user: 请从给定的汇编指令推导出C源代码：

```asm
<fdiff>:
  endbr64
  push   %rbp
  mov    %rsp,%rbp
  push   %rbx
  sub    $0x48,%rsp
  mov    %rdi,-0x48(%rbp)
  mov    %rsi,-0x50(%rbp)
  mov    $0x400,%edi
  call   <malloc@plt>
  mov    %rax,-0x38(%rbp)
  mov    $0x400,%edi
  call   <malloc@plt>
  mov    %rax,-0x30(%rbp)
  mov    $0xfa000,%edi
  call   <malloc@plt>
  mov    %rax,-0x28(%rbp)
  mov    $0xfa000,%edi
  call   <malloc@plt>
  mov    %rax,-0x20(%rbp)
  jmp    L62
L63:
  mov    -0x38(%rbp),%rdx
  mov    -0x28(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
L62:
  mov    -0x48(%rbp),%rdx
  mov    -0x38(%rbp),%rax
  mov    $0x8,%esi
  mov    %rax,%rdi
  call   <fgets@plt>
  test   %rax,%rax
  jne    L63
  jmp    L81
L43:
  mov    -0x30(%rbp),%rdx
  mov    -0x20(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
L81:
  mov    -0x50(%rbp),%rdx
  mov    -0x30(%rbp),%rax
  mov    $0x8,%esi
  mov    %rax,%rdi
  call   <fgets@plt>
  test   %rax,%rax
  jne    L43
  mov    $0xfa000,%edi
  call   <malloc@plt>
  mov    %rax,-0x18(%rbp)
  mov    -0x28(%rbp),%rax
  mov    %rax,%rdi
  call   <zstrlen@plt>
  mov    %eax,%ebx
  mov    -0x20(%rbp),%rax
  mov    %rax,%rdi
  call   <zstrlen@plt>
  cmp    %eax,%ebx
  jle    L37
  movl   $0x0,-0x40(%rbp)
  jmp    L9
L112:
  mov    -0x40(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x40(%rbp),%eax
  movslq %eax,%rcx
  mov    -0x20(%rbp),%rax
  add    %rcx,%rax
  movzbl (%rax),%eax
  cmp    %al,%dl
  je     L90
  mov    -0x40(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rax,%rdx
  mov    -0x18(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
L90:
  addl   $0x1,-0x40(%rbp)
L9:
  mov    -0x28(%rbp),%rax
  mov    %rax,%rdi
  call   <zstrlen@plt>
  cmp    %eax,-0x40(%rbp)
  jl     L112
  jmp    L77
L37:
  movl   $0x0,-0x3c(%rbp)
  jmp    L97
L58:
  mov    -0x3c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x28(%rbp),%rax
  add    %rdx,%rax
  movzbl (%rax),%edx
  mov    -0x3c(%rbp),%eax
  movslq %eax,%rcx
  mov    -0x20(%rbp),%rax
  add    %rcx,%rax
  movzbl (%rax),%eax
  cmp    %al,%dl
  je     L6
  mov    -0x3c(%rbp),%eax
  movslq %eax,%rdx
  mov    -0x20(%rbp),%rax
  add    %rax,%rdx
  mov    -0x18(%rbp),%rax
  mov    %rdx,%rsi
  mov    %rax,%rdi
  call   <strcat@plt>
L6:
  addl   $0x1,-0x3c(%rbp)
L97:
  mov    -0x20(%rbp),%rax
  mov    %rax,%rdi
  call   <zstrlen@plt>
  cmp    %eax,-0x3c(%rbp)
  jl     L58
L77:
  mov    -0x18(%rbp),%rax
  mov    -0x8(%rbp),%rbx
  leave
  ret
```

assistant: ```c
char *fdiff(FILE *f1, FILE *f2) {
  char *buff1 = malloc(1024);
  char *buff2 = malloc(1024);
  char *fstr1 = malloc(1024000);
  char *fstr2 = malloc(1024000);
  while (fgets(buff1, sizeof(buff1), f1)) {
    strcat(fstr1, buff1);
  }
  while (fgets(buff2, sizeof(buff2), f2)) {
    strcat(fstr2, buff2);
  }
  char *diff = malloc(1024000);
  if (zstrlen(fstr1) > zstrlen(fstr2)) {
    for (int i = 0; i < zstrlen(fstr1); i++) {
      if (fstr1[i] != fstr2[i]) {
        strcat(diff, &fstr1[i]);
      } else {
      }
    }
  } else {
    for (int i = 0; i < zstrlen(fstr2); i++) {
      if (fstr1[i] != fstr2[i]) {
        strcat(diff, &fstr2[i]);
      }
    }
  }
  return diff;
}
```