Add simple parser for UNIX configuration files.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

lfile.c

@@ -0,0 +1,220 @@
+/* Parse UNIX /etc configuration files like /etc/protocols and /etc/services
+ *
+ * Copyright (c) 2015  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <errno.h>
+#include <stdio.h>		/* FILE */
+#include <stdlib.h>		/* atoi() */
+#include <string.h>		/* strlen(), strncmp(), strtok_r() */
+#include <sys/param.h>		/* MAX() */
+
+typedef struct {
+	FILE *fp;
+	char buf[256];
+	char *sep, *save;
+} lfile_t;
+
+/**
+ * lfopen - Open file and return parsing context
+ * @file: File to parse
+ * @sep:  Separator(s) to use in lftok()
+ *
+ * Returns:
+ * Pointer to a &lftile_t parser context, or %NULL on error.
+ */
+lfile_t *lfopen(char *file, char *sep)
+{
+	lfile_t *lf;
+
+	if (!file || !sep) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	/* Use calloc for clearing buf on behalf of lftok() */
+	lf = calloc(sizeof(*lf), sizeof(char));
+	if (lf) {
+		lf->fp  = fopen(file, "r");
+		lf->sep = sep;
+
+		if (!lf->fp) {
+			free(lf);
+			return NULL;
+		}
+	}
+
+	return lf;
+}
+
+/**
+ * lfclose - Close a parser context
+ * @lf: Pointer to &lfile_t context from lfopen()
+ */
+void lfclose(lfile_t *lf)
+{
+	if (!lf)
+		return;
+
+	if (lf->fp)
+		fclose(lf->fp);
+	free(lf);
+}
+
+/**
+ * lftok - Get next token in file
+ * @lf: Pointer to &lfile_t context from lfopen()
+ *
+ * Returns:
+ * Next token, read from file previously opened with lfopen(),
+ * or %NULL if EOF.
+ */
+char *lftok(lfile_t *lf)
+{
+	char *token;
+
+	if (!lf || !lf->fp || !lf->sep) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	token = strtok_r(NULL, lf->sep, &lf->save);
+	if (!token) {
+		while (fgets(lf->buf, sizeof(lf->buf), lf->fp)) {
+			if (lf->buf[0] == '#')
+				continue;
+
+			token = strtok_r(lf->buf, lf->sep, &lf->save);
+			if (!token)
+				continue;
+			
+			return token;
+		}
+
+		errno = ENOENT;
+		return NULL;
+	}
+
+	return token;
+}
+
+/**
+ * lfgetkey - Find key in file
+ * @lf:  Pointer to &lfile_t context from lfopen()
+ * @key: Key to look for
+ *
+ * Locate @key from the current position in the file parser context
+ * returned from lfopen().  Please note, the search for @key does not
+ * start from the beginning of the file, it searches from the current
+ * position.  To restart search from the beginning use rewind() on the
+ * lf->fp.
+ *
+ * Returns:
+ * The value to @key, or %NULL if not found.
+ */
+char *lfgetkey(lfile_t *lf, char *key)
+{
+	char *token;
+
+	while ((token = lftok(lf))) {
+		if (token[0] == '#')
+			continue;
+
+		if (!strncmp(token, key, MAX(strlen(token), strlen(key))))
+			return lftok(lf);
+	}
+
+	return NULL;
+}
+
+/**
+ * lfgetint - Same as lfgetkey() but returns an integer
+ * @lf:  Pointer to &lfile_t context from lfopen()
+ * @key: Key to look for
+ *
+ * This function is the same as lfgetkey() but returns the positive
+ * integer value for the matching @key, if found.
+ *
+ * Returns:
+ * The positive integer value for @key, or -1 if not found.
+ */
+int lfgetint(lfile_t *lf, char *key)
+{
+	char *token = lfgetkey(lf, key);
+
+	if (token)
+		return atoi(token);
+
+	return -1;
+}
+
+/**
+ * fgetint - Find the integer value for key in a file
+ * @file: File to search for @key
+ * @sep:  Separator for tokens in @file
+ * @key:  Key to look for in @file
+ *
+ * This is a convenience wrapper for lfopen(), lfgetint(), and
+ * lfclose().
+ *
+ * Returns:
+ * The positive integer value for @key, or -1 if not found.
+ */
+int fgetint(char *file, char *sep, char *key)
+{
+	int val = -1;
+	lfile_t *lf;
+
+	lf = lfopen(file, sep);
+	if (lf) {
+		val = lfgetint(lf, key);
+		lfclose(lf);
+	}
+
+	return val;
+}
+
+#ifdef UNITTEST
+int main(void)
+{
+	int val;
+	lfile_t lf;
+
+	val = fgetint("/etc/protocols", " \n\t", "udp");
+	if (val == -1) {
+		perror("Failed locating 'udp' protocol");
+		return 1;
+	}
+	printf("udp has proto %d\n", val);
+
+	val = fgetint("/etc/services", " /\n\t", "ftp");
+	if (val == -1) {
+		perror("Failed locating 'ftp' service");
+		return 1;
+	}
+	printf("ftp is inet port %d\n", val);
+
+	return 0;
+}
+#endif
+
+/**
+ * Local Variables:
+ *  compile-command: "make V=1 -f lfile.mk"
+ *  version-control: t
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */