user: 请显示与下面列出的汇编代码相匹配的C语言实现:

```asm
<dfct>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  sub    $0x70,%rsp
  mov    %edi,-0x44(%rbp)
  mov    %rsi,-0x50(%rbp)
  mov    %rdx,-0x58(%rbp)
  mov    %rcx,-0x60(%rbp)
  mov    %r8,-0x68(%rbp)
  mov    -0x60(%rbp),%rax
  mov    (%rax),%eax
  mov    %eax,-0x2c(%rbp)
  mov    -0x2c(%rbp),%eax
  shl    $0x3,%eax
  cmp    %eax,-0x44(%rbp)
  jle    L184
  mov    -0x44(%rbp),%eax
  sar    $0x3,%eax
  mov    %eax,-0x2c(%rbp)
  mov    -0x68(%rbp),%rdx
  mov    -0x60(%rbp),%rcx
  mov    -0x2c(%rbp),%eax
  mov    %rcx,%rsi
  mov    %eax,%edi
  call   <makewt@plt>
L184:
  mov    -0x60(%rbp),%rax
  mov    0x4(%rax),%eax
  mov    %eax,-0x28(%rbp)
  mov    -0x28(%rbp),%eax
  add    %eax,%eax
  cmp    %eax,-0x44(%rbp)
  jle    L12
  mov    -0x44(%rbp),%eax
  sar    %eax
  mov    %eax,-0x28(%rbp)
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  add    %rax,%rdx
  mov    -0x60(%rbp),%rcx
  mov    -0x28(%rbp),%eax
  mov    %rcx,%rsi
  mov    %eax,%edi
  call   <makect@plt>
L12:
  mov    -0x44(%rbp),%eax
  sar    %eax
  mov    %eax,-0x30(%rbp)
  mov    -0x30(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x18(%rbp)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  mov    -0x50(%rbp),%rax
  movsd  %xmm0,(%rax)
  movsd  -0x18(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  mov    -0x58(%rbp),%rax
  movsd  %xmm0,(%rax)
  mov    -0x30(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x18(%rbp),%xmm0
  addsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  cmpl   $0x2,-0x44(%rbp)
  jle    L107
  mov    -0x30(%rbp),%eax
  sar    %eax
  mov    %eax,-0x24(%rbp)
  movl   $0x1,-0x3c(%rbp)
  jmp    L55
L24:
  mov    -0x30(%rbp),%eax
  sub    -0x3c(%rbp),%eax
  mov    %eax,-0x38(%rbp)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  sub    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x10(%rbp)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  sub    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x18(%rbp)
  mov    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  sub    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  subsd  %xmm1,%xmm0
  movsd  %xmm0,-0x8(%rbp)
  mov    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  sub    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  movsd  %xmm0,-0x20(%rbp)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x10(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x8(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x18(%rbp),%xmm0
  subsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  -0x18(%rbp),%xmm0
  addsd  -0x20(%rbp),%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x1,-0x3c(%rbp)
L55:
  mov    -0x3c(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L24
  mov    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  sub    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x44(%rbp),%eax
  sub    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x28(%rbp),%edx
  mov    -0x50(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %eax,%edi
  call   <dctsub@plt>
  cmpl   $0x4,-0x30(%rbp)
  jle    L36
  mov    -0x60(%rbp),%rax
  lea    0x8(%rax),%rdi
  mov    -0x68(%rbp),%rcx
  mov    -0x2c(%rbp),%edx
  mov    -0x50(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %rcx,%r8
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %eax,%edi
  call   <cftfsub@plt>
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x28(%rbp),%edx
  mov    -0x50(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %eax,%edi
  call   <rftfsub@plt>
  jmp    L198
L36:
  cmpl   $0x4,-0x30(%rbp)
  jne    L198
  mov    -0x60(%rbp),%rax
  lea    0x8(%rax),%rdi
  mov    -0x68(%rbp),%rcx
  mov    -0x2c(%rbp),%edx
  mov    -0x50(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %rcx,%r8
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %eax,%edi
  call   <cftfsub@plt>
L198:
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  mov    -0x50(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  cltq
  shl    $0x3,%rax
  lea    -0x8(%rax),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm1
  mov    -0x50(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x50(%rbp),%rax
  add    $0x8,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x30(%rbp),%eax
  sub    $0x2,%eax
  mov    %eax,-0x3c(%rbp)
  jmp    L85
L125:
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x3c(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x3c(%rbp),%eax
  add    %eax,%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x3c(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x3c(%rbp),%eax
  add    %eax,%eax
  cltq
  shl    $0x3,%rax
  lea    -0x8(%rax),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  subl   $0x2,-0x3c(%rbp)
L85:
  cmpl   $0x1,-0x3c(%rbp)
  jg     L125
  movl   $0x2,-0x34(%rbp)
  mov    -0x24(%rbp),%eax
  mov    %eax,-0x30(%rbp)
  jmp    L116
L19:
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x28(%rbp),%edx
  mov    -0x58(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %eax,%edi
  call   <dctsub@plt>
  cmpl   $0x4,-0x30(%rbp)
  jle    L30
  mov    -0x60(%rbp),%rax
  lea    0x8(%rax),%rdi
  mov    -0x68(%rbp),%rcx
  mov    -0x2c(%rbp),%edx
  mov    -0x58(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %rcx,%r8
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %eax,%edi
  call   <cftfsub@plt>
  mov    -0x2c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x68(%rbp),%rax
  lea    (%rdx,%rax,1),%rcx
  mov    -0x28(%rbp),%edx
  mov    -0x58(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %eax,%edi
  call   <rftfsub@plt>
  jmp    L81
L30:
  cmpl   $0x4,-0x30(%rbp)
  jne    L81
  mov    -0x60(%rbp),%rax
  lea    0x8(%rax),%rdi
  mov    -0x68(%rbp),%rcx
  mov    -0x2c(%rbp),%edx
  mov    -0x58(%rbp),%rsi
  mov    -0x30(%rbp),%eax
  mov    %rcx,%r8
  mov    %edx,%ecx
  mov    %rdi,%rdx
  mov    %eax,%edi
  call   <cftfsub@plt>
L81:
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  mov    -0x58(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  sub    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm1
  mov    -0x58(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  movl   $0x0,-0x38(%rbp)
  movl   $0x2,-0x3c(%rbp)
  jmp    L63
L98:
  mov    -0x34(%rbp),%eax
  shl    $0x2,%eax
  add    %eax,-0x38(%rbp)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x3c(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x38(%rbp),%eax
  sub    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x3c(%rbp),%eax
  cltq
  add    $0x1,%rax
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x38(%rbp),%edx
  mov    -0x34(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x2,-0x3c(%rbp)
L63:
  mov    -0x3c(%rbp),%eax
  cmp    -0x30(%rbp),%eax
  jl     L98
  shll   -0x34(%rbp)
  mov    -0x30(%rbp),%eax
  sar    %eax
  mov    %eax,-0x24(%rbp)
  movl   $0x0,-0x3c(%rbp)
  jmp    L102
L65:
  mov    -0x30(%rbp),%eax
  sub    -0x3c(%rbp),%eax
  mov    %eax,-0x38(%rbp)
  mov    -0x30(%rbp),%edx
  mov    -0x38(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x30(%rbp),%edx
  mov    -0x3c(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x3c(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x30(%rbp),%edx
  mov    -0x38(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm1
  mov    -0x30(%rbp),%edx
  mov    -0x3c(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  movsd  (%rax),%xmm0
  mov    -0x38(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rdx,%rax
  addsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  addl   $0x1,-0x3c(%rbp)
L102:
  mov    -0x3c(%rbp),%eax
  cmp    -0x24(%rbp),%eax
  jl     L65
  mov    -0x30(%rbp),%edx
  mov    -0x24(%rbp),%eax
  add    %edx,%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x58(%rbp),%rax
  add    %rax,%rdx
  mov    -0x24(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rcx
  mov    -0x58(%rbp),%rax
  add    %rcx,%rax
  movsd  (%rdx),%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x24(%rbp),%eax
  mov    %eax,-0x30(%rbp)
L116:
  cmpl   $0x1,-0x30(%rbp)
  jg     L19
  mov    -0x34(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rax,%rdx
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,(%rdx)
  mov    -0x58(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm0
  mov    -0x58(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm1
  mov    -0x44(%rbp),%eax
  cltq
  lea    0x0(,%rax,8),%rdx
  mov    -0x50(%rbp),%rax
  add    %rdx,%rax
  subsd  %xmm1,%xmm0
  movsd  %xmm0,(%rax)
  mov    -0x58(%rbp),%rax
  add    $0x10,%rax
  movsd  (%rax),%xmm1
  mov    -0x58(%rbp),%rax
  add    $0x8,%rax
  movsd  (%rax),%xmm0
  addsd  %xmm1,%xmm0
  mov    -0x50(%rbp),%rax
  movsd  %xmm0,(%rax)
  jmp    L57
L107:
  mov    -0x50(%rbp),%rax
  lea    0x8(%rax),%rdx
  mov    -0x50(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,(%rdx)
  mov    -0x50(%rbp),%rax
  lea    0x10(%rax),%rdx
  mov    -0x58(%rbp),%rax
  movsd  (%rax),%xmm0
  movsd  %xmm0,(%rdx)
  mov    -0x58(%rbp),%rax
  movsd  0x8(%rax),%xmm0
  mov    -0x50(%rbp),%rax
  movsd  %xmm0,(%rax)
L57:
  nop
  leave
  ret
```

assistant: ```c
void dfct(int n, double *a, double *t, int *ip, double *w) {
  void makewt(int nw, int *ip, double *w);
  void makect(int nc, int *ip, double *c);
  void cftfsub(int n, double *a, int *ip, int nw, double *w);
  void rftfsub(int n, double *a, int nc, double *c);
  void dctsub(int n, double *a, int nc, double *c);
  int j, k, l, m, mh, nw, nc;
  double xr, xi, yr, yi;
  nw = ip[0];
  if (n > (nw << 3)) {
    nw = n >> 3;
    makewt(nw, ip, w);
  }
  nc = ip[1];
  if (n > (nc << 1)) {
    nc = n >> 1;
    makect(nc, ip, w + nw);
  }
  m = n >> 1;
  yi = a[m];
  xi = a[0] + a[n];
  a[0] -= a[n];
  t[0] = xi - yi;
  t[m] = xi + yi;
  if (n > 2) {
    mh = m >> 1;
    for (j = 1; j < mh; j++) {
      k = m - j;
      xr = a[j] - a[n - j];
      xi = a[j] + a[n - j];
      yr = a[k] - a[n - k];
      yi = a[k] + a[n - k];
      a[j] = xr;
      a[k] = yr;
      t[j] = xi - yi;
      t[k] = xi + yi;
    }
    t[mh] = a[mh] + a[n - mh];
    a[mh] -= a[n - mh];
    dctsub(m, a, nc, w + nw);
    if (m > 4) {
      cftfsub(m, a, ip + 2, nw, w);
      rftfsub(m, a, nc, w + nw);
    } else if (m == 4) {
      cftfsub(m, a, ip + 2, nw, w);
    }
    a[n - 1] = a[0] - a[1];
    a[1] = a[0] + a[1];
    for (j = m - 2; j >= 2; j -= 2) {
      a[2 * j + 1] = a[j] + a[j + 1];
      a[2 * j - 1] = a[j] - a[j + 1];
    }
    l = 2;
    m = mh;
    while (m >= 2) {
      dctsub(m, t, nc, w + nw);
      if (m > 4) {
        cftfsub(m, t, ip + 2, nw, w);
        rftfsub(m, t, nc, w + nw);
      } else if (m == 4) {
        cftfsub(m, t, ip + 2, nw, w);
      }
      a[n - l] = t[0] - t[1];
      a[l] = t[0] + t[1];
      k = 0;
      for (j = 2; j < m; j += 2) {
        k += l << 2;
        a[k - l] = t[j] - t[j + 1];
        a[k + l] = t[j] + t[j + 1];
      }
      l <<= 1;
      mh = m >> 1;
      for (j = 0; j < mh; j++) {
        k = m - j;
        t[j] = t[m + k] - t[m + j];
        t[k] = t[m + k] + t[m + j];
      }
      t[mh] = t[m + mh];
      m = mh;
    }
    a[l] = t[0];
    a[n] = t[2] - t[1];
    a[0] = t[2] + t[1];
  } else {
    a[1] = a[0];
    a[2] = t[0];
    a[0] = t[1];
  }
}
```