98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
#include <stdio.h> // printf za izpis
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#include <stdlib.h> // srand, rand za RNG
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#include <time.h> // time za seedanje PRNG
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#include <stdint.h> // fiksne velikosti int podatkov
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#include <zlib.h> // CRC32
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// Kristjan Komloši, 2024
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// UUID generator, 1. domača naloga POKS
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// Program se prevede z
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// gcc uuid-gen.c -lz
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union serial_union // za razbijanje serijske na posamezne bajte
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{
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uint32_t serial; // serijska
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uint8_t bytes[4]; // za CRC32, ki pričakuje posamezne bajte
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};
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// struktura, ki skupaj poveze serijsko, nakljucni uuid in CRC32
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struct uuid_uint128
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{
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uint8_t uuid_byte[16];
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union serial_union serial;
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uint32_t crc;
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};
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void get_uuid(struct uuid_uint128 *uuid)
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{
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// funkcija v pokazano UUID strukturo vpise v4 uuid (nakljucni) s serijsko stevilko in CRCjem
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// xx xx xx xx - xx xx - Mx xx - Nx xx - xx xx xx xx xx xx
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// M = verzija (0x4)
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// N = varianta (0b10xx)
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// byte maske za te vrednosti
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static uint32_t serial = 1;
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const uint8_t version_mask_or = 0x40;
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const uint8_t version_mask_and = 0x0F;
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const uint8_t variant_mask_or = 0x80;
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const uint8_t variant_mask_and = 0x3F;
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uuid->serial.serial = serial++; // nastavimo naslednjo serijsko
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for (int c = 0; c < sizeof(uuid->uuid_byte); c++)
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{
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// vzamemo stevilo iz RNG, ga prestavimo v interval [0,255], vpisemo
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uuid->uuid_byte[c] = (uint8_t)((double)rand() / RAND_MAX * 255);
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}
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// maskiranje bitov za verzijo in varianto
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uuid->uuid_byte[6] &= version_mask_and;
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uuid->uuid_byte[6] |= version_mask_or;
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uuid->uuid_byte[8] &= variant_mask_and;
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uuid->uuid_byte[8] |= variant_mask_or;
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// Zlib ima implementacijo CRC-32
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// Glej https://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/zlib-crc32-1.html
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uuid->crc = crc32(0, Z_NULL, 0); // inicializacija
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uuid->crc = crc32(uuid->crc, uuid->serial.bytes, sizeof(uuid->serial.bytes)); // dodamo serijsko
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uuid->crc = crc32(uuid->crc, uuid->uuid_byte, sizeof(uuid->uuid_byte)); // dodamo vse byte UUIDja
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};
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void print_uuid(struct uuid_uint128 uuid)
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{
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// funkcija je samo alias za ta dolgovezni printf
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printf("%08d-%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x %08x\n",
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uuid.serial.serial,
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uuid.uuid_byte[0],
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uuid.uuid_byte[1],
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uuid.uuid_byte[2],
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uuid.uuid_byte[3],
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uuid.uuid_byte[4],
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uuid.uuid_byte[5],
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uuid.uuid_byte[6],
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uuid.uuid_byte[7],
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uuid.uuid_byte[8],
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uuid.uuid_byte[9],
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uuid.uuid_byte[10],
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uuid.uuid_byte[11],
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uuid.uuid_byte[12],
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uuid.uuid_byte[13],
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uuid.uuid_byte[14],
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uuid.uuid_byte[15],
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uuid.crc
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);
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}
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int main(void)
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{
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srand(time(NULL)); // seed RNG
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struct uuid_uint128 uuid;
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for (int i = 0; i < 100; i++)
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{
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get_uuid(&uuid);
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print_uuid(uuid);
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}
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}
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