8add06857 — BusyBox

Subject

mt: eliminate vector of structures with pointers (bad for libbusybox). It's a win for static build too:

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Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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miscutils/mt.c +79 -56

miscutils/mt.c+79 -56

@@ -6,58 +6,87 @@
	#include "libbb.h"
	#include <sys/mtio.h>

-	struct mt_opcodes {
-	const char *name;
-	short value;
-	};
-
	/* missing: eod/seod, stoptions, stwrthreshold, densities */
-	static const struct mt_opcodes opcodes[] = {
-	{"bsf", MTBSF},
-	{"bsfm", MTBSFM},
-	{"bsr", MTBSR},
-	{"bss", MTBSS},
-	{"datacompression", MTCOMPRESSION},
-	{"eom", MTEOM},
-	{"erase", MTERASE},
-	{"fsf", MTFSF},
-	{"fsfm", MTFSFM},
-	{"fsr", MTFSR},
-	{"fss", MTFSS},
-	{"load", MTLOAD},
-	{"lock", MTLOCK},
-	{"mkpart", MTMKPART},
-	{"nop", MTNOP},
-	{"offline", MTOFFL},
-	{"rewoffline", MTOFFL},
-	{"ras1", MTRAS1},
-	{"ras2", MTRAS2},
-	{"ras3", MTRAS3},
-	{"reset", MTRESET},
-	{"retension", MTRETEN},
-	{"rewind", MTREW},
-	{"seek", MTSEEK},
-	{"setblk", MTSETBLK},
-	{"setdensity", MTSETDENSITY},
-	{"drvbuffer", MTSETDRVBUFFER},
-	{"setpart", MTSETPART},
-	{"tell", MTTELL},
-	{"wset", MTWSM},
-	{"unload", MTUNLOAD},
-	{"unlock", MTUNLOCK},
-	{"eof", MTWEOF},
-	{"weof", MTWEOF},
-	{0, 0}
+	static const short opcode_value[] = {
+	MTBSF,
+	MTBSFM,
+	MTBSR,
+	MTBSS,
+	MTCOMPRESSION,
+	MTEOM,
+	MTERASE,
+	MTFSF,
+	MTFSFM,
+	MTFSR,
+	MTFSS,
+	MTLOAD,
+	MTLOCK,
+	MTMKPART,
+	MTNOP,
+	MTOFFL,
+	MTOFFL,
+	MTRAS1,
+	MTRAS2,
+	MTRAS3,
+	MTRESET,
+	MTRETEN,
+	MTREW,
+	MTSEEK,
+	MTSETBLK,
+	MTSETDENSITY,
+	MTSETDRVBUFFER,
+	MTSETPART,
+	MTTELL,
+	MTWSM,
+	MTUNLOAD,
+	MTUNLOCK,
+	MTWEOF,
+	MTWEOF
	};

+	static const char opcode_name[] ALIGN1 =
+	"bsf" "\0"
+	"bsfm" "\0"
+	"bsr" "\0"
+	"bss" "\0"
+	"datacompression" "\0"
+	"eom" "\0"
+	"erase" "\0"
+	"fsf" "\0"
+	"fsfm" "\0"
+	"fsr" "\0"
+	"fss" "\0"
+	"load" "\0"
+	"lock" "\0"
+	"mkpart" "\0"
+	"nop" "\0"
+	"offline" "\0"
+	"rewoffline" "\0"
+	"ras1" "\0"
+	"ras2" "\0"
+	"ras3" "\0"
+	"reset" "\0"
+	"retension" "\0"
+	"rewind" "\0"
+	"seek" "\0"
+	"setblk" "\0"
+	"setdensity" "\0"
+	"drvbuffer" "\0"
+	"setpart" "\0"
+	"tell" "\0"
+	"wset" "\0"
+	"unload" "\0"
+	"unlock" "\0"
+	"eof" "\0"
+	"weof" "\0";
+
	int mt_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
	int mt_main(int argc, char **argv)
	{
	const char *file = "/dev/tape";
-	const struct mt_opcodes *code = opcodes;
	struct mtop op;
	struct mtpos position;
-	int fd, mode;
+	int fd, mode, idx;

	if (argc < 2) {
	bb_show_usage();
@@ -72,24 +101,18 @@ int mt_main(int argc, char **argv)
	argc -= 2;
	}

-	while (code->name != 0) {
-	if (strcmp(code->name, argv[1]) == 0)
-	break;
-	code++;
-	}
+	idx = index_in_strings(opcode_name, argv[1]);

-	if (code->name == 0) {
-	bb_error_msg("unrecognized opcode %s", argv[1]);
-	return EXIT_FAILURE;
-	}
+	if (idx < 0)
+	bb_error_msg_and_die("unrecognized opcode %s", argv[1]);

-	op.mt_op = code->value;
+	op.mt_op = opcode_value[idx];
	if (argc >= 3)
	op.mt_count = xatoi_u(argv[2]);
	else
	op.mt_count = 1; /* One, not zero, right? */

-	switch (code->value) {
+	switch (opcode_value[idx]) {
	case MTWEOF:
	case MTERASE:
	case MTWSM:
@@ -104,10 +127,10 @@ int mt_main(int argc, char **argv)

	fd = xopen(file, mode);

-	switch (code->value) {
+	switch (opcode_value[idx]) {
	case MTTELL:
	ioctl_or_perror_and_die(fd, MTIOCPOS, &position, "%s", file);
-	printf("At block %d.\n", (int) position.mt_blkno);
+	printf("At block %d\n", (int) position.mt_blkno);
	break;

	default: