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>

9 files changed, 49 insertions, 33 deletions

diff --git a/libbb/appletlib.c b/libbb/appletlib.c
index 54300bd87..8fd8fd525 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -193,7 +193,7 @@ void lbb_prepare(const char *applet
         if (argv[1]
          && !argv[2]
          && strcmp(argv[1], "--help") == 0
-         && strncmp(applet, "busybox", 7) != 0
+         && !is_prefixed_with(applet, "busybox")
         ) {
                 /* Special case. POSIX says "test --help"
                  * should be no different from e.g. "test --foo".  */
@@ -673,7 +673,7 @@ static int busybox_main(char **argv)
                 return 0;
         }
 
-        if (strncmp(argv[1], "--list", 6) == 0) {
+        if (is_prefixed_with(argv[1], "--list")) {
                 unsigned i = 0;
                 const char *a = applet_names;
                 dup2(1, 2);
@@ -778,7 +778,7 @@ void FAST_FUNC run_applet_and_exit(const char *name, char **argv)
         int applet = find_applet_by_name(name);
         if (applet >= 0)
                 run_applet_no_and_exit(applet, argv);
-        if (strncmp(name, "busybox", 7) == 0)
+        if (is_prefixed_with(name, "busybox"))
                 exit(busybox_main(argv));
 }
 
@@ -817,7 +817,7 @@ int main(int argc UNUSED_PARAM, char **argv)
 
 #if defined(SINGLE_APPLET_MAIN)
         /* Only one applet is selected in .config */
-        if (argv[1] && strncmp(argv[0], "busybox", 7) == 0) {
+        if (argv[1] && is_prefixed_with(argv[0], "busybox")) {
                 /* "busybox <applet> <params>" should still work as expected */
                 argv++;
         }
diff --git a/libbb/compare_string_array.c b/libbb/compare_string_array.c
index 4b10cc138..e24815a03 100644
--- a/libbb/compare_string_array.c
+++ b/libbb/compare_string_array.c
@@ -5,6 +5,24 @@
 
 #include "libbb.h"
 
+char* FAST_FUNC is_prefixed_with(const char *string, const char *key)
+{
+#if 0   /* Two passes over key - probably slower */
+        int len = strlen(key);
+        if (strncmp(string, key, len) == 0)
+                return string + len;
+        return NULL;
+#else   /* Open-coded */
+        while (*key != '\0') {
+                if (*key != *string)
+                        return NULL;
+                key++;
+                string++;
+        }
+        return (char*)string;
+#endif
+}
+
 /* returns the array index of the string */
 /* (index of first match is returned, or -1) */
 int FAST_FUNC index_in_str_array(const char *const string_array[], const char *key)
@@ -39,10 +57,9 @@ int FAST_FUNC index_in_strings(const char *strings, const char *key)
 int FAST_FUNC index_in_substr_array(const char *const string_array[], const char *key)
 {
         int i;
-        int len = strlen(key);
-        if (len) {
+        if (key[0]) {
                 for (i = 0; string_array[i] != 0; i++) {
-                        if (strncmp(string_array[i], key, len) == 0) {
+                        if (is_prefixed_with(string_array[i], key)) {
                                 return i;
                         }
                 }
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 249b401b4..a83e07c0c 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -681,7 +681,7 @@ static NOINLINE unsigned complete_username(const char *ud)
         setpwent();
         while ((pw = getpwent()) != NULL) {
                 /* Null usernames should result in all users as possible completions. */
-                if (/*!userlen || */ strncmp(ud, pw->pw_name, userlen) == 0) {
+                if (/* !ud[0] || */ is_prefixed_with(pw->pw_name, ud)) {
                         add_match(xasprintf("~%s/", pw->pw_name));
                 }
         }
@@ -792,7 +792,7 @@ static NOINLINE unsigned complete_cmd_dir_file(const char *command, int type)
                         if (!pfind[0] && DOT_OR_DOTDOT(name_found))
                                 continue;
                         /* match? */
-                        if (strncmp(name_found, pfind, pf_len) != 0)
+                        if (!is_prefixed_with(name_found, pfind))
                                 continue; /* no */
 
                         found = concat_path_file(paths[i], name_found);
@@ -1879,15 +1879,16 @@ static void parse_and_put_prompt(const char *prmt_ptr)
                                                 cwd_buf = xrealloc_getcwd_or_warn(NULL);
                                                 if (!cwd_buf)
                                                         cwd_buf = (char *)bb_msg_unknown;
-                                                else {
+                                                else if (home_pwd_buf[0]) {
+                                                        char *after_home_user;
+
                                                         /* /home/user[/something] -> ~[/something] */
-                                                        l = strlen(home_pwd_buf);
-                                                        if (l != 0
-                                                         && strncmp(home_pwd_buf, cwd_buf, l) == 0
-                                                         && (cwd_buf[l] == '/' || cwd_buf[l] == '\0')
+                                                        after_home_user = is_prefixed_with(cwd_buf, home_pwd_buf);
+                                                        if (after_home_user
+                                                         && (*after_home_user == '/' || *after_home_user == '\0')
                                                         ) {
                                                                 cwd_buf[0] = '~';
-                                                                overlapping_strcpy(cwd_buf + 1, cwd_buf + l);
+                                                                overlapping_strcpy(cwd_buf + 1, after_home_user);
                                                         }
                                                 }
                                         }
diff --git a/libbb/match_fstype.c b/libbb/match_fstype.c
index 32c3d7f18..b066b4211 100644
--- a/libbb/match_fstype.c
+++ b/libbb/match_fstype.c
@@ -17,7 +17,6 @@
 int FAST_FUNC match_fstype(const struct mntent *mt, const char *t_fstype)
 {
         int match = 1;
-        int len;
 
         if (!t_fstype)
                 return match;
@@ -27,10 +26,10 @@ int FAST_FUNC match_fstype(const struct mntent *mt, const char *t_fstype)
                 t_fstype += 2;
         }
 
-        len = strlen(mt->mnt_type);
         while (1) {
-                if (strncmp(mt->mnt_type, t_fstype, len) == 0
-                 && (t_fstype[len] == '\0' || t_fstype[len] == ',')
+                char *after_mnt_type = is_prefixed_with(t_fstype, mt->mnt_type);
+                if (after_mnt_type
+                 && (*after_mnt_type == '\0' || *after_mnt_type == ',')
                 ) {
                         return match;
                 }
diff --git a/libbb/procps.c b/libbb/procps.c
index 5b68d3431..948b91ee6 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -205,11 +205,11 @@ int FAST_FUNC procps_read_smaps(pid_t pid, struct smaprec *total,
                 // Rss:                 nnn kB
                 // .....
 
-                char *tp = buf, *p;
+                char *tp, *p;
 
 #define SCAN(S, X) \
-                if (strncmp(tp, S, sizeof(S)-1) == 0) {              \
-                        tp = skip_whitespace(tp + sizeof(S)-1);      \
+                if ((tp = is_prefixed_with(buf, S)) != NULL) {       \
+                        tp = skip_whitespace(tp);                    \
                         total->X += currec.X = fast_strtoul_10(&tp); \
                         continue;                                    \
                 }
@@ -247,7 +247,7 @@ int FAST_FUNC procps_read_smaps(pid_t pid, struct smaprec *total,
                         // skipping "rw-s FILEOFS M:m INODE "
                         tp = skip_whitespace(skip_fields(tp, 4));
                         // filter out /dev/something (something != zero)
-                        if (strncmp(tp, "/dev/", 5) != 0 || strcmp(tp, "/dev/zero\n") == 0) {
+                        if (!is_prefixed_with(tp, "/dev/") || strcmp(tp, "/dev/zero\n") == 0) {
                                 if (currec.smap_mode[1] == 'w') {
                                         currec.mapped_rw = currec.smap_size;
                                         total->mapped_rw += currec.smap_size;
@@ -497,8 +497,8 @@ procps_status_t* FAST_FUNC procps_scan(procps_status_t* sp, int flags)
                                 while (fgets(buf, sizeof(buf), file)) {
                                         char *tp;
 #define SCAN_TWO(str, name, statement) \
-        if (strncmp(buf, str, sizeof(str)-1) == 0) { \
-                tp = skip_whitespace(buf + sizeof(str)-1); \
+        if ((tp = is_prefixed_with(buf, str)) != NULL) { \
+                tp = skip_whitespace(tp); \
                 sscanf(tp, "%u", &sp->name); \
                 statement; \
         }
diff --git a/libbb/rtc.c b/libbb/rtc.c
index 6d06d57f9..c4117ba34 100644
--- a/libbb/rtc.c
+++ b/libbb/rtc.c
@@ -22,7 +22,7 @@ int FAST_FUNC rtc_adjtime_is_utc(void)
                 char buffer[128];
 
                 while (fgets(buffer, sizeof(buffer), f)) {
-                        if (strncmp(buffer, "UTC", 3) == 0) {
+                        if (is_prefixed_with(buffer, "UTC")) {
                                 utc = 1;
                                 break;
                         }
diff --git a/libbb/skip_whitespace.c b/libbb/skip_whitespace.c
index 8c7b674c3..b6cfbba4d 100644
--- a/libbb/skip_whitespace.c
+++ b/libbb/skip_whitespace.c
@@ -33,7 +33,7 @@ char* FAST_FUNC skip_non_whitespace(const char *s)
 
 char* FAST_FUNC skip_dev_pfx(const char *tty_name)
 {
-        if (strncmp(tty_name, "/dev/", 5) == 0)
+        if (is_prefixed_with(tty_name, "/dev/"))
                 tty_name += 5;
         return (char*)tty_name;
 }
diff --git a/libbb/update_passwd.c b/libbb/update_passwd.c
index dc26ebd1d..a2004f480 100644
--- a/libbb/update_passwd.c
+++ b/libbb/update_passwd.c
@@ -84,7 +84,6 @@ int FAST_FUNC update_passwd(const char *filename,
         char *fnamesfx;
         char *sfx_char;
         char *name_colon;
-        unsigned user_len;
         int old_fd;
         int new_fd;
         int i;
@@ -108,7 +107,6 @@ int FAST_FUNC update_passwd(const char *filename,
         fnamesfx = xasprintf("%s+", filename);
         sfx_char = &fnamesfx[strlen(fnamesfx)-1];
         name_colon = xasprintf("%s:", name ? name : "");
-        user_len = strlen(name_colon);
 
         if (shadow)
                 old_fp = fopen(filename, "r+");
@@ -179,7 +177,7 @@ int FAST_FUNC update_passwd(const char *filename,
                         while (list) {
                                 list++;
  next_list_element:
-                                if (strncmp(list, member, member_len) == 0) {
+                                if (is_prefixed_with(list, member)) {
                                         char c;
                                         changed_lines++;
                                         c = list[member_len];
@@ -201,13 +199,14 @@ int FAST_FUNC update_passwd(const char *filename,
                         goto next;
                 }
 
-                if (strncmp(name_colon, line, user_len) != 0) {
+                cp = is_prefixed_with(line, name_colon);
+                if (!cp) {
                         fprintf(new_fp, "%s\n", line);
                         goto next;
                 }
 
                 /* We have a match with "name:"... */
-                cp = line + user_len; /* move past name: */
+                /* cp points past "name:" */
 
 #if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
                 if (member) {
diff --git a/libbb/xconnect.c b/libbb/xconnect.c
index 1c8bb2b73..2a96e03dc 100644
--- a/libbb/xconnect.c
+++ b/libbb/xconnect.c
@@ -171,7 +171,7 @@ IF_NOT_FEATURE_IPV6(sa_family_t af = AF_INET;)
         const char *cp;
         struct addrinfo hint;
 
-        if (ENABLE_FEATURE_UNIX_LOCAL && strncmp(host, "local:", 6) == 0) {
+        if (ENABLE_FEATURE_UNIX_LOCAL && is_prefixed_with(host, "local:")) {
                 struct sockaddr_un *sun;
 
                 r = xzalloc(LSA_LEN_SIZE + sizeof(struct sockaddr_un));