Lua进行二进制文件的位操作

1.纯lua的二进制位操作

lua的二进制文件主要利用string.byte()读取某个字节，string.char()写入，示例代码如下：

function v:xorFile(inputFile,outputFile)local fileIn,err = io.open(inputFile,"rb")local content = fileIn:read("*all")local length = fileIn:seek("end")fileIn:close()local fileOut,err = io.open(outputFile,"wb")fileOut:seek("set",0)local itemfor i=1,length doitem = tonumber(string.byte(content,i))item = bit:_xor(item,186)fileOut:write(string.char(item))endfileOut:close()
end

这是对整个二进制文件进行异或操作，那么对某个32位的uint如何操作？比如把第posSrc位的uint32异或posDst位的uint32

function v:XORuint32(inputFile,outputFile,posSrc,posDst)local fileIn,err = io.open(inputFile,"rb")local content = fileIn:read("*all")local length = fileIn:seek("end")fileIn:seek("set",0)local dataA = fileIn:read(posSrc-1)fileIn:seek("set",posSrc+4)local dataB = fileIn:read("*all")fileIn:close()local value1 = tonumber(string.byte(content,posSrc+1))local value2 = tonumber(string.byte(content,posSrc+2))local value3 = tonumber(string.byte(content,posSrc+3))local value4 = tonumber(string.byte(content,posSrc+4))local key1 = tonumber(string.byte(content,posDst+1))local key2 = tonumber(string.byte(content,posDst+2))local key3 = tonumber(string.byte(content,posDst+3))local key4 = tonumber(string.byte(content,posDst+4))value1 = bit:_xor(value1,key1)value2 = bit:_xor(value2,key2)value3 = bit:_xor(value3,key3)value1 = bit:_xor(value4,key4)local fileOut,err = io.open(outputFile,"wb")fileOut:seek("set",0)fileOut:write(dataA)fileOut:write(string.char(value1))fileOut:write(string.char(value2))fileOut:write(string.char(value3))fileOut:write(string.char(value4))fileOut:write(dataB)fileOut:close()
end

附上bit的代码

bit={data32={}}
for i=1,32 dobit.data32[i]=2^(32-i)
endfunction bit:d2b(arg)local   tr={}for i=1,32 doif arg >= self.data32[i] thentr[i]=1arg=arg-self.data32[i]elsetr[i]=0endendreturn   tr
end   --bit:d2bfunction    bit:b2d(arg)local   nr=0for i=1,32 doif arg[i] ==1 thennr=nr+2^(32-i)endendreturn  nr
end   --bit:b2dfunction    bit:_xor(a,b)local   op1=self:d2b(a)local   op2=self:d2b(b)local   r={}for i=1,32 doif op1[i]==op2[i] thenr[i]=0elser[i]=1endendreturn  self:b2d(r)
end --bit:xorfunction    bit:_and(a,b)local   op1=self:d2b(a)local   op2=self:d2b(b)local   r={}for i=1,32 doif op1[i]==1 and op2[i]==1  thenr[i]=1elser[i]=0endendreturn  self:b2d(r)end --bit:_andfunction    bit:_or(a,b)local   op1=self:d2b(a)local   op2=self:d2b(b)local   r={}for i=1,32 doif  op1[i]==1 or   op2[i]==1   thenr[i]=1elser[i]=0endendreturn  self:b2d(r)
end --bit:_orfunction    bit:_not(a)local   op1=self:d2b(a)local   r={}for i=1,32 doif  op1[i]==1   thenr[i]=0elser[i]=1endendreturn  self:b2d(r)
end --bit:_notfunction    bit:_rshift(a,n)local   op1=self:d2b(a)local   r=self:d2b(0)if n < 32 and n > 0 thenfor i=1,n dofor i=31,1,-1 doop1[i+1]=op1[i]endop1[1]=0endr=op1endreturn  self:b2d(r)
end --bit:_rshiftfunction    bit:_lshift(a,n)local   op1=self:d2b(a)local   r=self:d2b(0)if n < 32 and n > 0 thenfor i=1,n   dofor i=1,31 doop1[i]=op1[i+1]endop1[32]=0endr=op1endreturn  self:b2d(r)
end --bit:_lshiftfunction    bit:print(ta)local   sr=""for i=1,32 dosr=sr..ta[i]endprint(sr)
end

以上代码异或整个文件，1M的文件需要15秒左右，显然太慢，于是换个脚本，用python试试

2.python的二进制位操作

import binascii
import struct
import sysdef str2hex(str):hexs = []for s in str:tmp = (hex(ord(s)).replace('0x',''))if len(tmp) == 2:hexs.append(tmp)else:hexs.append('0'+tmp)return hexsarr= ['0','1','2','3','4','5','6','7','8','9','a','b','c','d','e','f']
arr2 = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]def tran(r):for i in range(len(arr)):if r == arr[i]:return arr2[i]def packRes(input,output,key):f = open(input,'rb+')hexs = []while True:t = f.read(1)if len(t) == 0:breakhexs.extend(str2hex(t))f.close()ff = open(output,'wb')for i in  range(len(hexs)):a = tran(hexs[i][0])*16+tran(hexs[i][1])B = struct.pack('B',a^key)ff.write(B)ff.close()def main(p1,p2,p3):print(p1)print(p2)print(p3)try:packRes(p1,p2,int(p3))sys.exit(0)except:sys.exit(1)finally:passif __name__ == "__main__":if len(sys.argv) >= 1:p1 = sys.argv[1]p2 = sys.argv[2]p3 = sys.argv[3]main(p1,p2,p3)

同样的文件要1秒左右，效率提升显著，然而还是不满足需求，还是试试C++吧

3.c++的二进制位操作

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <cstdlib> int main(int argc, char* argv[])
{int i, count, len;int key;char buff[1024];static char tmpfile[] = "~u~0_sw~.f~l";FILE * in, *out;if (argc <3){printf("Less Parameter !\n");printf("Parameter number must at least 2 !!\n");return 1;}len = strlen(argv[2]);in = fopen(argv[1], "rb");out = fopen(tmpfile, "wb"); /* creat a temp file */key = std::atoi(argv[3]);if (in == NULL){printf("Input File \'%s\' not found !!\n", argv[1]);exit(1);}if (out == NULL){printf("Can not creat temp file \'%s\'\n", tmpfile);exit(2);}while (!feof(in)){count = fread(buff, 1, 1024, in);for (i = 0;i <count;i++)buff[i] ^= 119;//buff[i] ^= argv[2][i%len];fwrite(buff, 1, count, out);}fclose(in);fclose(out);//printf(argv[1]);//printf(argv[2]);if( strcmp(argv[1], argv[2]) == 0){remove(argv[1]);printf("the key is: %d", key);}rename(tmpfile, argv[2]);return 0;
}

注意再创建控制台应用程序的设置，不要预编译头，否则cpp在MAC下会不兼容。

1M左右，大概需要0.0006秒左右。因为我们最终是在lua脚本里用，所以接下来说下lua如何调用python

4.lua调用python和C

lua里面用os.excute来调用本地脚本。

首先看下调用python,由于python是跨平台的，MAC和WIN10下代码一致：

os.excute("python xxx.py inputFIle outputFile key")

在win10下调用控制台程序的话：VS新建控制台应用程序，调试成功后cd到exe 目录

os.excute("xxx.exe inputFIle outputFile key")

在mac下先cd到cpp目录用g++编译

g++ xxx.cpp

生成a.out

os.excute("./a.out inputFIle outputFile key")

5.小结

有人会喜欢那语言做比较，我认为语言是看场合的，就像你比较匕首和导弹，没有太大的意义。主要看武器在谁的手里，怎么去使用它。

上面对比来看，貌似python比lua效率高很多，然而，我们本不该在lua里面执行大体积二进制文件的位操作，Lua作为C的触手，应该在C里面绑定一个方法让lua调用，这样lua的效率就是C的效率（当然，要扣除一点调用C的成本）。

lua和python在不同场合有着各自的生命力。