text: /****************************************************************************
   * libs/libc/time/lib_strftime.c
   *
   * Licensed to the Apache Software Foundation (ASF) under one or more
   * contributor license agreements.  See the NOTICE file distributed with
   * this work for additional information regarding copyright ownership.  The
   * ASF licenses this file to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance with the
   * License.  You may obtain a copy of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
   * License for the specific language governing permissions and limitations
   * under the License.
   *
   ****************************************************************************/
  
  /****************************************************************************
   * Included Files
   ****************************************************************************/
  
  #include <nuttx/config.h>
  #include <sys/types.h>
  
  #include <stdio.h>
  #include <time.h>
  #include <debug.h>
  
  #include <nuttx/time.h>
  
  /****************************************************************************
   * Pre-processor Definitions
   ****************************************************************************/
  
  /****************************************************************************
   * Private Type Declarations
   ****************************************************************************/
  
  /****************************************************************************
   * Private Function Prototypes
   ****************************************************************************/
  
  /****************************************************************************
   * Public Constant Data
   ****************************************************************************/
  
  /****************************************************************************
   * Public Data
   ****************************************************************************/
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  static const char * const g_abbrev_wdayname[7] =
  {
    "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"
  };
  
  static const char * const g_wdayname[7] =
  {
    "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday",
    "Saturday"
  };
  
  static const char * const g_abbrev_monthname[12] =
  {
    "Jan", "Feb", "Mar", "Apr", "May", "Jun",
    "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
  };
  
  static const char * const g_monthname[12] =
  {
    "January", "February", "March",     "April",   "May",      "June",
    "July",    "August",   "September", "October", "November", "December"
  };
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name:  strftime
   *
   * Description:
   *   The  strftime()  function  formats the broken-down time tm according to
   *   the format specification format and places the result in the  character
   *   array s of size max.
   *
   *   Ordinary characters placed in the format string are copied to s without
   *   conversion.  Conversion specifications are introduced by a '%'  charac-
   *   ter,  and  terminated  by  a  conversion  specifier  character, and are
   *   replaced in s as follows:
   *
   *   %a     The abbreviated weekday name according to the current locale.
   *   %A     The full weekday name according to the current locale.
   *   %b     The abbreviated month name according to the current locale.
   *   %B     The full month name according to the current locale.
   *   %C     The century number (year/100) as a 2-digit integer. (SU)
   *   %d     The day of the month as a decimal number (range 01 to 31).
   *   %e     Like %d, the day of the month as a decimal number, but a leading
   *          zero is replaced by a space.
   *   %h     Equivalent to %b.  (SU)
   *   %H     The hour as a decimal number using a 24-hour clock
   *          (range 00 to 23).
   *   %I     The  hour as a decimal number using a 12-hour clock
   *          (range 01 to 12).
   *   %j     The day of the year as a decimal number (range 001 to 366).
   *   %k     The hour (24-hour clock) as a decimal number (range  0  to  23);
   *          single digits are preceded by a blank.  (See also %H.)  (TZ)
   *   %l     The  hour  (12-hour  clock) as a decimal number (range 1 to 12);
   *          single digits are preceded by a blank.  (See also %I.)  (TZ)
   *   %m     The month as a decimal number (range 01 to 12).
   *   %M     The minute as a decimal number (range 00 to 59).
   *   %n     A newline character. (SU)
   *   %p     Either "AM" or "PM" according to the given time  value, or the
   *          corresponding  strings  for the current locale.  Noon is treated
   *          as "PM" and midnight as "AM".
   *   %P     Like %p but in lowercase: "am" or "pm" or a corresponding string
   *          for the current locale. (GNU)
   *   %s     The number of seconds since the Epoch, that is, since 1970-01-01
   *          00:00:00 UTC. (TZ)
   *   %S     The second as a decimal number (range 00 to 60).  (The range is
   *          up to 60 to allow for occasional leap seconds.)
   *   %t     A tab character. (SU)
   *   %y     The year as a decimal number without a century (range 00 to 99).
   *   %Y     The year as a decimal number including the century.
   *   %%     A literal '%' character.
   *
   * Returned Value:
   *   The strftime() function returns the number of characters placed in  the
   *   array s, not including the terminating null byte, provided the string,
   *   including the terminating null byte, fits.  Otherwise,  it returns 0,
   *   and the contents of the array is undefined.
   *
   ****************************************************************************/
  
  size_t strftime(FAR char *s, size_t max, FAR const char *format,
                  FAR const struct tm *tm)
  {
    FAR const char *str;
    FAR char       *dest   = s;
    int             chleft = max;
    int             value;
    int             len;
  
    while (*format && chleft > 0)
      {
        /* Just copy regular characters */
  
        if (*format != '%')
          {
             *dest++ = *format++;
             chleft--;
             continue;
          }
  
        /* Handle the format character */
  
         format++;
         len   = 0;
  
         switch (*format++)
           {
             /* %a: A three-letter abbreviation for the day of the week. */
  
             case 'a':
               {
                 if (tm->tm_wday < 7)
                   {
                     str = g_abbrev_wdayname[tm->tm_wday];
                     len = snprintf(dest, chleft, "%s", str);
                   }
               }
               break;
  
             /* %A: The full name for the day of the week. */
  
             case 'A':
               {
                 if (tm->tm_wday < 7)
                   {
                     str = g_wdayname[tm->tm_wday];
                     len = snprintf(dest, chleft, "%s", str);
                   }
               }
               break;
  
             /* %h: Equivalent to %b */
  
             case 'h':
  
             /* %b: The abbreviated month name according to the current
              * locale.
              */
  
             case 'b':
               {
                 if (tm->tm_mon < 12)
                   {
                     str = g_abbrev_monthname[tm->tm_mon];
                     len = snprintf(dest, chleft, "%s", str);
                   }
               }
               break;
  
             /* %B: The full month name according to the current locale. */
  
             case 'B':
               {
                 if (tm->tm_mon < 12)
                   {
                     str = g_monthname[tm->tm_mon];
                     len = snprintf(dest, chleft, "%s", str);
                   }
               }
               break;
  
             /* %C: The century number (year/100) as a 2-digit integer. */
  
             case 'C':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_year / 100);
               }
               break;
  
             /* %d: The day of the month as a decimal number
              * (range 01 to 31).
              */
  
             case 'd':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_mday);
               }
               break;
  
             /* %e: Like %d, the day of the month as a decimal number, but
              * a leading zero is replaced by a space.
              */
  
             case 'e':
               {
                 len = snprintf(dest, chleft, "%2d", tm->tm_mday);
               }
               break;
  
             /* %H: The hour as a decimal number using a 24-hour clock
              * (range 00  to 23).
              */
  
             case 'H':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_hour);
               }
               break;
  
             /* %I: The  hour as a decimal number using a 12-hour clock
              * (range 01 to 12).
              */
  
             case 'I':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_hour % 12);
               }
               break;
  
             /* %j: The day of the year as a decimal number
              * (range 001 to 366).
              */
  
             case 'j':
               {
                 if (tm->tm_mon < 12)
                   {
                     value = clock_daysbeforemonth(tm->tm_mon,
                             clock_isleapyear(tm->tm_year)) + tm->tm_mday;
                     len   = snprintf(dest, chleft, "%03d", value);
                   }
               }
               break;
  
             /* %k: The hour (24-hour clock) as a decimal number
              * (range  0  to  23);
              * single digits are preceded by a blank.
              */
  
             case 'k':
               {
                 len = snprintf(dest, chleft, "%2d", tm->tm_hour);
               }
               break;
  
             /* %l: The  hour  (12-hour  clock) as a decimal number
              * (range 1 to 12);
              * single digits are preceded by a blank.
              */
  
             case 'l':
               {
                 len = snprintf(dest, chleft, "%2d", tm->tm_hour % 12);
               }
               break;
  
             /* %m: The month as a decimal number (range 01 to 12). */
  
             case 'm':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_mon + 1);
               }
               break;
  
             /* %M: The minute as a decimal number (range 00 to 59). */
  
             case 'M':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_min);
               }
               break;
  
             /* %n: A newline character. */
  
             case 'n':
               {
                 *dest = '\n';
                 len   = 1;
               }
               break;
  
             /* %p: Either "AM" or "PM" according to the given time  value. */
  
             case 'p':
               {
                 if (tm->tm_hour >= 12)
                   {
                     str = "PM";
                   }
                 else
                   {
                     str = "AM";
                   }
  
                 len = snprintf(dest, chleft, "%s", str);
               }
               break;
  
             /* %P: Like %p but in lowercase: "am" or "pm" */
  
             case 'P':
               {
                 if (tm->tm_hour >= 12)
                   {
                     str = "pm";
                   }
                 else
                   {
                     str = "am";
                   }
  
                 len = snprintf(dest, chleft, "%s", str);
               }
               break;
  
             /* %s: The number of seconds since the Epoch, that is,
              * since 1970-01-01 00:00:00 UTC.
              * Hmmm... mktime argume is not 'const'.
              */
  
             case 's':
               {
                 len = snprintf(dest, chleft, "%ju",
                                (uintmax_t)mktime((FAR struct tm *)tm));
               }
               break;
  
             /* %S: The second as a decimal number (range 00 to 60).
              * (The range is up to 60 to allow for occasional leap seconds.)
              */
  
             case 'S':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_sec);
               }
               break;
  
             /* %t: A tab character. */
  
             case 't':
               {
                 *dest = '\t';
                 len   = 1;
               }
               break;
  
             /* %y: The year as a decimal number without a century
              * (range 00 to 99).
              */
  
             case 'y':
               {
                 len = snprintf(dest, chleft, "%02d", tm->tm_year % 100);
               }
               break;
  
             /* %Y: The year as a decimal number including the century. */
  
             case 'Y':
               {
                 len = snprintf(dest, chleft, "%04d", tm->tm_year + 1900);
               }
               break;
  
             /* %%:  A literal '%' character. */
  
             case '%':
               {
                 *dest = '%';
                 len   = 1;
               }
               break;
          }
  
        /* Update counts and pointers */
  
        dest   += len;
        chleft -= len;
      }
  
    /* We get here because either we have reached the end of the format string
     * or because there is no more space in the user-provided buffer and the
     * resulting string has been truncated.
     *
     * Is there space remaining in the user-provided buffer for the NUL
     * terminator?
     */
  
    if (chleft > 0)
      {
        /* Yes, append terminating NUL byte */
  
        *dest = '\0';
  
        /* And return the number of bytes in the resulting string (excluding
         * the NUL terminator).
         */
  
        return max - chleft;
      }
  
    /* The string was truncated and/or not properly terminated.  Return
     * zero.
     */
  
    return 0;
  }
  