CFReadStreamOpen Returns Error kCFStreamErrorDomainPOSIXDomain

Question

I want to make a MD5 of an Image so I am doing this with below code

CFStringRef FileMD5HashCreateWithPath(CFStringRef filePath, size_t chunkSizeForReadingData, BOOL *isAbort)
{
    // Declare needed variables
    CFStringRef result = NULL;
    CFReadStreamRef readStream = NULL;

    // Get the file URL
    CFURLRef fileURL =
    CFURLCreateWithFileSystemPath(kCFAllocatorDefault,
                                  (CFStringRef)filePath,
                                  kCFURLPOSIXPathStyle,
                                  (Boolean)false);
    if (!fileURL) goto done;

    // Create and open the read stream
    readStream = CFReadStreamCreateWithFile(kCFAllocatorDefault,
                                            (CFURLRef)fileURL);
    if (!readStream) goto done;
    bool didSucceed = (bool)CFReadStreamOpen(readStream);
    if (!didSucceed) goto done;

    // Initialize the hash object
    CC_MD5_CTX hashObject;
    CC_MD5_Init(&hashObject);

    // Make sure chunkSizeForReadingData is valid
    if (!chunkSizeForReadingData) {
        chunkSizeForReadingData = FileHashDefaultChunkSizeForReadingData;
    }

    // Feed the data to the hash object
    bool hasMoreData = true;
    while (hasMoreData) {

        if(*isAbort){
            NSLog(@"hasMoreData isAborted");
            if (readStream) {
                CFReadStreamClose(readStream);
                CFRelease(readStream);
            }
            if (fileURL) {
                CFRelease(fileURL);
            }
            return nil;
        }

        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;
}

Above code is properly working in Mac OS, But I am doing the same thing in iOS and it is not working. As far as I know I am passing the fileUrl exactly right but in the CFReadStreamOpen() it returns the kCFStreamErrorDomainPOSIX and I came to know that this error no is 1 and it states that it is "Operation Not Permitted"

I have gone through this link

What to do in order to read the stream of any PHAsset of iOS device

does changing the below file ownership affects in this context:

Answer 1

PHAsset contains only metadata about image. In order to fetch image data you need to use PHImageManager.

func requestImageData(for asset: PHAsset, 
              options: PHImageRequestOptions?, 
        resultHandler: @escaping (Data?, String?, UIImageOrientation, [AnyHashable : Any]?) -> Void) -> PHImageRequestID

You can use CFReadStreamCreateWithBytesNoCopy to create CFReadStreamRef with data.