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diff --git a/lib/include/libcfg.h b/lib/include/libcfg.h
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+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * Copyright (C) 2018 - David Oberhollenzer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+#ifndef LIBCONFIG_H
+#define LIBCONFIG_H
+
+#include <stdbool.h>
+
+typedef struct {
+ int fd; /* input file descriptor */
+ const char *argstr; /* if not NULL, read from this instead */
+
+ const char *filename; /* input file name */
+ size_t lineno; /* current line number */
+
+ size_t i; /* buffer offset */
+ char buffer[256]; /* current line, null-terminated */
+
+ int argc;
+ const char *const *argv;
+
+ bool string; /* inside a string? */
+ bool escape; /* reading an escape sequence? */
+ bool comment; /* inside a comment */
+} rdline_t;
+
+/*
+ Initialize the config line scanner.
+
+ The scanner reads from the provided fd. The filename is used for
+ error reporting. An argument count and vector can be set for argument
+ substitution in rdline.
+*/
+void rdline_init(rdline_t *t, int fd, const char *filename,
+ int argc, const char *const *argv);
+
+/*
+ Read from file until end-of-file or a line feed is encountered.
+
+ Returns -1 on failure, +1 if end of file was reached,
+ 0 if data was read successfully.
+
+ The following transformations are applied:
+ - Space characters are replaced with regular white space characters.
+ - Sequences of space characters are truncated to a single space.
+ - A '#' sign is interpreted as the start of a comment and removed,
+ together with everything that follows.
+ - Padding spaces are removed from the line.
+ - If a '"' is encounterd, the above rules are disabled, until a
+ after the matching '"' is read. A '"' can be escaped by preceeding
+ it with a backslash.
+ - If a second, coresponding '"' is not found, processing fails.
+ - If a '%' character is encountered, the next character is expected
+ to be a single digit index into argv. If it is not a digit or
+ outside the bounds set by argc, processing fails. On success,
+ the argv value is inserted and processed as described above.
+ - A '%' character can be escaped by writing '%%' or, if inside
+ a double quite string, by writing \%.
+ - An attempt to use such an indexed argument inside an argument
+ expansion, results in failure.
+ - If the resulting line is empty, processing is restarted.
+*/
+int rdline(rdline_t *t);
+
+/*
+ Remove double quotes ('"') from a string and substitute escape
+ sequences in between double quotes.
+*/
+int unescape(char *src);
+
+/*
+ Replace spaces in 'str' with null bytes. Tread strings (started and
+ terminated with double-quotes which can be escaped) as a single block.
+ Such strings are run through unescap(). All elements are tightly
+ packed together and the function returns the number of consecutive
+ argument strings that are now inside 'str'.
+
+ Returns a negative value if unescape() fails, a string is not
+ termianted or two such strings touch each other without a white
+ space in between.
+*/
+int pack_argv(char *str);
+
+#endif /* LIBCONFIG_H */