buffer: improve copy() performance
Results of included benchmark:
confidence improvement accuracy (*) (**) (***)
buffers/buffer-copy.js n=6000000 partial='false' bytes=0 *** 580.96 % ±3.05% ±4.06% ±5.30%
buffers/buffer-copy.js n=6000000 partial='false' bytes=8 *** 179.90 % ±5.71% ±7.69% ±10.20%
buffers/buffer-copy.js n=6000000 partial='false' bytes=128 *** 174.81 % ±1.17% ±1.56% ±2.05%
buffers/buffer-copy.js n=6000000 partial='false' bytes=32768 * 3.62 % ±3.30% ±4.44% ±5.89%
buffers/buffer-copy.js n=6000000 partial='true' bytes=0 *** 566.67 % ±3.63% ±4.87% ±6.42%
buffers/buffer-copy.js n=6000000 partial='true' bytes=8 *** 24.66 % ±1.17% ±1.57% ±2.05%
buffers/buffer-copy.js n=6000000 partial='true' bytes=128 *** 19.53 % ±0.61% ±0.81% ±1.06%
buffers/buffer-copy.js n=6000000 partial='true' bytes=32768 -0.52 % ±0.98% ±1.31% ±1.70%
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
commit message follows commit guidelines