[src/trunk]: src/bin/sh Alternative way of writing (part of) the arithmetic l...

[kre <kre%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9343cb3e5fa2
branches:  trunk
changeset: 822437:9343cb3e5fa2
user:      kre <kre%NetBSD.org@localhost>
date:      Mon Mar 20 11:31:00 2017 +0000

description:
Alternative way of writing (part of) the arithmetic lexical analyzer
- committed separately to make it easier to swap back if desired.

This version avoids open coding is_name() and isdigit() - measurements
show it is perhaps fractionally faster (though the difference is so small
as to probably be statistically insignifigant - if I were a statician
I might understand that) and just a little larger than the previous version.

diffstat:

 bin/sh/arith_token.c |  61 +++++++++++++++++++++++++++------------------------
 1 files changed, 32 insertions(+), 29 deletions(-)

diffs (89 lines):

diff -r 84a501acbbde -r 9343cb3e5fa2 bin/sh/arith_token.c
--- a/bin/sh/arith_token.c      Mon Mar 20 11:26:07 2017 +0000
+++ b/bin/sh/arith_token.c      Mon Mar 20 11:31:00 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: arith_token.c,v 1.1 2017/03/20 11:26:07 kre Exp $      */
+/*     $NetBSD: arith_token.c,v 1.2 2017/03/20 11:31:00 kre Exp $      */
 
 /*-
  * Copyright (c) 2002
@@ -39,7 +39,7 @@
 #include <sys/cdefs.h>
 
 #ifndef lint
-__RCSID("$NetBSD: arith_token.c,v 1.1 2017/03/20 11:26:07 kre Exp $");
+__RCSID("$NetBSD: arith_token.c,v 1.2 2017/03/20 11:31:00 kre Exp $");
 #endif /* not lint */
 
 #include <inttypes.h>
@@ -79,7 +79,36 @@
        for (;;) {
                token = *buf;
 
-               switch (token) {
+               if (isdigit(token)) {
+                       /*
+                        * Numbers all start with a digit, and nothing
+                        * else does, the number ends wherever
+                        * strtoimax() stops...
+                        */
+                       a_t_val.val = strtoimax(buf, &end, 0);
+                       arith_buf = end;
+                       return ARITH_NUM;
+
+               } else if (is_name(token) {
+                       /*
+                        * Variable names all start with an alpha (or '_')
+                        * and nothing else does.  They continue for the
+                        * longest unbroken sequence of alphanumerics ( + _ )
+                        */
+                       p = buf;
+                       while (buf++, is_in_name(*buf))
+                               ;
+                       a_t_val.name = stalloc(buf - p + 1);
+                       memcpy(a_t_val.name, p, buf - p);
+                       a_t_val.name[buf - p] = '\0';
+                       arith_buf = buf;
+                       return ARITH_VAR;
+
+               } else switch (token) {
+                       /*
+                        * everything else must be some kind of
+                        * operator, white space, or an error.
+                        */
                case ' ':
                case '\t':
                case '\n':
@@ -91,32 +120,6 @@
                            token, token);
                        /* NOTREACHED */
 
-               case '0': case '1': case '2': case '3': case '4':
-               case '5': case '6': case '7': case '8': case '9':
-                       a_t_val.val = strtoimax(buf, &end, 0);
-                       arith_buf = end;
-                       return ARITH_NUM;
-
-               case 'A': case 'B': case 'C': case 'D': case 'E':
-               case 'F': case 'G': case 'H': case 'I': case 'J':
-               case 'K': case 'L': case 'M': case 'N': case 'O':
-               case 'P': case 'Q': case 'R': case 'S': case 'T':
-               case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
-               case 'a': case 'b': case 'c': case 'd': case 'e':
-               case 'f': case 'g': case 'h': case 'i': case 'j':
-               case 'k': case 'l': case 'm': case 'n': case 'o':
-               case 'p': case 'q': case 'r': case 's': case 't':
-               case 'u': case 'v': case 'w': case 'x': case 'y': case 'z':
-               case '_':
-                       p = buf;
-                       while (buf++, is_in_name(*buf))
-                               ;
-                       a_t_val.name = stalloc(buf - p + 1);
-                       memcpy(a_t_val.name, p, buf - p);
-                       a_t_val.name[buf - p] = '\0';
-                       arith_buf = buf;
-                       return ARITH_VAR;
-
                case '=':
                        token = ARITH_ASS;
  checkeq: