decode protobuff wireformat

decodePB.py

#coding:utf8
#解析protobuf wireformat
#https://developers.google.com/protocol-buffers/docs/encoding

import struct

f = open('server0_5.json').read()

#filenum << type value
#0 varint
# 1 fix64
# 2 length-delimited
# 5 fix32

#读取一个变长整数
#返回新的位置
def readVarint(stream, start):
    result = 0
    c = 0
    while True:
        byte = stream[start]
        intv = struct.unpack('B', byte)[0]
        print 'byte', hex(intv), intv, bin(intv)
        more = intv& 0b10000000
        v = intv & 0b01111111
        result += v << c
        print 'ret', result, v, c, bin(v), more
        c += 7
        if more == 0:
            break
        else:
            start += 1
    print result 
        
    start += 1
    wireType = result & 0b111
    fieldNum = result >> 3
    print bin(fieldNum), bin(wireType)
    print fieldNum, wireType

    print start, result, fieldNum, wireType
    return start, result, fieldNum, wireType

         
state = 0
readState = 0
i = 0
form = ''
while i < len(f):
    if state == 0:
        i, result, fieldNum, wireType = readVarint(f, i)
        if wireType == 2:
            i, length, _, _ = readVarint(f, i)
            form += str(['fieldNum', fieldNum, 'wireType', wireType, 'length', length, 'value', f[i:i+length]])+'\n'
            i += length
        elif wireType == 0:
            i, value, _, _ = readVarint(f, i)
            form += str(['fieldNum', fieldNum, 'wireType', wireType, 'value', value])+'\n'
        else:
            print 'Error: UnSupport Type', wireType
            

    

readVarint(f, 0)

print form