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List:       busybox
Subject:    [PATCH 2/2] applet_tables: avoid duplication of applet names
From:       Ron Yorston <rmy () pobox ! com>
Date:       2016-03-22 17:17:34
Message-ID: 56f17e2e.x+VCzXdxUTEEamQx%rmy () pobox ! com
[Download RAW message or body]

Modify the applet_tables utility so that, by suitably tweaking the name
offsets, applet names which appear as part of another name don't have to
be stored separately.  Instead of:

   const char applet_names[] ALIGN1 = ""
   "[" "\0"
   "[[" "\0"

   const uint16_t applet_nameofs[] ALIGN2 = {
   0x0000,
   0x0002,

we get:

   const char applet_names[] ALIGN1 = ""
   "[[" "\0"

   const uint16_t applet_nameofs[] ALIGN2 = {
   0x0001,
   0x0000,

The APPLET_NAME macro should be used to access applet names.

function                                             old     new   delta
applet_names                                        2510    2332    -178
.rodata                                           155866  155688    -178
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 0/2 up/down: 0/-356)           Total: -356 bytes
   text	   data	    bss	    dec	    hex	filename
 823829	   4078	   9088	 836995	  cc583	busybox_old
 823651	   4078	   9088	 836817	  cc4d1	busybox_unstripped

Signed-off-by: Ron Yorston <rmy@pobox.com>
---
 applets/applet_tables.c | 58 ++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 6 deletions(-)

diff --git a/applets/applet_tables.c b/applets/applet_tables.c
index 92bf1e4..092a13b 100644
--- a/applets/applet_tables.c
+++ b/applets/applet_tables.c
@@ -42,6 +42,11 @@ struct bb_applet {
 enum { NUM_APPLETS = ARRAY_SIZE(applets) };
 
 static int offset[NUM_APPLETS];
+/*
+ * If subset[i] is non-negative applets.name[i] appears at the end
+ * of applets.name[subset[i]].
+ */
+static int subset[NUM_APPLETS];
 
 static int cmp_name(const void *a, const void *b)
 {
@@ -60,19 +65,58 @@ static int str_isalnum_(const char *s)
 	return 1;
 }
 
+/* return 0 if s is longer than t and ends with t */
+static int end_match(const char *s, const char *t)
+{
+	int delta = strlen(s) - strlen(t);
+
+	if (delta <= 0)
+		return -1;
+
+	return strcmp(s+delta, t);
+}
+
 int main(int argc, char **argv)
 {
-	int i;
+	int i, j;
 	int ofs;
 //	unsigned MAX_APPLET_NAME_LEN = 1;
 
 	qsort(applets, NUM_APPLETS, sizeof(applets[0]), cmp_name);
 
+	/* find which applet names are subsets of others */
+	for (i = 0; i < NUM_APPLETS; i++) {
+		subset[i] = -1;
+		for (j = 0; j < NUM_APPLETS; j++) {
+			if ( end_match(applets[j].name, applets[i].name) == 0 ) {
+				subset[i] = j;
+				break;
+			}
+		}
+	}
+
 	ofs = 0;
+	/* obtain offsets for names that will be output */
 	for (i = 0; i < NUM_APPLETS; i++) {
-		offset[i] = ofs;
-		ofs += strlen(applets[i].name) + 1;
+		if (subset[i] < 0) {
+			offset[i] = ofs;
+			ofs += strlen(applets[i].name) + 1;
+		}
 	}
+
+	/* obtain offsets for names that are contained in those output */
+	for (i = 0; i < NUM_APPLETS; i++) {
+		if (subset[i] >= 0) {
+			/* allow for indirection:  sh -> ash -> fbsplash */
+			j = i;
+			while (subset[j] >= 0) {
+				j = subset[j];
+			}
+			offset[i] = offset[j] + strlen(applets[j].name) -
+						strlen(applets[i].name);
+		}
+	}
+
 	/* We reuse 4 high-order bits of offset array for other purposes,
 	 * so if they are indeed needed, refuse to proceed */
 	if (ofs > 0xfff)
@@ -99,9 +143,11 @@ int main(int argc, char **argv)
 	//printf("#ifndef SKIP_definitions\n");
 	printf("const char applet_names[] ALIGN1 = \"\"\n");
 	for (i = 0; i < NUM_APPLETS; i++) {
-		printf("\"%s\" \"\\0\"\n", applets[i].name);
-//		if (MAX_APPLET_NAME_LEN < strlen(applets[i].name))
-//			MAX_APPLET_NAME_LEN = strlen(applets[i].name);
+		if (subset[i] < 0) {
+			printf("\"%s\" \"\\0\"\n", applets[i].name);
+//			if (MAX_APPLET_NAME_LEN < strlen(applets[i].name))
+//				MAX_APPLET_NAME_LEN = strlen(applets[i].name);
+		}
 	}
 	printf(";\n\n");
 
-- 
2.5.5

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