[PATCH v2] Simplify alias storage.

[Harald van Dijk <harald@gigawatt.nl>]

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On 26/04/2024 03:49, Herbert Xu wrote:
> Could you please post a combined patch? Thanks!

Okay, the attached patch combines both. It applies on top of 177072c2.

Cheers,
Harald van Dijk

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From 109bf32ad5b14ec3c6d05d97a87f56c233bec5df Mon Sep 17 00:00:00 2001
From: Harald van Dijk <harald@gigawatt.nl>
Date: Sun, 28 Apr 2024 01:38:34 +0100
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/input.c |  4 ++--
 src/var.c   | 27 +++++++++++----------------
 src/var.h   | 15 +++++++++++++++
 4 files changed, 38 insertions(+), 40 deletions(-)

diff --git a/src/alias.c b/src/alias.c
index cee07e9..17e0f1b 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;
 }
 
@@ -151,8 +153,7 @@ aliascmd(int argc, char **argv)
 			} else
 				printalias(ap);
 		} else {
-			*v++ = '\0';
-			setalias(n, v);
+			setalias(n, v + 1);
 		}
 	}
 
@@ -191,36 +192,23 @@ 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/input.c b/src/input.c
index 38969a7..4604945 100644
--- a/src/input.c
+++ b/src/input.c
@@ -386,7 +386,7 @@ pushstring(char *s, void *ap)
 	sp->ap = (struct alias *)ap;
 	if (ap) {
 		((struct alias *)ap)->flag |= ALIASINUSE;
-		sp->string = s;
+		sp->string = ((struct alias *)ap)->name;
 	}
 	parsefile->nextc = s;
 	parsefile->nleft = len;
@@ -405,7 +405,7 @@ static void popstring(void)
 		    parsefile->nextc[-1] == '\t') {
 			checkkwd |= CHKALIAS;
 		}
-		if (sp->string != sp->ap->val) {
+		if (sp->string != sp->ap->name) {
 			ckfree(sp->string);
 		}
 	}
diff --git a/src/var.c b/src/var.c
index 895eabc..35ea7c6 100644
--- a/src/var.c
+++ b/src/var.c
@@ -622,12 +622,7 @@ 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];
 }
 
 
@@ -641,19 +636,19 @@ 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 953a694..f6fb320 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);
 }
-- 
2.43.0