buffer: implement iterable interface

[vkurchatkin]

See #204

R=@bnoordhuis

[vkurchatkin]

Benchmark results:

buffers/buffer-iterate.js size=16 type=fast method=for n=1000: 317787
buffers/buffer-iterate.js size=16 type=fast method=forOf n=1000: 709499
buffers/buffer-iterate.js size=16 type=slow method=for n=1000: 1252185
buffers/buffer-iterate.js size=16 type=slow method=forOf n=1000: 782374
buffers/buffer-iterate.js size=512 type=fast method=for n=1000: 740854
buffers/buffer-iterate.js size=512 type=fast method=forOf n=1000: 67528
buffers/buffer-iterate.js size=512 type=slow method=for n=1000: 522403
buffers/buffer-iterate.js size=512 type=slow method=forOf n=1000: 60941
buffers/buffer-iterate.js size=1024 type=fast method=for n=1000: 491065
buffers/buffer-iterate.js size=1024 type=fast method=forOf n=1000: 34168
buffers/buffer-iterate.js size=1024 type=slow method=for n=1000: 557932
buffers/buffer-iterate.js size=1024 type=slow method=forOf n=1000: 27384
buffers/buffer-iterate.js size=4096 type=fast method=for n=1000: 233263
buffers/buffer-iterate.js size=4096 type=fast method=forOf n=1000: 8853
buffers/buffer-iterate.js size=4096 type=slow method=for n=1000: 148115
buffers/buffer-iterate.js size=4096 type=slow method=forOf n=1000: 8643
buffers/buffer-iterate.js size=16386 type=fast method=for n=1000: 53974
buffers/buffer-iterate.js size=16386 type=fast method=forOf n=1000: 2312
buffers/buffer-iterate.js size=16386 type=slow method=for n=1000: 65763
buffers/buffer-iterate.js size=16386 type=slow method=forOf n=1000: 2175

[vkurchatkin]

Basically it's 30 times slower. Not that bad. Eventually will become faster: https://code.google.com/p/v8/issues/detail?id=3822

Looks like functions with for..of cannot be optimized at the moment:

[disabled optimization for 0x383853e26119 <SharedFunctionInfo stuff>, reason: ForOfStatement]

[rvagg]

Another one for 1.1.0 perhaps

[bnoordhuis]

@vkurchatkin Can you drop the license boilerplate? The TC recently decided to do away with it.

[bnoordhuis]

LGTM but like @rvagg said, on hold for 1.1. The strategy for minor version bumps will be discussed in tomorrow's TC meeting. But thanks for doing this, Vladimir!

[feross]

@vkurchatkin If you're feeling ambitious, please also send a PR to the npm module buffer so browserify users get these same improvements too!

[vkurchatkin]

@feross I'll look into it, but a quick test shows that it works already in Chrome since Uint8Array is iterable.

[vkurchatkin]

added one more benchmark case which use iterator, but not for..of:

variter=buffer[Symbol.iterator]();varcur=iter.next();while(!cur.done){console.log(cur.value);cur=iter.next();}

Results:

buffers/buffer-iterate.js size=16 type=fast method=for n=1000: 1234429
buffers/buffer-iterate.js size=16 type=fast method=forOf n=1000: 689413
buffers/buffer-iterate.js size=16 type=fast method=iterator n=1000: 704994
buffers/buffer-iterate.js size=16 type=slow method=for n=1000: 1037244
buffers/buffer-iterate.js size=16 type=slow method=forOf n=1000: 763083
buffers/buffer-iterate.js size=16 type=slow method=iterator n=1000: 648382
buffers/buffer-iterate.js size=512 type=fast method=for n=1000: 761231
buffers/buffer-iterate.js size=512 type=fast method=forOf n=1000: 67708
buffers/buffer-iterate.js size=512 type=fast method=iterator n=1000: 260788
buffers/buffer-iterate.js size=512 type=slow method=for n=1000: 548060
buffers/buffer-iterate.js size=512 type=slow method=forOf n=1000: 65271
buffers/buffer-iterate.js size=512 type=slow method=iterator n=1000: 259855
buffers/buffer-iterate.js size=1024 type=fast method=for n=1000: 418621
buffers/buffer-iterate.js size=1024 type=fast method=forOf n=1000: 34951
buffers/buffer-iterate.js size=1024 type=fast method=iterator n=1000: 182922
buffers/buffer-iterate.js size=1024 type=slow method=for n=1000: 457019
buffers/buffer-iterate.js size=1024 type=slow method=forOf n=1000: 34288
buffers/buffer-iterate.js size=1024 type=slow method=iterator n=1000: 191319
buffers/buffer-iterate.js size=4096 type=fast method=for n=1000: 232112
buffers/buffer-iterate.js size=4096 type=fast method=forOf n=1000: 9086
buffers/buffer-iterate.js size=4096 type=fast method=iterator n=1000: 70217
buffers/buffer-iterate.js size=4096 type=slow method=for n=1000: 206603
buffers/buffer-iterate.js size=4096 type=slow method=forOf n=1000: 8845
buffers/buffer-iterate.js size=4096 type=slow method=iterator n=1000: 68734
buffers/buffer-iterate.js size=16386 type=fast method=for n=1000: 66488
buffers/buffer-iterate.js size=16386 type=fast method=forOf n=1000: 2094
buffers/buffer-iterate.js size=16386 type=fast method=iterator n=1000: 19092
buffers/buffer-iterate.js size=16386 type=slow method=for n=1000: 65570
buffers/buffer-iterate.js size=16386 type=slow method=forOf n=1000: 2210
buffers/buffer-iterate.js size=16386 type=slow method=iterator n=1000: 19635

I think we can expect at least as much speed with for..of in the future

[rvagg]

this was tagged with tc-agenda but I'm not sure we properly covered it, @bnoordhuis your call as to whether the tag is removed or left for next meeting bundled with further versioning discussion

[rvagg]

#625 being merged has forced us to a semver-minor situation so this could probably be merged now so it makes it in to 1.1.0, I don't see any -1s here.

[vkurchatkin]

landed in 45d8d9f