From cf3a34cbef269506b36331a14c1de352926e08de Mon Sep 17 00:00:00 2001
From: martin <martin@c6295689-39f2-0310-b995-f0e70906c6a9>
Date: Mon, 23 May 2011 17:32:43 +0000
Subject: [PATCH] OpenPGP: re-factor pgp_select_file()

* remove unnecessary copy operations with a temporary path object,
  instead increase the start index.
* addd comments

Signed-off-by: Peter Marschall <peter@adpm.de>

git-svn-id: https://www.opensc-project.org/svnp/opensc/trunk@5489 c6295689-39f2-0310-b995-f0e70906c6a9
---
 src/libopensc/card-openpgp.c | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/src/libopensc/card-openpgp.c b/src/libopensc/card-openpgp.c
index 55554387..ba1f6c29 100644
--- a/src/libopensc/card-openpgp.c
+++ b/src/libopensc/card-openpgp.c
@@ -460,14 +460,11 @@ pgp_select_file(sc_card_t *card, const sc_path_t *path, sc_file_t **ret)
 {
 	struct pgp_priv_data *priv = DRVDATA(card);
 	struct blob	*blob;
-	sc_path_t	path_copy;
+	unsigned int	path_start;
 	unsigned int	n;
-	int		r;
 
 	LOG_FUNC_CALLED(card->ctx);
 
-	memset(&path_copy, 0, sizeof(path_copy));
-
 	if (path->type == SC_PATH_TYPE_DF_NAME)
 		LOG_FUNC_RETURN(card->ctx, iso_ops->select_file(card, path, ret));
 
@@ -479,24 +476,23 @@ pgp_select_file(sc_card_t *card, const sc_path_t *path, sc_file_t **ret)
 		LOG_TEST_RET(card->ctx, SC_ERROR_INVALID_ARGUMENTS,
 				"invalid path length");
 
-	if (!memcmp(path->value, "\x3f\x00", 2)) {
-		memcpy(path_copy.value, path->value + 2, path->len - 2);
-		path_copy.len = path->len - 2;
-		path = &path_copy;
-	}
+	/* ignore explicitely mentioned MF at the path's beginning */
+	path_start = (memcmp(path->value, "\x3f\x00", 2) == 0) ? 2 : 0;
 
+	/* starting with the MF ... */
 	blob = priv->mf;
-	for (n = 0; n < path->len; n += 2) {
-		r = pgp_get_blob(card, blob,
-				(path->value[n] << 8) | path->value[n+1],
-				&blob);
-		if (r < 0) {
+	/* ... recurse through the tree following the path */
+	for (n = path_start; n < path->len; n += 2) {
+		unsigned int	id = bebytes2ushort(path->value + n);
+		int		r = pgp_get_blob(card, blob, id, &blob);
+
+		if (r < 0) {	/* failure */
 			priv->current = NULL;
 			LOG_FUNC_RETURN(card->ctx, r);
 		}
 	}
 
-	/* select file = set "current" pointer to blob found */
+	/* success: select file = set "current" pointer to blob found */
 	priv->current = blob;
 
 	if (ret)