/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
│                                                                              │
│ Permission to use, copy, modify, and/or distribute this software for         │
│ any purpose with or without fee is hereby granted, provided that the         │
│ above copyright notice and this permission notice appear in all copies.      │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
│ PERFORMANCE OF THIS SOFTWARE.                                                │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/fmt/itoa.h"
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/asmflag.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/consts/pr.h"
#include "libc/thread/posixthread.internal.h"

/**
 * Registers custom name of thread with system, e.g.
 *
 *     void *worker(void *arg) {
 *       pthread_setname_np(pthread_self(), "justine");
 *       pause();
 *       return 0;
 *     }
 *
 *     int main(int argc, char *argv[]) {
 *       pthread_t id;
 *       pthread_create(&id, 0, worker, 0);
 *       pthread_join(id, 0);
 *     }
 *
 * ProTip: The `htop` software is good at displaying thread names.
 *
 * @return 0 on success, or errno on error
 * @raise ERANGE if length of `name` exceeded system limit, in which
 *    case the name may have still been set with os using truncation
 * @raise ENOSYS on MacOS, Windows, and OpenBSD
 * @see pthread_getname_np()
 */
errno_t pthread_setname_np(pthread_t thread, const char *name) {
  char path[128], *p;
  int fd, rc, tid, len, e = errno;

  tid = ((struct PosixThread *)thread)->tid;
  len = strlen(name);

  if (IsLinux()) {
    if (tid == gettid()) {
      if (prctl(PR_SET_NAME, name) == -1) {
        rc = errno;
        errno = e;
        return rc;
      }
    } else {
      p = path;
      p = stpcpy(p, "/proc/self/task/");
      p = FormatUint32(p, tid);
      p = stpcpy(p, "/comm");
      if ((fd = sys_open(path, O_WRONLY | O_CLOEXEC, 0)) == -1) {
        rc = errno;
        errno = e;
        return rc;
      }
      rc = sys_write(fd, name, len);
      rc |= sys_close(fd);
      if (rc == -1) {
        rc = errno;
        errno = e;
        return rc;
      }
    }
    if (len > 15) {
      // linux is documented as truncating here. we still set the name
      // since the limit might be raised in the future checking return
      // value of this function is a bummer. Grep it for TASK_COMM_LEN
      return ERANGE;
    }
    return 0;

  } else if (IsFreebsd()) {
    char cf;
    int ax, dx;
    asm volatile(CFLAG_ASM("syscall")
                 : CFLAG_CONSTRAINT(cf), "=a"(ax), "=d"(dx)
                 : "1"(323 /* thr_set_name */), "D"(tid), "S"(name)
                 : "rcx", "r8", "r9", "r10", "r11", "memory");
    return !cf ? 0 : ax;

  } else if (IsNetbsd()) {
    char cf;
    int ax, dx;
    asm volatile(CFLAG_ASM("syscall")
                 : CFLAG_CONSTRAINT(cf), "=a"(ax), "=d"(dx)
                 : "1"(323 /* _lwp_setname */), "D"(tid), "S"(name)
                 : "rcx", "r8", "r9", "r10", "r11", "memory");
    return !cf ? 0 : ax;

  } else {
    return ENOSYS;
  }
}
