user: 请从给定的汇编指令推导出C源代码：

```asm
<fc_damerau0>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  mov    %r8d,%r13d
  push   %r12
  mov    %rcx,%r12
  push   %rbp
  mov    %rsi,%rbp
  push   %rbx
  mov    %rdi,%rbx
  sub    $0x18,%rsp
  cmp    %r8d,%edx
  setge  %r14b
  cmp    $0x1000,%r8d
  mov    %edx,(%rsp)
  setbe  %al
  and    %r14d,%eax
  cmp    $0x1000,%edx
  setbe  %dil
  movzbl %dil,%edi
  and    %eax,%edi
  call   <assert@plt>
  movzbl %r14b,%edi
  call   <assert@plt>
  test   %r13d,%r13d
  mov    (%rsp),%edx
  jne    L127
  jmp    L64
L146:
  add    $0x8,%rbp
  add    $0x8,%r12
  sub    $0x1,%edx
  sub    $0x1,%r13d
  je     L64
L127:
  mov    (%r12),%r14
  cmp    %r14,0x0(%rbp)
  je     L146
  movslq %r13d,%rdi
  movslq %edx,%rax
  sub    %rdi,%rax
  lea    0x0(%rbp,%rax,8),%rax
  jmp    L201
  nop
L198:
  sub    $0x1,%rdi
  sub    $0x1,%edx
  test   %edi,%edi
  je     L64
L201:
  mov    -0x8(%r12,%rdi,8),%rcx
  mov    %edi,%r15d
  cmp    %rcx,-0x8(%rax,%rdi,8)
  je     L198
  lea    0x4(,%rdi,4),%rax
  mov    %edi,%esi
  lea    (%rbx,%rax,1),%r10
  mov    %rax,0x8(%rsp)
  lea    (%r10,%rax,1),%r9
  xor    %eax,%eax
  test   %edi,%edi
  js     L145
  nopl   0x0(%rax,%rax,1)
L62:
  mov    %rax,%rcx
  mov    %eax,(%r10,%rax,4)
  add    $0x1,%rax
  cmp    %rsi,%rcx
  jne    L62
L145:
  test   %edx,%edx
  jle    L217
  lea    0x1(%rdx),%eax
  mov    $0x1,%r11d
  mov    %edi,%edi
  mov    %rax,(%rsp)
  nopw   0x0(%rax,%rax,1)
L102:
  mov    %r11d,(%r9)
  test   %r15d,%r15d
  jle    L7
  mov    -0x8(%rbp,%r11,8),%r13
  mov    %r14,%r8
  mov    $0x1,%eax
  jmp    L67
  nopw   0x0(%rax,%rax,1)
L91:
  mov    -0x4(%r9,%rax,4),%esi
  lea    0x1(%rsi),%edx
  mov    (%r10,%rax,4),%esi
  add    $0x1,%esi
  cmp    %esi,%edx
  cmovg  %esi,%edx
  add    $0x1,%ecx
  cmp    %ecx,%edx
  cmovg  %ecx,%edx
  mov    %edx,(%r9,%rax,4)
  cmp    $0x1,%r11d
  jle    L215
  cmp    $0x1,%eax
  jle    L215
  cmp    %r8,-0x10(%rbp,%r11,8)
  je     L54
L215:
  cmp    %rax,%rdi
  je     L7
L168:
  mov    (%r12,%rax,8),%r8
  add    $0x1,%rax
L67:
  mov    -0x4(%r10,%rax,4),%ecx
  cmp    %r8,%r13
  jne    L91
  mov    %ecx,(%r9,%rax,4)
L162:
  cmp    %rax,%rdi
  jne    L168
L7:
  mov    %r10,%rax
  add    $0x1,%r11
  mov    %r9,%r10
  cmp    %r11,(%rsp)
  je     L39
  mov    %rbx,%r9
  mov    %rax,%rbx
  jmp    L102
  nopl   (%rax)
L64:
  add    $0x18,%rsp
  mov    %edx,%eax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
  nopl   0x0(%rax)
L54:
  cmp    -0x10(%r12,%rax,8),%r13
  jne    L215
  mov    -0x8(%rbx,%rax,4),%ecx
  add    $0x1,%ecx
  cmp    %edx,%ecx
  cmovg  %edx,%ecx
  mov    %ecx,(%r9,%rax,4)
  jmp    L162
L217:
  mov    %r10,%r9
L39:
  mov    0x8(%rsp),%rax
  mov    -0x4(%r9,%rax,1),%eax
  add    $0x18,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
```

assistant: ```c
int32_t fc_damerau0(int32_t *matrix, const char32_t *seq1, int32_t len1, const char32_t *seq2, int32_t len2) {
  assert((len1 >= 0 && len1 <= 4096) && (len2 >= 0 && len2 <= 4096) && len1 >= len2);
  do {
    assert(len1 >= len2);
    while (len2 && *seq1 == *seq2) {
      seq1++;
      seq2++;
      len1--;
      len2--;
    }
    while (len2 && seq1[len1 - 1] == seq2[len2 - 1]) {
      len1--;
      len2--;
    }
  } while (0);
  if (len2 == 0)
    return len1;
  int32_t *transpos = matrix;
  int32_t *previous = &transpos[len2 + 1];
  int32_t *current = &previous[len2 + 1];
  for (int32_t j = 0; j <= len2; j++)
    previous[j] = j;
  for (int32_t i = 1; i <= len1; i++) {
    current[0] = i;
    for (int32_t j = 1; j <= len2; j++) {
      if (seq1[i - 1] == seq2[j - 1]) {
        current[j] = previous[j - 1];
      } else {
        const int32_t ic = current[j - 1] + 1;
        const int32_t dc = previous[j] + 1;
        const int32_t rc = previous[j - 1] + 1;
        current[j] = ((ic) < (((dc) < (rc) ? (dc) : (rc))) ? (ic) : (((dc) < (rc) ? (dc) : (rc))));
        if ((i > 1 && j > 1 && seq1[i - 2] == seq2[j - 1] && seq1[i - 1] == seq2[j - 2])) {
          const int32_t tc = transpos[j - 2] + 1;
          current[j] = ((tc) < (current[j]) ? (tc) : (current[j]));
        }
      }
    }
    do {
      int32_t *tmp = transpos;
      transpos = previous;
      previous = current;
      current = tmp;
    } while (0);
  }
  return previous[len2];
}
```