iphone - developer - sdk ios 11

API de compresión en el iPhone

Question

¿Hay una API de compresión disponible para usar en el iPhone? Estamos creando algunos servicios web RESTful para nuestra aplicación de iPhone con los que hablar, pero queremos comprimir al menos algunas de las conversaciones por eficiencia.

No me importa cuál es el formato (ZIP, LHA, lo que sea), y no es necesario que sea seguro.

Algunos encuestados han señalado que el servidor puede comprimir su salida, y el iPhone puede consumir eso. El escenario que tenemos es exactamente el inverso. Publicaremos contenido comprimido en el servicio web. No nos preocupa que la compresión vaya hacia otro lado.

Answer 1

Creo que zlib está disponible en el teléfono.

Answer 2

La compresión de compilación incorporada de Apple ya está disponible para iOS 9. A continuación, se muestra un ejemplo corto de compressor_encode_buffer para comprimir NSData.

@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);

Hay varios algoritmos diferentes disponibles:

• LZMA
• LZ4
• ZLIB
• LZFSE

La compresión de bloque o la compresión de flujo son compatibles.

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

Answer 3

NSURL dice que admite la codificación gzip, por lo que no debería tener que hacer nada más que hacer que su servicio web RESTful devuelva contenido codificado gzip cuando corresponda. Toda la decodificación se hará debajo de las cubiertas.

Answer 4

Si almacena los datos de las conversaciones en un objeto NSData, los usuarios de la wiki CocoaDev publicaron una categoría NSData que agrega compresión / descompresión gzip y zlib como métodos simples. Estos han funcionado bien para mí en mi aplicación de iPhone .

Como el enlace anterior se ha extinguido mientras la wiki de CocoaDev se está moviendo a un nuevo host, he reproducido esta categoría en su totalidad a continuación.

Interfaz:

@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

Implementación:

#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 5

Si solo tiene datos comprimidos y conoce el tamaño sin comprimir, puede usar:

#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

créanme la mejor opción es utilizar ZipArchive ver: ¿Cómo descomprimir un archivo Zip cifrado AES-256?

listo para ayuda si es necesario.

Answer 7

zlib y bzip2 están disponibles. Y siempre puede agregar otros, siempre que (generalmente) compilen bajo OS X.

bzip2 es una mejor opción para los tamaños de archivo más pequeños, pero requiere mucha más potencia de CPU para comprimir y descomprimir.

Además, como estás hablando con un servicio web, es posible que no tengas que hacer mucho. NSURLRequest acepta la codificación gzip de forma transparente en las respuestas del servidor.

Answer 8

Objective-Zip es otra opción. Vea estas excelentes instructions .

Nota: tuve que convertir el código fuente para usar ARC usando XCode-> Edit-> Refactor-> Convert to Objective C ARC.