E9UGTYd1

1program main;
2
3(*
4    This program performs XOR operation on input data from standard input and
5    sends to standard output.
6*)
7
8uses
9  SysUtils;
10
11const
12  stdin  = 0;
13  stdout = 1;
14  stderr = 2;
15
16const
17  sl = #10;
18  dl = sl+sl;
19
20var
21  fd0        : file of byte;
22  buf0       : ^byte;
23  count_read : sizeint;
24  count_read2: sizeint;
25  secret_key : ^byte;
26  key_len    : sizeuint;
27  key_pos    : sizeuint;
28  lp0        : sizeuint;
29
30var
31  exe_name: string;
32
33procedure show_help();
34begin
35  Write({$I %DATE%},' - ',{$I %TIME%},' BRT',sl);
36  Write('xor is a program to perform xor operation on files.',dl);
37
38  Write('Usage:',sl);
39  Write('To xor a file:',sl);
40  Write('  cat /path/to/file.data | ',exe_name,' /path/to/key.data',dl);
41
42  Write('Note:',sl);
43  Write('  Key file must be of same length as input data.',sl);
44
45  halt(0);
46end;
47
48begin
49  exe_name := ExtractFileName(ParamStr(0));
50
51  count_read := 0;
52
53  if (ParamCount <> 1) or not (FileExists(ParamStr(1))) then show_help();
54
55  // read key data from file
56  Assign(fd0, ParamStr(1));
57  Reset(fd0);
58
59  secret_key := GetMem(1024*1024);
60  buf0       := GetMem(1024*1024);
61
62  BlockRead(fd0, secret_key^, 1024*1024, count_read);
63
64  key_len := count_read;
65  key_pos := 0;
66
67  repeat
68    count_read2 := FileRead(stdin, buf0^, 1024*1024);
69
70    if count_read2 = 0 then break;
71
72    for lp0 := 0 to count_read2-1 do
73    begin
74      buf0[lp0] := buf0[lp0] xor secret_key[key_pos];
75
76      inc(key_pos);
77
78      if key_pos = key_len then
79      begin
80        BlockRead(fd0, secret_key^, 1024*1024, count_read);
81
82        key_len := count_read;
83        key_pos := 0;
84      end;
85    end;
86
87    FileWrite(stdout, buf0^, count_read2);
88  until 0<>0;
89
90  FreeMem(buf0);
91  FreeMem(secret_key);
92end.