Add function to check if we have access to IsoFileSource contents.

src/fs_local.c

@@ -13,6 +13,9 @@
 #include "fsource.h"
 #include "error.h"
 
+/* for eaccess, define in unistd.h */
+#define __USE_GNU
+
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -141,6 +144,45 @@ int lfs_stat(IsoFileSource *src, struct stat *info)
     return ISO_SUCCESS;
 }
 
+static
+int lfs_access(IsoFileSource *src)
+{
+    _LocalFsFileSource *data;
+
+    if (src == NULL) {
+        return ISO_NULL_POINTER;
+    }
+    data = src->data;
+
+    if (eaccess(data->path, R_OK) != 0) {
+        int err;
+
+        /* error, choose an appropriate return code */
+        switch (errno) {
+        case EACCES:
+            err = ISO_FILE_ACCESS_DENIED;
+            break;
+        case ENOTDIR:
+        case ENAMETOOLONG:
+        case ELOOP:
+            err = ISO_FILE_BAD_PATH;
+            break;
+        case ENOENT:
+            err = ISO_FILE_DOESNT_EXIST;
+            break;
+        case EFAULT:
+        case ENOMEM:
+            err = ISO_MEM_ERROR;
+            break;
+        default:
+            err = ISO_FILE_ERROR;
+            break;
+        }
+        return err;
+    }
+    return ISO_SUCCESS;
+}
+
 static
 int lfs_open(IsoFileSource *src)
 {
@@ -394,6 +436,7 @@ IsoFileSourceIface lfs_class = {
     lfs_get_name,
     lfs_lstat,
     lfs_stat,
+    lfs_access,
     lfs_open,
     lfs_close,
     lfs_read,

src/fsource.h

@@ -119,6 +119,26 @@ typedef struct IsoFileSource_Iface
      */
     int (*stat)(IsoFileSource *src, struct stat *info);
 
+    /**
+     * Check if the process has access to read file contents. Note that this
+     * is not necessarily related with (l)stat functions. For example, in a
+     * filesystem implementation to deal with an ISO image, if the user has
+     * read access to the image it will be able to read all files inside it,
+     * despite of the particular permission of each file in the RR tree, that
+     * are what the above functions return.
+     * 
+     * @return
+     *     1 if process has read access, < 0 on error
+     *      Error codes:
+     *         ISO_FILE_ACCESS_DENIED
+     *         ISO_FILE_BAD_PATH
+     *         ISO_FILE_DOESNT_EXIST
+     *         ISO_MEM_ERROR
+     *         ISO_FILE_ERROR
+     *         ISO_NULL_POINTER
+     */
+    int (*access)(IsoFileSource *src);
+
     /**
      * Opens the source.
      * @return 1 on success, < 0 on error
@@ -263,6 +283,12 @@ int iso_file_source_lstat(IsoFileSource *src, struct stat *info)
     return src->class->lstat(src, info);
 }
 
+extern inline
+int iso_file_source_access(IsoFileSource *src)
+{
+    return src->class->access(src);
+}
+
 extern inline
 int iso_file_source_stat(IsoFileSource *src, struct stat *info)
 {