ucm: allow to escape the trailing variable substitution character

Example:

  ${find-device:ctl='hw:0',type=pcm,field=id,regex='USB A{1\\}'}

Unescaped find-device arguments:

  ctl='hw:0',type=pcm,field=id,regex='USB A{1}'

Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/src/ucm/ucm_subs.c b/src/ucm/ucm_subs.c
index c902346..b9fee72 100644 (file)
--- a/src/ucm/ucm_subs.c
+++ b/src/ucm/ucm_subs.c
@@ -594,13 +594,52 @@ static char *rval_var(snd_use_case_mgr_t *uc_mgr, const char *id)
                goto __match2;                                          \
        }
 
+/*
+ * skip escaped } character (simple version)
+ */
+static inline const char *strchr_with_escape(const char *str, char c)
+{
+       char *s;
+
+       while (1) {
+               s = strchr(str, c);
+               if (s && s != str) {
+                       if (*(s - 1) == '\\') {
+                               str = s + 1;
+                               continue;
+                       }
+               }
+               return s;
+       }
+}
+
+/*
+ * remove escaped } character (simple version)
+ */
+static inline void strncpy_with_escape(char *dst, const char *src, size_t len)
+{
+       char c;
+
+       c = *src++;
+       while (c != '\0' && len > 0) {
+               if (c == '\\' && *src == '}') {
+                       c = *src++;
+                       len--;
+               }
+               *dst++ = c;
+               len--;
+               c = *src++;
+       }
+       *dst = '\0';
+}
+
 int uc_mgr_get_substituted_value(snd_use_case_mgr_t *uc_mgr,
                                 char **_rvalue,
                                 const char *value)
 {
        size_t size, nsize, idsize, rvalsize, dpos = 0;
        const char *tmp;
-       char *r, *nr, *rval, v2[48];
+       char *r, *nr, *rval, v2[128];
        bool ignore_error, allow_empty;
        char *(*fcn2)(snd_use_case_mgr_t *, const char *id);
        int err;
@@ -658,15 +697,14 @@ __merr:
                }
                goto __error;
 __match2:
-               tmp = strchr(value + idsize, '}');
+               tmp = strchr_with_escape(value + idsize, '}');
                if (tmp) {
                        rvalsize = tmp - (value + idsize);
                        if (rvalsize >= sizeof(v2)) {
                                err = -ENOMEM;
                                goto __error;
                        }
-                       strncpy(v2, value + idsize, rvalsize);
-                       v2[rvalsize] = '\0';
+                       strncpy_with_escape(v2, value + idsize, rvalsize);
                        idsize += rvalsize + 1;
                        if (*v2 == '$' && uc_mgr->conf_format >= 3) {
                                tmp = uc_mgr_get_variable(uc_mgr, v2 + 1);