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

```asm
<BN_GF2m_mod_exp_arr>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x50,%rsp
  mov    %rdi,-0x28(%rbp)
  mov    %rsi,-0x30(%rbp)
  mov    %rdx,-0x38(%rbp)
  mov    %rcx,-0x40(%rbp)
  mov    %r8,-0x48(%rbp)
  movl   $0x0,-0x14(%rbp)
  mov    -0x30(%rbp),%rax
  mov    %rax,%rdi
  call   <bn_check_top@plt>
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <bn_check_top@plt>
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_is_zero@plt>
  test   %rax,%rax
  je     L139
  mov    -0x28(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_one@plt>
  jmp    L143
L139:
  mov    -0x38(%rbp),%rax
  mov    $0x1,%esi
  mov    %rax,%rdi
  call   <BN_abs_is_word@plt>
  test   %rax,%rax
  je     L112
  mov    -0x30(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <BN_copy@plt>
  test   %rax,%rax
  setne  %al
  movzbl %al,%eax
  jmp    L143
L112:
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_CTX_start@plt>
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_CTX_get@plt>
  mov    %rax,-0x8(%rbp)
  cmpq   $0x0,-0x8(%rbp)
  je     L57
  mov    -0x40(%rbp),%rdx
  mov    -0x30(%rbp),%rcx
  mov    -0x8(%rbp),%rax
  mov    %rcx,%rsi
  mov    %rax,%rdi
  call   <BN_GF2m_mod_arr@plt>
  test   %eax,%eax
  je     L110
  mov    -0x38(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_num_bits@plt>
  sub    $0x1,%eax
  mov    %eax,-0xc(%rbp)
  mov    -0xc(%rbp),%eax
  sub    $0x1,%eax
  mov    %eax,-0x10(%rbp)
  jmp    L106
L86:
  mov    -0x48(%rbp),%rcx
  mov    -0x40(%rbp),%rdx
  mov    -0x8(%rbp),%rsi
  mov    -0x8(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_GF2m_mod_sqr_arr@plt>
  test   %eax,%eax
  je     L64
  mov    -0x10(%rbp),%edx
  mov    -0x38(%rbp),%rax
  mov    %edx,%esi
  mov    %rax,%rdi
  call   <BN_is_bit_set@plt>
  test   %rax,%rax
  je     L159
  mov    -0x48(%rbp),%rdi
  mov    -0x40(%rbp),%rcx
  mov    -0x30(%rbp),%rdx
  mov    -0x8(%rbp),%rsi
  mov    -0x8(%rbp),%rax
  mov    %rdi,%r8
  mov    %rax,%rdi
  call   <BN_GF2m_mod_mul_arr@plt>
  test   %eax,%eax
  je     L99
L159:
  subl   $0x1,-0x10(%rbp)
L106:
  cmpl   $0x0,-0x10(%rbp)
  jns    L86
  mov    -0x8(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <BN_copy@plt>
  test   %rax,%rax
  je     L26
  mov    -0x28(%rbp),%rax
  mov    %rax,%rdi
  call   <bn_check_top@plt>
  movl   $0x1,-0x14(%rbp)
  jmp    L117
L57:
  nop
  jmp    L117
L110:
  nop
  jmp    L117
L64:
  nop
  jmp    L117
L99:
  nop
  jmp    L117
L26:
  nop
L117:
  mov    -0x48(%rbp),%rax
  mov    %rax,%rdi
  call   <BN_CTX_end@plt>
  mov    -0x14(%rbp),%eax
L143:
  leave
  ret
```

assistant: ```c
int BN_GF2m_mod_exp_arr(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const int p[], BN_CTX *ctx) {
  int ret = 0, i, n;
  BIGNUM *u;
  bn_check_top(a);
  bn_check_top(b);
  if (BN_is_zero(b))
    return (BN_one(r));
  if (BN_abs_is_word(b, 1))
    return (BN_copy(r, a) != NULL);
  BN_CTX_start(ctx);
  if ((u = BN_CTX_get(ctx)) == NULL)
    goto err;
  if (!BN_GF2m_mod_arr(u, a, p))
    goto err;
  n = BN_num_bits(b) - 1;
  for (i = n - 1; i >= 0; i--) {
    if (!BN_GF2m_mod_sqr_arr(u, u, p, ctx))
      goto err;
    if (BN_is_bit_set(b, i)) {
      if (!BN_GF2m_mod_mul_arr(u, u, a, p, ctx))
        goto err;
    }
  }
  if (!BN_copy(r, u))
    goto err;
  bn_check_top(r);
  ret = 1;
err:
  BN_CTX_end(ctx);
  return ret;
}
```