Move icon cache to a separate file; protect cache with file locks

src/util/cache.c

@@ -0,0 +1,156 @@
+/**************************************************************************
+*
+* Tint2 : cache
+*
+* Copyright (C) 2016 @o9000
+*
+* This program is free software; you can redistribute it and/or
+* modify it under the terms of the GNU General Public License version 2
+* as published by the Free Software Foundation.
+*
+* 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, write to the Free Software
+* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+**************************************************************************/
+
+#include "cache.h"
+
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "common.h"
+
+void init_cache(Cache *cache)
+{
+	if (cache->_table)
+		free_cache(cache);
+	cache->_table = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);
+	cache->dirty = FALSE;
+	cache->loaded = FALSE;
+}
+
+void free_cache(Cache *cache)
+{
+	if (cache->_table)
+		g_hash_table_destroy(cache->_table);
+	cache->_table = NULL;
+	cache->dirty = FALSE;
+	cache->loaded = FALSE;
+}
+
+void load_cache(Cache *cache, const gchar *cache_path)
+{
+	init_cache(cache);
+
+	int fd = open(cache_path, O_RDONLY);
+	if (fd == -1)
+		return;
+	flock(fd, LOCK_SH);
+
+	FILE *f = fopen(cache_path, "rt");
+	if (!f)
+		goto unlock;
+
+	char *line = NULL;
+	size_t line_size;
+
+	while (getline(&line, &line_size, f) >= 0) {
+		char *key, *value;
+
+		size_t line_len = strlen(line);
+		gboolean has_newline = FALSE;
+		if (line_len >= 1) {
+			if (line[line_len - 1] == '\n') {
+				line[line_len - 1] = '\0';
+				line_len--;
+				has_newline = TRUE;
+			}
+		}
+		if (!has_newline)
+			break;
+
+		if (line_len == 0)
+			continue;
+
+		if (parse_line(line, &key, &value)) {
+			g_hash_table_insert(cache->_table, g_strdup(key), g_strdup(value));
+		}
+	}
+	free(line);
+	fclose(f);
+
+	cache->loaded = TRUE;
+
+unlock:
+	flock(fd, LOCK_UN);
+	close(fd);
+}
+
+void write_cache_line(gpointer key, gpointer value, gpointer user_data)
+{
+	gchar *k = key;
+	gchar *v = value;
+	FILE *f = user_data;
+
+	fprintf(f, "%s=%s\n", k, v);
+}
+
+void save_cache(Cache *cache, const gchar *cache_path)
+{
+	int fd = open(cache_path, O_RDONLY | O_CREAT);
+	if (fd == -1)
+		return;
+	flock(fd, LOCK_EX);
+
+	FILE *f = fopen(cache_path, "w");
+	if (!f) {
+		gchar *dir_path = g_path_get_dirname(cache_path);
+		g_mkdir_with_parents(dir_path, 0700);
+		g_free(dir_path);
+		f = fopen(cache_path, "w");
+		if (!f) {
+			fprintf(stderr, RED "Could not save icon theme cache!" RESET "\n");
+			goto unlock;
+		}
+	}
+	g_hash_table_foreach(cache->_table, write_cache_line, f);
+	fclose(f);
+	cache->dirty = FALSE;
+
+unlock:
+	flock(fd, LOCK_UN);
+	close(fd);
+}
+
+const gchar *get_from_cache(Cache *cache, const gchar *key)
+{
+	if (!cache->_table)
+		return NULL;
+	return g_hash_table_lookup(cache->_table, key);
+}
+
+void add_to_cache(Cache *cache, const gchar *key, const gchar *value)
+{
+	if (!cache->_table)
+		init_cache(cache);
+
+	if (!key || !value)
+		return;
+
+	gchar *old_value = g_hash_table_lookup(cache->_table, key);
+	if (old_value && g_str_equal(old_value, value))
+		return;
+
+	g_hash_table_insert(cache->_table, g_strdup(key), g_strdup(value));
+	cache->dirty = TRUE;
+}

src/util/cache.h

@@ -0,0 +1,39 @@
+#ifndef CACHE_H
+#define CACHE_H
+
+#include <glib.h>
+
+// A cache with string keys and values, backed by a file.
+// The strings must not be NULL and are stripped of any whitespace at start and end.
+typedef struct Cache {
+	gboolean dirty;
+	gboolean loaded;
+	GHashTable *_table;
+} Cache;
+
+// Initializes the cache. You can also call load_cache directly if you set the memory contents to zero first.
+void init_cache(Cache *cache);
+
+// Clears the cache contents and releases all memory, but not the object.
+// You can use init_cache or load_cache afterwards.
+void free_cache(Cache *cache);
+
+// Clears the cache contents and loads new contents from a file.
+// Sets the loaded flag to TRUE.
+void load_cache(Cache *cache, const gchar *cache_path);
+
+// Saves the cache contents to a file.
+// Clears the dirty flag.
+void save_cache(Cache *cache, const gchar *cache_path);
+
+// Returns a pointer to the value in the cache, or NULL if not found.
+// Do not free the returned value!
+const gchar *get_from_cache(Cache *cache, const gchar *key);
+
+// Adds a key-value pair to the cache. NULL keys or values are not allowed.
+// If the key already exists, the old value is and replaced with the new value.
+// Does not take ownership of the pointers (neither key, nor value); instead it makes copies.
+// Sets the dirty flag to TRUE.
+void add_to_cache(Cache *cache, const gchar *key, const gchar *value);
+
+#endif