आईफोन पर संपीड़न API

Question

क्या आईफोन पर उपयोग के लिए कोई संपीड़न API उपलब्ध है? हम अपने आईफोन ऐप से बात करने के लिए कुछ रीस्टफुल वेब सेवाएं बना रहे हैं, लेकिन हम दक्षता के लिए कम से कम कुछ बातचीत को संपीड़ित करना चाहते हैं।

मुझे परवाह नहीं है कि प्रारूप (ज़िप, एलएचए, जो कुछ भी) है, और इसे सुरक्षित होने की आवश्यकता नहीं है।

कुछ उत्तरदाताओं ने इंगित किया है कि सर्वर अपने आउटपुट को संपीड़ित कर सकता है, और आईफोन इसका उपभोग कर सकता है। हमारे पास परिदृश्य बिल्कुल विपरीत है। हम संपीड़ित सामग्री वेब सेवा पोस्ट करेंगे। हम दूसरी तरफ संपीड़न से चिंतित नहीं हैं।

Answer 1

zlib और bzip2 उपलब्ध हैं। और आप हमेशा दूसरों को जोड़ सकते हैं, जब तक वे ओएस एक्स

bzip2 छोटे फ़ाइल आकारों के लिए बेहतर विकल्प है, लेकिन कंप्रेसर और डिकंप्रेस करने के लिए अधिक सीपीयू पावर की आवश्यकता होती है।

इसके अलावा, चूंकि आप किसी वेब सेवा से बात कर रहे हैं, तो आपको अधिक कुछ नहीं करना पड़ सकता है। NSURLRequest सर्वर प्रतिक्रियाओं में पारदर्शी रूप से gzip एन्कोडिंग स्वीकार करता है।

Answer 2

मेरा मानना ​​है कि zlib फोन पर उपलब्ध है।

Answer 3

एनएसआरएल का कहना है कि यह जीजीआईपी एन्कोडिंग का समर्थन करता है, इसलिए आपको उचित समय पर अपनी रीस्टफुल वेब सेवा रिटर्न gzip एन्कोडेड सामग्री की तुलना में कुछ भी नहीं करना चाहिए। सभी डिकोडिंग कवर के तहत किया जाएगा।

Answer 4

यदि आप किसी NSData ऑब्जेक्ट में वार्तालापों के लिए डेटा संग्रहीत करते हैं, तो कोकोडेव विकी के लोगों ने NSData category पोस्ट किया है जो gzip और zlib संपीड़न/डिकंप्रेशन को सरल तरीकों के रूप में जोड़ता है। इन्हें my iPhone application में मेरे लिए अच्छा काम किया है।

जैसा कि उपरोक्त लिंक मर गया है, जबकि कोकोडेव विकी को नए होस्ट में स्थानांतरित किया जा रहा है, मैंने इस श्रेणी को पूरी तरह से नीचे प्रस्तुत किया है।

इंटरफ़ेस:

@interface NSData (NSDataExtension) 

// Returns range [start, null byte), or (NSNotFound, 0). 
- (NSRange) rangeOfNullTerminatedBytesFrom:(int)start; 

// Canonical Base32 encoding/decoding. 
+ (NSData *) dataWithBase32String:(NSString *)base32; 
- (NSString *) base32String; 

// COBS is an encoding that eliminates 0x00. 
- (NSData *) encodeCOBS; 
- (NSData *) decodeCOBS; 

// ZLIB 
- (NSData *) zlibInflate; 
- (NSData *) zlibDeflate; 

// GZIP 
- (NSData *) gzipInflate; 
- (NSData *) gzipDeflate; 

//CRC32 
- (unsigned int)crc32; 

// Hash 
- (NSData*) md5Digest; 
- (NSString*) md5DigestString; 
- (NSData*) sha1Digest; 
- (NSString*) sha1DigestString; 
- (NSData*) ripemd160Digest; 
- (NSString*) ripemd160DigestString; 

@end 

कार्यान्वयन:

#import "NSData+CocoaDevUsersAdditions.h" 
#include <zlib.h> 
#include <openssl/md5.h> 
#include <openssl/sha.h> 
#include <openssl/ripemd.h> 


@implementation NSData (NSDataExtension) 

// Returns range [start, null byte), or (NSNotFound, 0). 
- (NSRange) rangeOfNullTerminatedBytesFrom:(int)start 
{ 
    const Byte *pdata = [self bytes]; 
    int len = [self length]; 
    if (start < len) 
    { 
     const Byte *end = memchr (pdata + start, 0x00, len - start); 
     if (end != NULL) return NSMakeRange (start, end - (pdata + start)); 
    } 
    return NSMakeRange (NSNotFound, 0); 
} 

+ (NSData *) dataWithBase32String:(NSString *)encoded 
{ 
    /* First valid character that can be indexed in decode lookup table */ 
    static int charDigitsBase = '2'; 

    /* Lookup table used to decode() characters in encoded strings */ 
    static int charDigits[] = 
    { 26,27,28,29,30,31,-1,-1,-1,-1,-1,-1,-1,-1 // 23456789:;<=>? 
     ,-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14 // @ABCDEFGHIJKLMNO 
     ,15,16,17,18,19,20,21,22,23,24,25,-1,-1,-1,-1,-1 // PQRSTUVWXYZ[\]^_ 
     ,-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14 // `abcdefghijklmno 
     ,15,16,17,18,19,20,21,22,23,24,25    // pqrstuvwxyz 
    }; 

    if (! [encoded canBeConvertedToEncoding:NSASCIIStringEncoding]) return nil; 
    const char *chars = [encoded cStringUsingEncoding:NSASCIIStringEncoding]; // avoids using characterAtIndex. 
    int charsLen = [encoded lengthOfBytesUsingEncoding:NSASCIIStringEncoding]; 

    // Note that the code below could detect non canonical Base32 length within the loop. However canonical Base32 length can be tested before entering the loop. 
    // A canonical Base32 length modulo 8 cannot be: 
    // 1 (aborts discarding 5 bits at STEP n=0 which produces no byte), 
    // 3 (aborts discarding 7 bits at STEP n=2 which produces no byte), 
    // 6 (aborts discarding 6 bits at STEP n=1 which produces no byte). 
    switch (charsLen & 7) { // test the length of last subblock 
     case 1: // 5 bits in subblock: 0 useful bits but 5 discarded 
     case 3: // 15 bits in subblock: 8 useful bits but 7 discarded 
     case 6: // 30 bits in subblock: 24 useful bits but 6 discarded 
      return nil; // non-canonical length 
    } 
    int charDigitsLen = sizeof(charDigits); 
    int bytesLen = (charsLen * 5) >> 3; 
    Byte bytes[bytesLen]; 
    int bytesOffset = 0, charsOffset = 0; 
    // Also the code below does test that other discarded bits 
    // (1 to 4 bits at end) are effectively 0. 
    while (charsLen > 0) 
    { 
     int digit, lastDigit; 
     // STEP n = 0: Read the 1st Char in a 8-Chars subblock 
     // Leave 5 bits, asserting there's another encoding Char 
     if ((digit = (int)chars[charsOffset] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     lastDigit = digit << 3; 
     // STEP n = 5: Read the 2nd Char in a 8-Chars subblock 
     // Insert 3 bits, leave 2 bits, possibly trailing if no more Char 
     if ((digit = (int)chars[charsOffset + 1] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     bytes[bytesOffset] = (Byte)((digit >> 2) | lastDigit); 
     lastDigit = (digit & 3) << 6; 
     if (charsLen == 2) { 
      if (lastDigit != 0) return nil; // non-canonical end 
      break; // discard the 2 trailing null bits 
     } 
     // STEP n = 2: Read the 3rd Char in a 8-Chars subblock 
     // Leave 7 bits, asserting there's another encoding Char 
     if ((digit = (int)chars[charsOffset + 2] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     lastDigit |= (Byte)(digit << 1); 
     // STEP n = 7: Read the 4th Char in a 8-chars Subblock 
     // Insert 1 bit, leave 4 bits, possibly trailing if no more Char 
     if ((digit = (int)chars[charsOffset + 3] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     bytes[bytesOffset + 1] = (Byte)((digit >> 4) | lastDigit); 
     lastDigit = (Byte)((digit & 15) << 4); 
     if (charsLen == 4) { 
      if (lastDigit != 0) return nil; // non-canonical end 
      break; // discard the 4 trailing null bits 
     } 
     // STEP n = 4: Read the 5th Char in a 8-Chars subblock 
     // Insert 4 bits, leave 1 bit, possibly trailing if no more Char 
     if ((digit = (int)chars[charsOffset + 4] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     bytes[bytesOffset + 2] = (Byte)((digit >> 1) | lastDigit); 
     lastDigit = (Byte)((digit & 1) << 7); 
     if (charsLen == 5) { 
      if (lastDigit != 0) return nil; // non-canonical end 
      break; // discard the 1 trailing null bit 
     } 
     // STEP n = 1: Read the 6th Char in a 8-Chars subblock 
     // Leave 6 bits, asserting there's another encoding Char 
     if ((digit = (int)chars[charsOffset + 5] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     lastDigit |= (Byte)(digit << 2); 
     // STEP n = 6: Read the 7th Char in a 8-Chars subblock 
     // Insert 2 bits, leave 3 bits, possibly trailing if no more Char 
     if ((digit = (int)chars[charsOffset + 6] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     bytes[bytesOffset + 3] = (Byte)((digit >> 3) | lastDigit); 
     lastDigit = (Byte)((digit & 7) << 5); 
     if (charsLen == 7) { 
      if (lastDigit != 0) return nil; // non-canonical end 
      break; // discard the 3 trailing null bits 
     } 
     // STEP n = 3: Read the 8th Char in a 8-Chars subblock 
     // Insert 5 bits, leave 0 bit, next encoding Char may not exist 
     if ((digit = (int)chars[charsOffset + 7] - charDigitsBase) < 0 || digit >= charDigitsLen || (digit = charDigits[digit]) == -1) 
      return nil; // invalid character 
     bytes[bytesOffset + 4] = (Byte)(digit | lastDigit); 
     //// This point is always reached for chars.length multiple of 8 
     charsOffset += 8; 
     bytesOffset += 5; 
     charsLen -= 8; 
    } 
    // On loop exit, discard the n trailing null bits 
    return [NSData dataWithBytes:bytes length:sizeof(bytes)]; 
} 

- (NSString *) base32String 
{ 
    /* Lookup table used to canonically encode() groups of data bits */ 
    static char canonicalChars[] = 
    { 'A','B','C','D','E','F','G','H','I','J','K','L','M' // 00..12 
     ,'N','O','P','Q','R','S','T','U','V','W','X','Y','Z' // 13..25 
     ,'2','3','4','5','6','7'        // 26..31 
    }; 
    const Byte *bytes = [self bytes]; 
    int bytesOffset = 0, bytesLen = [self length]; 
    int charsOffset = 0, charsLen = ((bytesLen << 3) + 4)/5; 
    char chars[charsLen]; 
    while (bytesLen != 0) { 
     int digit, lastDigit; 
     // INVARIANTS FOR EACH STEP n in [0..5[; digit in [0..31[; 
     // The remaining n bits are already aligned on top positions 
     // of the 5 least bits of digit, the other bits are 0. 
     ////// STEP n = 0: insert new 5 bits, leave 3 bits 
     digit = bytes[bytesOffset] & 255; 
     chars[charsOffset] = canonicalChars[digit >> 3]; 
     lastDigit = (digit & 7) << 2; 
     if (bytesLen == 1) { // put the last 3 bits 
      chars[charsOffset + 1] = canonicalChars[lastDigit]; 
      break; 
     } 
     ////// STEP n = 3: insert 2 new bits, then 5 bits, leave 1 bit 
     digit = bytes[bytesOffset + 1] & 255; 
     chars[charsOffset + 1] = canonicalChars[(digit >> 6) | lastDigit]; 
     chars[charsOffset + 2] = canonicalChars[(digit >> 1) & 31]; 
     lastDigit = (digit & 1) << 4; 
     if (bytesLen == 2) { // put the last 1 bit 
      chars[charsOffset + 3] = canonicalChars[lastDigit]; 
      break; 
     } 
     ////// STEP n = 1: insert 4 new bits, leave 4 bit 
     digit = bytes[bytesOffset + 2] & 255; 
     chars[charsOffset + 3] = canonicalChars[(digit >> 4) | lastDigit]; 
     lastDigit = (digit & 15) << 1; 
     if (bytesLen == 3) { // put the last 1 bits 
      chars[charsOffset + 4] = canonicalChars[lastDigit]; 
      break; 
     } 
     ////// STEP n = 4: insert 1 new bit, then 5 bits, leave 2 bits 
     digit = bytes[bytesOffset + 3] & 255; 
     chars[charsOffset + 4] = canonicalChars[(digit >> 7) | lastDigit]; 
     chars[charsOffset + 5] = canonicalChars[(digit >> 2) & 31]; 
     lastDigit = (digit & 3) << 3; 
     if (bytesLen == 4) { // put the last 2 bits 
      chars[charsOffset + 6] = canonicalChars[lastDigit]; 
      break; 
     } 
     ////// STEP n = 2: insert 3 new bits, then 5 bits, leave 0 bit 
     digit = bytes[bytesOffset + 4] & 255; 
     chars[charsOffset + 6] = canonicalChars[(digit >> 5) | lastDigit]; 
     chars[charsOffset + 7] = canonicalChars[digit & 31]; 
     //// This point is always reached for bytes.length multiple of 5 
     bytesOffset += 5; 
     charsOffset += 8; 
     bytesLen -= 5; 
    } 
    return [NSString stringWithCString:chars length:sizeof(chars)]; 
} 

#define FinishBlock(X) \ 
(*code_ptr = (X), \ 
code_ptr = dst++, \ 
code = 0x01) 

- (NSData *) encodeCOBS 
{ 
    if ([self length] == 0) return self; 

    NSMutableData *encoded = [NSMutableData dataWithLength:([self length] + [self length]/254 + 1)]; 
    unsigned char *dst = [encoded mutableBytes]; 
    const unsigned char *ptr = [self bytes]; 
    unsigned long length = [self length]; 
    const unsigned char *end = ptr + length; 
    unsigned char *code_ptr = dst++; 
    unsigned char code = 0x01; 
    while (ptr < end) 
    { 
     if (*ptr == 0) FinishBlock(code); 
     else 
     { 
      *dst++ = *ptr; 
      code++; 
      if (code == 0xFF) FinishBlock(code); 
     } 
     ptr++; 
    } 
    FinishBlock(code); 

    [encoded setLength:((Byte *)dst - (Byte *)[encoded mutableBytes])]; 
    return [NSData dataWithData:encoded]; 
} 

- (NSData *) decodeCOBS 
{ 
    if ([self length] == 0) return self; 

    const Byte *ptr = [self bytes]; 
    unsigned length = [self length]; 
    NSMutableData *decoded = [NSMutableData dataWithLength:length]; 
    Byte *dst = [decoded mutableBytes]; 
    Byte *basedst = dst; 

    const unsigned char *end = ptr + length; 
    while (ptr < end) 
    { 
     int i, code = *ptr++; 
     for (i=1; i<code; i++) *dst++ = *ptr++; 
     if (code < 0xFF) *dst++ = 0; 
    } 

    [decoded setLength:(dst - basedst)]; 
    return [NSData dataWithData:decoded]; 
} 

- (NSData *)zlibInflate 
{ 
    if ([self length] == 0) return self; 

    unsigned full_length = [self length]; 
    unsigned half_length = [self length]/2; 

    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length]; 
    BOOL done = NO; 
    int status; 

    z_stream strm; 
    strm.next_in = (Bytef *)[self bytes]; 
    strm.avail_in = [self length]; 
    strm.total_out = 0; 
    strm.zalloc = Z_NULL; 
    strm.zfree = Z_NULL; 

    if (inflateInit (&strm) != Z_OK) return nil; 

    while (!done) 
    { 
     // Make sure we have enough room and reset the lengths. 
     if (strm.total_out >= [decompressed length]) 
      [decompressed increaseLengthBy: half_length]; 
     strm.next_out = [decompressed mutableBytes] + strm.total_out; 
     strm.avail_out = [decompressed length] - strm.total_out; 

     // Inflate another chunk. 
     status = inflate (&strm, Z_SYNC_FLUSH); 
     if (status == Z_STREAM_END) done = YES; 
     else if (status != Z_OK) break; 
    } 
    if (inflateEnd (&strm) != Z_OK) return nil; 

    // Set real length. 
    if (done) 
    { 
     [decompressed setLength: strm.total_out]; 
     return [NSData dataWithData: decompressed]; 
    } 
    else return nil; 
} 

- (NSData *)zlibDeflate 
{ 
    if ([self length] == 0) return self; 

    z_stream strm; 

    strm.zalloc = Z_NULL; 
    strm.zfree = Z_NULL; 
    strm.opaque = Z_NULL; 
    strm.total_out = 0; 
    strm.next_in=(Bytef *)[self bytes]; 
    strm.avail_in = [self length]; 

    // Compresssion Levels: 
    // Z_NO_COMPRESSION 
    // Z_BEST_SPEED 
    // Z_BEST_COMPRESSION 
    // Z_DEFAULT_COMPRESSION 

    if (deflateInit(&strm, Z_DEFAULT_COMPRESSION) != Z_OK) return nil; 

    NSMutableData *compressed = [NSMutableData dataWithLength:16384]; // 16K chuncks for expansion 

    do { 

     if (strm.total_out >= [compressed length]) 
      [compressed increaseLengthBy: 16384]; 

     strm.next_out = [compressed mutableBytes] + strm.total_out; 
     strm.avail_out = [compressed length] - strm.total_out; 

     deflate(&strm, Z_FINISH); 

    } while (strm.avail_out == 0); 

    deflateEnd(&strm); 

    [compressed setLength: strm.total_out]; 
    return [NSData dataWithData: compressed]; 
} 

- (NSData *)gzipInflate 
{ 
    if ([self length] == 0) return self; 

    unsigned full_length = [self length]; 
    unsigned half_length = [self length]/2; 

    NSMutableData *decompressed = [NSMutableData dataWithLength: full_length + half_length]; 
    BOOL done = NO; 
    int status; 

    z_stream strm; 
    strm.next_in = (Bytef *)[self bytes]; 
    strm.avail_in = [self length]; 
    strm.total_out = 0; 
    strm.zalloc = Z_NULL; 
    strm.zfree = Z_NULL; 

    if (inflateInit2(&strm, (15+32)) != Z_OK) return nil; 
    while (!done) 
    { 
     // Make sure we have enough room and reset the lengths. 
     if (strm.total_out >= [decompressed length]) 
      [decompressed increaseLengthBy: half_length]; 
     strm.next_out = [decompressed mutableBytes] + strm.total_out; 
     strm.avail_out = [decompressed length] - strm.total_out; 

     // Inflate another chunk. 
     status = inflate (&strm, Z_SYNC_FLUSH); 
     if (status == Z_STREAM_END) done = YES; 
     else if (status != Z_OK) break; 
    } 
    if (inflateEnd (&strm) != Z_OK) return nil; 

    // Set real length. 
    if (done) 
    { 
     [decompressed setLength: strm.total_out]; 
     return [NSData dataWithData: decompressed]; 
    } 
    else return nil; 
} 

- (NSData *)gzipDeflate 
{ 
    if ([self length] == 0) return self; 

    z_stream strm; 

    strm.zalloc = Z_NULL; 
    strm.zfree = Z_NULL; 
    strm.opaque = Z_NULL; 
    strm.total_out = 0; 
    strm.next_in=(Bytef *)[self bytes]; 
    strm.avail_in = [self length]; 

    // Compresssion Levels: 
    // Z_NO_COMPRESSION 
    // Z_BEST_SPEED 
    // Z_BEST_COMPRESSION 
    // Z_DEFAULT_COMPRESSION 

    if (deflateInit2(&strm, Z_DEFAULT_COMPRESSION, Z_DEFLATED, (15+16), 8, Z_DEFAULT_STRATEGY) != Z_OK) return nil; 

    NSMutableData *compressed = [NSMutableData dataWithLength:16384]; // 16K chunks for expansion 

    do { 

     if (strm.total_out >= [compressed length]) 
      [compressed increaseLengthBy: 16384]; 

     strm.next_out = [compressed mutableBytes] + strm.total_out; 
     strm.avail_out = [compressed length] - strm.total_out; 

     deflate(&strm, Z_FINISH); 

    } while (strm.avail_out == 0); 

    deflateEnd(&strm); 

    [compressed setLength: strm.total_out]; 
    return [NSData dataWithData:compressed]; 
} 

// --------------------------------CRC32------------------------------- 
static const unsigned long crc32table[] = 
{ 
    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 
    0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 
    0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 
    0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 
    0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 
    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 
    0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f, 
    0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 
    0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433, 
    0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01, 
    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 
    0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 
    0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 
    0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 
    0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 
    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 
    0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 
    0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 
    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 
    0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 
    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 
    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 
    0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 
    0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 
    0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 
    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 
    0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 
    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 
    0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 
    0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 
    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 
    0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d 
}; 

- (unsigned int)crc32 
{ 
    unsigned int crcval; 
    unsigned int x, y; 
    const void  *bytes; 
    unsigned int max; 

    bytes = [self bytes]; 
    max = [self length]; 
    crcval = 0xffffffff; 
    for (x = 0, y = max; x < y; x++) { 
     crcval = ((crcval >> 8) & 0x00ffffff)^crc32table[(crcval^(*((unsigned char *)bytes + x))) & 0xff]; 
    } 

    return crcval^0xffffffff; 
} 

// Hash function, by [[DamienBob]] 

#define HEComputeDigest(method)      \ 
method##_CTX ctx;        \ 
unsigned char digest[method##_DIGEST_LENGTH];  \ 
method##_Init(&ctx);       \ 
method##_Update(&ctx, [self bytes], [self length]);  \ 
method##_Final(digest, &ctx); 

#define HEComputeDigestNSData(method)    \ 
HEComputeDigest(method)      \ 
return [NSData dataWithBytes:digest length:method##_DIGEST_LENGTH]; 

#define HEComputeDigestNSString(method)    \ 
static char __HEHexDigits[] = "abcdef";  \ 
unsigned char digestString[2*method##_DIGEST_LENGTH];\ 
unsigned int i;         \ 
HEComputeDigest(method)      \ 
for(i=0; i<method##_DIGEST_LENGTH; i++) {    \ 
    digestString[2*i] = __HEHexDigits[digest[i] >> 4]; \ 
    digestString[2*i+1] = __HEHexDigits[digest[i] & 0x0f];\ 
}           \ 
return [NSString stringWithCString:(char *)digestString length:2*method##_DIGEST_LENGTH]; 

#define SHA1_CTX    SHA_CTX 
#define SHA1_DIGEST_LENGTH  SHA_DIGEST_LENGTH 

- (NSData*) md5Digest 
{ 
    HEComputeDigestNSData(MD5); 
} 

- (NSString*) md5DigestString 
{ 
    HEComputeDigestNSString(MD5); 
} 

- (NSData*) sha1Digest 
{ 
    HEComputeDigestNSData(SHA1); 
} 

- (NSString*) sha1DigestString 
{ 
    HEComputeDigestNSString(SHA1); 
} 

- (NSData*) ripemd160Digest 
{ 
    HEComputeDigestNSData(RIPEMD160); 
} 

- (NSString*) ripemd160DigestString 
{ 
    HEComputeDigestNSString(RIPEMD160); 
} 

@end 

Answer 5

आप केवल संकुचित डेटा है और असंपीड़ित आकार जानते हैं कि आप उपयोग कर सकते हैं:

#import "zlib.h" 


int datal = [zipedData length]; 
Bytef *buffer[uncompressedSize]; 
Bytef *dataa[datal]; 

[zipedData getBytes:dataa]; 

Long *ld; 

uLong sl = datal; 
*ld = uncompressedSize; 
if(uncompress(buffer, ld, dataa, sl) == Z_OK) 
{ 
NSData *uncompressedData = [NSData dataWithBytes:buffer length:uncompressedSize]; 
NSString *txtFile = [[NSString alloc] initWithData:uncompressedData encoding:NSUTF8StringEncoding]; 
} 

Answer 6

मुझ पर भरोसा सबसे अच्छा विकल्प है ZipArchive का उपयोग करें देखें: How to decompress an AES-256 encrypted Zip file?

यदि आवश्यक हो तो सहायता के लिए तैयार है।

Answer 7

Objective-Zip एक और विकल्प है। इन उत्कृष्ट instructions देखें।

नोट मुझे एक्सकोड-> संपादन-> रिएक्टर-> उद्देश्य सी एआरसी में कनवर्ट करके एआरसी का उपयोग करने के लिए स्रोत कोड को परिवर्तित करना था।

Answer 8

ऐप्पल का निर्माण libcompression में अब आईओएस 9 के लिए उपलब्ध है। Compression_encode_buffer का संक्षिप्त उदाहरण NSData को संपीड़ित करने के लिए नीचे दिखाया गया है।

@import Compression; 

NSData *theData = [NSData dataWithContentsOfFile:[<some file> path]]; 
size_t theDataSize = [theData length]; 
const uint8_t *buf = (const uint8_t *)[theData bytes]; 
uint8_t *destBuf = malloc(sizeof(uint8_t) * theDataSize); 
size_t compressedSize = compression_encode_buffer(destBuf, theDataSize, buf, theDataSize, NULL, COMPRESSION_LZFSE); 
self.<NSData item> = [NSData dataWithBytes:destBuf length:compressedSize]; 

NSLog(@"originalsize:%zu compressed:%zu", theDataSize, compressedSize); 
free(destBuf); 

अलग एल्गोरिदम के एक नंबर उपलब्ध हैं:

• LZMA
• LZ4
• zlib
• LZFSE

ब्लॉक संपीड़न या धारा संपीड़न दोनों समर्थित हैं।

https://developer.apple.com/library/mac/documentation/Performance/Reference/Compression/