clang-format --style='{IndentPPDirectives: AfterHash}' cpp.c

从 #if __INCLUDE_LEVEL__ > 12 一行开始，接下来就是大段的 #if S == xx。在每个 #if 之后紧跟的又是 #unset S 和 #define 新 S，对应的是 S++。每个 S 对应一条不同的指令。

简单观察一条指令，不难发现其每次都会对 0-7 进行 define。比如上面截图里就 define 了 R0-R7。因此不难想到一个 R 其实是由 8 位构成的，即一个字节。因此之后的整理也就基本基于这个思路了。

#if __INCLUDE_LEVEL__ > 12
#  if S == 0
#    define S 24
#  endif
#  if S == 1
//#  S++
//#  R = !R
#  endif
#  if S == 2
//#  S++
//#  Z = 0b00000001
#  endif
#  if S == 3
//#  S++
//#  R = R + Z
#  endif
#  if S == 4
//#  S++
//#  R = R + Z
#  endif
#  if S == 5
//#  S++
//#  if R == 0 {
//#    S = 38
//#  }
#  endif
#  if S == 6
//#  S++
//#  R = R + Z
#  endif
#  if S == 7
//#  S++
//#  if R == 0 {
//#    S = 59
//#  }
#  endif
#  if S == 8
//#  S++
//#  R = R + Z
#  endif
#  if S == 9
//#  S++
//#  if R == 0 {
//#    S = 59
//#  }
#  endif
#  if S == 10
//#  S++
#    error "BUG"
#  endif
#  if S == 11
//#  S = -1
#  endif
#  if S == 12
//#  S++
//#  X = 0b00000001
#  endif
#  if S == 13
//#  S++
//#  Y = 0
#  endif
#  if S == 14
//#  S++
//#  if X == 0 {
//#    S = 22
//#  }
#  endif
#  if S == 15
//#  S++
//#  Z = X
#  endif
#  if S == 16
//#  S++
//#  Z = Z & B
#  endif
#  if S == 17
//#  S++
//#  if Z == 0 {
//#    S = 19
//#  }
#  endif
#  if S == 18
//#  S++
//#  Y = Y + A
#  endif
#  if S == 19
//#  S++
//#  X = X + X
#  endif
#  if S == 20
//#  S++
//#  A = A + A
#  endif
#  if S == 21
//#  S = 14
#  endif
#  if S == 22
//#  S++
//#  A = Y
#  endif
#  if S == 23
//#  S = 1
#  endif
#  if S == 24
//#  S++
//#  I = 0
#  endif
#  if S == 25
//#  S++
//#  M = 0
#  endif
#  if S == 26
//#  S++
//#  N = 0b00000001
#  endif
#  if S == 27
//#  S++
//#  P = 0
#  endif
#  if S == 28
//#  S++
//#  Q = 0
#  endif
#  if S == 29
//#  S++
//#  B = 0b11100101
#  endif
#  if S == 30
//#  S++
//#  B = B + I
#  endif
#  if S == 31
//#  S++
//#  if B == 0 {
//#    S = 56
//#  }
#  endif
#  if S == 32
//#  S++
//#  B = 0b10000000
#  endif
#  if S == 33
//#  S++
//#  B = B + I
#  endif
#  if S == 34
//#  S++
//#  l = B
//#  A = [l]
#  endif
#  if S == 35
//#  S++
//#  l = I
//#  B = [l]
#  endif
#  if S == 36
//#  S++
//#  R = 0b00000001
#  endif
#  if S == 37
//#  S = 12
#  endif
#  if S == 38
//#  S++
//#  O = M
#  endif
#  if S == 39
//#  S++
//#  O = O + N
#  endif
#  if S == 40
//#  S++
//#  M = N
#  endif
#  if S == 41
//#  S++
//#  N = O
#  endif
#  if S == 42
//#  S++
//#  A = A + M
#  endif
#  if S == 43
//#  S++
//#  B = 0b00100000
#  endif
#  if S == 44
//#  S++
//#  B = B + I
#  endif
#  if S == 45
//#  S++
//#  l = B
//#  C = [l]
#  endif
#  if S == 46
//#  S++
//#  A = A ^ C
#  endif
#  if S == 47
//#  S++
//#  P = P + A
#  endif
#  if S == 48
//#  S++
//#  B = 0b01000000
#  endif
#  if S == 49
//#  S++
//#  B = B + I
#  endif
#  if S == 50
//#  S++
//#  l = B
//#  A = [l]
#  endif
#  if S == 51
//#  S++
//#  A = P ^ A
#  endif
#  if S == 52
//#  S++
//#  Q = Q | A
#  endif
#  if S == 53
//#  S++
//#  A = 0b00000001
#  endif
#  if S == 54
//#  S++
//#  I = A + I
#  endif
#  if S == 55
//#  S = 29
#  endif
#  if S == 56
//#  S++
//#  if Q == 0 {
//#    S = 58
//#  }
#  endif
#  if S == 57
//#  S++
#    error "INVALID_FLAG"
#  endif
#  if S == 58
//#  S = -1
#  endif
#else
#  if S != -1
#    include "cpp.c"
#  endif
#  if S != -1
#    include "cpp.c"
#  endif
#endif
_1:
if (R == 1)
  R = !R
  RET
}
if (R == 2)
  R = !R
  JMP _59 (return)
}
if (R == 3)
  R = !R
  JMP _59 (return)
}
unreachable!()
_11:
return
############################################
// for (X = 1, Y = 0; X != 0; X *= 2, A *= 2)
_12:
X = 1
Y = 0
while(X != 0) {
  Z = X & B
  if (Z != 0) {
    Y = Y + A
  }
  X *= 2 // 8 times
  A *= 2
}
//for (X = 1; X <= 8; X++) {
//  if (B & (1 << X)) {
//    Y += A * (1 << X)
//  }
//}
############################################
_22:
A = Y
JMP _1
_main:
I = 0
M = 0
N = 1
P = 0
Q = 0
_29:
B = 229 + I
if (B == 0) {
  if (Q == 0) {
    return
  } else {
    invalid flag
  }
}
########################
A = FLAG[I]
B = [I]
R = 1
CALL _12
// A = A * [I]
########################
O = M + N
M = N
N = O
// M: 1 1 2 3 5 8 13 21 34 55 89 144 233 121 98 219 61 24 85 109 194 47 241 32 17 49 66
// A += fib(I)
A = A + M
B = I + 32
C = [B]
A = A ^ C
// P += (FLAG[I]*[I] + fib(I)) ^ [32+I]
P = P + A
B = I + 64
A = [B]
// P == [64+I]
A = A ^ P
Q = Q | A
I++
JMP _29
function to_byte(n) {
  return n & 0xff;
}
const first = [
  0b10111011, 0b01010101, 0b10101011, 0b11000101, 0b10111001, 0b10011101,
  0b11001001, 0b01101001, 0b10111011, 0b00110111, 0b11011001, 0b11001101,
  0b00100001, 0b10110011, 0b11001111, 0b11001111, 0b10011111, 0b00001001,
  0b10110101, 0b00111101, 0b11101011, 0b01111111, 0b01010111, 0b10100001,
  0b11101011, 0b10000111, 0b01100111,
];
const second = [
  0b00001000, 0b01100100, 0b01100100, 0b00110101, 0b10010001, 0b01100100,
  0b11100111, 0b10100000, 0b00000110, 0b10101010, 0b11011101, 0b01110101,
  0b00010111, 0b10011101, 0b01101101, 0b01011100, 0b01011110, 0b00011001,
  0b11111101, 0b11101001, 0b00001100, 0b11111001, 0b10110100, 0b10000011,
  0b10000110, 0b00100010, 0b01000010,
];
const third = [
  0b11111010, 0b01111011, 0b00011011, 0b10111010, 0b00011110, 0b10110100,
  0b10110011, 0b01011000, 0b11000110, 0b11110011, 0b10001100, 0b10010000,
  0b00111011, 0b10111010, 0b00011001, 0b01101110, 0b11001110, 0b11011111,
  0b11110001, 0b00100101, 0b10001101, 0b01000000, 0b10000000, 0b01110000,
  0b11100000, 0b01001101, 0b00011100,
];
const possible =
  "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789{}_"
    .split("")
    .map(c => c.charCodeAt(0));
const fib = [
  1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584,
  4181, 6765, 10946, 17711, 28657, 46368, 75025, 121393, 196418,
].map(to_byte);
function guess(i) {
  return possible
    .filter(c => {
      let P = i === 0 ? 0 : third[i - 1];
      P += (to_byte(c * first[i]) + fib[i]) ^ second[i];
      P = to_byte(P);
      return P === third[i];
    })
    .map(c => String.fromCharCode(c));
}
[...Array(27).keys()]
  .map(i => guess(i))
  .map(a => a[0])
  .join("");