(Objective-C) Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks.

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#import <CkoCrypt2.h>
#import <CkoBinData.h>
#import <NSString.h>

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];
crypt.HashAlgorithm = @"sha256";
crypt.Charset = @"utf-8";

CkoBinData *bd = [[CkoBinData alloc] init];

NSString *s = @"The quick brown fox jumped over the lazy dog.\r\n";

// Accumulate the text in a StringBuilder.  We'll demonstrate hashing the text in chunks,
// and then also hashing the entire text at once to show the results are the same.

[bd AppendString: s charset: @"utf-8"];
BOOL success = [crypt HashBeginString: s];

int i = 0;
while (i < 200) {
    [bd AppendString: s charset: @"utf-8"];
    [crypt HashMoreString: s];
    i = i + 1;
}

// Get the hash in base64 format.
crypt.EncodingMode = @"base64";

NSString *encodedHash = [crypt HashFinalENC];
NSLog(@"%@%@",@"Hash computed in chunks: ",encodedHash);

// Let's alternatively compute the hash of the entire amount of data at once,
// to show the hash computation is the same:
encodedHash = [crypt HashBdENC: bd];
NSLog(@"%@%@",@"Hash computed in 1 step: ",encodedHash);

// Output:

// Hash computed in chunks: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=
// Hash computed in 1 step: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=