Add iso8601_add_multiple()

Add a function to efficiently add (or subtract) a multiple of a period
to a timestamp.

src/libiso8601/000_TopSource.c

@@ -13,6 +13,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <inttypes.h>
 #include <sys/time.h>
 
 /* Useful define to alleviate typos */

src/libiso8601/400_manip.c

@@ -98,6 +98,23 @@ void iso8601_subtract_elapsed(struct iso8601_date* date, const struct iso8601_el
 
 
 
+void iso8601_add_multiple(struct iso8601_date* date, const struct iso8601_elapsed* per, int n)
+{
+    intmax_t nsec;
+    imaxdiv_t qr;
+    struct iso8601_elapsed mult;
+
+    nsec = per->nsec * imaxabs(n);
+    qr = imaxdiv(nsec, BILLION);
+    mult.sec = qr.quot + per->sec * imaxabs(n);
+    mult.nsec = qr.rem;
+
+    if(n < 0) iso8601_subtract_elapsed(date, &mult);
+    else iso8601_add_elapsed(date, &mult);
+}
+
+
+
 void iso8601_difference(const struct iso8601_date* d1, const struct iso8601_date* d2,
     struct iso8601_elapsed* per, int* sign)
 {

src/libiso8601/400_manip.h

@@ -73,6 +73,20 @@ void iso8601_subtract_elapsed(struct iso8601_date* date, const struct iso8601_el
 
 
 
+/*! \brief Add a multiple of a period to a date.
+
+\param[in,out] date Date to modify.
+\param per Period to advance date/time by.
+\param n Multiple of \a per.
+
+Adds \a n multiples of \a per to \a date. \a n may be 0 or negative. The result is stored in
+\a date. This is an efficient implementation which avoids loops, but it does use 64-bit arithmetic.
+
+*/
+void iso8601_add_multiple(struct iso8601_date* date, const struct iso8601_elapsed* per, int n);
+
+
+
 /*! \brief Find difference between dates.
 
 \param d1 First date.
@@ -93,5 +107,5 @@ void iso8601_difference(const struct iso8601_date* d1, const struct iso8601_date
 /*!@}*/
 /* options for text editors
 kate: replace-trailing-space-save true; space-indent true; tab-width 4;
-vim: expandtab:ts=4:sw=4
+vim: expandtab:ts=4:sw=4:syntax=ch.doxygen
 */

src/tests/manip.c

@@ -92,13 +92,26 @@ void date_stack_push_elapsed(const struct iso8601_elapsed* per)
 
 
 
+/* date_stack_pop()
+ *  Pops an element from the date stack.
+ */
+void date_stack_pop(void)
+{
+    struct date_stack* next;
+
+    --date_stack_size;
+    next = date_stack_top->next;
+    free(date_stack_top);
+    date_stack_top = next;
+}
+
+
+
 /* date_stack_pop_date()
  *  Pops a date from the stack, returning non-0 on error (underflow or type mismatch).
  */
 int date_stack_pop_date(struct iso8601_date* d, struct iso8601_details* det)
 {
-    struct date_stack* next;
-
     if(!date_stack_top) {
         fputs("Stack underflow.\n", stderr);
         return -1;
@@ -110,11 +123,7 @@ int date_stack_pop_date(struct iso8601_date* d, struct iso8601_details* det)
 
     *d = date_stack_top->u.date.d;
     *det = date_stack_top->u.date.det;
-
-    --date_stack_size;
-    next = date_stack_top->next;
-    free(date_stack_top);
-    date_stack_top = next;
+    date_stack_pop();
 
     return 0;
 }
@@ -126,8 +135,6 @@ int date_stack_pop_date(struct iso8601_date* d, struct iso8601_details* det)
  */
 int date_stack_pop_elapsed(struct iso8601_elapsed* per)
 {
-    struct date_stack* next;
-
     if(!date_stack_top) {
         fputs("Stack underflow.\n", stderr);
         return -1;
@@ -138,17 +145,40 @@ int date_stack_pop_elapsed(struct iso8601_elapsed* per)
     }
 
     *per = date_stack_top->u.per;
-
-    --date_stack_size;
-    next = date_stack_top->next;
-    free(date_stack_top);
-    date_stack_top = next;
+    date_stack_pop();
 
     return 0;
 }
 
 
 
+/* date_stack_dump()
+ *  Dumps and clears the contents of the date stack.
+ */
+void date_stack_dump(void)
+{
+    while(date_stack_top) {
+        switch(date_stack_top->type) {
+        case date_stack_type_date:
+            fprintf(stderr, "Date (day=%d, sec=%d, nsec=%d)\n",
+                date_stack_top->u.date.d.day, date_stack_top->u.date.d.sec, date_stack_top->u.date.d.nsec);
+            break;
+            
+        case date_stack_type_per:
+            fprintf(stderr, "Period (sec=%d, nsec=%d)\n",
+                date_stack_top->u.per.sec, date_stack_top->u.per.nsec);
+            break;
+
+        default:
+            fprintf(stderr, "Unknown type %d.\n", date_stack_top->type);
+            break;
+        }
+        date_stack_pop();
+    }
+}
+
+
+
 /* usage()
  *  Displays help.
  */
@@ -159,11 +189,14 @@ void usage(void)
         "Operators:\n"
         "   +   (date, period)      Advance date by elapsed time, push date.\n"
         "   -   (date, period)      Regress date by elapsed time, push date.\n"
+        "   +*  (date, period, num) Advance date by elapsed time multiplied by num, push date.\n"
+        "   -*  (date, period, num) Regress date by elapsed time multiplied by num, push date.\n"
         "   dp  (date, date)        Compute difference, print elapsed time.\n"
         "   <   (date, date)        Prints 1 if first date less than second.\n"
         "   <=  (date, date)        Prints 1 if first date less than or equal to second.\n"
         "   ==  (date, date)        Prints 1 if dates equal.\n"
         "   p   (date)              Prints a date.\n"
+        "   ds                      Dump stack.\n"
         "\n"
         "Type help for this screen at any point.\n"
     "\n", stdout);
@@ -175,7 +208,7 @@ int parse_command(char* cmd)
 {
     struct iso8601_date date, date2;
     struct iso8601_details details, details2;
-    struct iso8601_elapsed period;
+    struct iso8601_elapsed period, num;
     double period_d;
     char date_str[40];
     int ret = 0, sign;
@@ -209,6 +242,27 @@ int parse_command(char* cmd)
 
             }
 
+        } else if(!strcmp(cmd, "+*") || !strcmp(cmd, "-*")) {
+            if(date_stack_pop_elapsed(&num)) {
+                ret = 1;
+
+            } else if(num.nsec) {
+                ret = 1;
+                fputs("Number cannot be fractional.\n", stderr);
+
+            } else {
+
+                if(date_stack_pop_elapsed(&period) || date_stack_pop_date(&date, &details)) {
+                    ret = 1;
+
+                } else {
+                    iso8601_add_multiple(&date, &period, ((cmd[0] == '-') ? -1 : 1) * num.sec);
+                    date_stack_push_date(&date, &details);
+
+                }
+
+            }
+
         } else if(!strcmp(cmd, "dp")) {
             if(date_stack_pop_date(&date, &details) || date_stack_pop_date(&date2, &details2)) {
                 ret = 1;
@@ -259,6 +313,9 @@ int parse_command(char* cmd)
                 putc('\n', stdout);
             }
 
+        } else if(!strcmp(cmd, "ds")) {
+            date_stack_dump();
+
         } else {
             fputs("Unrecognised command or argument.\n", stderr);
             ret = 1;