计算 MD5值

//
//  MD5Value.h
//  iOSEdu
//
//  Created by littest on 16/2/26.
//  Copyright © 2016年 littest. All rights reserved.
//

#import <Foundation/Foundation.h>
#import <CommonCrypto/CommonDigest.h>
#define FileHashDefaultChunkSizeForReadingData 1024*8 // 8K
@interface MD5Value : NSObject
// 计算 NSData 的 MD5 值

+(NSString*)getMD5WithData:(NSData*)data;

// 计算字符串的 MD5 值，

+(NSString*)getmd5WithString:(NSString*)string;

// 计算大文件的 MD5 值

+(NSString*)getFileMD5WithPath:(NSString*)path;
@end

//
//  MD5Value.m
//  iOSEdu
//
//  Created by littest on 16/2/26.
//  Copyright © 2016年 littest. All rights reserved.
//

#import "MD5Value.h"

@implementation MD5Value
+ (NSString*)getmd5WithString:(NSString *)string

{

    const char* original_str=[string UTF8String];

    unsigned char digist[CC_MD5_DIGEST_LENGTH]; //CC_MD5_DIGEST_LENGTH = 16

    CC_MD5(original_str, strlen(original_str), digist);

    NSMutableString* outPutStr = [NSMutableString stringWithCapacity:10];

    for(int  i =0; i<CC_MD5_DIGEST_LENGTH;i++){

        [outPutStr appendFormat:@"%02x", digist[i]];// 小写 x 表示输出的是小写 MD5 ，大写 X 表示输出的是大写 MD5

    }

    return [outPutStr lowercaseString];

}

+ (NSString*)getMD5WithData:(NSData *)data{

    const char* original_str = (const char *)[data bytes];

    unsigned char digist[CC_MD5_DIGEST_LENGTH]; //CC_MD5_DIGEST_LENGTH = 16

    CC_MD5(original_str, strlen(original_str), digist);

    NSMutableString* outPutStr = [NSMutableString stringWithCapacity:10];

    for(int  i =0; i<CC_MD5_DIGEST_LENGTH;i++){

        [outPutStr appendFormat:@"%02x",digist[i]];// 小写 x 表示输出的是小写 MD5 ，大写 X 表示输出的是大写 MD5

    }

    // 也可以定义一个字节数组来接收计算得到的 MD5 值

    //    Byte byte[16];

    //    CC_MD5(original_str, strlen(original_str), byte);

    //    NSMutableString* outPutStr = [NSMutableString stringWithCapacity:10];

    //    for(int  i = 0; i<CC_MD5_DIGEST_LENGTH;i++){

    //        [outPutStr appendFormat:@"%02x",byte[i]];

    //    }

    //    [temp release];

    return [outPutStr lowercaseString];

}

+(NSString*)getFileMD5WithPath:(NSString*)path

{

    return (__bridge  NSString *)FileMD5HashCreateWithPath((__bridge CFStringRef)path,FileHashDefaultChunkSizeForReadingData);

}

CFStringRef FileMD5HashCreateWithPath(CFStringRef filePath,

                                      size_t chunkSizeForReadingData) {

    // Declare needed variables

    CFStringRef result = NULL;

    CFReadStreamRef readStream = NULL;

    // Get the file URL

    CFURLRef fileURL =

    CFURLCreateWithFileSystemPath(kCFAllocatorDefault,

                                  (CFStringRef)filePath,

                                  kCFURLPOSIXPathStyle,

                                  (Boolean)false);

    CC_MD5_CTX hashObject;

    bool hasMoreData = true;

    bool didSucceed;

    if (!fileURL) goto done;

    // Create and open the read stream

    readStream = CFReadStreamCreateWithFile(kCFAllocatorDefault,

                                            (CFURLRef)fileURL);

    if (!readStream) goto done;

    didSucceed = (bool)CFReadStreamOpen(readStream);

    if (!didSucceed) goto done;

    // Initialize the hash object

    CC_MD5_Init(&hashObject);

    // Make sure chunkSizeForReadingData is valid

    if (!chunkSizeForReadingData) {

        chunkSizeForReadingData = FileHashDefaultChunkSizeForReadingData;

    }

    // Feed the data to the hash object

    while (hasMoreData) {

        uint8_t buffer[chunkSizeForReadingData];

        CFIndex readBytesCount = CFReadStreamRead(readStream,

                                                  (UInt8 *)buffer,

                                                  (CFIndex)sizeof(buffer));

        if (readBytesCount == -1)break;

        if (readBytesCount == 0) {

            hasMoreData =false;

            continue;

        }

        CC_MD5_Update(&hashObject,(const void *)buffer,(CC_LONG)readBytesCount);

    }

    // Check if the read operation succeeded

    didSucceed = !hasMoreData;

    // Compute the hash digest

    unsigned char digest[CC_MD5_DIGEST_LENGTH];

    CC_MD5_Final(digest, &hashObject);

    // Abort if the read operation failed

    if (!didSucceed) goto done;

    // Compute the string result

    char hash[2 *sizeof(digest) + 1];

    for (size_t i =0; i < sizeof(digest); ++i) {

        snprintf(hash + (2 * i),3, "%02x", (int)(digest[i]));

    }

    result = CFStringCreateWithCString(kCFAllocatorDefault,

                                       (const char *)hash,

                                       kCFStringEncodingUTF8);

done:

    if (readStream) {

        CFReadStreamClose(readStream);

        CFRelease(readStream);

    }

    if (fileURL) {

        CFRelease(fileURL);

    }

    return result;

}
@end