add upstream 12.412.4

1 files changed, 13 insertions, 3 deletions

diff --git a/zen/serialize.h b/zen/serialize.h
index 8ccecd53..02dcd2b2 100644
--- a/zen/serialize.h
+++ b/zen/serialize.h
@@ -261,11 +261,21 @@ BinContainer unbufferedLoad(Function tryRead /*(void* buffer, size_t bytesToRead
     BinContainer buf;
     for (;;)
     {
-        warn_static("don't need zero-initialization!")
-        buf.resize(buf.size() + blockSize);
+#ifndef ZEN_HAVE_RESIZE_AND_OVERWRITE
+#error include legacy_compiler.h!
+#endif
+#if ZEN_HAVE_RESIZE_AND_OVERWRITE //permature(?) perf optimization; avoid needless zero-initialization:
+        size_t bytesRead = 0;
+        buf.resize_and_overwrite(buf.size() + blockSize, [&, bufSizeOld = buf.size()](char* rawBuf, size_t /*rawBufSize: caveat: may be larger than what's requested*/)
+        {
+            bytesRead = tryRead(rawBuf + bufSizeOld, blockSize); //throw X; may return short; only 0 means EOF
+            return bufSizeOld + bytesRead;
+        });
+#else
+        buf.resize(buf.size() + blockSize); //needless zero-initialization!
         const size_t bytesRead = tryRead(buf.data() + buf.size() - blockSize, blockSize); //throw X; may return short; only 0 means EOF
         buf.resize(buf.size() - blockSize + bytesRead); //caveat: unsigned arithmetics
-
+#endif
         if (bytesRead == 0) //end of file
         {
             //caveat: memory consumption of returned string!