//
//  Utils.m
//  ActsBluetoothOTA
//
//  Created by inidhu on 2019/5/22.
//  Copyright © 2019 Actions. All rights reserved.
//

#import "Utils.h"

@implementation Utils


+ (UInt32)bytes2UInt32:(Byte*)bytes index:(NSInteger)index {
    return (((bytes[index + 3] & 0xFF) << 24) + ((bytes[index + 2] & 0xFF) << 16)) + ((bytes[index + 1] & 0xFF) << 8) + (bytes[index] & 0xFF);
}

+ (UInt16)bytes2Short:(Byte*)bytes index:(NSInteger)index {
    return ((bytes[index + 1] & 0xFF) << 8) + (bytes[index] & 0xFF);
}

/* 计算0比特位的个数 */
+ (NSInteger)countZeroBit:(NSData *) bitmap {
    NSInteger count = 0;
    
    Byte *bytes = (Byte *)[bitmap bytes];
    NSInteger length = bitmap.length;
    
    for (int i = 0; i < length; i++ ) {
        Byte x = bytes[i];
        while ((x + 1) != 0) {
            x |= (x + 1);
            count++;
        }
    }
    
    return count;
}

/* 从bitmap获取相应0bit位的索引 */
+ (NSArray *)getZeroBitIndexMap:(NSData *) bitmap groupNum:(int) groupNum{
    NSMutableArray *indexMap = [[NSMutableArray alloc] init];
    
    NSInteger count = 0;
    NSInteger index = 0;
    Byte *bytes = (Byte *)[bitmap bytes];
    for (NSInteger i = 0; i < bitmap.length; i++) {
        Byte b = bytes[i];
        for (NSInteger j = 0; j < groupNum; j++) {
            int offset = (index % groupNum);
            
            if ((b & (0x1 << offset)) == 0x0) {
                [indexMap addObject:[NSNumber numberWithInteger:index]];
                count++;
            }
            
            index++;
        }
    }
    
    return indexMap;
}

+ (int32_t)crc32:(NSData *)data {
    uint32_t *table = malloc(sizeof(uint32_t) * 256);
    uint32_t crc = 0xffffffff;
    uint8_t *bytes = (uint8_t *)[data bytes];
    
    for (uint32_t i=0; i<256; i++) {
        table[i] = i;
        for (int j=0; j<8; j++) {
            if (table[i] & 1) {
                table[i] = (table[i] >>= 1) ^ 0xedb88320;
            } else {
                table[i] >>= 1;
            }
        }
    }
    
    for (int i=0; i<data.length; i++) {
        crc = (crc >> 8) ^ table[crc & 0xff ^ bytes[i]];
    }
    crc ^= 0xffffffff;
    
    free(table);
    return crc;
}

@end