Implement support for PCRE regular expressions for all criteria (for_window, commands, assignments)

src/regex.c

@@ -0,0 +1,63 @@
+/*
+ * vim:ts=4:sw=4:expandtab
+ *
+ * i3 - an improved dynamic tiling window manager
+ * © 2009-2011 Michael Stapelberg and contributors (see also: LICENSE)
+ *
+ *
+ */
+
+#include "all.h"
+
+/*
+ * Creates a new 'regex' struct containing the given pattern and a PCRE
+ * compiled regular expression. Also, calls pcre_study because this regex will
+ * most likely be used often (like for every new window and on every relevant
+ * property change of existing windows).
+ *
+ * Returns NULL if the pattern could not be compiled into a regular expression
+ * (and ELOGs an appropriate error message).
+ *
+ */
+struct regex *regex_new(const char *pattern) {
+    const char *error;
+    int offset;
+
+    struct regex *re = scalloc(sizeof(struct regex));
+    re->pattern = sstrdup(pattern);
+    if (!(re->regex = pcre_compile(pattern, 0, &error, &offset, NULL))) {
+        ELOG("PCRE regular expression compilation failed at %d: %s",
+             offset, error);
+        return NULL;
+    }
+    re->extra = pcre_study(re->regex, 0, &error);
+    return re;
+}
+
+/*
+ * Checks if the given regular expression matches the given input and returns
+ * true if it does. In either case, it logs the outcome using LOG(), so it will
+ * be visible without any debug loglevel.
+ *
+ */
+bool regex_matches(struct regex *regex, const char *input) {
+    int rc;
+
+    /* TODO: is strlen(input) correct for UTF-8 matching? */
+    /* TODO: enable UTF-8 */
+    if ((rc = pcre_exec(regex->regex, regex->extra, input, strlen(input), 0, 0, NULL, 0)) == 0) {
+        LOG("Regular expression \"%s\" matches \"%s\"\n",
+            regex->pattern, input);
+        return true;
+    }
+
+    if (rc == PCRE_ERROR_NOMATCH) {
+        LOG("Regular expression \"%s\" does not match \"%s\"\n",
+            regex->pattern, input);
+        return false;
+    }
+
+    /* TODO: handle the other error codes */
+    LOG("PCRE error\n");
+    return false;
+}