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

```asm
<poly1305_mac>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0xf8,%rsp
  mov    %rdi,%r14
  mov    %rsi,%r12
  mov    %rdx,%rbp
  mov    %rcx,%r13
  mov    %fs:0x28,%rax
  mov    %rax,0xe8(%rsp)
  xor    %eax,%eax
  movzbl (%rcx),%eax
  mov    %eax,(%rsp)
  movzbl 0x1(%rcx),%eax
  mov    %eax,0x4(%rsp)
  movzbl 0x2(%rcx),%eax
  mov    %eax,0x8(%rsp)
  movzbl 0x3(%rcx),%eax
  and    $0xf,%eax
  mov    %eax,0xc(%rsp)
  movzbl 0x4(%rcx),%eax
  and    $0xfc,%eax
  mov    %eax,0x10(%rsp)
  movzbl 0x5(%rcx),%eax
  mov    %eax,0x14(%rsp)
  movzbl 0x6(%rcx),%eax
  mov    %eax,0x18(%rsp)
  movzbl 0x7(%rcx),%eax
  and    $0xf,%eax
  mov    %eax,0x1c(%rsp)
  movzbl 0x8(%rcx),%eax
  and    $0xfc,%eax
  mov    %eax,0x20(%rsp)
  movzbl 0x9(%rcx),%eax
  mov    %eax,0x24(%rsp)
  movzbl 0xa(%rcx),%eax
  mov    %eax,0x28(%rsp)
  movzbl 0xb(%rcx),%eax
  and    $0xf,%eax
  mov    %eax,0x2c(%rsp)
  movzbl 0xc(%rcx),%eax
  and    $0xfc,%eax
  mov    %eax,0x30(%rsp)
  movzbl 0xd(%rcx),%eax
  mov    %eax,0x34(%rsp)
  movzbl 0xe(%rcx),%eax
  mov    %eax,0x38(%rsp)
  movzbl 0xf(%rcx),%eax
  and    $0xf,%eax
  mov    %eax,0x3c(%rsp)
  movl   $0x0,0x40(%rsp)
  lea    0x50(%rsp),%rax
  lea    0x94(%rsp),%rdx
L67:
  movl   $0x0,(%rax)
  add    $0x4,%rax
  cmp    %rdx,%rax
  jne    L67
  lea    0xe4(%rsp),%rbx
  test   %rbp,%rbp
  jne    L85
  jmp    L106
L34:
  mov    %edx,%edx
  movl   $0x1,0xa0(%rsp,%rdx,4)
  add    %rdx,%r12
  sub    %rdx,%rbp
  lea    0xa0(%rsp),%rsi
  lea    0x50(%rsp),%r15
  mov    %r15,%rdi
  call   <add@plt>
  mov    %rsp,%rsi
  mov    %r15,%rdi
  call   <mulmod@plt>
  test   %rbp,%rbp
  je     L106
L85:
  lea    0xa0(%rsp),%rax
L83:
  movl   $0x0,(%rax)
  add    $0x4,%rax
  cmp    %rax,%rbx
  jne    L83
  test   %rbp,%rbp
  je     L69
  movzbl (%r12),%eax
  mov    %eax,0xa0(%rsp)
  mov    $0x1,%eax
L57:
  mov    %eax,%edx
  cmp    %rax,%rbp
  je     L34
  movzbl (%r12,%rax,1),%edx
  mov    %edx,0xa0(%rsp,%rax,4)
  lea    0x1(%rax),%edx
  add    $0x1,%rax
  cmp    $0x10,%rax
  jne    L57
  jmp    L34
L69:
  movl   $0x1,0xa0(%rsp)
  lea    0xa0(%rsp),%rsi
  lea    0x50(%rsp),%rbx
  mov    %rbx,%rdi
  call   <add@plt>
  mov    %rsp,%rsi
  mov    %rbx,%rdi
  call   <mulmod@plt>
L106:
  lea    0x50(%rsp),%rdi
  call   <freeze@plt>
  mov    $0x0,%eax
L30:
  movzbl 0x10(%r13,%rax,1),%edx
  mov    %edx,0xa0(%rsp,%rax,4)
  add    $0x1,%rax
  cmp    $0x10,%rax
  jne    L30
  movl   $0x0,0xe0(%rsp)
  lea    0xa0(%rsp),%rsi
  lea    0x50(%rsp),%rdi
  call   <add@plt>
  mov    $0x0,%eax
L95:
  mov    0x50(%rsp,%rax,4),%edx
  mov    %dl,(%r14,%rax,1)
  add    $0x1,%rax
  cmp    $0x10,%rax
  jne    L95
  mov    0xe8(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L25
  mov    $0x0,%eax
  add    $0xf8,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L25:
  call   <__stack_chk_fail@plt>
```

assistant: ```c
int poly1305_mac(unsigned char *out, const unsigned char *in, unsigned long long inlen, const unsigned char *k) {
  unsigned int j;
  unsigned int r[17];
  unsigned int h[17];
  unsigned int c[17];
  r[0] = k[0];
  r[1] = k[1];
  r[2] = k[2];
  r[3] = k[3] & 15;
  r[4] = k[4] & 252;
  r[5] = k[5];
  r[6] = k[6];
  r[7] = k[7] & 15;
  r[8] = k[8] & 252;
  r[9] = k[9];
  r[10] = k[10];
  r[11] = k[11] & 15;
  r[12] = k[12] & 252;
  r[13] = k[13];
  r[14] = k[14];
  r[15] = k[15] & 15;
  r[16] = 0;
  for (j = 0; j < 17; ++j)
    h[j] = 0;
  while (inlen > 0) {
    for (j = 0; j < 17; ++j)
      c[j] = 0;
    for (j = 0; (j < 16) && (j < inlen); ++j)
      c[j] = in[j];
    c[j] = 1;
    in += j;
    inlen -= j;
    add(h, c);
    mulmod(h, r);
  }
  freeze(h);
  for (j = 0; j < 16; ++j)
    c[j] = k[j + 16];
  c[16] = 0;
  add(h, c);
  for (j = 0; j < 16; ++j)
    out[j] = h[j];
  return 0;
}
```