user: 请将这段汇编代码片段转换成等效的C代码：

```asm
<deduct>:
  endbr64
  push   %rbx
  mov    %esi,%eax
  mov    %rdx,%r8
  mov    %ecx,%r10d
  cmp    %ecx,%esi
  je     L32
  test   %ecx,%ecx
  js     L275
  movslq %ecx,%r11
  lea    (%rdx,%r11,1),%rdx
  lea    -0x1(%r8,%r11,1),%r9
  mov    %ecx,%ecx
  sub    %rcx,%r9
  movslq %esi,%rbx
L69:
  movzbl (%rdx),%esi
  mov    %rdx,%rcx
  sub    %r11,%rcx
  mov    %sil,(%rcx,%rbx,1)
  movb   $0x0,(%rdx)
  sub    $0x1,%rdx
  cmp    %r9,%rdx
  jne    L69
L275:
  mov    %eax,%edx
  test   %eax,%eax
  js     L192
L86:
  sub    $0x1,%edx
  movslq %edx,%rcx
  jmp    L49
L280:
  movslq %ecx,%rdx
  lea    (%rdi,%rdx,1),%r9
  movzbl (%r9),%esi
  lea    -0x1(%rdi,%rdx,1),%rdx
  test   %sil,%sil
  jne    L64
L169:
  movb   $0xff,(%r9)
  mov    %rdx,%r9
  sub    $0x1,%rdx
  movzbl 0x1(%rdx),%esi
  test   %sil,%sil
  je     L169
L64:
  sub    $0x1,%esi
  mov    %sil,(%r9)
  movzbl 0x1(%rdi,%rcx,1),%edx
  sub    0x1(%r8,%rcx,1),%dl
L138:
  mov    %dl,0x1(%rdi,%rcx,1)
  sub    $0x1,%rcx
  mov    %ecx,%ebx
  add    $0x1,%ebx
  js     L229
L49:
  movzbl 0x1(%rdi,%rcx,1),%edx
  movzbl 0x1(%r8,%rcx,1),%esi
  cmp    %sil,%dl
  jb     L280
  sub    %esi,%edx
  jmp    L138
L229:
  cmp    %r10d,%eax
  je     L10
  test   %eax,%eax
  js     L106
  movslq %eax,%r9
  mov    $0x0,%r10d
  lea    0x1(%r8),%r11
  jmp    L281
L106:
  mov    %eax,%esi
  jmp    L45
L10:
  test   %r10d,%r10d
  js     L67
  mov    %r10d,%esi
  jmp    L19
L67:
  mov    %r10d,%esi
  jmp    L45
L167:
  movb   $0x0,(%r8,%r9,1)
  add    $0x1,%r10
  sub    $0x1,%r9
  cmp    %r10d,%r9d
  jl     L35
L281:
  cmpb   $0x0,(%r8,%r10,1)
  jne    L35
  test   %r9d,%r9d
  jle    L167
  mov    %r8,%rdx
  lea    -0x1(%r9),%esi
  add    %r11,%rsi
L295:
  movzbl 0x1(%rdx),%ecx
  mov    %cl,(%rdx)
  add    $0x1,%rdx
  cmp    %rsi,%rdx
  jne    L295
  jmp    L167
L298:
  movb   $0x0,0x1(%rdi,%r8,1)
  sub    $0x1,%esi
  add    $0x1,%r9
  sub    $0x1,%r8
  cmp    %r9d,%esi
  jl     L45
L131:
  cmpb   $0x0,(%rdi,%r9,1)
  jne    L45
  test   %esi,%esi
  jle    L298
  mov    %rdi,%rax
  mov    %r8d,%ecx
  add    %r10,%rcx
L284:
  movzbl 0x1(%rax),%edx
  mov    %dl,(%rax)
  add    $0x1,%rax
  cmp    %rcx,%rax
  jne    L284
  jmp    L298
L35:
  mov    %eax,%esi
L19:
  lea    -0x1(%rsi),%r8d
  movslq %r8d,%r8
  mov    $0x0,%r9d
  lea    0x1(%rdi),%r10
  jmp    L131
L32:
  mov    %ecx,%edx
  mov    %ecx,%esi
  test   %ecx,%ecx
  jns    L86
  jmp    L45
L192:
  mov    %eax,%esi
L45:
  mov    %esi,%eax
  pop    %rbx
  ret
```

assistant: ```c
int deduct(unsigned char *a, int a_len, unsigned char *b, int b_len) {
  int i, j, k;
  if (a_len != b_len) {
    for (i = a_len, j = b_len; j >= 0; i--, j--) {
      b[i] = b[j];
      b[j] = 0;
    }
  }
  for (i = a_len; i >= 0; i--) {
    if (a[i] >= b[i])
      a[i] -= b[i];
    else {
      j = i - 1;
      while (1) {
        if (a[j] > 0) {
          a[j]--;
          a[i] += 256 - b[i];
          break;
        } else
          a[j] = 255;
        j--;
      }
    }
  }
  if (a_len != b_len) {
    b_len = a_len;
    for (i = 0; i <= b_len; i++) {
      if (b[i] > 0)
        break;
      else {
        for (j = 0, k = 1; k <= b_len; j++, k++)
          b[j] = b[k];
        b[b_len] = 0;
        b_len--;
      }
    }
  }
  for (i = 0; i <= a_len; i++) {
    if (a[i] > 0)
      break;
    else {
      for (j = 0, k = 1; k <= a_len; j++, k++)
        a[j] = a[k];
      a[a_len] = 0;
      a_len--;
    }
  }
  return a_len;
}
```