Rewritten and extended the whole code for the instructions definitions compiler.

git-svn-id: svn://svn.gna.org/svn/chrysalide/trunk@419 abbe820e-26c8-41b2-8c08-b7b2b41f8b0a

1 files changed, 67 insertions, 0 deletions

diff --git a/src/common/asm.c b/src/common/asm.c
new file mode 100644
index 0000000..597013a
--- /dev/null
+++ b/src/common/asm.c
@@ -0,0 +1,67 @@
+
+/* Chrysalide - Outil d'analyse de fichiers binaires
+ * asm.c - implémentations génériques de fonctionnalités spécifiques
+ *
+ * Copyright (C) 2014 Cyrille Bagard
+ *
+ *  This file is part of Chrysalide.
+ *
+ *  OpenIDA 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.
+ *
+ *  OpenIDA 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 Foobar.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+#include "asm.h"
+
+
+
+/******************************************************************************
+*                                                                             *
+*  Paramètres  : v = valeur quelconque sur 32 bits.                           *
+*                p = position du premier bit à 1 (poids fort). [OUT]          *
+*                                                                             *
+*  Description : Détermine l'indice du premier bit à 1, côté gauche.          *
+*                                                                             *
+*  Retour      : true si le nombre est différent de zéro, false sinon.        *
+*                                                                             *
+*  Remarques   : -                                                            *
+*                                                                             *
+******************************************************************************/
+
+bool msb_32(uint32_t v, unsigned int *p)
+{
+    static const unsigned int bval[] = { 0, 1, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4 };
+
+    /* S'il n'y a aucun bit à 1... */
+    if (v == 0) return false;
+
+    /**
+     * Il existe de nombreuses méthodes pour obtenir le résultat attendu
+     * sans recourir à des extensions GCC ou à des instructions d'assembleur :
+     *
+     *  - http://stackoverflow.com/questions/2589096/find-most-significant-bit-left-most-that-is-set-in-a-bit-array
+     *  - http://graphics.stanford.edu/~seander/bithacks.html#IntegerLogObvious
+     *
+     */
+
+    *p = 0;
+
+    if (v & 0xffff0000) { *p += 16 / 1; v >>= 16 / 1; }
+    if (v & 0x0000ff00) { *p += 16 / 2; v >>= 16 / 2; }
+    if (v & 0x000000f0) { *p += 16 / 4; v >>= 16 / 4; }
+
+    *p += bval[v];
+
+    return true;
+
+}