/*

    Copyright (C) 2016 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Calculates an authenticated message digest for some data using the HMAC-SHA algorithm.

 */

#import "QCCHMACSHAAuthentication.h"

#include <CommonCrypto/CommonCrypto.h>

NS_ASSUME_NONNULL_BEGIN

@interface QCCHMACSHAAuthentication ()

// read/write versions of public properties

@property (atomic, copy,   readwrite, nullable) NSData *        outputHMAC;

@end

NS_ASSUME_NONNULL_END

@implementation QCCHMACSHAAuthentication

- (instancetype)init {

    abort();

}

- (instancetype)initWithAlgorithm:(QCCHMACSHAAuthenticationAlgorithm)algorithm inputData:(NSData *)inputData keyData:(NSData *)keyData {

    NSParameterAssert(inputData != nil);

    NSParameterAssert(keyData != nil);

    self = [super init];

    if (self != nil) {

        self->_algorithm = algorithm;

        self->_inputData = [inputData copy];

        self->_keyData = [keyData copy];

    }

    return self;

}

- (void)main {

    static const size_t kDigestSize[5] = {

        CC_SHA1_DIGEST_LENGTH, 

        CC_SHA224_DIGEST_LENGTH, 

        CC_SHA256_DIGEST_LENGTH, 

        CC_SHA384_DIGEST_LENGTH, 

        CC_SHA512_DIGEST_LENGTH

    };

    static const CCHmacAlgorithm kCCAlgorithm[5] = {

        kCCHmacAlgSHA1,

        kCCHmacAlgSHA224, 

        kCCHmacAlgSHA256, 

        kCCHmacAlgSHA384, 

        kCCHmacAlgSHA512

    };

    NSMutableData *         hmac;

    // The output length is determined by the hash algorithm, for example, SHA1 

    // implies that hmac must be CC_SHA1_DIGEST_LENGTH bytes long.

    hmac = [[NSMutableData alloc] initWithLength:kDigestSize[self.algorithm]];

    CCHmac(kCCAlgorithm[self.algorithm], self.keyData.bytes, self.keyData.length, self.inputData.bytes, self.inputData.length, hmac.mutableBytes);

    self.outputHMAC = hmac;

}

@end