curcur commented on a change in pull request #13456:
URL: https://github.com/apache/flink/pull/13456#discussion_r494377293
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File path:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/BufferBuilder.java
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@@ -86,11 +94,34 @@ public int append(ByteBuffer source) {
int available = getMaxCapacity() - positionMarker.getCached();
int toCopy = Math.min(needed, available);
+ // Each Data BufferBuilder starts with a 4-byte integer header
+ // Since length can only be 0 or positive numbers, the first
bit of the integer
+ // is used to identify whether the first record is partial (1)
or not (0)
+ // The remaining 31 bits stands for the length of the record
remaining.
+ // The data written is not made visible to reader until {@link
#commit()}, so the BufferBuilder
+ // ends either with a complete record or full buffer after
append();
+ if (isEmptyBufferBuilder()) {
+ available = available - BUFFER_BUILDER_HEADER_SIZE;
+ toCopy = Math.min(needed, available);
Review comment:
> Can `available` be less than `BUFFER_BUILDER_HEADER_SIZE`?
> Then `toCopy` can be negative.
the `if` clause check makes sure the builder is empty; buffer size minimal
be 4096 bytes, so no.
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