Compression API auf dem iPhone

Question

Gibt es eine Kompression API auf dem iPhone zur Verfügung? Wir bauen einige RESTful Web-Services für unsere iPhone App zu sprechen, aber wir wollen zumindest einige der Gespräche für Effizienz komprimieren.

ist mir egal, was das Format (ZIP, LHA, was auch immer), und es muss nicht sicher sein.

Einige der Befragten haben darauf hingewiesen, dass der Server seine Ausgabe komprimieren kann, und das iPhone kann, dass verbrauchen. Das Szenario, das wir haben, ist genau das Gegenteil. Wir werden POSTen komprimierten Inhalt auf den Web-Service. Wir sind nicht mit Kompression geht in die andere Richtung geht.

Answer 1

zlib und bzip2 stehen zur Verfügung. Und Sie können immer andere hinzufügen, solange sie werden (in der Regel) kompilieren unter OS X.

bzip2 ist eine bessere Wahl für kleinste Dateigrößen, erfordert aber viel mehr CPU-Leistung zu komprimieren und dekomprimieren.

Auch da Sie zu einem Web-Service sprechen, kann man nicht viel zu tun hat. NSURLRequest akzeptiert gzip-Kodierung transparent in Server-Antworten.

Answer 2

Wenn Sie die Daten für die Gespräche in einem NSData Objekt speichern, haben die Leute im CocoaDev Wiki veröffentlichte ein .

Wie der obige Link tot gegangen ist, während das CocoaDev Wiki auf einen neuen Host verschoben wird, habe ich diese Kategorie in seiner Gesamtheit im Folgenden wiedergegeben.

Schnittstelle:

@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

Umsetzung:

#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[] = "0123456789abcdef";       \
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 3

Apple in libcompression gebaut für iOS jetzt verfügbar ist 9. Ein kurzes Beispiel compression_encode_buffer ist unten zum Komprimieren NSData gezeigt.

@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);

Eine Reihe unterschiedlicher Algorithmen zur Verfügung:

• LZMA
• LZ 4
• ZLIB
• LZFSE

Block Kompression oder Stream Kompression werden beide unterstützt.

Siehe https://developer.apple.com/library/ mac / Dokumentation / Leistung / Reference / Kompressions /

Answer 4

Wenn Sie nur komprimierte Daten haben und wissen, unkomprimierte Größe können Sie:

#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 5

Ich glaube, zlib am Telefon zur Verfügung steht.

Answer 6

vertrauen Sie mir die beste Wahl zu ZipArchive sehen verwenden: Wie eine AES-256 verschlüsselte Zip-Datei entpacken?

bereit für Hilfe, wenn nötig.

Answer 7

Objective-Zip ist eine weitere Option. Sehen Sie diese hervorragende Anweisungen .

Hinweis: Ich hatte den Quellcode umwandeln ARC zu verwenden, indem die XCode- mit> Bearbeiten-> Refactor-> Konvertieren in Objective C ARC.

Answer 8

NSURL sagt es die gzip-Codierung unterstützt, so sollten Sie nicht alles tun müssen, um mehr als die RESTful Web Service Rückkehr gzip codierten Inhalt hat, wenn angemessen. Alle die Decodierung wird unter der Decke erfolgen.