Synnefo » Pithos MacOS Client

//

//  HashMapHash.m

//  pithos-macos

//

// Copyright 2011 GRNET S.A. All rights reserved.

//

// Redistribution and use in source and binary forms, with or

// without modification, are permitted provided that the following

// conditions are met:

// 

//   1. Redistributions of source code must retain the above

//      copyright notice, this list of conditions and the following

//      disclaimer.

// 

//   2. Redistributions in binary form must reproduce the above

//      copyright notice, this list of conditions and the following

//      disclaimer in the documentation and/or other materials

//      provided with the distribution.

// 

// THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS

// OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

// PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR

// CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

// USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED

// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN

// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

// POSSIBILITY OF SUCH DAMAGE.

// 

// The views and conclusions contained in the software and

// documentation are those of the authors and should not be

// interpreted as representing official policies, either expressed

// or implied, of GRNET S.A.

#import "HashMapHash.h"

#import <CommonCrypto/CommonHMAC.h>

@implementation HashMapHash

+ (NSString *)calculateHashMapHash:(NSArray *)hashes {

    const char padding[] = {

        '\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0',

        '\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0','\0'};

    if ([hashes count] == 0)

        return [HashMapHash formatHash:[HashMapHash calculateHash:[NSData dataWithBytes:padding length:0]]];

    if ([hashes count] == 1)

        return [HashMapHash formatHash:[hashes objectAtIndex:0]];

    int s = 2;

    while (s < [hashes count])

        s = s * 2;

    NSMutableArray *h = [NSMutableArray array];

    for (int i = 0; i < [hashes count]; i++)

        [h addObject:[hashes objectAtIndex:i]];

    for (int i = 0; i < s - [hashes count]; i++)

        [h addObject:[NSMutableData dataWithBytes:padding length:32]];

    while ([h count] > 1) {

        for (int i = 0; i < [h count]; i = i + 2) {

            NSMutableData *bytesData = [h objectAtIndex:i];

            [bytesData appendData:[h objectAtIndex:i + 1]];

            [h replaceObjectAtIndex:i withObject:[HashMapHash calculateHash:bytesData]];

        }

        NSMutableIndexSet *indicesToRemove = [NSMutableIndexSet indexSet];

        for (int i = 0; i < [h count]; i = i + 2) 

            [indicesToRemove addIndex:i + 1]; 

        [h removeObjectsAtIndexes:indicesToRemove];

    }

    return [HashMapHash formatHash:[h objectAtIndex:0]];

}

+ (NSData *)calculateHash:(NSData *)data {

    unsigned char hash[CC_SHA256_DIGEST_LENGTH];

    CC_SHA256([data bytes], (unsigned int)[data length], hash);

    return [NSMutableData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];

}

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

    NSString *hashString;

    hashString = [NSString stringWithFormat:@"%@", data];

    hashString = [hashString stringByReplacingOccurrencesOfString:@" " withString:@""];

    hashString = [hashString stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"<>"]];

    return hashString;

}

// XXX hardcoded hash algorithm for now

+ (NSArray *)calculateObjectHashMap:(NSString *)filePath withBlockHash:(NSString *)blockHash andBlockSize:(NSUInteger)blockSize {

    NSFileHandle *fh = [NSFileHandle fileHandleForReadingAtPath:filePath];

    if (fh == nil) {

        NSLog(@"failed to open file: %@", filePath);

        return nil;

    }

    NSFileManager *fm = [NSFileManager defaultManager];

    NSDictionary *attributes = [fm attributesOfItemAtPath:filePath error:nil];

    NSUInteger endOfFile = [attributes fileSize];

    NSUInteger fileOffset = 0;

    [fh seekToFileOffset:fileOffset];

    NSMutableArray *hashes = [[[NSMutableArray alloc] init] autorelease];

    while(fileOffset < endOfFile){

        NSData *data = [fh readDataOfLength:blockSize];

        // Strip trailing slashes.

        const char *bytes = [data bytes];

        NSInteger i;

        for (i = [data length] - 1; i >= 0; i--)

            if (bytes[i] != '\0')

                break;

        if (i != [data length] - 1) {

            if (i >= 0)

                data = [data subdataWithRange:NSMakeRange(0, i + 1)];

            else

                data = [NSData data];

        }

        unsigned char hash[CC_SHA256_DIGEST_LENGTH];

        if ( CC_SHA256([data bytes], (unsigned int)[data length], hash) ) {

            NSData *sha256 = [NSMutableData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];

            [hashes addObject:sha256];

        }

        fileOffset += blockSize;

        [fh seekToFileOffset:fileOffset];

    }

    [fh closeFile];

    NSArray *hashMap = [NSArray arrayWithArray:hashes];

    return hashMap;

}

+ (NSArray *)objectHashMapStrings:(NSString *)filePath withBlockHash:(NSString *)blockHash andBlockSize:(NSUInteger)blockSize {

    NSArray *hashHexes = [HashMapHash calculateObjectHashMap:filePath withBlockHash:blockHash andBlockSize:blockSize];

    if (hashHexes == nil)

        return nil;

    NSMutableArray *hashStrings = [[[NSMutableArray alloc] init] autorelease];

    for (NSData *hashHex in hashHexes) {

        [hashStrings addObject:[HashMapHash formatHash:hashHex]];

    }

    NSArray *hashMap = [NSArray arrayWithArray:hashStrings];

    return hashMap;

}

@end