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From: t3rmin4t0r <git@git.apache.org>
To: dev@orc.apache.org
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References: <git-pr-186-orc@git.apache.org>
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Subject: [GitHub] orc pull request #186: ORC-187: BitFieldReader has an unnecessary loop
Content-Type: text/plain
Message-Id: <20171103063832.5A0F9DFBD7@git1-us-west.apache.org>
Date: Fri,  3 Nov 2017 06:38:32 +0000 (UTC)
archived-at: Fri, 03 Nov 2017 06:38:34 -0000

Github user t3rmin4t0r commented on a diff in the pull request:

    https://github.com/apache/orc/pull/186#discussion_r148716091
  
    --- Diff: java/core/src/java/org/apache/orc/impl/BitFieldReader.java ---
    @@ -162,53 +92,32 @@ public void seek(PositionProvider index) throws IOException {
               consumed + " in " + input);
         } else if (consumed != 0) {
           readByte();
    -      bitsLeft = 8 - consumed;
    +      currentIdx = (byte) consumed;
         } else {
    -      bitsLeft = 0;
    +      currentIdx = 8;
         }
       }
     
       public void skip(long items) throws IOException {
    -    long totalBits = bitSize * items;
    -    if (bitsLeft >= totalBits) {
    -      bitsLeft -= totalBits;
    +    final long totalBits = bitSize * items;
    +    final int availableBits = 8 - (currentIdx + 1);
    +    if (totalBits <= availableBits) {
    +      currentIdx += totalBits;
         } else {
    -      totalBits -= bitsLeft;
    -      input.skip(totalBits / 8);
    -      current = input.next();
    -      bitsLeft = (int) (8 - (totalBits % 8));
    +      final long bitsToSkip = (totalBits - availableBits);
    +      input.skip(Math.min(1, bitsToSkip / 8));
    --- End diff --
    
    Looks a bit odd - the min(1) might be a problem if 
    
    availableBits = 0 and items=3, it will end up skip(1) where it should really be doing skip(0).


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