How to find 32bit CRC for a file in objective C - objective-c

Question

I want to find out CRC for a bin file in my iOS application. Is there already a function which will accept filename as input and return 32 bit CRC value? Please share me if any code available.

Answer 1

You can use this file I modeled on the ios common crypto library functions:
crc32.h
#ifndef sessionTest_crc32_h
#define sessionTest_crc32_h
// Standard library
#include <stdint.h>
#include <stdio.h>
#define CC_CRC32_DIGEST_LENGTH 4
typedef struct {
uint32_t crc;
} CC_CRC32_CTX;
static uint32_t crc32_tbl[256] =
{
0x00000000L, 0x77073096L, 0xEE0E612CL, 0x990951BAL, 0x076DC419L,
0x706AF48FL, 0xE963A535L, 0x9E6495A3L, 0x0EDB8832L, 0x79DCB8A4L,
0xE0D5E91EL, 0x97D2D988L, 0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L,
0x90BF1D91L, 0x1DB71064L, 0x6AB020F2L, 0xF3B97148L, 0x84BE41DEL,
0x1ADAD47DL, 0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L, 0x136C9856L,
0x646BA8C0L, 0xFD62F97AL, 0x8A65C9ECL, 0x14015C4FL, 0x63066CD9L,
0xFA0F3D63L, 0x8D080DF5L, 0x3B6E20C8L, 0x4C69105EL, 0xD56041E4L,
0xA2677172L, 0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL, 0xA50AB56BL,
0x35B5A8FAL, 0x42B2986CL, 0xDBBBC9D6L, 0xACBCF940L, 0x32D86CE3L,
0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L, 0x26D930ACL, 0x51DE003AL,
0xC8D75180L, 0xBFD06116L, 0x21B4F4B5L, 0x56B3C423L, 0xCFBA9599L,
0xB8BDA50FL, 0x2802B89EL, 0x5F058808L, 0xC60CD9B2L, 0xB10BE924L,
0x2F6F7C87L, 0x58684C11L, 0xC1611DABL, 0xB6662D3DL, 0x76DC4190L,
0x01DB7106L, 0x98D220BCL, 0xEFD5102AL, 0x71B18589L, 0x06B6B51FL,
0x9FBFE4A5L, 0xE8B8D433L, 0x7807C9A2L, 0x0F00F934L, 0x9609A88EL,
0xE10E9818L, 0x7F6A0DBBL, 0x086D3D2DL, 0x91646C97L, 0xE6635C01L,
0x6B6B51F4L, 0x1C6C6162L, 0x856530D8L, 0xF262004EL, 0x6C0695EDL,
0x1B01A57BL, 0x8208F4C1L, 0xF50FC457L, 0x65B0D9C6L, 0x12B7E950L,
0x8BBEB8EAL, 0xFCB9887CL, 0x62DD1DDFL, 0x15DA2D49L, 0x8CD37CF3L,
0xFBD44C65L, 0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L, 0xD4BB30E2L,
0x4ADFA541L, 0x3DD895D7L, 0xA4D1C46DL, 0xD3D6F4FBL, 0x4369E96AL,
0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L, 0x44042D73L, 0x33031DE5L,
0xAA0A4C5FL, 0xDD0D7CC9L, 0x5005713CL, 0x270241AAL, 0xBE0B1010L,
0xC90C2086L, 0x5768B525L, 0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L, 0xC7D7A8B4L, 0x59B33D17L,
0x2EB40D81L, 0xB7BD5C3BL, 0xC0BA6CADL, 0xEDB88320L, 0x9ABFB3B6L,
0x03B6E20CL, 0x74B1D29AL, 0xEAD54739L, 0x9DD277AFL, 0x04DB2615L,
0x73DC1683L, 0xE3630B12L, 0x94643B84L, 0x0D6D6A3EL, 0x7A6A5AA8L,
0xE40ECF0BL, 0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L, 0xF00F9344L,
0x8708A3D2L, 0x1E01F268L, 0x6906C2FEL, 0xF762575DL, 0x806567CBL,
0x196C3671L, 0x6E6B06E7L, 0xFED41B76L, 0x89D32BE0L, 0x10DA7A5AL,
0x67DD4ACCL, 0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L, 0x60B08ED5L,
0xD6D6A3E8L, 0xA1D1937EL, 0x38D8C2C4L, 0x4FDFF252L, 0xD1BB67F1L,
0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL, 0xD80D2BDAL, 0xAF0A1B4CL,
0x36034AF6L, 0x41047A60L, 0xDF60EFC3L, 0xA867DF55L, 0x316E8EEFL,
0x4669BE79L, 0xCB61B38CL, 0xBC66831AL, 0x256FD2A0L, 0x5268E236L,
0xCC0C7795L, 0xBB0B4703L, 0x220216B9L, 0x5505262FL, 0xC5BA3BBEL,
0xB2BD0B28L, 0x2BB45A92L, 0x5CB36A04L, 0xC2D7FFA7L, 0xB5D0CF31L,
0x2CD99E8BL, 0x5BDEAE1DL, 0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL,
0x026D930AL, 0x9C0906A9L, 0xEB0E363FL, 0x72076785L, 0x05005713L,
0x95BF4A82L, 0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L, 0x92D28E9BL,
0xE5D5BE0DL, 0x7CDCEFB7L, 0x0BDBDF21L, 0x86D3D2D4L, 0xF1D4E242L,
0x68DDB3F8L, 0x1FDA836EL, 0x81BE16CDL, 0xF6B9265BL, 0x6FB077E1L,
0x18B74777L, 0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL, 0x11010B5CL,
0x8F659EFFL, 0xF862AE69L, 0x616BFFD3L, 0x166CCF45L, 0xA00AE278L,
0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L, 0xA7672661L, 0xD06016F7L,
0x4969474DL, 0x3E6E77DBL, 0xAED16A4AL, 0xD9D65ADCL, 0x40DF0B66L,
0x37D83BF0L, 0xA9BCAE53L, 0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L, 0x24B4A3A6L, 0xBAD03605L,
0xCDD70693L, 0x54DE5729L, 0x23D967BFL, 0xB3667A2EL, 0xC4614AB8L,
0x5D681B02L, 0x2A6F2B94L, 0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL,
0x2D02EF8DL
};
static inline int CC_CRC32_Init(CC_CRC32_CTX *c) {
c->crc = 0xFFFFFFFFL;
return 1;
}
static inline int CC_CRC32_Update(CC_CRC32_CTX *c, const uint8_t *data, uint32_t len) {
for(uint32_t i=0; i<len;i++)
c->crc = (c->crc>>8) ^ crc32_tbl[(c->crc&0xFF) ^ *data++];
return 1;
}
static inline int CC_CRC32_Final(unsigned char *md, CC_CRC32_CTX *c) {
c->crc = c->crc ^ 0xFFFFFFFFL;
md[0] = (c->crc & 0xff000000UL) >> 24;
md[1] = (c->crc & 0x00ff0000UL) >> 16;
md[2] = (c->crc & 0x0000ff00UL) >> 8;
md[3] = (c->crc & 0x000000ffUL) ;
return 1;
}
#endif
And an example to use it:
// Declare needed variables and buffers
CFStringRef result = NULL;
CFReadStreamRef readStream = NULL;
unsigned char digest[CC_CRC32_DIGEST_LENGTH];
char hash[2 * CC_CRC32_DIGEST_LENGTH + 1];
int chunkSizeForReadingData = 4096;
CC_CRC32_CTX ctx;
// Get the file URL
CFURLRef fileURL = //something...
// Create and open the read stream
readStream = CFReadStreamCreateWithFile(kCFAllocatorDefault,
(CFURLRef)fileURL);
bool didSucceed = (bool)CFReadStreamOpen(readStream);
// Initialize the hash object
CC_CRC32_Init(&ctx);
// Feed the data
bool hasMoreData = true;
while (hasMoreData) {
uint8_t buffer[chunkSizeForReadingData];
CFIndex readBytesCount = CFReadStreamRead(readStream,
(UInt8 *)buffer,
(CFIndex)sizeof(buffer));
if (readBytesCount == -1) break;
if (readBytesCount == 0) {
hasMoreData = false;
continue;
}
CC_CRC32_Update(&ctx, (const void*)buffer, (CC_LONG)readBytesCount);
}
// Compute the digest
CC_CRC32_Final(digest, &c);
// Compute the string result
for (size_t i = 0; i < chunkSizeForReadingData; ++i) {
snprintf(hash + (2 * i), 3, "%02x", (int)(digest[i]));
}
result = CFStringCreateWithCString(kCFAllocatorDefault,
(const char *)hash,
kCFStringEncodingUTF8);
But I would mostly recommend you used this Gist:
https://gist.github.com/paul-delange/6808278