cutils: Provide strchrnul

strchrnul is a GNU extension and thus unavailable on a number of targets.
In the review for a commit removing strchrnul from 9p, I was asked to
create a qemu_strchrnul helper to factor out this functionality.
Do so, and use it in a number of other places in the code base that inlined
the replacement pattern in a place where strchrnul could be used.

Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Acked-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Greg Kurz <groug@kaod.org>

configure

@@ -4793,6 +4793,21 @@ if compile_prog "" "" ; then
     sem_timedwait=yes
 fi
 
+##########################################
+# check if we have strchrnul
+
+strchrnul=no
+cat > $TMPC << EOF
+#include <string.h>
+int main(void);
+// Use a haystack that the compiler shouldn't be able to constant fold
+char *haystack = (char*)&main;
+int main(void) { return strchrnul(haystack, 'x') != &haystack[6]; }
+EOF
+if compile_prog "" "" ; then
+    strchrnul=yes
+fi
+
 ##########################################
 # check if trace backend exists
 
@@ -6276,6 +6291,9 @@ fi
 if test "$sem_timedwait" = "yes" ; then
   echo "CONFIG_SEM_TIMEDWAIT=y" >> $config_host_mak
 fi
+if test "$strchrnul" = "yes" ; then
+  echo "HAVE_STRCHRNUL=y" >> $config_host_mak
+fi
 if test "$byteswap_h" = "yes" ; then
   echo "CONFIG_BYTESWAP_H=y" >> $config_host_mak
 fi

hmp.c

@@ -2140,12 +2140,12 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
     int has_hold_time = qdict_haskey(qdict, "hold-time");
     int hold_time = qdict_get_try_int(qdict, "hold-time", -1);
     Error *err = NULL;
-    char *separator;
+    const char *separator;
     int keyname_len;
 
     while (1) {
-        separator = strchr(keys, '-');
-        keyname_len = separator ? separator - keys : strlen(keys);
+        separator = qemu_strchrnul(keys, '-');
+        keyname_len = separator - keys;
 
         /* Be compatible with old interface, convert user inputted "<" */
         if (keys[0] == '<' && keyname_len == 1) {
@@ -2182,7 +2182,7 @@ void hmp_sendkey(Monitor *mon, const QDict *qdict)
             keylist->value->u.qcode.data = idx;
         }
 
-        if (!separator) {
+        if (!*separator) {
             break;
         }
         keys = separator + 1;

hw/9pfs/9p-local.c

@@ -65,7 +65,7 @@ int local_open_nofollow(FsContext *fs_ctx, const char *path, int flags,
         assert(*path != '/');
 
         head = g_strdup(path);
-        c = strchrnul(path, '/');
+        c = qemu_strchrnul(path, '/');
         if (*c) {
             /* Intermediate path element */
             head[c - path] = 0;

include/qemu/cutils.h

@@ -122,6 +122,14 @@ int qemu_strnlen(const char *s, int max_len);
  * Returns: the pointer originally in @input.
  */
 char *qemu_strsep(char **input, const char *delim);
+#ifdef HAVE_STRCHRNUL
+static inline const char *qemu_strchrnul(const char *s, int c)
+{
+    return strchrnul(s, c);
+}
+#else
+const char *qemu_strchrnul(const char *s, int c);
+#endif
 time_t mktimegm(struct tm *tm);
 int qemu_fdatasync(int fd);
 int fcntl_setfl(int fd, int flag);

monitor.c

@@ -820,9 +820,7 @@ static int compare_cmd(const char *name, const char *list)
     p = list;
     for(;;) {
         pstart = p;
-        p = strchr(p, '|');
-        if (!p)
-            p = pstart + strlen(pstart);
+        p = qemu_strchrnul(p, '|');
         if ((p - pstart) == len && !memcmp(pstart, name, len))
             return 1;
         if (*p == '\0')
@@ -3489,9 +3487,7 @@ static void cmd_completion(Monitor *mon, const char *name, const char *list)
     p = list;
     for(;;) {
         pstart = p;
-        p = strchr(p, '|');
-        if (!p)
-            p = pstart + strlen(pstart);
+        p = qemu_strchrnul(p, '|');
         len = p - pstart;
         if (len > sizeof(cmd) - 2)
             len = sizeof(cmd) - 2;

util/cutils.c

@@ -544,6 +544,21 @@ int qemu_strtou64(const char *nptr, const char **endptr, int base,
     return check_strtox_error(nptr, ep, endptr, errno);
 }
 
+/**
+ * Searches for the first occurrence of 'c' in 's', and returns a pointer
+ * to the trailing null byte if none was found.
+ */
+#ifndef HAVE_STRCHRNUL
+const char *qemu_strchrnul(const char *s, int c)
+{
+    const char *e = strchr(s, c);
+    if (!e) {
+        e = s + strlen(s);
+    }
+    return e;
+}
+#endif
+
 /**
  * parse_uint:
  *

util/qemu-option.c

@@ -77,11 +77,7 @@ const char *get_opt_value(const char *p, char **value)
 
     *value = NULL;
     while (1) {
-        offset = strchr(p, ',');
-        if (!offset) {
-            offset = p + strlen(p);
-        }
-
+        offset = qemu_strchrnul(p, ',');
         length = offset - p;
         if (*offset != '\0' && *(offset + 1) == ',') {
             length++;

util/uri.c

@@ -52,6 +52,7 @@
  */
 
 #include "qemu/osdep.h"
+#include "qemu/cutils.h"
 
 #include "qemu/uri.h"
 
@@ -2266,10 +2267,7 @@ struct QueryParams *query_params_parse(const char *query)
         /* Find the next separator, or end of the string. */
         end = strchr(query, '&');
         if (!end) {
-            end = strchr(query, ';');
-        }
-        if (!end) {
-            end = query + strlen(query);
+            end = qemu_strchrnul(query, ';');
         }
 
         /* Find the first '=' character between here and end. */