NSMutableData的內存問題

Question

我已將我的項目轉換爲ARC。後來，我發現與我正在加載的PDF相關的內存泄漏。實際發生的情況是，當我回來時，一旦從導航控制器彈出PDF視圖，內存就無法正常釋放。然後我使用Instrument來查看哪些代碼行負責此內存泄漏。

在下面我已經解釋了發生了什麼。

首先我檢查我的pdf是否加密（它是加密的）。使用delegate.That方法：然後我解密使用StringEncryption類

StringEncryption *crypto = [[StringEncryption alloc]init]; 
self.stringEncryption = crypto; 
[self.stringEncryption setDelegate:self]; 
NSData *encryptedPDFData = [NSData dataWithContentsOfFile:pdfPath]; 
[crypto decryptUsingBGProcess:encryptedPDFData key:[key dataUsingEncoding:NSUTF8StringEncoding]]; 

decryptUsingBGProcess方法如下

@autoreleasepool {{ 
    CCOptions padding = kCCOptionPKCS7Padding; 
    NSMutableData *decryptedData =[self doCipher:plainText key:aSymmetricKey context:kCCDecrypt padding:&padding ]; 
    if(!decryptedData)NSLog(@"0001 , EVT,%@, %@,Decryption failed ",[[self class] description],NSStringFromSelector(_cmd)); 
    if(delegate && [delegate respondsToSelector:@selector(decryptionCompleted:)]){ 
     if([delegate isKindOfClass:[PDFAnnotationSampleViewController class]]) 
      [((PDFAnnotationSampleViewController*)delegate) performSelectorOnMainThread:@selector(decryptionCompleted:) withObject:decryptedData waitUntilDone:NO]; 
     else [delegate decryptionCompleted:decryptedData]; 
    } 
} 

docyper方法如下

- (NSMutableData *)doCipher:(NSData *)plainText key:(NSData *)aSymmetricKey 
      context:(CCOperation)encryptOrDecrypt padding:(CCOptions *)pkcs7 
{ 
    CCCryptorStatus ccStatus = kCCSuccess; 
    // Symmetric crypto reference. 
    CCCryptorRef thisEncipher = NULL; 
    // Cipher Text container. 
    NSMutableData * cipherOrPlainText = nil; 
    // Pointer to output buffer. 
    uint8_t * bufferPtr = NULL; 
    // Total size of the buffer. 
    size_t bufferPtrSize = 0; 
    // Remaining bytes to be performed on. 
    size_t remainingBytes = 0; 
    // Number of bytes moved to buffer. 
    size_t movedBytes = 0; 
    // Length of plainText buffer. 
    size_t plainTextBufferSize = 0; 
    // Placeholder for total written. 
    size_t totalBytesWritten = 0; 
    // A friendly helper pointer. 
    uint8_t * ptr; 

    // Initialization vector; dummy in this case 0's. 
    uint8_t iv[kChosenCipherBlockSize]; 
    memset((void *) iv, 0x0, (size_t) sizeof(iv)); 

    //NSLog(@"doCipher: plaintext: %@", plainText); 
    NSLog(@"doCipher: key length: %d", [aSymmetricKey length]); 

    plainTextBufferSize = [plainText length]; 

    //LOGGING_FACILITY(plainTextBufferSize > 0, @"Empty plaintext passed in."); 

    NSLog(@"pkcs7: %d", *pkcs7); 
    // We don't want to toss padding on if we don't need to 
    if(encryptOrDecrypt == kCCEncrypt) { 
     if(*pkcs7 != kCCOptionECBMode) { 
      if((plainTextBufferSize % kChosenCipherBlockSize) == 0) { 
       *pkcs7 = 0x0000; 
      } else { 
       *pkcs7 = kCCOptionPKCS7Padding; 
      } 
     } 
    } else if(encryptOrDecrypt != kCCDecrypt) { 
     NSLog(@"Invalid CCOperation parameter [%d] for cipher context.", *pkcs7); 
    } 

    // Create and Initialize the crypto reference. 
    ccStatus = CCCryptorCreate(encryptOrDecrypt, 
           kCCAlgorithmAES128, 
           *pkcs7, 
           (const void *)[aSymmetricKey bytes], 
           kChosenCipherKeySize, 
           (const void *)iv, 
           &thisEncipher 
           ); 

    //LOGGING_FACILITY1(ccStatus == kCCSuccess, @"Problem creating the context, ccStatus == %d.", ccStatus); 

    // Calculate byte block alignment for all calls through to and including final. 
    bufferPtrSize = CCCryptorGetOutputLength(thisEncipher, plainTextBufferSize, true); 

    // Allocate buffer. 
    bufferPtr = malloc(bufferPtrSize * sizeof(uint8_t)); 

    // Zero out buffer. 
    memset((void *)bufferPtr, 0x0, bufferPtrSize); 

    // Initialize some necessary book keeping. 

    ptr = bufferPtr; 

    // Set up initial size. 
    remainingBytes = bufferPtrSize; 

    // Actually perform the encryption or decryption. 
    ccStatus = CCCryptorUpdate(thisEncipher, 
           (const void *) [plainText bytes], 
           plainTextBufferSize, 
           ptr, 
           remainingBytes, 
           &movedBytes 
           ); 

    //LOGGING_FACILITY1(ccStatus == kCCSuccess, @"Problem with CCCryptorUpdate, ccStatus == %d.", ccStatus); 

    // Handle book keeping. 
    ptr += movedBytes; 
    remainingBytes -= movedBytes; 
    totalBytesWritten += movedBytes; 

    // Finalize everything to the output buffer. 
    ccStatus = CCCryptorFinal(thisEncipher, 
           ptr, 
           remainingBytes, 
           &movedBytes 
          ); 

    totalBytesWritten += movedBytes; 

    if(thisEncipher) { 
     (void) CCCryptorRelease(thisEncipher); 
     thisEncipher = NULL; 
    } 

    if (ccStatus == kCCSuccess) 
     cipherOrPlainText = [NSData dataWithBytes:(const void *)bufferPtr length:(NSUInteger)totalBytesWritten]; 
    else 
     cipherOrPlainText = nil; 

    if(bufferPtr) free(bufferPtr); 

    return cipherOrPlainText; 

} 


// this added by David 
- (NSData*) md5data: (NSString *) str 
{ 
    const char *cStr = [str UTF8String]; 
    unsigned char result[CC_MD5_DIGEST_LENGTH]; 
    CC_MD5(cStr, strlen(cStr), result); 
    NSString* temp = [NSString stringWithFormat: 
      @"02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X%02X", 
      result[0], result[1], result[2], result[3], result[4], 
      result[5], result[6], result[7], 
      result[8], result[9], result[10], result[11], result[12], 
      result[13], result[14], result[15] 
      ]; 
    return [NSData dataWithBytes:[temp UTF8String] length:[temp length]]; 

} 

decrpting它之後調用decryptionCompleted方法如下

-(void)decryptionCompleted:(NSData*)decryptedData{ 
    /* PDF has decrypted successfully */ 
    NSLog(@"0403 , EVT,%@, %@,Paper is Decrypted successfuly ",[[self class] description],NSStringFromSelector(_cmd)); 
    NSMutableData *decryptedMData = [[NSMutableData alloc] initWithData:decryptedData]; 
    APPDFDocument *pdfFile = [[APPDFDocument alloc] initWithPDFData:decryptedMData information:self.pdfInfo]; 
    self.passwordEncrypted = [pdfFile isEncrypted]; 
    NSLog(@"0404 , EVT,%@, %@,Paper is Decrypted paper has password encryption = %@ ",[[self class] description],NSStringFromSelector(_cmd),self.passwordEncrypted?@"YES":@"NO"); 
    [self loadPDF:pdfFile]; 
} 

這裏是顯示內存泄漏發生的地方。請參閱Profiler的以下屏幕截圖。

（這裏我有放大的問題，區） 一些能幫助我找到了什麼問題。否則請指導我如何做進一步的分析

Answer 1

嘗試這樣的：

NSMutableData *decryptedMData = [decryptedData mutableCopy]; 

而且也把這個方法裏面的自動釋放塊太像這樣：

-(void)decryptionCompleted:(NSData*)decryptedData{ 
@autoreleasepool{ 
     /* PDF has decrypted successfully */ 
     NSLog(@"0403 , EVT,%@, %@,Paper is Decrypted successfuly ",[[self class] description],NSStringFromSelector(_cmd)); 
     NSMutableData *decryptedMData = [[NSMutableData alloc] initWithData:decryptedData]; 
     APPDFDocument *pdfFile = [[APPDFDocument alloc] initWithPDFData:decryptedMData information:self.pdfInfo]; 
     self.passwordEncrypted = [pdfFile isEncrypted]; 
     NSLog(@"0404 , EVT,%@, %@,Paper is Decrypted paper has password encryption = %@ ",[[self class] description],NSStringFromSelector(_cmd),self.passwordEncrypted?@"YES":@"NO"); 
     [self loadPDF:pdfFile]; 
} 
}