libbb: introduce and use is_prefixed_with()

function                                             old     new   delta
is_prefixed_with                                       -      18     +18
complete_username                                     78      77      -1
man_main                                             737     735      -2
fsck_device                                          429     427      -2
unpack_ar_archive                                     80      76      -4
strip_unsafe_prefix                                  105     101      -4
singlemount                                         1054    1050      -4
rtc_adjtime_is_utc                                    90      86      -4
resolve_mount_spec                                    88      84      -4
parse_one_line                                      1029    1025      -4
parse_conf                                          1460    1456      -4
may_wakeup                                            83      79      -4
loadkmap_main                                        219     215      -4
get_irqs_from_stat                                   103      99      -4
get_header_cpio                                      913     909      -4
findfs_main                                           79      75      -4
fbsplash_main                                       1230    1226      -4
load_crontab                                         776     771      -5
expand_vars_to_list                                 1151    1146      -5
date_main                                            881     876      -5
skip_dev_pfx                                          30      24      -6
make_device                                         2199    2193      -6
complete_cmd_dir_file                                773     767      -6
run_applet_and_exit                                  715     708      -7
uudecode_main                                        321     313      -8
pwdx_main                                            197     189      -8
execute                                              568     560      -8
i2cdetect_main                                      1186    1176     -10
procps_scan                                         1242    1230     -12
procps_read_smaps                                   1017    1005     -12
process_module                                       746     734     -12
patch_main                                          1903    1891     -12
nfsmount                                            3572    3560     -12
stack_machine                                        126     112     -14
process_timer_stats                                  449     435     -14
match_fstype                                         111      97     -14
do_ipaddr                                           1344    1330     -14
open_list_and_close                                  359     343     -16
get_header_tar                                      1795    1779     -16
prepend_new_eth_table                                340     323     -17
fsck_main                                           1811    1794     -17
find_iface_state                                      56      38     -18
dnsd_main                                           1321    1303     -18
base_device                                          179     158     -21
find_keyword                                         104      82     -22
handle_incoming_and_exit                            2785    2762     -23
parse_and_put_prompt                                 774     746     -28
modinfo                                              347     317     -30
find_action                                          204     171     -33
update_passwd                                       1470    1436     -34
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/49 up/down: 18/-540)         Total: -522 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 27 insertions, 28 deletions

diff --git a/modutils/depmod.c b/modutils/depmod.c
index 37a8482d9..9713aef92 100644
--- a/modutils/depmod.c
+++ b/modutils/depmod.c
@@ -55,7 +55,7 @@ static int FAST_FUNC parse_module(const char *fname, struct stat *sb UNUSED_PARA
 			NULL
 	);
 	for (ptr = image; ptr < image + len - 10; ptr++) {
-		if (strncmp(ptr, "depends=", 8) == 0) {
+		if (is_prefixed_with(ptr, "depends=")) {
 			char *u;
 
 			ptr += 8;
@@ -64,15 +64,15 @@ static int FAST_FUNC parse_module(const char *fname, struct stat *sb UNUSED_PARA
 					*u = '_';
 			ptr += string_to_llist(ptr, &info->dependencies, ",");
 		} else if (ENABLE_FEATURE_MODUTILS_ALIAS
-		 && strncmp(ptr, "alias=", 6) == 0
+		 && is_prefixed_with(ptr, "alias=")
 		) {
 			llist_add_to(&info->aliases, xstrdup(ptr + 6));
 			ptr += strlen(ptr);
 		} else if (ENABLE_FEATURE_MODUTILS_SYMBOLS
-		 && strncmp(ptr, "__ksymtab_", 10) == 0
+		 && is_prefixed_with(ptr, "__ksymtab_")
 		) {
 			ptr += 10;
-			if (strncmp(ptr, "gpl", 3) == 0
+			if (is_prefixed_with(ptr, "gpl")
 			 || strcmp(ptr, "strings") == 0
 			) {
 				continue;
diff --git a/modutils/modinfo.c b/modutils/modinfo.c
index ee379304c..8e74b6438 100644
--- a/modutils/modinfo.c
+++ b/modutils/modinfo.c
@@ -62,7 +62,7 @@ static void modinfo(const char *path, const char *version,
 		"firmware",
 	};
 	size_t len;
-	int j, length;
+	int j;
 	char *ptr, *the_module;
 	const char *field = env->field;
 	int tags = env->tags;
@@ -94,16 +94,18 @@ static void modinfo(const char *path, const char *version,
 		pattern = field;
 		if ((1<<j) & OPT_TAGS)
 			pattern = shortcuts[j];
-		length = strlen(pattern);
 		ptr = the_module;
 		while (1) {
+			char *after_pattern;
+
 			ptr = memchr(ptr, *pattern, len - (ptr - (char*)the_module));
 			if (ptr == NULL) /* no occurance left, done */
 				break;
-			if (strncmp(ptr, pattern, length) == 0 && ptr[length] == '=') {
+			after_pattern = is_prefixed_with(ptr, pattern);
+			if (after_pattern && *after_pattern == '=') {
 				/* field prefixes are 0x80 or 0x00 */
-				if ((ptr[-1] & 0x7F) == '\0') {
-					ptr += length + 1;
+				if ((ptr[-1] & 0x7F) == 0x00) {
+					ptr = after_pattern + 1;
 					display(ptr, pattern, (1<<j) != tags);
 					ptr += strlen(ptr);
 				}
diff --git a/modutils/modprobe-small.c b/modutils/modprobe-small.c
index ed177bb9b..9c941064b 100644
--- a/modutils/modprobe-small.c
+++ b/modutils/modprobe-small.c
@@ -116,21 +116,21 @@ static char* copy_stringbuf(void)
 
 static char* find_keyword(char *ptr, size_t len, const char *word)
 {
-	int wlen;
-
 	if (!ptr) /* happens if xmalloc_open_zipped_read_close cannot read it */
 		return NULL;
 
-	wlen = strlen(word);
-	len -= wlen - 1;
+	len -= strlen(word) - 1;
 	while ((ssize_t)len > 0) {
 		char *old = ptr;
+		char *after_word;
+
 		/* search for the first char in word */
-		ptr = memchr(ptr, *word, len);
+		ptr = memchr(ptr, word[0], len);
 		if (ptr == NULL) /* no occurance left, done */
 			break;
-		if (strncmp(ptr, word, wlen) == 0)
-			return ptr + wlen; /* found, return ptr past it */
+		after_word = is_prefixed_with(ptr, word);
+		if (after_word)
+			return after_word; /* found, return ptr past it */
 		++ptr;
 		len -= (ptr - old);
 	}
@@ -536,7 +536,7 @@ static module_info** find_alias(const char *alias)
 // TODO: open only once, invent config_rewind()
 static int already_loaded(const char *name)
 {
-	int ret, namelen;
+	int ret;
 	char *line;
 	FILE *fp;
 
@@ -545,15 +545,16 @@ static int already_loaded(const char *name)
 	fp = fopen_for_read("/proc/modules");
 	if (!fp)
 		return 0;
-	namelen = strlen(name);
 	while ((line = xmalloc_fgetline(fp)) != NULL) {
 		char *live;
+		char *after_name;
 
 		// Examples from kernel 3.14.6:
 		//pcspkr 12718 0 - Live 0xffffffffa017e000
 		//snd_timer 28690 2 snd_seq,snd_pcm, Live 0xffffffffa025e000
 		//i915 801405 2 - Live 0xffffffffa0096000
-		if (strncmp(line, name, namelen) != 0 || line[namelen] != ' ') {
+		after_name = is_prefixed_with(line, name);
+		if (!after_name || *after_name != ' ') {
 			free(line);
 			continue;
 		}
diff --git a/modutils/modprobe.c b/modutils/modprobe.c
index 0e8aa9e85..996de4074 100644
--- a/modutils/modprobe.c
+++ b/modutils/modprobe.c
@@ -260,7 +260,7 @@ static void add_probe(const char *name)
 	llist_add_to_end(&G.probes, m);
 	G.num_unresolved_deps++;
 	if (ENABLE_FEATURE_MODUTILS_SYMBOLS
-	 && strncmp(m->modname, "symbol:", 7) == 0
+	 && is_prefixed_with(m->modname, "symbol:")
 	) {
 		G.need_symbols = 1;
 	}
@@ -353,22 +353,18 @@ static char *parse_and_add_kcmdline_module_options(char *options, const char *mo
 	char *kcmdline_buf;
 	char *kcmdline;
 	char *kptr;
-	int len;
 
 	kcmdline_buf = xmalloc_open_read_close("/proc/cmdline", NULL);
 	if (!kcmdline_buf)
 		return options;
 
 	kcmdline = kcmdline_buf;
-	len = strlen(modulename);
 	while ((kptr = strsep(&kcmdline, "\n\t ")) != NULL) {
-		if (strncmp(modulename, kptr, len) != 0)
-			continue;
-		kptr += len;
-		if (*kptr != '.')
+		char *after_modulename = is_prefixed_with(kptr, modulename);
+		if (!after_modulename || *after_modulename != '.')
 			continue;
 		/* It is "modulename.xxxx" */
-		kptr++;
+		kptr = after_modulename + 1;
 		if (strchr(kptr, '=') != NULL) {
 			/* It is "modulename.opt=[val]" */
 			options = gather_options_str(options, kptr);
diff --git a/modutils/modutils-24.c b/modutils/modutils-24.c
index 12cb75c54..fe46fc3fd 100644
--- a/modutils/modutils-24.c
+++ b/modutils/modutils-24.c
@@ -2255,7 +2255,7 @@ static int add_symbols_from(struct obj_file *f,
 		 * symbols so they cannot fudge it by adding the prefix on
 		 * their references.
 		 */
-		if (strncmp((char *)s->name, "GPLONLY_", 8) == 0) {
+		if (is_prefixed_with((char *)s->name, "GPLONLY_")) {
 #if ENABLE_FEATURE_CHECK_TAINTED_MODULE
 			if (gpl)
 				s->name += 8;