user: 请从给定的汇编指令推导出C源代码：

```asm
<process_buffer>:
  endbr64
  push   %r14
  mov    %rdx,%r14
  push   %r13
  push   %r12
  push   %rbp
  mov    %rdi,%rbp
  lea    D1(%rip),%rdi
  push   %rbx
  mov    %esi,%ebx
  sub    $0x40,%rsp
  mov    %fs:0x28,%rax
  mov    %rax,0x38(%rsp)
  xor    %eax,%eax
  call   <printf@plt>
  test   %ebx,%ebx
  jle    L84
  xor    %r13d,%r13d
  lea    D18(%rip),%r12
  jmp    L21
  nopl   0x0(%rax,%rax,1)
L42:
  cmp    $0x80,%al
  je     L8
  add    $0x1,%r13d
L133:
  mov    0x18(%rsp),%r14
  cmp    %ebx,%r13d
  jge    L84
L21:
  movslq %r13d,%rdi
  add    %rbp,%rdi
  movzbl (%rdi),%eax
  test   $0x40,%al
  je     L42
  lea    0xc(%rsp),%rcx
  lea    0x8(%rsp),%rdx
  lea    0x18(%rsp),%rsi
  lea    0x14(%rsp),%r9
  lea    0x10(%rsp),%r8
  call   <decode_long_entry@plt>
  mov    0x8(%rsp),%edi
  mov    0x10(%rsp),%edx
  lea    0x28(%rsp),%rcx
  mov    0xc(%rsp),%esi
  lea    0x30(%rsp),%r9
  lea    0x20(%rsp),%r8
  call   <ecef_to_geo@plt>
  mov    0x18(%rsp),%rdi
  test   %r14,%r14
  jle    L25
  add    $0xe10,%r14
  cmp    %rdi,%r14
  jl     L75
L25:
  mov    0x14(%rsp),%esi
  movsd  0x30(%rsp),%xmm2
  add    $0x12,%r13d
  movsd  0x28(%rsp),%xmm1
  movsd  0x20(%rsp),%xmm0
  call   <output_gpx_trk_point@plt>
  mov    0x18(%rsp),%r14
  cmp    %ebx,%r13d
  jl     L21
L84:
  mov    0x38(%rsp),%rax
  sub    %fs:0x28,%rax
  jne    L95
  add    $0x40,%rsp
  mov    %r14,%rax
  pop    %rbx
  pop    %rbp
  pop    %r12
  pop    %r13
  pop    %r14
  ret
L8:
  lea    0xc(%rsp),%rcx
  lea    0x8(%rsp),%rdx
  lea    0x18(%rsp),%rsi
  lea    0x14(%rsp),%r9
  lea    0x10(%rsp),%r8
  call   <decode_short_entry@plt>
  mov    0x8(%rsp),%edi
  mov    0x10(%rsp),%edx
  lea    0x28(%rsp),%rcx
  mov    0xc(%rsp),%esi
  lea    0x30(%rsp),%r9
  lea    0x20(%rsp),%r8
  call   <ecef_to_geo@plt>
  mov    0x18(%rsp),%rdi
  test   %r14,%r14
  jle    L86
  add    $0xe10,%r14
  cmp    %rdi,%r14
  jl     L137
L86:
  mov    0x14(%rsp),%esi
  movsd  0x30(%rsp),%xmm2
  add    $0x8,%r13d
  movsd  0x28(%rsp),%xmm1
  movsd  0x20(%rsp),%xmm0
  call   <output_gpx_trk_point@plt>
  jmp    L133
  nopl   0x0(%rax,%rax,1)
L75:
  mov    %r12,%rdi
  call   <printf@plt>
  mov    0x18(%rsp),%rdi
  jmp    L25
  nopw   0x0(%rax,%rax,1)
L137:
  mov    %r12,%rdi
  call   <printf@plt>
  mov    0x18(%rsp),%rdi
  jmp    L86
L95:
  call   <__stack_chk_fail@plt>
```

tool_calls: name: disassemble_data
arguments: tag: D1
type_guessed: string
name: disassemble_data
arguments: tag: D18
type_guessed: string

tool: D1: <!-- next sector -->


tool: D18: </trkseg>
<trkseg>


assistant: ```c
long process_buffer(const unsigned char *buffer, const int length, const long first_timestamp) {
  int offset = 0;
  long time;
  int ecef_x, ecef_y, ecef_z, speed;
  double latitude, longitude, height;
  int tagged_entry = 0;
  long last_timestamp = first_timestamp;
  ;
  printf("<!-- next sector -->\n");
  while (offset < length) {
    if (buffer[offset] & 0x40) {
      decode_long_entry(buffer + offset, &time, &ecef_x, &ecef_y, &ecef_z, &speed);
      ecef_to_geo(ecef_x, ecef_y, ecef_z, &longitude, &latitude, &height);
      if (buffer[offset] & 0x20) {
        tagged_entry = 1;
      }
      if ((last_timestamp > 0) && (time > (last_timestamp + 3600l))) {
        printf("</trkseg>\n<trkseg>\n");
      }
      output_gpx_trk_point(time, latitude, longitude, height, speed);
      offset += 18;
    } else if (buffer[offset] == 0x80) {
      decode_short_entry(buffer + offset, &time, &ecef_x, &ecef_y, &ecef_z, &speed);
      ecef_to_geo(ecef_x, ecef_y, ecef_z, &longitude, &latitude, &height);
      if ((last_timestamp > 0) && (time > (last_timestamp + 3600l))) {
        printf("</trkseg>\n<trkseg>\n");
      }
      output_gpx_trk_point(time, latitude, longitude, height, speed);
      offset += 8;
    } else {
      offset++;
    }
    last_timestamp = time;
  }
  return last_timestamp;
}
```