From bf63f78b6698f33ed3acbd4aed8822a35688c1ba Mon Sep 17 00:00:00 2001
From: David Oberhollenzer <david.oberhollenzer@tele2.at>
Date: Wed, 23 May 2018 22:26:17 +0200
Subject: Split configuration parser and utility library

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
---
 lib/include/libcfg.h | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 98 insertions(+)
 create mode 100644 lib/include/libcfg.h

(limited to 'lib/include/libcfg.h')

diff --git a/lib/include/libcfg.h b/lib/include/libcfg.h
new file mode 100644
index 0000000..5724bdc
--- /dev/null
+++ b/lib/include/libcfg.h
@@ -0,0 +1,98 @@
+/* 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 */
-- 
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