BIND 10 #536: Make OutputBuffer more lightweight

[BIND 10 Development]

#536: Make OutputBuffer more lightweight
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                 Reporter:  vorner   |                Owner:  shane
                     Type:  task     |               Status:  accepted
                 Priority:  major    |            Milestone:
                Component:           |  Sprint-20110419
  DNSPacket API                      |           Resolution:
                 Keywords:           |            Sensitive:  0
Estimated Number of Hours:  7.0      |  Add Hours to Ticket:  0
                Billable?:  1        |          Total Hours:  0
                Internal?:  0        |
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Changes (by shane):

 * owner:  UnAssigned => shane
 * status:  reviewing => accepted


Comment:

 I had a quick look through this.

 One actual point:

   We check for buffer size of 0 in ensureAllocated(), but not in our
 constructor(s). malloc() may return NULL in some cases if we try to
 allocate 0 bytes, but not always (it's up to the system). I think we
 should either explicitly disallow zero-sized buffers or we should check
 for 0-bytes and set our buffer to NULL rather than try malloc(). (The
 realloc() command always works, since we always insure at least 1024
 bytes.)

 We may want to experiment with reference counts and copy-on-write rather
 than actual memory allocation in our assignment operators if we need
 further optimizations here in the future. :)

 I know this code hasn't changed, but I wonder if this:

 {{{
         buffer_[size_ ++] = static_cast<uint8_t>((data & 0xff00U) >> 8);
         buffer_[size_ ++] = static_cast<uint8_t>(data & 0x00ffU);
 }}}

 Might be more efficient if written as array access somehow rather than bit
 shifting. Hopefully modern compilers optimize that away, but maybe some
 micro-benchmarking would reveal more.

-- 
Ticket URL: <https://bind10.isc.org/ticket/536#comment:8>
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