From dd2e898a13855acd7034a2ee73584995d7452f4f Mon Sep 17 00:00:00 2001
From: markus schnalke <meillo@marmaro.de>
Date: Wed, 7 Sep 2016 16:31:58 +0200
Subject: [PATCH] Replace lookup tables for obscure hashes with more readable
 code

Time-performance doesn't matter here. If you think differently,
demonstrate it convincingly!
---
 sbr/dtimep.lex |   81 +++++++++++++++-----------------------------------------
 1 file changed, 21 insertions(+), 60 deletions(-)

diff --git a/sbr/dtimep.lex b/sbr/dtimep.lex
index db2b193..0581736 100644
--- a/sbr/dtimep.lex
+++ b/sbr/dtimep.lex
@@ -56,67 +56,29 @@
 */
 int europeandate = 0;
 
-/*
-** Table to convert month names to numeric month.  We use the
-** fact that the low order 5 bits of the sum of the 2nd & 3rd
-** characters of the name is a hash with no collisions for the 12
-** valid month names.  (The mask to 5 bits maps any combination of
-** upper and lower case into the same hash value).
-*/
-static int month_map[] = {
-	0,
-	6,	/* 1 - Jul */
-	3,	/* 2 - Apr */
-	5,	/* 3 - Jun */
-	0,
-	10,	/* 5 - Nov */
-	0,
-	1,	/* 7 - Feb */
-	11,	/* 8 - Dec */
-	0,
-	0,
-	0,
-	0,
-	0,
-	0,
-	0,	/*15 - Jan */
-	0,
-	0,
-	0,
-	2,	/*19 - Mar */
-	0,
-	8,	/*21 - Sep */
-	0,
-	9,	/*23 - Oct */
-	0,
-	0,
-	4,	/*26 - May */
-	0,
-	7	/*28 - Aug */
+static char *monthnames[] = {
+	"Jan", "Feb", "Mar", "Apr", "May", "Jun",
+	"Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
+	NULL
 };
 
-/*
-** Lookup table for day-of-week using the same hash trick as for above
-** name-of-month table, but using the first and second character, not
-** second and third.
-**
-** Compute index into table using: (day_name[0] & 7) + (day_name[1] & 4)
-*/
-static int day_map[] = {
-	0,
-	0,
-	0,
-	6,	/* 3 - Sat */
-	4,	/* 4 - Thu */
-	0,
-	5,	/* 6 - Fri */
-	0,	/* 7 - Sun */
-	2,	/* 8 - Tue */
-	1	/* 9 - Mon */,
-	0,
-	3	/*11 - Wed */
+static char *daynames[] = {
+	"Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", NULL
 };
 
+static int
+name2num(char *name, char *names[])
+{
+	int i;
+
+	for (i=0; names[i]; i++) {
+		if (strncasecmp(name, names[i], strlen(names[i]))==0) {
+			return i;
+		}
+	}
+	return 0;
+}
+
 /*
 ** The SET* macros will parse for the appropriate field, and leave the
 ** cp pointer at the first character after the desired field. Be
@@ -129,10 +91,9 @@ static int day_map[] = {
 */
 
 #define INIT() { cp = yytext;}
-#define SETWDAY()  { tw.tw_wday= day_map[(cp[0] & 7) + (cp[1] & 4)]; \
+#define SETWDAY()  { tw.tw_wday = name2num(cp, daynames); \
 	tw.tw_flags &= ~TW_SDAY; tw.tw_flags |= TW_SEXP; SKIPA(); }
-#define SETMON()  { cp++; tw.tw_mon = month_map[(cp[0] + cp[1]) & 0x1f]; \
-	SKIPA(); }
+#define SETMON()  { tw.tw_mon = name2num(cp, monthnames); SKIPA(); }
 #define SETMON_NUM()  { tw.tw_mon = atoi(cp)-1; SKIPD(); }
 #define SETYEAR()  { tw.tw_year = atoi(cp); SKIPD(); }
 #define SETDAY()  { tw.tw_mday = atoi(cp); tw.tw_flags |= TW_YES; SKIPD(); }
-- 
1.7.10.4