From: Ben Harris <bjh21@bjh21.me.uk>
Date: Thu, 18 Jul 2024 11:59:55 +0000 (+0100)
Subject: Put bitmap data and alias target into a union
X-Git-Tag: bedstead-002.007~11
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=874a12b047ea5126e9cfe1be083eb36fedf1d37f;p=bedstead.git

Put bitmap data and alias target into a union

A character can't both be an alias and have its own bitmap data, so we
may as well overlap them.  Wrapping them in a union doesn't require any
changes to the syntax of the glyphs array because C allows for
incomplete bracketing of initialisers.  Because the union doesn't have a
name, its members can be accessed as though they're members of the
containing struct, which means that accesses to them don't need to
change.

There is a new flag to mark a glyph as an alias since "alias_of == NULL"
no longer works, and a corresponding change to the ALIAS() macro.

This saves about 20K of bedstead's data segment on a 64-bit system,
which is kind of silly but it's satisfying nonetheless.
---

diff --git a/bedstead.c b/bedstead.c
index 1031a32..ebdb1b3 100644
--- a/bedstead.c
+++ b/bedstead.c
@@ -194,10 +194,13 @@ static void glyph_complement(void);
 
 /* U(N) sets the code point and name of a glyph not in AGLFN */
 #define U(N) 0x ## N, 0x ## N >= 0x10000 ? "u" #N : "uni" #N
-#define ALIAS(alias, canonical) {{},-1,alias,0,canonical}
+#define ALIAS(alias, canonical) {{.alias_of=canonical},-1,alias,IS_ALIAS}
 
 static struct glyph {
-	char data[YSIZE];
+	union {
+		char data[YSIZE];
+		char const *alias_of;
+	};
 	int_least32_t unicode;
 	char const *name;
 	uint_least8_t flags;
@@ -206,7 +209,7 @@ static struct glyph {
 #define MOS4 0x04 /* 4-cell mosaic graphics character */
 #define SEP6 (SEP | MOS6)
 #define SEP4 (SEP | MOS4)
-	char const *alias_of;
+#define IS_ALIAS 0x08
 } glyphs[] = {
  /*
   * The first batch of glyphs comes from the code tables at the end of
@@ -2859,7 +2862,7 @@ main(int argc, char **argv)
 			printf("Flags: HW\n");
 		printf("LayerCount: 2\n");
 		dolookups(&glyphs[i]);
-		if (glyphs[i].alias_of != NULL)
+		if (glyphs[i].flags & IS_ALIAS)
 			doalias(glyphs[i].alias_of);
 		else if	(glyphs[i].flags & MOS6)
 			domosaic(glyphs[i].data[0],
@@ -2998,7 +3001,7 @@ dopalt(struct glyph const *g)
 	unsigned char cols = 0;
 	int dx = 0, dh = 0;
 
-	while (g->alias_of != NULL)
+	while (g->flags & IS_ALIAS)
 		g = get_glyph_by_name(g->alias_of);
 	if (g->flags & (MOS6|MOS4)) return;
 	/*