ضغط API على اي فون
https://stackoverflow.com/questions/230984
-
04-07-2019 - |
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Russianسؤال
هل هناك ضغط API المتاحة للاستخدام على اي فون ؟ نحن نقوم ببناء بعض خدمات الويب مريحة لدينا اي فون التطبيق التحدث, ولكن نريد أن ضغط بعض على الأقل من المحادثات في الكفاءة.
لا يهمني ما شكل (ZIP, LHA, أيا كان) هو أنها لا تحتاج إلى أن تكون آمنة.
بعض المشاركين أشاروا إلى أن الملقم يمكن ضغط انتاجها ، و اي فون يمكن أن تستهلك هذا.السيناريو لدينا هو بالضبط عكس ذلك.سوف يتم نشر محتوى مضغوط إلى خدمة ويب.نحن لا نشعر بالقلق مع ضغط الذهاب في الاتجاه الآخر.
المحلول
zlib و bzip2 المتاحة.ويمكنك دائما إضافة الآخرين ، طالما أنها سوف (عموما) ترجمة تحت OS X.
bzip2 هو الخيار الأفضل بالنسبة أصغر أحجام الملفات ، ولكن تتطلب المزيد من الطاقة وحدة المعالجة المركزية لضغط و فك ضغط.
أيضا بما أنك تتحدث إلى خدمة ويب, قد لا يكون لديك أن تفعل الكثير.NSURLRequest تقبل gzip ترميز بشفافية في الردود الخادم.
نصائح أخرى
إذا قمت بتخزين بيانات المحادثات في NSData وجوه الناس في CocoaDev ويكي قد نشرت NSData الفئة أن يضيف gzip و zlib الضغط / كما طرق بسيطة.هذه عملت بشكل جيد بالنسبة لي في اي فون بلدي التطبيق.
كما في الرابط أعلاه قد ماتت حين CocoaDev ويكي يتم نقله إلى مضيف جديد ، لقد استنسخ هذه الفئة في مجملها أدناه.
واجهة:
@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
التنفيذ:
#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
أبل المدمج في libcompression متوفر الآن على iOS 9.مثال قصيرة compression_encode_buffer هو مبين أدناه لضغط 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);
عدد من خوارزميات مختلفة متاحة:
- LZMA
- LZ4
- ZLIB
- LZFSE
ضغط كتلة أو تيار ضغط كلاهما معتمد.
انظر https://developer.apple.com/library/mac/documentation/Performance/Reference/Compression/
إذا كان لديك فقط ضغط البيانات غير المضغوطة الحجم يمكنك استخدام:
#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];
}
أعتقد zlib متاح على الهاتف.
صدقني أفضل خيار هو استخدام ZipArchive انظر: كيفية فك الضغط وهو AES-256 Zip مشفرة الملف ؟
على استعداد للمساعدة إذا لزم الأمر.
NSURL يقول أنه يدعم gzip ترميز لذلك يجب أن لا يكون على فعل أي شيء أكثر من الخاص بك مريح خدمة ويب بإرجاع gzip ترميز المحتوى عند الاقتضاء.كل فك وسيتم ذلك تحت الأغطية.
لا تنتمي إلى StackOverflow
