user: Please show me the C implementation that matches the assembly code listed below:

```asm
<merge>:
  endbr64
  push   %r15
  push   %r14
  push   %r13
  push   %r12
  push   %rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rdi,0x20(%rsp)
  mov    %esi,%ebx
  mov    %edx,%r13d
  mov    %edx,0x34(%rsp)
  mov    %ecx,%ebp
  mov    %ecx,0x10(%rsp)
  mov    %r8d,%r15d
  mov    %r8d,0x30(%rsp)
  mov    %r9,0x28(%rsp)
  lea    0x1(%rcx),%r14d
  mov    %r8d,%eax
  sub    %edx,%eax
  add    $0x1,%eax
  imul   %esi,%eax
  mov    %eax,0x3c(%rsp)
  mov    %eax,%edi
  call   <malloc@plt>
  mov    %rax,0x18(%rsp)
  test   %rax,%rax
  je     L19
  cmp    %ebp,%r13d
  jle    L68
  cmp    %r15d,%r14d
  jg     L65
L68:
  mov    0x34(%rsp),%r15d
  mov    $0x0,%r13d
  movslq %ebx,%rax
  mov    %rax,0x8(%rsp)
  jmp    L55
L120:
  mov    0x30(%rsp),%esi
  cmp    %r14d,%esi
  jl     L109
  mov    %ebx,%eax
  imul   %r13d,%eax
  cltq
  mov    0x18(%rsp),%rcx
  lea    (%rcx,%rax,1),%r12
  mov    0x20(%rsp),%rdx
  sub    %rcx,%rdx
  mov    %ebx,%ecx
  imul   %r14d,%ecx
  movslq %ecx,%rcx
  add    %rcx,%rdx
  sub    %rax,%rdx
  mov    %r14d,%ebp
  mov    %r14d,0x14(%rsp)
  mov    %r15d,0x38(%rsp)
  mov    %rdx,%r15
  mov    %esi,%r14d
L69:
  lea    (%r12,%r15,1),%rsi
  mov    %ebx,%edx
  mov    %r12,%rdi
  call   <memcpy@plt>
  add    $0x1,%ebp
  lea    0x0(%r13,%rbp,1),%eax
  sub    0x14(%rsp),%eax
  add    0x8(%rsp),%r12
  cmp    %ebp,%r14d
  jge    L69
  mov    0x38(%rsp),%r15d
  mov    %eax,%r13d
  mov    %ebp,%r14d
L109:
  cmp    0x10(%rsp),%r15d
  jle    L55
  cmp    0x30(%rsp),%r14d
  jle    L55
L65:
  mov    0x34(%rsp),%eax
  imul   %ebx,%eax
  cltq
  mov    0x20(%rsp),%rdi
  add    %rax,%rdi
  mov    0x3c(%rsp),%edx
  mov    0x18(%rsp),%rbx
  mov    %rbx,%rsi
  call   <memcpy@plt>
  mov    %rbx,%rdi
  call   <free@plt>
  mov    $0x0,%eax
L11:
  add    $0x48,%rsp
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  pop    %r15
  ret
L97:
  mov    %ebx,%eax
  imul   %r13d,%eax
  cltq
  mov    0x18(%rsp),%rcx
  lea    (%rax,%rcx,1),%r12
  mov    0x20(%rsp),%rdx
  sub    %rcx,%rdx
  mov    %ebx,%ecx
  imul   %r15d,%ecx
  movslq %ecx,%rcx
  add    %rcx,%rdx
  sub    %rax,%rdx
  mov    %r15d,%ebp
  mov    %r14d,0x38(%rsp)
  mov    %r15d,0x14(%rsp)
  mov    %rdx,%r14
  mov    0x10(%rsp),%r15d
L61:
  lea    (%r12,%r14,1),%rsi
  mov    %ebx,%edx
  mov    %r12,%rdi
  call   <memcpy@plt>
  add    $0x1,%ebp
  lea    0x0(%r13,%rbp,1),%eax
  sub    0x14(%rsp),%eax
  add    0x8(%rsp),%r12
  cmp    %ebp,%r15d
  jge    L61
  mov    0x38(%rsp),%r14d
  mov    %eax,%r13d
  mov    %ebp,%r15d
  jmp    L109
L126:
  mov    %ebx,%edi
  imul   %r13d,%edi
  movslq %edi,%rdi
  add    0x18(%rsp),%rdi
  mov    %ebx,%edx
  mov    %r12,%rsi
  call   <memcpy@plt>
  add    $0x1,%r15d
  add    $0x1,%r13d
L55:
  cmp    %r15d,0x10(%rsp)
  jl     L120
  cmp    %r14d,0x30(%rsp)
  jl     L97
  mov    %ebx,%ebp
  imul   %r14d,%ebp
  movslq %ebp,%rbp
  mov    0x20(%rsp),%rax
  add    %rax,%rbp
  mov    %ebx,%r12d
  imul   %r15d,%r12d
  movslq %r12d,%r12
  add    %rax,%r12
  mov    %rbp,%rsi
  mov    %r12,%rdi
  mov    0x28(%rsp),%rax
  call   *%rax
  test   %eax,%eax
  js     L126
  mov    %ebx,%edi
  imul   %r13d,%edi
  movslq %edi,%rdi
  add    0x18(%rsp),%rdi
  mov    %ebx,%edx
  mov    %rbp,%rsi
  call   <memcpy@plt>
  add    $0x1,%r14d
  add    $0x1,%r13d
  jmp    L55
L19:
  mov    $0xffffffff,%eax
  jmp    L11
```

assistant: ```c
int merge(void *data, int esize, int i, int j, int k, int (*compare)(const void *key1, const void *key2)) {
  char *a = data, *m;
  int ipos, jpos, mpos;
  ipos = i;
  jpos = j + 1;
  mpos = 0;
  if ((m = (char *)malloc(esize * (k - i + 1))) == NULL)
    return -1;
  while (ipos <= j || jpos <= k) {
    if (ipos > j) {
      while (jpos <= k) {
        memcpy(&m[mpos * esize], &a[jpos * esize], esize);
        jpos++;
        mpos++;
      }
      continue;
    } else if (jpos > k) {
      while (ipos <= j) {
        memcpy(&m[mpos * esize], &a[ipos * esize], esize);
        ipos++;
        mpos++;
      }
      continue;
    }
    if (compare(&a[ipos * esize], &a[jpos * esize]) < 0) {
      memcpy(&m[mpos * esize], &a[ipos * esize], esize);
      ipos++;
      mpos++;
    } else {
      memcpy(&m[mpos * esize], &a[jpos * esize], esize);
      jpos++;
      mpos++;
    }
  }
  memcpy(&a[i * esize], m, esize * (k - i + 1));
  free(m);
  return 0;
}
```