I was wondering what the fastest way (most highly performant) was to
parse data structures serialized as an array of bytes. In my case its
like a network packet (a true array of bytes where I need to peel of 1,
2, 4, and 8 byte integers, or variable length ASCII (8-bit) strings, etc.)
Note I am after the FASTEST way to do this in Java (and/or Scala). Is
it better to use the stream based classes, or is it better to do direct
array accesses and do bit shift operations and masks with 0xff etc (to
strip sign extension Java will do otherwise)? I suspect the stream
based approaches would be slower. Sample code that sneaks in:
byte b1 = buf[i++];
byte b2 = buf[i++];
byte b3 = buf[i++];
byte b4 = buf[i++];
int n = (b1 << 24) | ((b2 & 0xff) << 16) | ((b3 & 0xff) << 8) | (b4
& 0xff); // Must mask with 0xff or else sign extension will mess up the
result. Java does not have unsigned bytes or ints!
I was looking into array bounds checks, and what I found via Google
indicated that hotspot leaves in array bounds checks as there was only a
minor performance improvement found in practice. This lead me to wonder
if there is a faster way to do the code since I would be doing lots of
array accesses, each with a bounds check.
Just curious!
Thanks!
Alan
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