install: check file/directory permissions for Shaarli resources

Relates to #40
Relates to #372

Additions:
 - FileUtils: IOException
 - ApplicationUtils:
   - check if Shaarli resources are accessible with sufficient permissions
   - basic test coverage
 - index.php:
   - check access permissions and redirect to an error page if needed:
     - before running the first installation

Modifications:
 - LinkDB:
   - factorize datastore write code
   - check if the datastore
     (exists AND is writeable) OR (doesn't exist AND its parent dir is writable)
   - raise an IOException if needed

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

1 files changed, 19 insertions, 0 deletions

diff --git a/application/FileUtils.php b/application/FileUtils.php
new file mode 100644
index 00000000..6a12ef0e
--- /dev/null
+++ b/application/FileUtils.php
@@ -0,0 +1,19 @@
+<?php
+/**
+ * Exception class thrown when a filesystem access failure happens
+ */
+class IOException extends Exception
+{
+    private $path;
+
+    /**
+     * Construct a new IOException
+     *
+     * @param string $path path to the ressource that cannot be accessed
+     */
+    public function __construct($path)
+    {
+        $this->path = $path;
+        $this->message = 'Error accessing '.$this->path;
+    }
+}