user: Converte this assembly snippet into its equivalent C code:

```asm
<longdivision>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  mov    %rdi,%r12
  push   %rbp
  mov    %rcx,%rbp
  push   %rbx
  mov    %rsi,%rbx
  sub    $0x68,%rsp
  mov    %rdx,0x10(%rsp)
  mov    %r8,0x18(%rsp)
  mov    %r9d,0x20(%rsp)
  mov    %fs:0x28,%rax
  mov    %rax,0x58(%rsp)
  xor    %eax,%eax
  cmpb   $0x1,(%rdi)
  mov    $0x0,%eax
  movl   $0x0,0x4c(%rsp)
  movl   $0x0,0x50(%rsp)
  movl   $0x0,0x54(%rsp)
  mov    %ax,(%rcx)
  je     L13
  cmpb   $0x0,(%rdi)
  jne    L18
  cmpb   $0x0,0x1(%rdi)
  lea    0x1(%rdi),%r15
  jne    L195
  cmpb   $0x0,0x2(%rdi)
  lea    0x2(%rdi),%r15
  jne    L205
  cmpb   $0x0,0x3(%rdi)
  lea    0x3(%rdi),%r15
  jne    L232
  cmpb   $0x0,0x4(%rdi)
  lea    0x4(%rdi),%r15
  jne    L98
  movl   $0x4,0xc(%rsp)
  lea    0x5(%rdi),%r15
  movl   $0x5,0x8(%rsp)
L175:
  movzbl (%rbx),%edi
  test   %dil,%dil
  jne    L138
  movzbl 0x1(%rbx),%edi
  test   %dil,%dil
  jne    L76
  movzbl 0x2(%rbx),%edi
  test   %dil,%dil
  jne    L291
  movzbl 0x3(%rbx),%edi
  test   %dil,%dil
  jne    L199
  movzbl 0x4(%rbx),%edi
  test   %dil,%dil
  jne    L137
  movzbl 0x5(%rbx),%edi
  call   <miLookup@plt>
  movzbl (%r15),%esi
  movzbl %al,%r13d
  mov    %r13d,%edi
  call   <bd@plt>
  movslq 0x8(%rsp),%rcx
  mov    %al,0x2(%rbp)
L121:
  movzbl 0x4(%r12),%r14d
  mov    %r13d,%edi
  mov    $0x1,%r15d
  lea    0x4b(%rsp),%r13
  mov    %r14b,0x53(%rsp)
  movzbl 0x50(%rsp,%rcx,1),%esi
  call   <bd@plt>
  mov    %al,0x3(%rbp)
L107:
  movzbl (%rbx,%r15,1),%esi
  movzbl %al,%edi
  call   <bd@plt>
  mov    %al,0x0(%r13,%r15,1)
  add    $0x1,%r15
  cmp    $0x5,%r15
  je     L243
  movzbl 0x3(%rbp),%eax
  jmp    L107
  nopl   0x0(%rax)
L243:
  mov    0x10(%rsp),%rcx
  xor    0x4f(%rsp),%r14b
  mov    %rbp,%rsi
  movzbl 0x4e(%rsp),%eax
  movzwl 0x4c(%rsp),%edx
  movslq 0x20(%rsp),%rbx
  xor    0x50(%rsp),%dx
  mov    %r14b,0x4(%rcx)
  xor    0x52(%rsp),%al
  mov    0x18(%rsp),%r14
  mov    %dx,0x1(%rcx)
  lea    0x54(%rsp),%rdx
  movb   $0x0,(%rcx)
  shl    $0x2,%rbx
  mov    %al,0x3(%rcx)
  lea    (%r14,%rbx,1),%rdi
  call   <modprod@plt>
  lea    0x4(%r14,%rbx,1),%rax
  lea    -0x4(%r14,%rbx,1),%rdx
L304:
  movzbl 0x54(%rsp),%ecx
  xor    (%rdx),%cl
  mov    %cl,(%rax)
  movzbl 0x55(%rsp),%ecx
  xor    0x1(%rdx),%cl
  mov    %cl,0x1(%rax)
  movzbl 0x56(%rsp),%ecx
  xor    0x2(%rdx),%cl
  mov    %cl,0x2(%rax)
  movzbl 0x3(%rdx),%edx
  xor    0x57(%rsp),%dl
  mov    %dl,0x3(%rax)
  mov    0x58(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L58
  add    $0x68,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L13:
  movzbl 0x1(%rsi),%edi
  xor    %r14d,%r14d
  lea    0x4c(%rsp),%r15
  call   <miLookup@plt>
  mov    %al,0xc(%rsp)
  movzbl %al,%r13d
L140:
  movzbl 0x2(%rbx,%r14,1),%esi
  mov    %r13d,%edi
  call   <bd@plt>
  mov    %al,(%r15,%r14,1)
  add    $0x1,%r14
  cmp    $0x3,%r14
  jne    L140
  movzbl 0x4(%r12),%eax
  movzbl 0x4c(%rsp),%esi
  mov    %r13d,%edi
  mov    $0x1,%r12d
  lea    0x4f(%rsp),%r14
  mov    %al,0x8(%rsp)
  movzbl 0xc(%rsp),%eax
  mov    %esi,%r15d
  mov    %al,0x2(%rbp)
  call   <bd@plt>
  mov    %al,0x3(%rbp)
  movzbl %al,%r13d
L228:
  movzbl (%rbx,%r12,1),%esi
  mov    %r13d,%edi
  call   <bd@plt>
  mov    %al,(%r14,%r12,1)
  add    $0x1,%r12
  cmp    $0x5,%r12
  jne    L228
  mov    0x10(%rsp),%rbx
  movzwl 0x4d(%rsp),%eax
  lea    0x54(%rsp),%rdx
  mov    %rbp,%rsi
  xor    0x51(%rsp),%ax
  xor    0x50(%rsp),%r15b
  mov    %ax,0x2(%rbx)
  movzbl 0x8(%rsp),%eax
  xor    0x53(%rsp),%al
  mov    0x18(%rsp),%r14
  movb   $0x0,(%rbx)
  mov    %r15b,0x1(%rbx)
  mov    %al,0x4(%rbx)
  movslq 0x20(%rsp),%rbx
  shl    $0x2,%rbx
  lea    (%r14,%rbx,1),%rdi
  call   <modprod@plt>
  lea    0x4(%r14,%rbx,1),%rax
  lea    -0x4(%r14,%rbx,1),%rdx
  jmp    L304
  nopl   (%rax)
L138:
  xor    %ecx,%ecx
L257:
  mov    0x8(%rsp),%eax
  mov    %ecx,0x30(%rsp)
  sub    %ecx,%eax
  add    $0x4,%eax
  mov    %eax,0x24(%rsp)
  call   <miLookup@plt>
  movzbl (%r15),%esi
  lea    0x4c(%rsp),%r15
  movzbl %al,%r13d
  mov    %r13d,%edi
  call   <bd@plt>
  movslq 0xc(%rsp),%rdx
  movslq 0x30(%rsp),%rcx
  mov    %rbx,0x38(%rsp)
  mov    %al,0x2(%rbp)
  sub    %rdx,%rcx
  mov    %rdx,0x28(%rsp)
  add    %rbx,%rcx
  mov    0x24(%rsp),%ebx
  mov    %r12,0x30(%rsp)
  mov    %rdx,%r12
  mov    %rcx,%r14
L68:
  movzbl (%r14,%r12,1),%esi
  movzbl %al,%edi
  call   <bd@plt>
  mov    %al,(%r15,%r12,1)
  add    $0x1,%r12
  cmp    %r12d,%ebx
  jle    L173
  movzbl 0x2(%rbp),%eax
  jmp    L68
  nopl   0x0(%rax)
L173:
  mov    0x28(%rsp),%rdx
  mov    0x30(%rsp),%r12
  movslq 0x8(%rsp),%rcx
  mov    0xc(%rsp),%edi
  mov    0x24(%rsp),%r10d
  mov    0x38(%rsp),%rbx
  movzbl (%r12,%rcx,1),%eax
  xor    0x4c(%rsp,%rdx,1),%al
  mov    %al,0x50(%rsp,%rdx,1)
  lea    0x1(%rdi),%eax
  cmp    %eax,%r10d
  jle    L121
  lea    0x1(%rcx),%edx
  cltq
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%edx
  xor    0x4c(%rsp,%rax,1),%dl
  mov    %dl,0x50(%rsp,%rax,1)
  lea    0x2(%rdi),%eax
  cmp    %eax,%r10d
  jle    L121
  lea    0x2(%rcx),%edx
  cltq
  movslq %edx,%rdx
  movzbl (%r12,%rdx,1),%edx
  xor    0x4c(%rsp,%rax,1),%dl
  mov    %dl,0x50(%rsp,%rax,1)
  mov    %edi,%eax
  add    $0x3,%eax
  cmp    %eax,%r10d
  jle    L121
  movslq %eax,%rdx
  mov    %ecx,%eax
  add    $0x3,%eax
  cltq
  movzbl (%r12,%rax,1),%eax
  xor    0x4c(%rsp,%rdx,1),%al
  mov    %al,0x50(%rsp,%rdx,1)
  jmp    L121
  cs nopw 0x0(%rax,%rax,1)
L18:
  movl   $0x0,0x8(%rsp)
  mov    %rdi,%r15
L7:
  mov    0x8(%rsp),%eax
  sub    $0x1,%eax
  mov    %eax,0xc(%rsp)
  jmp    L175
  nopl   0x0(%rax,%rax,1)
L195:
  movl   $0x1,0x8(%rsp)
  jmp    L7
  nopw   0x0(%rax,%rax,1)
L76:
  mov    $0x1,%ecx
  jmp    L257
L291:
  mov    $0x2,%ecx
  jmp    L257
L205:
  movl   $0x2,0x8(%rsp)
  jmp    L7
L232:
  movl   $0x3,0x8(%rsp)
  jmp    L7
L199:
  mov    $0x3,%ecx
  jmp    L257
L137:
  mov    $0x4,%ecx
  jmp    L257
L98:
  movl   $0x4,0x8(%rsp)
  jmp    L7
L58:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
void longdivision(unsigned char a[5], unsigned char b[5], unsigned char dest[5], unsigned char quo[4], unsigned char x[6][4], int round) {
  int i, j;
  int index_a;
  int index_b;
  unsigned char inv;
  unsigned char prod[4] = {0, 0, 0, 0};
  unsigned char temp[4] = {0, 0, 0, 0};
  unsigned char tempx[4] = {0, 0, 0, 0};
  if (a[0] == 1) {
    quo[0] = 0;
    quo[1] = 0;
    inv = miLookup(b[1]);
    for (i = 0; i < 3; i++) {
      prod[i] = bd(inv, b[i + 2]);
    }
    prod[3] = a[4];
    quo[2] = inv;
    inv = bd(inv, prod[0]);
    quo[3] = inv;
    for (i = 0; i < 4; i++) {
      temp[i] = bd(inv, b[i + 1]);
    }
    dest[0] = 0x0;
    for (i = 0; i < 4; i++) {
      dest[i + 1] = prod[i] ^ temp[i];
    }
    modprod(x[round], quo, tempx);
    for (i = 0; i < 4; i++) {
      x[round + 1][i] = x[round - 1][i] ^ tempx[i];
    }
  } else {
    quo[0] = 0;
    quo[1] = 0;
    for (index_a = 0; index_a < 5; index_a++) {
      if (a[index_a] != 0) {
        break;
      }
    }
    for (index_b = 0; index_b < 5; index_b++) {
      if (b[index_b] != 0x0) {
        break;
      }
    }
    inv = miLookup(b[index_b]);
    quo[2] = bd(inv, a[index_a]);
    j = 0;
    for (i = index_a - 1; i < 4 - index_b + index_a; i++, j++) {
      prod[i] = bd(quo[2], b[index_b + j]);
    }
    j = 0;
    for (i = index_a - 1; i < 4 - index_b + index_a; i++, j++) {
      temp[i] = a[index_a + j] ^ prod[i];
    }
    temp[3] = a[4];
    quo[3] = bd(inv, temp[index_a]);
    for (i = 0; i < 4; i++) {
      prod[i] = bd(quo[3], b[i + 1]);
    }
    dest[0] = 0x0;
    for (i = 0; i < 4; i++) {
      dest[i + 1] = prod[i] ^ temp[i];
    }
    modprod(x[round], quo, tempx);
    for (i = 0; i < 4; i++) {
      x[round + 1][i] = x[round - 1][i] ^ tempx[i];
    }
  }
}
```