Commits on Sep 7, 2021

1. avoid double alloc in NewCidV1 …

   We allocate once via "make([]byte, len)",
   and again when that buffer is converted to a string.
   
   Thankfully, since Go 1.10 we have strings.Builder,
   designed specifically for this use case.
   
   In a downstream benchmark in go-car,
   which needs to reconstruct many CID values,
   we see small but nice gains:
   
       name           old time/op    new time/op    delta
       ReadBlocks-16    1.09ms ± 4%    1.06ms ± 5%   -3.33%  (p=0.007 n=11+11)
   
       name           old speed      new speed      delta
       ReadBlocks-16   478MB/s ± 4%   494MB/s ± 5%   +3.46%  (p=0.007 n=11+11)
   
       name           old alloc/op   new alloc/op   delta
       ReadBlocks-16    1.30MB ± 0%    1.25MB ± 0%   -3.86%  (p=0.000 n=12+12)
   
       name           old allocs/op  new allocs/op  delta
       ReadBlocks-16     9.50k ± 0%     8.45k ± 0%  -11.05%  (p=0.000 n=12+12)

   

   mvdan committed Sep 7, 2021
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