2e6cfbe69f
findlongest.c:101:28: error: argument 1 value ‘2147483648’ exceeds maximum object size 2147483647 [-Werror=alloc-size-larger-than=]
101 | uint8_t *stringsSeen = calloc((uint64_t)1 << (MAX_STRING_SIZE-3u), sizeof(uint8_t));
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
112 lines
3.1 KiB
C
Executable File
112 lines
3.1 KiB
C
Executable File
// Find the longest repeated binary sequence in a file.
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <time.h>
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#define MAX_STRING_SIZE 34u
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// Generate random data for use in testing.
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static bool *generateRandomData(uint32_t size) {
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bool *data = calloc(size, sizeof(bool));
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srand(time(NULL));
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uint32_t i;
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for(i = 0u; i < size; ) {
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uint32_t randVal = rand();
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uint32_t j;
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for(j = 0u; j < 16u; j++) {
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if(randVal & 1u) {
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data[i] = true;
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}
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i++;
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randVal >>= 1u;
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}
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}
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return data;
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}
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static bool *readDataFromFile(char *fileName, uint64_t *length) {
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printf("Reading data\n");
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FILE *file = fopen(fileName, "r");
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if(file == NULL) {
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fprintf(stderr, "Unable to open file %s\n", fileName);
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exit(1);
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}
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uint64_t pos = 0u;
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uint64_t size = 16384u;
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bool *data = calloc(size, sizeof(bool));
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int c = getc(file);
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while(c != EOF) {
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if(pos*8u + 8u >= size) {
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size <<= 1u;
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data = realloc(data, size);
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}
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uint8_t v = c;
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uint32_t i;
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for(i = 0u; i < 8u; i++) {
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if(v & 1u){
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data[8u*pos + 7u - i] = true;
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}
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v >>= 1u;
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}
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pos++;
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c = getc(file);
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}
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fclose(file);
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*length = pos*8u;
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printf("Read %llu bits\n", (long long)(*length));
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return data;
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}
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// Find out if the string has a repeated sub-string of the given length.
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static bool hasSubstringOfLength(uint32_t substringLen, bool *data, uint32_t dataLen, uint8_t *stringsSeen) {
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memset(stringsSeen, 0, 1u << (substringLen-3));
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uint64_t value = 0u;
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uint32_t i;
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for(i = 0u; i < substringLen; i++) {
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value = (value << 1u) | data[i];
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}
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for(i = substringLen; i < dataLen; i++) {
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if(stringsSeen[value >> 3u] & (1u << (value & 0x7u))) {
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printf("Found duplicate substring of length %u at %u(%x.%u): %llx\n", substringLen,
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i, i >> 3u, i & 0x7u, (long long)value);
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return true;
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}
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stringsSeen[value >> 3u] |= 1u << (value & 0x7u);
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value = ((value << 1u) | data[i]) & (((uint64_t)1u << substringLen)-1u);
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}
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return false;
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}
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int main(int argc, char **argv) {
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bool test = false;
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if(argc != 2) {
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fprintf(stderr, "Usage: findlongest file\n"
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" findlongest --test\n");
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return 1;
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}
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if(!strcmp(argv[1], "--test")) {
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test = true;
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}
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uint64_t dataLen;
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bool *data;
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if(test) {
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dataLen = 1u << 24u;
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data = generateRandomData(dataLen);
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} else {
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data = readDataFromFile(argv[1], &dataLen);
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}
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uint8_t *stringsSeen = calloc((uint64_t)1 << (MAX_STRING_SIZE-4u), sizeof(uint8_t));
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uint32_t len;
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for(len = 4u; len <= MAX_STRING_SIZE; len++) {
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if(!hasSubstringOfLength(len, data, dataLen, stringsSeen)) {
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printf("Maximum substring is %u long\n", len-1u);
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return 0;
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}
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}
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printf("Maximum substring is at least %u long\n", MAX_STRING_SIZE);
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return 0;
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}
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