Use getfield instead of getproperty for performance

[bicycle1885]

This fixes #139.

For some unknown reason, Julia seems to fail to inline getproperty of StreamReader, which causes significant performance degradation as reported in #139.

This change works around the problem by directly calling getfield(reader, :ptr) in some performance-critical functions. The performance improvement was ~20% in uniprot_sprot.xml.gz downloaded from https://www.uniprot.org/downloads.

using EzXML
using Printf

function scan(filepath)
    s = time()
    n = 0
    open(EzXML.StreamReader, filepath) do reader
        for node in reader
            n += 1
            if n % (1 << 20) == 0
                t = time() - s
                @printf "%10d nodes - %.1fk nodes/sec\n" n (n / t / 1000)
                if t > 5
                    break
                end
            end
        end
    end
    return n
end

for _ in 1:3
    scan("uniprot_sprot.xml.gz")
end

Before:

   1048576 nodes - 1542.3k nodes/sec
   2097152 nodes - 1588.9k nodes/sec
   3145728 nodes - 1620.1k nodes/sec
   4194304 nodes - 1659.2k nodes/sec
   5242880 nodes - 1705.0k nodes/sec
   6291456 nodes - 1739.3k nodes/sec
   7340032 nodes - 1768.2k nodes/sec
   8388608 nodes - 1786.7k nodes/sec
   9437184 nodes - 1800.8k nodes/sec
   1048576 nodes - 1941.0k nodes/sec
   2097152 nodes - 1935.6k nodes/sec
   3145728 nodes - 1932.0k nodes/sec
   4194304 nodes - 1928.1k nodes/sec
   5242880 nodes - 1928.4k nodes/sec
   6291456 nodes - 1929.7k nodes/sec
   7340032 nodes - 1936.2k nodes/sec
   8388608 nodes - 1938.6k nodes/sec
   9437184 nodes - 1937.2k nodes/sec
  10485760 nodes - 1939.2k nodes/sec
   1048576 nodes - 1950.4k nodes/sec
   2097152 nodes - 1947.5k nodes/sec
   3145728 nodes - 1935.5k nodes/sec
   4194304 nodes - 1930.1k nodes/sec
   5242880 nodes - 1928.0k nodes/sec
   6291456 nodes - 1928.6k nodes/sec
   7340032 nodes - 1934.5k nodes/sec
   8388608 nodes - 1934.9k nodes/sec
   9437184 nodes - 1934.0k nodes/sec
  10485760 nodes - 1935.9k nodes/sec

After:

   1048576 nodes - 2111.7k nodes/sec
   2097152 nodes - 2077.4k nodes/sec
   3145728 nodes - 2176.8k nodes/sec
   4194304 nodes - 2243.5k nodes/sec
   5242880 nodes - 2280.7k nodes/sec
   6291456 nodes - 2309.4k nodes/sec
   7340032 nodes - 2319.1k nodes/sec
   8388608 nodes - 2339.3k nodes/sec
   9437184 nodes - 2352.7k nodes/sec
  10485760 nodes - 2366.4k nodes/sec
  11534336 nodes - 2375.7k nodes/sec
  12582912 nodes - 2381.3k nodes/sec
   1048576 nodes - 2459.0k nodes/sec
   2097152 nodes - 2470.2k nodes/sec
   3145728 nodes - 2468.4k nodes/sec
   4194304 nodes - 2466.8k nodes/sec
   5242880 nodes - 2465.2k nodes/sec
   6291456 nodes - 2465.9k nodes/sec
   7340032 nodes - 2474.2k nodes/sec
   8388608 nodes - 2477.2k nodes/sec
   9437184 nodes - 2467.1k nodes/sec
  10485760 nodes - 2470.8k nodes/sec
  11534336 nodes - 2471.1k nodes/sec
  12582912 nodes - 2470.6k nodes/sec
   1048576 nodes - 2488.9k nodes/sec
   2097152 nodes - 2481.8k nodes/sec
   3145728 nodes - 2472.1k nodes/sec
   4194304 nodes - 2468.2k nodes/sec
   5242880 nodes - 2462.9k nodes/sec
   6291456 nodes - 2466.1k nodes/sec
   7340032 nodes - 2472.9k nodes/sec
   8388608 nodes - 2475.4k nodes/sec
   9437184 nodes - 2474.2k nodes/sec
  10485760 nodes - 2474.1k nodes/sec
  11534336 nodes - 2472.8k nodes/sec
  12582912 nodes - 2470.5k nodes/sec

Versioninfo:

julia> versioninfo()
Julia Version 1.4.1
Commit 381693d3df* (2020-04-14 17:20 UTC)
Platform Info:
  OS: Linux (x86_64-pc-linux-gnu)
  CPU: AMD Ryzen 5 2400G with Radeon Vega Graphics
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-8.0.1 (ORCJIT, znver1)
Environment:
  JULIA_PROJECT = @.

[codecov]

Codecov Report

Merging #142 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #142   +/-   ##
=======================================
  Coverage   93.55%   93.55%           
=======================================
  Files           7        7           
  Lines         760      760           
=======================================
  Hits          711      711           
  Misses         49       49           

Impacted Files	Coverage Δ
src/streamreader.jl	89.93% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 830d3c2...904ef69. Read the comment docs.