user: Demonstrate the C code that generates the assembly output below:

```asm
<str_decode>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbx
  sub    $0x158,%rsp
  mov    %rdi,-0x168(%rbp)
  mov    %rsi,-0x170(%rbp)
  mov    %fs:0x28,%rax
  mov    %rax,-0x38(%rbp)
  xor    %eax,%eax
  mov    -0x170(%rbp),%rax
  mov    %rax,%rdi
  call   <ignorestr@plt>
  test   %rax,%rax
  je     L214
  mov    -0x170(%rbp),%rdx
  mov    -0x168(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcpy@plt>
  jmp    L544
L214:
  mov    -0x170(%rbp),%rcx
  lea    -0x140(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  mov    -0x168(%rbp),%rax
  mov    %rax,-0x158(%rbp)
  mov    -0x170(%rbp),%rax
  mov    %rax,-0x150(%rbp)
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  mov    $0x0,%r15d
  mov    %r15d,-0x178(%rbp)
  mov    %r15d,-0x174(%rbp)
  jmp    L187
L458:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L273
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L273:
  cmp    $0x3f,%ebx
  jne    L27
  mov    -0x170(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x3d,%al
  jne    L27
  addq   $0x1,-0x170(%rbp)
  jmp    L101
L27:
  cmp    $0xa,%ebx
  jne    L194
  addq   $0x1,-0x170(%rbp)
  mov    $0x0,%r15d
  mov    %r15d,-0x178(%rbp)
  mov    %r15d,-0x174(%rbp)
  jmp    L101
L194:
  test   %r15d,%r15d
  je     L422
  cmp    $0x3d,%ebx
  jne    L422
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L136
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L136:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%ebx
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L339
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L339:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%r12d
  mov    %ebx,%edi
  call   <qp_code@plt>
  shl    $0x4,%eax
  mov    %eax,%ebx
  mov    %r12d,%edi
  call   <qp_code@plt>
  or     %eax,%ebx
  mov    %ebx,%ecx
  mov    -0x168(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x168(%rbp)
  mov    %ecx,%edx
  mov    %dl,(%rax)
  jmp    L101
L422:
  cmpl   $0x0,-0x178(%rbp)
  je     L112
  cmpl   $0x0,-0x174(%rbp)
  jne    L112
  jmp    L344
L40:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L244
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L244:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%ebx
L344:
  mov    %ebx,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L40
  test   %ebx,%ebx
  je     L494
L636:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L26
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L26:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%r12d
  mov    %r12d,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L636
  test   %r12d,%r12d
  je     L540
L183:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L593
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L593:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%r13d
  mov    %r13d,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L183
  test   %r13d,%r13d
  je     L584
L49:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L201
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L201:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%r14d
  mov    %r14d,%edi
  call   <isspace@plt>
  test   %rax,%rax
  jne    L49
  test   %r14d,%r14d
  je     L334
  cmp    $0x3d,%ebx
  je     L389
  cmp    $0x3d,%r12d
  jne    L351
L389:
  movl   $0x1,-0x174(%rbp)
  jmp    L101
L351:
  mov    %r12d,%edi
  call   <base64_code@plt>
  mov    %eax,%r12d
  mov    %ebx,%edi
  call   <base64_code@plt>
  shl    $0x2,%eax
  mov    %eax,%edx
  mov    %r12d,%eax
  sar    $0x4,%eax
  and    $0x3,%eax
  mov    %edx,%ecx
  or     %eax,%ecx
  mov    -0x168(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x168(%rbp)
  mov    %ecx,%edx
  mov    %dl,(%rax)
  cmp    $0x3d,%r13d
  jne    L517
  movl   $0x1,-0x174(%rbp)
  jmp    L101
L517:
  mov    %r13d,%edi
  call   <base64_code@plt>
  mov    %eax,%r13d
  mov    %r12d,%eax
  shl    $0x4,%eax
  mov    %eax,%edx
  mov    %r13d,%eax
  sar    $0x2,%eax
  and    $0xf,%eax
  mov    %edx,%ecx
  or     %eax,%ecx
  mov    -0x168(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x168(%rbp)
  mov    %ecx,%edx
  mov    %dl,(%rax)
  cmp    $0x3d,%r14d
  jne    L42
  movl   $0x1,-0x174(%rbp)
  jmp    L101
L42:
  mov    %r13d,%eax
  shl    $0x6,%eax
  mov    %eax,%ebx
  mov    %r14d,%edi
  call   <base64_code@plt>
  or     %eax,%ebx
  mov    %ebx,%ecx
  mov    -0x168(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x168(%rbp)
  mov    %ecx,%edx
  mov    %dl,(%rax)
  jmp    L101
L112:
  cmp    $0x3d,%ebx
  jne    L324
  mov    -0x170(%rbp),%rax
  add    $0x1,%rax
  movzbl (%rax),%eax
  cmp    $0x3f,%al
  jne    L324
  mov    $0x0,%r13d
  mov    %r13d,%r12d
L425:
  mov    -0x170(%rbp),%rax
  mov    -0x150(%rbp),%rdx
  sub    %rdx,%rax
  mov    %rax,-0x148(%rbp)
  cmpq   $0xfe,-0x148(%rbp)
  jle    L270
  lea    -0x140(%rbp),%rcx
  mov    -0x158(%rbp),%rax
  mov    $0x100,%edx
  mov    %rcx,%rsi
  mov    %rax,%rdi
  mov    $0x0,%eax
  call   <memcpy@plt>
  jmp    L544
L270:
  addq   $0x1,-0x170(%rbp)
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%ebx
  cmp    $0x3f,%ebx
  je     L392
  cmp    $0x2,%r12d
  jne    L425
  or     $0x20,%ebx
  mov    %ebx,%r13d
  jmp    L425
L392:
  add    $0x1,%r12d
  cmp    $0x2,%r12d
  jg     L59
  jmp    L425
L59:
  nop
  cmp    $0x71,%r13d
  jne    L426
  mov    $0x1,%r15d
  jmp    L86
L426:
  cmp    $0x62,%r13d
  jne    L86
  movl   $0x1,-0x178(%rbp)
  jmp    L86
L324:
  mov    -0x168(%rbp),%rax
  lea    0x1(%rax),%rdx
  mov    %rdx,-0x168(%rbp)
  mov    %ebx,%edx
  mov    %dl,(%rax)
  jmp    L101
L86:
  nop
L101:
  addq   $0x1,-0x170(%rbp)
L187:
  mov    -0x170(%rbp),%rax
  movzbl (%rax),%eax
  movzbl %al,%ebx
  test   %ebx,%ebx
  jne    L458
  jmp    L230
L494:
  nop
  jmp    L230
L540:
  nop
  jmp    L230
L584:
  nop
  jmp    L230
L334:
  nop
L230:
  mov    -0x168(%rbp),%rax
  movb   $0x0,(%rax)
L544:
  mov    -0x38(%rbp),%rax
  sub    %fs:0x28,%rax
  je     L369
  call   <__stack_chk_fail@plt>
L369:
  add    $0x158,%rsp
  pop    %rbx
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  pop    %rbp
  ret
```

assistant: ```c
void str_decode(unsigned char *dst, unsigned char *src) {
  register int is_qp, is_base64, is_done;
  register int c1, c2, c3, c4;
  char *dsttmp;
  char *srctmp;
  char srcbuf[256];
  long pos;
  if (ignorestr((char *)src)) {
    strcpy((char *)dst, (char *)src);
    return;
  }
  memcpy(srcbuf, src, 256);
  dsttmp = (char *)dst;
  srctmp = (char *)src;
  pos = (long)src - (long)srctmp;
  for (is_done = is_qp = is_base64 = 0; (c1 = *src) != 0; src++) {
    pos = (long)src - (long)srctmp;
    if (pos > 254) {
      memcpy(dsttmp, srcbuf, 256);
      return;
    }
    if (c1 == '?' && src[1] == '=') {
      src++;
      continue;
    } else if (c1 == '\n') {
      src++;
      is_done = is_qp = is_base64 = 0;
      continue;
    } else if (is_qp && c1 == '=') {
      pos = (long)src - (long)srctmp;
      if (pos > 254) {
        memcpy(dsttmp, srcbuf, 256);
        return;
      }
      c1 = *++src;
      pos = (long)src - (long)srctmp;
      if (pos > 254) {
        memcpy(dsttmp, srcbuf, 256);
        return;
      }
      c2 = *++src;
      *dst++ = (qp_code(c1) << 4) | qp_code(c2);
    } else if (is_base64 && !is_done) {
      while (isspace(c1)) {
        pos = (long)src - (long)srctmp;
        if (pos > 254) {
          memcpy(dsttmp, srcbuf, 256);
          return;
        }
        c1 = *++src;
      }
      if (!c1)
        break;
      do {
        pos = (long)src - (long)srctmp;
        if (pos > 254) {
          memcpy(dsttmp, srcbuf, 256);
          return;
        }
        c2 = *++src;
      } while (isspace(c2));
      if (!c2)
        break;
      do {
        pos = (long)src - (long)srctmp;
        if (pos > 254) {
          memcpy(dsttmp, srcbuf, 256);
          return;
        }
        c3 = *++src;
      } while (isspace(c3));
      if (!c3)
        break;
      do {
        pos = (long)src - (long)srctmp;
        if (pos > 254) {
          memcpy(dsttmp, srcbuf, 256);
          return;
        }
        c4 = *++src;
      } while (isspace(c4));
      if (!c4)
        break;
      if (c1 == '=' || c2 == '=') {
        is_done = 1;
        continue;
      }
      c2 = base64_code(c2);
      *dst++ = (base64_code(c1) << 2) | ((c2 & 0x30) >> 4);
      if (c3 == '=')
        is_done = 1;
      else {
        c3 = base64_code(c3);
        *dst++ = ((c2 & 0xF) << 4) | ((c3 & 0x3c) >> 2);
        if (c4 == '=')
          is_done = 1;
        else {
          *dst++ = ((c3 & 0x03) << 6) | base64_code(c4);
        }
      }
    } else if ((c1 == '=') && (src[1] == '?')) {
      c2 = c3 = 0;
      for (;;) {
        pos = (long)src - (long)srctmp;
        if (pos > 254) {
          memcpy(dsttmp, srcbuf, 256);
          return;
        }
        c1 = *++src;
        if (c1 != '?') {
          if (c2 == 2)
            c3 = c1 | 0x20;
        } else {
          if (++c2 >= 3)
            break;
        }
      }
      if (c3 == 'q')
        is_qp = 1;
      else if (c3 == 'b')
        is_base64 = 1;
    } else
      *dst++ = c1;
  }
  *dst = '\0';
}
```