From 199eaf4c5787c79ebab9589dbd28e6e742b5cb94 Mon Sep 17 00:00:00 2001
From: Yucheng Low <ylow@graphlab.com>
Date: Tue, 8 Dec 2015 21:07:46 -0800
Subject: [PATCH] Adds a few more parsing input format flags

Adds a few more input format
%I,%l : 12 hour
%P: AM PM
%p: am pm

Modified %d to support single digit day.
This allows parsing of 1-1-1984 with %d-%m-%Y
---
 include/boost/date_time/time_facet.hpp | 82 ++++++++++++++++++++++++++++++++--
 1 file changed, 78 insertions(+), 4 deletions(-)

diff --git a/include/boost/date_time/time_facet.hpp b/include/boost/date_time/time_facet.hpp
index b9abedfb..2837b166 100644
--- a/include/boost/date_time/time_facet.hpp
+++ b/include/boost/date_time/time_facet.hpp
@@ -971,6 +971,8 @@ namespace date_time {
 
         // time elements
         hour_type hour = 0;
+        hour_type base_hour = 0; // used for AM/PM
+        bool has_am_pm = false;
         min_type min = 0;
         sec_type sec = 0;
         typename time_duration_type::fractional_seconds_type frac(0);
@@ -1090,7 +1092,7 @@ namespace date_time {
                 case 'd':
                   {
                     try {
-                      t_day = this->m_parser.parse_day_of_month(sitr, stream_end);
+                      t_day = this->m_parser.parse_var_day_of_month(sitr, stream_end);
                     }
                     catch(std::out_of_range&) { // base class for exception bad_day_of_month
                       match_results mr;
@@ -1107,13 +1109,77 @@ namespace date_time {
                 // time flags
                 case 'H':
                   {
-                    match_results mr;
-                    hour = fixed_string_to_int<hour_type, CharT>(sitr, stream_end, mr, 2);
+                    hour = var_string_to_int<hour_type, CharT>(sitr, stream_end,
+                                           2);
                     if(hour == -1){
                        return check_special_value(sitr, stream_end, t, c);
                     }
                     break;
                   }
+                case 'I':
+                case 'l':
+                  {
+                    hour = var_string_to_int<hour_type, CharT>(sitr, stream_end,
+                                           std::numeric_limits<hour_type>::digits10 + 1);
+                    if (hour > 12) {
+                      boost::throw_exception(
+                          std::ios_base::failure("Bad hour value"));
+                    }
+                    if(hour == -1){
+                       return check_special_value(sitr, stream_end, t, c);
+                    }
+                    break;
+                  }
+                case 'P':
+                  {
+                    char c[2];
+                    c[0] = *sitr;
+                    ++sitr;
+                    if (sitr == stream_end) {
+                      boost::throw_exception(
+                          std::ios_base::failure("Parse failed. Insufficient characters for %P"));
+                    }
+                    c[1] = *sitr;
+
+                    if (c[0] == 'P' && c[1] == 'M') {
+                      // PM
+                      base_hour = 12;
+                      has_am_pm = true;
+                    } else if (c[0] == 'A'&&  c[1] == 'M') {
+                      // AM
+                      base_hour = 0;
+                      has_am_pm = true;
+                    } else {
+                      boost::throw_exception(
+                          std::ios_base::failure("Parse failed. Invalid expression for %P"));
+                    }
+                    break;
+                  }
+                case 'p':
+                  {
+                    char c[2];
+                    c[0] = *sitr;
+                    ++sitr;
+                    if (sitr == stream_end) {
+                      boost::throw_exception(
+                          std::ios_base::failure("Parse failed. Insufficient characters for %P"));
+                    }
+                    c[1] = *sitr;
+
+                    if (c[0] == 'p' && c[1] == 'm') {
+                      // PM
+                      base_hour = 12;
+                      has_am_pm = true;
+                    } else if (c[0] == 'a' && c[1] == 'm') {
+                      // AM
+                      base_hour = 0;
+                      has_am_pm = true;
+                    } else {
+                      boost::throw_exception(
+                          std::ios_base::failure("Parse failed. Invalid expression for %P"));
+                    }
+                    break;
+                  }
                 case 'M':
                   {
                     match_results mr;
@@ -1231,7 +1297,15 @@ namespace date_time {
         else {
           d = date_type(t_year, t_month, t_day);
         }
-
+        // handle the case where 12:15am really means 0015
+        // and 12:15pm really means 12:15
+        // Also 12pm is noon, 12am is midnight
+        if (hour == 12 && has_am_pm) hour = 0;
+        hour += base_hour;
+        if (hour > 24 && min > 0) {
+          boost::throw_exception(
+              std::ios_base::failure("Bad hour value"));
+        }
         time_duration_type td(hour, min, sec, frac);
         t = time_type(d, td);
         return sitr;