common_functions.c

00001 /*
00002  * Copyright (c) 2014-2015 ARM Limited. All rights reserved.
00003  * SPDX-License-Identifier: Apache-2.0
00004  * Licensed under the Apache License, Version 2.0 (the License); you may
00005  * not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  * http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an AS IS BASIS, WITHOUT
00012  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 /*
00018  * Most functions can be inlined, and definitions are in common_functions.h.
00019  * Define COMMON_FUNCTIONS_FN before including it to generate external definitions.
00020  */
00021 #define COMMON_FUNCTIONS_FN extern
00022 
00023 #include "common_functions.h"
00024 
00025 #include <string.h>
00026 
00027 /* Returns mask for <split_value> (0-8) most-significant bits of a byte */
00028 static inline uint8_t context_split_mask(uint_fast8_t split_value)
00029 {
00030     return (uint8_t) - (0x100u >> split_value);
00031 }
00032 
00033 bool bitsequal(const uint8_t *a, const uint8_t *b, uint_fast8_t bits)
00034 {
00035     uint_fast8_t bytes = bits / 8;
00036     bits %= 8;
00037 
00038     if (memcmp(a, b, bytes)) {
00039         return false;
00040     }
00041 
00042     if (bits) {
00043         uint_fast8_t split_bit = context_split_mask(bits);
00044         if ((a[bytes] & split_bit) != (b[bytes] & split_bit)) {
00045             return false;
00046         }
00047     }
00048 
00049     return true;
00050 }
00051 
00052 uint8_t *bitcopy(uint8_t *restrict dst, const uint8_t *restrict src, uint_fast8_t bits)
00053 {
00054     uint_fast8_t bytes = bits / 8;
00055     bits %= 8;
00056 
00057     if (bytes) {
00058         dst = (uint8_t *) memcpy(dst, src, bytes) + bytes;
00059         src += bytes;
00060     }
00061 
00062     if (bits) {
00063         uint_fast8_t split_bit = context_split_mask(bits);
00064         *dst = (*src & split_bit) | (*dst & ~ split_bit);
00065     }
00066 
00067     return dst;
00068 }
00069 
00070 uint8_t *bitcopy0(uint8_t *restrict dst, const uint8_t *restrict src, uint_fast8_t bits)
00071 {
00072     uint_fast8_t bytes = bits / 8;
00073     bits %= 8;
00074 
00075     if (bytes) {
00076         dst = (uint8_t *) memcpy(dst, src, bytes) + bytes;
00077         src += bytes;
00078     }
00079 
00080     if (bits) {
00081         uint_fast8_t split_bit = context_split_mask(bits);
00082         *dst = (*src & split_bit);
00083     }
00084 
00085     return dst;
00086 }