user: What would the C source look like for the assembly code provided here:

```asm
<deduct>:
  endbr64
  push   %r14
  push   %r13
  push   %r12
  mov    %rdi,%r12
  mov    %rdx,%rdi
  push   %rbp
  mov    %esi,%ebp
  push   %rbx
  movslq %ecx,%rbx
  cmp    %ebx,%esi
  je     L16
  test   %ebx,%ebx
  js     L16
  movslq %ebx,%r8
  movslq %esi,%rcx
  lea    -0x1(%rdx,%r8,1),%r9
  lea    (%rdx,%r8,1),%rax
  sub    %r8,%r9
  nopl   0x0(%rax)
L172:
  movzbl (%rax),%esi
  mov    %rax,%rdx
  sub    $0x1,%rax
  sub    %r8,%rdx
  mov    %sil,(%rdx,%rcx,1)
  movb   $0x0,0x1(%rax)
  cmp    %r9,%rax
  jne    L172
L16:
  mov    %ebp,%r10d
  test   %ebp,%ebp
  js     L212
  movslq %ebp,%rcx
  lea    (%rdi,%rcx,1),%r9
  lea    -0x1(%r12,%rcx,1),%r8
  jmp    L15
  nopw   0x0(%rax,%rax,1)
L111:
  sub    %edx,%eax
L22:
  mov    %al,0x1(%r8)
  sub    $0x1,%r9
  sub    $0x1,%r8
  cmp    $0xffffffff,%r10d
  je     L122
L15:
  movzbl 0x1(%r8),%eax
  movzbl (%r9),%edx
  sub    $0x1,%r10d
  cmp    %dl,%al
  jae    L111
  movzbl (%r8),%eax
  test   %al,%al
  jne    L184
  movslq %r10d,%rax
  mov    %r8,%rsi
  lea    -0x1(%r12,%rax,1),%rdx
  nopl   0x0(%rax)
L204:
  movb   $0xff,(%rsi)
  mov    %rdx,%rsi
  movzbl (%rdx),%eax
  sub    $0x1,%rdx
  test   %al,%al
  je     L204
  sub    $0x1,%eax
  mov    %al,(%rsi)
  movzbl 0x1(%r8),%eax
  sub    (%r9),%al
  jmp    L22
L168:
  test   %ebp,%ebp
  jns    L126
L212:
  pop    %rbx
  mov    %ebp,%eax
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  ret
  nop
L122:
  cmp    %ebx,%ebp
  je     L168
  test   %ebp,%ebp
  js     L212
  mov    %rcx,%rbx
  xor    %r13d,%r13d
  lea    0x1(%rdi),%r14
  jmp    L89
  nopl   0x0(%rax)
L180:
  test   %ebx,%ebx
  jle    L152
  lea    -0x1(%rbx),%edx
  mov    %r14,%rsi
  add    $0x1,%rdx
  call   <memmove@plt>
  mov    %rax,%rdi
L152:
  movb   $0x0,(%rdi,%rbx,1)
  add    $0x1,%r13
  sub    $0x1,%rbx
  cmp    %r13d,%ebx
  jl     L224
L89:
  cmpb   $0x0,(%rdi,%r13,1)
  je     L180
L224:
  movslq %ebp,%rbx
L126:
  xor    %r13d,%r13d
  lea    0x1(%r12),%r14
  jmp    L149
  nopl   0x0(%rax,%rax,1)
L166:
  lea    -0x1(%rbx),%edx
  mov    %r14,%rsi
  mov    %r12,%rdi
  mov    %rdx,%rbp
  add    $0x1,%rdx
  call   <memmove@plt>
L99:
  movb   $0x0,(%r12,%rbx,1)
  add    $0x1,%r13
  sub    $0x1,%rbx
  cmp    %r13d,%ebx
  jl     L212
L149:
  cmpb   $0x0,(%r12,%r13,1)
  mov    %ebx,%ebp
  jne    L212
  test   %ebx,%ebx
  jg     L166
  lea    -0x1(%rbx),%ebp
  jmp    L99
L184:
  sub    $0x1,%eax
  mov    %r8,%rsi
  mov    %al,(%rsi)
  movzbl 0x1(%r8),%eax
  sub    (%r9),%al
  jmp    L22
```

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;
}
```