reduce encode_command cost about 60%+

[fuchaoqun]

import time

_converters = {
    bytes: lambda val: val,
    bytearray: lambda val: val,
    str: lambda val: val.encode(),
    int: lambda val: b'%d' % val,
    float: lambda val: b'%r' % val,
}

def encode_command(*args):
    """Encodes arguments into redis bulk-strings array.

    Raises TypeError if any of args not of bytearray, bytes, float, int, or str
    type.
    """
    buf = bytearray(b'*%d\r\n' % len(args))

    try:
        for arg in args:
            barg = _converters[type(arg)](arg)
            buf.extend(b'$%d\r\n%s\r\n' % (len(barg), barg))
    except:
        raise TypeError("Argument {!r} expected to be of bytearray, bytes,"
                        " float, int, or str type".format(arg))
    return buf


_converters_old = {
    bytes: lambda val: val,
    bytearray: lambda val: val,
    str: lambda val: val.encode('utf-8'),
    int: lambda val: str(val).encode('utf-8'),
    float: lambda val: str(val).encode('utf-8'),
}


def _bytes_len(sized):
    return str(len(sized)).encode('utf-8')


def encode_command_old(*args):
    """Encodes arguments into redis bulk-strings array.

    Raises TypeError if any of args not of bytearray, bytes, float, int, or str
    type.
    """
    buf = bytearray()

    def add(data):
        return buf.extend(data + b'\r\n')

    add(b'*' + _bytes_len(args))
    for arg in args:
        if type(arg) in _converters:
            barg = _converters_old[type(arg)](arg)
            add(b'$' + _bytes_len(barg))
            add(barg)
        else:
            raise TypeError("Argument {!r} expected to be of bytearray, bytes,"
                            " float, int, or str type".format(arg))
    return buf



t1 = time.time()
for i in range(10000):
    foo = encode_command(123, "abc", 4.567, b'890jqk')
print(time.time()-t1)
t1 = time.time()
for i in range(10000):
    bar = encode_command_old(123, "abc", 4.567, b'890jqk')
print(time.time()-t1)

assert foo == bar

on my mbp, the result is:

0.04150104522705078
0.09163022041320801

[codecov]

Codecov Report

Merging #397 into master will decrease coverage by 0.08%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #397      +/-   ##
==========================================
- Coverage   96.83%   96.75%   -0.09%     
==========================================
  Files          54       54              
  Lines        7452     7447       -5     
  Branches      526      525       -1     
==========================================
- Hits         7216     7205      -11     
- Misses        171      175       +4     
- Partials       65       67       +2

Impacted Files	Coverage Δ
aioredis/util.py	95% <100%> (-0.21%)	⬇️
tests/sentinel_failover_test.py	85.71% <0%> (-3.01%)	⬇️
aioredis/sentinel/pool.py	78.57% <0%> (-0.76%)	⬇️

---

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