deepstream_utc.c

/*
 * SPDX-FileCopyrightText: Copyright (c) 2019-2021 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 * SPDX-License-Identifier: LicenseRef-NvidiaProprietary
 *
 * NVIDIA CORPORATION, its affiliates and licensors retain all intellectual
 * property and proprietary rights in and to this material, related
 * documentation and any modifications thereto. Any use, reproduction,
 * disclosure or distribution of this material and related documentation
 * without an express license agreement from NVIDIA CORPORATION or
 * its affiliates is strictly prohibited.
 */

#define _DEFAULT_SOURCE
#define _XOPEN_SOURCE
#include "deepstream_test5_app.h"
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>


/** URI sample:
 * HWY_20_AND_BRYANT__WB__4_11_2018_4_59_59_485_AM_UTC-07_00.mp4
 *
 * Specification format:
 * __M_DD_YYYY_H_MIN_SEC_MSEC_AM/PM_UTC<Offset>.mp4
 * a) Offset is:
 * <+/-HOURS_MIN>
 * b) In ..AM/PM_TIMEZONE<Offset>.mp4
 * TIMEZONE will always be UTC
 * 
 * The __M_DD_YYYY_H_MIN_SEC_MSEC_AM/PM time
 * shall <Offset-period> behind UTC
 * 
 */
#define URI_UTC_START_DELIM "__"
#define URI_UTC_END_DELIM "_UTC"
#define MAX_UTC_STRING_LEN (256)
#define LENGTH__AMPM_UTC   (3)  //"_AM"
#define LENGTH_UTC_END_DELIM   (4)

static gboolean
extract_ms_from_utc (gchar * utc, guint32 * ms)
{
    /** find _UTC delim */
  gchar *utc_delim = (gchar *) strstr (utc, URI_UTC_END_DELIM);
  gint32 utc_string_length;
  if (!utc_delim) {
    return FALSE;
  }

    /** find the immediately preceeding '_' */
  utc_string_length =
      (guint32) (((size_t) utc_delim) - ((size_t) utc)) - LENGTH__AMPM_UTC - 1;
  gint32 i_ms = 0;   /**< index into utc at which ms is */
  for (i_ms = utc_string_length; ((i_ms >= 0) && (utc[i_ms] != '_')); i_ms--);
  if (i_ms < 0) {
    return FALSE;
  }

  guint32 input_items = sscanf (&utc[i_ms], "_%u_", ms);
  if (input_items != 1) {
    return FALSE;
  }

    /** also remove the ms part from utc string */
  strncpy (&utc[i_ms], (utc_delim - LENGTH__AMPM_UTC),
      MAX_UTC_STRING_LEN - utc_string_length);

  return TRUE;
}

/** 
 * @brief  Extracts and returns the <Offset> in nanoseconds
 */
static gboolean
extract_offset_from_utc (gchar * utc, gint64 * offset_nsec)
{
    /** find _UTC delim */
  gchar *utc_offset = (gchar *) strstr (utc, URI_UTC_END_DELIM);
  if (!utc_offset) {
    return FALSE;
  }
  gint32 hours;
  guint32 minutes;
  utc_offset += LENGTH_UTC_END_DELIM;
  sscanf (utc_offset, "%d_%u", &hours, &minutes);
  *offset_nsec = ((ABS (hours) * 60 + minutes) * 60) * GST_SECOND;
  if (hours > 0) {
        /** if positive, offset shall be subtracted from
         * __M_DD_YYYY_H_MIN_SEC_MSEC_AM/PM to arrive at UTC
         * Otherwise added
         */
    *offset_nsec = (*offset_nsec) * -1;
  }
  return TRUE;
}

struct timespec
extract_utc_from_uri (gchar * uri)
{
  gchar utc_string[MAX_UTC_STRING_LEN];
  struct tm utc_tmbroken = { 0 };
  struct timespec utc_timespec = { 0 };
  gchar *utc_iter = uri;
  gchar *utc = NULL;
  guint32 ms = 0;
  gint64 time_ns = 0;
    /** Find the beginning of UTC time field in URI
     * The URI delimiter
     */
  do {
    utc = utc_iter;
    utc_iter = (gchar *) strstr (utc, URI_UTC_START_DELIM);
    if (utc_iter) {
            /** skip the starting delim */
      utc_iter += strlen (URI_UTC_START_DELIM);
    }
  } while (utc_iter);

  if (utc == uri) {
        /** Invalid URI */
    return utc_timespec;
  }


    /** extract ms and remove ms_ */
  g_strlcpy (utc_string, utc, MAX_UTC_STRING_LEN);

  gboolean ok = extract_ms_from_utc (utc_string, &ms);
  if (!ok) {
        /** Invalid URI */
    return utc_timespec;
  }

    /** First generate the time tm structure from provided string;
     * Note: Assuming UTC always */
  gchar *first_char_not_processed =
      strptime ((const char *) utc_string, "%m_%d_%Y_%I_%M_%S_%p",
      &utc_tmbroken);
  if (!first_char_not_processed
      || strncmp (first_char_not_processed, URI_UTC_END_DELIM,
          LENGTH_UTC_END_DELIM) != 0) {
        /** first_char_not_processed should be URI_UTC_END_DELIM 
         * Otherwise, it is an error condition */
    return utc_timespec;
  }

  ok = extract_offset_from_utc (utc_string, &time_ns);
  if (!ok) {
        /** Invalid URI */
    return utc_timespec;
  }

    /** mktime(): Now convert the broken down tm struct to time_t, calendar time representation*/
  utc_timespec.tv_sec = timegm (&utc_tmbroken);
  utc_timespec.tv_nsec = ms * GST_MSECOND;

    /** final time is */
  time_ns = (gint64) (GST_TIMESPEC_TO_TIME (utc_timespec)) + time_ns;

  GST_TIME_TO_TIMESPEC (time_ns, utc_timespec);

  return utc_timespec;
}