[GitHub] [flink] fredia commented on a diff in pull request #20860: [FLINK-29347] [runtime] Fix ByteStreamStateHandle#read return -1 when read count is 0

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

fredia commented on code in PR #20860:
URL: https://github.com/apache/flink/pull/20860#discussion_r981058808


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flink-runtime/src/main/java/org/apache/flink/runtime/state/memory/ByteStreamStateHandle.java:
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@@ -148,7 +148,7 @@ public int read(byte[] b, int off, int len) throws IOException {
                 index += bytesToCopy;
                 return bytesToCopy;
             } else {
-                return -1;
+                return len == 0 ? 0 : -1;

Review Comment:
   Thanks for pointing this out, after rethinking the semantics of `read()`, I think changing the [NoFetchingInput#readBytes()](https://github.com/apache/flink/blob/9d2ae5572897f3e2d9089414261a250cfc2a2ab8/flink-core/src/main/java/org/apache/flink/api/java/typeutils/runtime/NoFetchingInput.java#L115-L140) is a better way to go.
   
   As https://docs.oracle.com/javase/8/docs/api/java/io/FileInputStream.html#read--  explained, 
   > Returns:
   the total number of bytes read into the buffer, or -1 if there is no more data because the end of the file has been reached.
   
   We should keep the semantics of `read()` consistent.
   



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