ucm: configuration - add DefineRegex

Syntax:

  DefineRegex.VariableName {
    String "something to match"
    Regex "(me)thi(ng)"
  }

Result:

- configuration variable "VariableName" is equal to "mething"
- configuration variable "VariableName1" is equal to "me"
- configuration variable "VariableName2" is equal to "ng"

Notes:

The "Flags" string in the DefineRegex compound may specify
the compilation flags (e = extended, i = ignore case,
s = no substitutes, n = newline). See 'man 3 regex' for
more details.

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

src/ucm/ucm_regex.c

@@ -0,0 +1,174 @@
+/*
+ *  This library is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU Lesser General Public
+ *  License as published by the Free Software Foundation; either
+ *  version 2 of the License, or (at your option) any later version.
+ *
+ *  This library is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  Lesser General Public License for more details.
+ *
+ *  You should have received a copy of the GNU Lesser General Public
+ *  License along with this library; if not, write to the Free Software
+ *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *  Support for the verb/device/modifier core logic and API,
+ *  command line tool and file parser was kindly sponsored by
+ *  Texas Instruments Inc.
+ *  Support for multiple active modifiers and devices,
+ *  transition sequences, multiple client access and user defined use
+ *  cases was kindly sponsored by Wolfson Microelectronics PLC.
+ *
+ *  Copyright (C) 2019 Red Hat Inc.
+ *  Authors: Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include "ucm_local.h"
+#include <ctype.h>
+#include <regex.h>
+
+static int get_string(snd_config_t *compound, const char *key, const char **str)
+{
+	snd_config_t *node;
+	int err;
+
+	err = snd_config_search(compound, key, &node);
+	if (err < 0)
+		return err;
+	return snd_config_get_string(node, str);
+}
+
+static char *extract_substring(const char *data, regmatch_t *match)
+{
+	char *s;
+	size_t len;
+
+	len = match->rm_eo - match->rm_so;
+	s = malloc(len + 1);
+	if (s == NULL)
+		return NULL;
+	memcpy(s, data + match->rm_so, len);
+	s[len] = '\0';
+	return s;
+}
+
+static int set_variables(snd_use_case_mgr_t *uc_mgr, const char *data,
+			 unsigned int match_size, regmatch_t *match,
+			 const char *name)
+{
+	size_t name2_len = strlen(name) + 16;
+	char *name2 = alloca(name2_len);
+	char *s;
+	unsigned int i;
+	int err;
+
+	if (match[0].rm_so < 0 || match[0].rm_eo < 0)
+		return 0;
+	s = extract_substring(data, &match[0]);
+	if (s == NULL)
+		return -ENOMEM;
+	err = uc_mgr_set_variable(uc_mgr, name, s);
+	free(s);
+	if (err < 0)
+		return err;
+	for (i = 1; i < match_size; i++) {
+		if (match[0].rm_so < 0 || match[0].rm_eo < 0)
+			return 0;
+		s = extract_substring(data, &match[i]);
+		if (s == NULL)
+			return -ENOMEM;
+		snprintf(name2, name2_len, "%s%u", name, i);
+		err = uc_mgr_set_variable(uc_mgr, name2, s);
+		free(s);
+		if (err < 0)
+			return err;
+	}
+	return 0;
+}
+
+int uc_mgr_define_regex(snd_use_case_mgr_t *uc_mgr, const char *name,
+			snd_config_t *eval)
+{
+	const char *string, *regex_string, *flags_string;
+	char *s;
+	regex_t re;
+	int options = 0;
+	regmatch_t match[20];
+	int err;
+
+	if (uc_mgr->conf_format < 3) {
+		uc_error("define regex is supported in v3+ syntax");
+		return -EINVAL;
+	}
+
+	if (snd_config_get_type(eval) != SND_CONFIG_TYPE_COMPOUND) {
+		uc_error("compound type expected for DefineRegex");
+		return -EINVAL;
+	}
+
+	err = get_string(eval, "String", &string);
+	if (err < 0) {
+		uc_error("DefineRegex error (String)");
+		return -EINVAL;
+	}
+
+	err = get_string(eval, "Regex", &regex_string);
+	if (err < 0) {
+		uc_error("DefineRegex error (Regex string)");
+		return -EINVAL;
+	}
+
+	err = get_string(eval, "Flags", &flags_string);
+	if (err == -ENOENT) {
+		options = REG_EXTENDED;
+	} else if (err < 0) {
+		uc_error("DefineRegex error (Flags string)");
+		return -EINVAL;
+	} else {
+		while (*flags_string) {
+			switch (tolower(*flags_string)) {
+			case 'e':
+				options |= REG_EXTENDED;
+				break;
+			case 'i':
+				options |= REG_ICASE;
+				break;
+			case 's':
+				options |= REG_NOSUB;
+				break;
+			case 'n':
+				options |= REG_NEWLINE;
+				break;
+			default:
+				uc_error("DefineRegex error (unknown flag '%c')", *flags_string);
+				return -EINVAL;
+			}
+			flags_string++;
+		}
+	}
+
+	err = uc_mgr_get_substituted_value(uc_mgr, &s, regex_string);
+	if (err < 0)
+		return err;
+	err = regcomp(&re, s, options);
+	free(s);
+	if (err) {
+		uc_error("Regex '%s' compilation failed (code %d)", err);
+		return -EINVAL;
+	}
+
+	err = uc_mgr_get_substituted_value(uc_mgr, &s, string);
+	if (err < 0) {
+		regfree(&re);
+		return err;
+	}
+	err = regexec(&re, s, ARRAY_SIZE(match), match, 0);
+	if (err < 0)
+		err = -errno;
+	else
+		err = set_variables(uc_mgr, s, ARRAY_SIZE(match), match, name);
+	free(s);
+	regfree(&re);
+	return err;
+}