1 files changed, 147 insertions, 0 deletions
diff --git a/xdg.c b/xdg.c
new file mode 100644
index 0000000..ded02af
--- /dev/null
+++ b/xdg.c
@@ -0,0 +1,147 @@
+/* Copyright (C) 2019, 2020  C. McEnroe <june@causal.agency>
+ *
+ * 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/>.
+ *
+ * Additional permission under GNU GPL version 3 section 7:
+ *
+ * If you modify this Program, or any covered work, by linking or
+ * combining it with OpenSSL (or a modified version of that library),
+ * containing parts covered by the terms of the OpenSSL License and the
+ * original SSLeay license, the licensors of this Program grant you
+ * additional permission to convey the resulting work. Corresponding
+ * Source for a non-source form of such a combination shall include the
+ * source code for the parts of OpenSSL used as well as that of the
+ * covered work.
+ */
+
+#include <err.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+
+#define SUBDIR "litterbox"
+
+struct Base {
+	const char *envHome;
+	const char *envDirs;
+	const char *defHome;
+	const char *defDirs;
+};
+
+static const struct Base Config = {
+	.envHome = "XDG_CONFIG_HOME",
+	.envDirs = "XDG_CONFIG_DIRS",
+	.defHome = ".config",
+	.defDirs = "/etc/xdg",
+};
+
+static const struct Base Data = {
+	.envHome = "XDG_DATA_HOME",
+	.envDirs = "XDG_DATA_DIRS",
+	.defHome = ".local/share",
+	.defDirs = "/usr/local/share:/usr/share",
+};
+
+static const char *basePath(
+	struct Base base,
+	char *buf, size_t cap, const char **dirs, const char *path
+) {
+	if (*dirs) {
+		if (!**dirs) return NULL;
+		size_t len = strcspn(*dirs, ":");
+		snprintf(buf, cap, "%.*s/" SUBDIR "/%s", (int)len, *dirs, path);
+		*dirs += len;
+		if (**dirs) *dirs += 1;
+		return buf;
+	}
+
+	if (path[0] == '/' || path[0] == '.') {
+		*dirs = "";
+		return path;
+	}
+
+	*dirs = getenv(base.envDirs);
+	if (!*dirs) *dirs = base.defDirs;
+
+	const char *home = getenv("HOME");
+	const char *baseHome = getenv(base.envHome);
+	if (baseHome) {
+		snprintf(buf, cap, "%s/" SUBDIR "/%s", baseHome, path);
+	} else {
+		if (!home) return NULL;
+		snprintf(buf, cap, "%s/%s/" SUBDIR "/%s", home, base.defHome, path);
+	}
+	return buf;
+}
+
+const char *
+configPath(char *buf, size_t cap, const char **dirs, const char *path) {
+	return basePath(Config, buf, cap, dirs, path);
+}
+
+const char *
+dataPath(char *buf, size_t cap, const char **dirs, const char *path) {
+	return basePath(Data, buf, cap, dirs, path);
+}
+
+FILE *configOpen(const char *path, const char *mode) {
+	const char *abs;
+	char buf[PATH_MAX];
+	const char *dirs = NULL;
+	while (NULL != (abs = configPath(buf, sizeof(buf), &dirs, path))) {
+		FILE *file = fopen(abs, mode);
+		if (file) return file;
+		if (errno != ENOENT) warn("%s", abs);
+	}
+	FILE *file = fopen(path, mode);
+	if (!file) warn("%s", path);
+	return file;
+}
+
+void dataMkdir(const char *path) {
+	char buf[PATH_MAX];
+	const char *dirs = NULL;
+	const char *abs = dataPath(buf, sizeof(buf), &dirs, path);
+	int error = mkdir(abs, S_IRWXU);
+	if (error && errno != EEXIST) warn("%s", abs);
+}
+
+FILE *dataOpen(const char *path, const char *mode) {
+	const char *abs;
+	char buf[PATH_MAX];
+	const char *dirs = NULL;
+	while (NULL != (abs = dataPath(buf, sizeof(buf), &dirs, path))) {
+		FILE *file = fopen(abs, mode);
+		if (file) return file;
+		if (errno != ENOENT) warn("%s", abs);
+	}
+
+	if (mode[0] != 'r') {
+		dirs = NULL;
+		abs = dataPath(buf, sizeof(buf), &dirs, path);
+		if (!abs) return NULL;
+
+		dataMkdir("");
+		FILE *file = fopen(abs, mode);
+		if (!file) warn("%s", abs);
+		return file;
+	}
+
+	FILE *file = fopen(path, mode);
+	if (!file) warn("%s", path);
+	return file;
+}