[resend] Simplify alias storage.

Commit Message

Harald van Dijk Jan. 11, 2023, 6:59 p.m. UTC

On 11/01/2023 18:23, Harald van Dijk wrote:
> Rather than storing the alias name and value separately, we can reduce
> simplify code and reduce code size by storing them in name=value form.
> This allows us to re-use some code from var.c to handle hashing and
> comparisons, so long as we update that to account for aliases' special
> handling of a leading = character. This is okay to do for variables as
> well, as for variables the leading character is guaranteed to not be =.

Apparently this got messed up when I actually sent it. Re-sending as an 
attachment. Apologies for the noise.

Cheers,
Harald van Dijk

Patch

From eaff1be753f58741a593e6b6a4035533b242a16d Mon Sep 17 00:00:00 2001
From: Harald van Dijk <[e-mail]>
Date: Wed, 11 Jan 2023 14:08:02 +0000
Subject: [PATCH] Simplify alias storage.

Rather than storing the alias name and value separately, we can reduce
simplify code and reduce code size by storing them in name=value form.
This allows us to re-use some code from var.c to handle hashing and
comparisons, so long as we update that to account for aliases' special
handling of a leading = character. This is okay to do for variables as
well, as for variables the leading character is guaranteed to not be =.
---
 src/alias.c | 32 ++++++++++----------------------
 src/var.c   | 27 +++++++++++----------------
 src/var.h   | 15 +++++++++++++++
 3 files changed, 36 insertions(+), 38 deletions(-)

diff --git a/src/alias.c b/src/alias.c
index fcad43b..bb963a6 100644
--- a/src/alias.c
+++ b/src/alias.c
@@ -41,6 +41,7 @@ 
 #include "mystring.h"
 #include "alias.h"
 #include "options.h"	/* XXX for argptr (should remove?) */
+#include "var.h"
 
 #define ATABSIZE 39
 
@@ -55,25 +56,26 @@  void
 setalias(const char *name, const char *val)
 {
 	struct alias *ap, **app;
+	size_t namelen;
 
 	app = __lookupalias(name);
 	ap = *app;
 	INTOFF;
 	if (ap) {
 		if (!(ap->flag & ALIASINUSE)) {
-			ckfree(ap->val);
+			ckfree(ap->name);
 		}
-		ap->val	= savestr(val);
 		ap->flag &= ~ALIASDEAD;
 	} else {
 		/* not found */
 		ap = ckmalloc(sizeof (struct alias));
-		ap->name = savestr(name);
-		ap->val = savestr(val);
 		ap->flag = 0;
 		ap->next = 0;
 		*app = ap;
 	}
+	namelen = val - name;
+	ap->name = savestr(name);
+	ap->val = ap->name + namelen;
 	INTON;
 }
 
@@ -150,8 +152,7 @@  aliascmd(int argc, char **argv)
 			} else
 				printalias(ap);
 		} else {
-			*v++ = '\0';
-			setalias(n, v);
+			setalias(n, v + 1);
 		}
 	}
 
@@ -190,36 +191,23 @@  freealias(struct alias *ap) {
 
 	next = ap->next;
 	ckfree(ap->name);
-	ckfree(ap->val);
 	ckfree(ap);
 	return next;
 }
 
 void
 printalias(const struct alias *ap) {
-	out1str(single_quote(ap->name));
-	out1fmt("=%s\n", single_quote(ap->val));
+	out1fmt("%s\n", single_quote(ap->name));
 }
 
 STATIC struct alias **
 __lookupalias(const char *name) {
-	unsigned int hashval;
 	struct alias **app;
-	const char *p;
-	unsigned int ch;
 
-	p = name;
-
-	ch = (unsigned char)*p;
-	hashval = ch << 4;
-	while (ch) {
-		hashval += ch;
-		ch = (unsigned char)*++p;
-	}
-	app = &atab[hashval % ATABSIZE];
+	app = &atab[hashval(name) % ATABSIZE];
 
 	for (; *app; app = &(*app)->next) {
-		if (equal(name, (*app)->name)) {
+		if (varequal(name, (*app)->name)) {
 			break;
 		}
 	}
diff --git a/src/var.c b/src/var.c
index b70d72c..64d93aa 100644
--- a/src/var.c
+++ b/src/var.c
@@ -625,12 +625,7 @@  void unsetvar(const char *s)
 STATIC struct var **
 hashvar(const char *p)
 {
-	unsigned int hashval;
-
-	hashval = ((unsigned char) *p) << 4;
-	while (*p && *p != '=')
-		hashval += (unsigned char) *p++;
-	return &vartab[hashval % VTABSIZE];
+	return &vartab[hashval(p) % VTABSIZE];
 }
 
 
@@ -644,19 +639,19 @@  hashvar(const char *p)
 int
 varcmp(const char *p, const char *q)
 {
-	int c, d;
-
-	while ((c = *p) == (d = *q)) {
-		if (!c || c == '=')
-			goto out;
+	int c = *p, d = *q;
+	while (c == d) {
+		if (!c)
+			break;
 		p++;
 		q++;
+		c = *p;
+		d = *q;
+		if (c == '=')
+			c = '\0';
+		if (d == '=')
+			d = '\0';
 	}
-	if (c == '=')
-		c = 0;
-	if (d == '=')
-		d = 0;
-out:
 	return c - d;
 }
 
diff --git a/src/var.h b/src/var.h
index aa7575a..2aece9d 100644
--- a/src/var.h
+++ b/src/var.h
@@ -153,6 +153,21 @@  int unsetcmd(int, char **);
 void unsetvar(const char *);
 int varcmp(const char *, const char *);
 
+static inline unsigned int hashval(const char *p)
+{
+	unsigned int hashval;
+
+	hashval = ((unsigned char) *p) << 4;
+	while (*p) {
+		hashval += (unsigned char) *p++;
+		if (*p == '=')
+			break;
+	}
+
+	return hashval;
+}
+
+
 static inline int varequal(const char *a, const char *b) {
 	return !varcmp(a, b);
 }
-- 
2.39.0