org>]

emmenlau commented on a change in pull request #2030:
URL: https://github.com/apache/thrift/pull/2030#discussion_r433739866



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File path: lib/cpp/src/thrift/transport/TBufferTransports.cpp
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@@ -360,15 +360,14 @@ void TMemoryBuffer::ensureCanWrite(uint32_t len) {
     throw TTransportException("Insufficient space in external MemoryBuffer");
   }
 
+  const uint32_t current_used = bufferSize_ - avail;
+  const uint32_t required_buffer_size = len + current_used;
+  const uint64_t new_size = static_cast<uint64_t>(std::exp2(std::ceil(std::log2(static_cast<double>(required_buffer_size)))));
+
   // Grow the buffer as necessary.
-  uint64_t new_size = bufferSize_;
-  while (len > avail) {
-    new_size = new_size > 0 ? new_size * 2 : 1;
-    if (new_size > maxBufferSize_) {
-      throw TTransportException(TTransportException::BAD_ARGS,
-                                "Internal buffer size overflow");
-    }
-    avail = available_write() + (static_cast<uint32_t>(new_size) - bufferSize_);
+  if (new_size > maxBufferSize_) {
+    throw TTransportException(TTransportException::BAD_ARGS,

Review comment:
       I agree, and I was slightly confused by the complexity and behavior of the old code. If you agree I will further simplify the code and only throw if the requested buffer can not be allocated.




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