diff options
Diffstat (limited to 'src/common')
| -rwxr-xr-x | src/common/Makefile.am | 1 | ||||
| -rw-r--r-- | src/common/asm.c | 67 | ||||
| -rw-r--r-- | src/common/asm.h | 38 |
3 files changed, 106 insertions, 0 deletions
diff --git a/src/common/Makefile.am b/src/common/Makefile.am index 198de32..7615f43 100755 --- a/src/common/Makefile.am +++ b/src/common/Makefile.am @@ -2,6 +2,7 @@ lib_LTLIBRARIES = libcommon.la libcommon_la_SOURCES = \ + asm.h asm.c \ bconst.h \ cpp.h \ dllist.h dllist.c \ 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; + +} diff --git a/src/common/asm.h b/src/common/asm.h new file mode 100644 index 0000000..047d8db --- /dev/null +++ b/src/common/asm.h @@ -0,0 +1,38 @@ + +/* Chrysalide - Outil d'analyse de fichiers binaires + * asm.h - prototypes pour les 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/>. + */ + + +#ifndef _COMMON_ASM_H +#define _COMMON_ASM_H + + +#include <stdbool.h> +#include <stdint.h> + + + +/* Détermine l'indice du premier bit à 1, côté gauche. */ +bool msb_32(uint32_t, unsigned int *); + + + +#endif /* _COMMON_ASM_H */ |