1 /* 2 * Copyright (C) 2015 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #define LOG_TAG "BitUtils" 18 //#define LOG_NDEBUG 0 19 20 #include "BitUtils.h" 21 22 #include <utils/Log.h> 23 24 // Enables debug output for hasKeyInRange 25 #define DEBUG_KEY_RANGE 0 26 27 namespace android { 28 29 #if DEBUG_KEY_RANGE 30 static const char* bitstrings[16] = { 31 "0000", "0001", "0010", "0011", 32 "0100", "0101", "0110", "0111", 33 "1000", "1001", "1010", "1011", 34 "1100", "1101", "1110", "1111", 35 }; 36 #endif 37 38 bool testBitInRange(const uint8_t arr[], size_t start, size_t end) { 39 #if DEBUG_KEY_RANGE 40 ALOGD("testBitInRange(%d, %d)", start, end); 41 #endif 42 // Invalid range! This is nonsense; just say no. 43 if (end <= start) return false; 44 45 // Find byte array indices. The end is not included in the range, nor is 46 // endIndex. Round up for endIndex. 47 size_t startIndex = start / 8; 48 size_t endIndex = (end + 7) / 8; 49 #if DEBUG_KEY_RANGE 50 ALOGD("startIndex=%d, endIndex=%d", startIndex, endIndex); 51 #endif 52 for (size_t i = startIndex; i < endIndex; ++i) { 53 uint8_t bits = arr[i]; 54 uint8_t mask = 0xff; 55 #if DEBUG_KEY_RANGE 56 ALOGD("block %04d: %s%s", i, bitstrings[bits >> 4], bitstrings[bits & 0x0f]); 57 #endif 58 if (bits) { 59 // Mask off bits before our start bit 60 if (i == startIndex) { 61 mask &= 0xff << (start % 8); 62 } 63 // Mask off bits after our end bit 64 if (i == endIndex - 1 && (end % 8)) { 65 mask &= 0xff >> (8 - (end % 8)); 66 } 67 #if DEBUG_KEY_RANGE 68 ALOGD("mask: %s%s", bitstrings[mask >> 4], bitstrings[mask & 0x0f]); 69 #endif 70 // Test the index against the mask 71 if (bits & mask) return true; 72 } 73 } 74 return false; 75 } 76 } // namespace android 77
