246 lines
8.0 KiB
C
246 lines
8.0 KiB
C
#include <errno.h>
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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 <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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off_t fsize(const char *filename) {
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struct stat st;
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if (stat(filename, &st) == 0)
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return st.st_size;
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fprintf(stderr, "Cannot determine size of %s: %s\n", filename,
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strerror(errno));
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return -1;
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}
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void helper() {
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printf("huffman compression algorithm implementation for educational "
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"purposes.\n\nSyntax:\nhuffman -f fileToCompress\t\tcompress the "
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"given file\nhuffman -xf fileToDecompress\t\tdecompress the given "
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"file\nhuffman -h\t\t\t\tshow this help\nhuffman -v\t\t\t\tverbose\n");
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}
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int main(int argc, char *argv[]) {
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int opt;
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bool extract_mode = false;
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bool verbose = false;
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bool debug = false;
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char *filestring = NULL;
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uint64_t filelen;
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FILE *fptrR = NULL; // file pointer for reading
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FILE *fptrW = NULL; // file pointer for writing
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while ((opt = getopt(argc, argv, "dvxhf:")) != -1) {
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if (debug)
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printf("optarg is: %s\n", optarg);
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switch (opt) {
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case 'v':
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verbose = true;
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break;
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case 'd':
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debug = true;
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break;
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case 'f':
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filestring = optarg;
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break;
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case 'h':
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helper();
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exit(0);
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break;
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case 'x':
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extract_mode = true;
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break;
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default:
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fprintf(stderr, "Usage: %s [-dvhx -f] [file]\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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}
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// Now optind (declared extern int by <unistd.h>) is the index of the first
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// non-option argument. If it is >= argc, there were no non-option arguments.
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if (verbose)
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printf("selected file: %s\n", filestring);
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if (filestring) {
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if(debug)
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printf("[DEBUG]processing given file argument.\n");
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// open the given file in binary mode, I want this to work with any files,
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// not just textfiles.
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fptrR = fopen(filestring, "rb");
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if (fptrR == NULL) {
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fprintf(stderr, "The given file does not exist or is unavailable.\n");
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exit(EXIT_FAILURE);
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}
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// causes bugs.
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fseek(fptrR, 0L, SEEK_END);
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filelen = ftell(fptrR);
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fseek(fptrR, 0L, SEEK_SET);
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}
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else {
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// empty filestring or filestring is NULL
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fprintf(stderr, "Usage: %s [-dvhx -f] [file]\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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// TODO check file size and spit a "what the heck im not a 10x dev, do a
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if(verbose)
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printf("filesize: %ldB\n", filelen);
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if (extract_mode) {
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printf("extracting is not yet implemented.\n");
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// decompress the file
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}
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else {
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// compress the file
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if (verbose)
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printf("compressing file...\n");
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// frequency analysis
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uint8_t buf[512];
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// dump start of file if debugging
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// FIXME add conditions if the part to print is smaller than 512B
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if(debug){
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printf("[DEBUG]First 512 bytes are:\n");
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fread(buf, 1, 512, fptrR);
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for(int i=0;i<512;i++){
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if(i%16==0)
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printf("%08x\t", i);
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printf("%02x ", buf[i]);
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if(i%16==7)
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printf(" ");
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if(i%16==15){
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printf("\n");
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}
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}
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}
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uint64_t occurences[256];
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for(int i=0;i<256;i++){
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occurences[i]=0;
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}
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// FIXME doesnt loop through full file! only 50% for larger files
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// Backup occurence counting algorithm
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/*
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while(!feof(fptrR)){
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fseek(fptrR, 512, SEEK_CUR);
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if(fread(buf, 1, 512, fptrR)){
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for(int i=0;i<512;i++){
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occurences[buf[i]]++;
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}
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}
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else{
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fprintf(stderr, "Error when processing file.\n");
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exit(EXIT_FAILURE);
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}
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// advance filepointer 512 bytes foreward. If not possible, set endOfFile flag.
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// FIXME
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offset += 512;
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}
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*/
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// backup
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while(1){
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fseek(fptrR, 512, SEEK_CUR); // this line seems the be making the most problems
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// On success, fread() and fwri)te() return the number of items read or written.
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// This number equals the number of bytes transferred only when size is
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// 1. If an error occurs, or the end of the file is reached, the return value is a short item count (or zero).
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// fread() does not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred.
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// FIXME )This is a buggy mess
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if(512 == fread(buf, 1, 512, fptrR)){
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for(int i=0;i<512;i++){
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occurences[buf[i]]++;
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}
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}
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else if(0 == fread(buf, 1, 512, fptrR)){
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if(debug)
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printf("[DEBUG]fread returned 0! ftell for current position is %lu\n", ftell(fptrR));
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break;
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}
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else{
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fprintf(stderr, "Error when processing file: %lu, At offset %lu\n",fread(buf, 1, 512, fptrR), ftell(fptrR));
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exit(EXIT_FAILURE);
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}
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if(ftell(fptrR) > filelen) {
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// ??? unknown error
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fprintf(stderr, "tried reading further than the file is long somehow?\n");
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exit(EXIT_FAILURE);
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}
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}
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// ALMOST WORKS! ~200 bytes lost for a 10M file!!!
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uint8_t bufMini[1];
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// while(1){
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// if(fread(bufMini, 1, 1, fptrR)){
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// occurences[buf[0]]++;
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// }
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// else{
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// if(ferror(fptrR)){
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// fprintf(stderr, "encountered error when reading file.\n");
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// exit(EXIT_FAILURE);
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// }
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// }
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// fseek(fptrR, 1, SEEK_SET);
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// if(ferror(fptrR)){
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// fprintf(stderr, "encountered error when reading file.\n");
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// exit(EXIT_FAILURE);
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// }
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// else if(feof(fptrR)){
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// break;
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// }
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// }
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if(debug){
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printf("Occurences (Hex):\n");
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for(int i=0;i<256;i++){
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if(i%4==0)
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printf("\n");
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printf("0x%02x: %016lx\t", i, occurences[i]);
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}
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printf("\n\nfile length(by pointer):\t\t%luB\n", filelen);
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long long int addedUpOccurences = 0; // FIXME might not be enough storage for larger files!
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for(int i=0;i<256;i++){
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addedUpOccurences += occurences[i];
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}
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printf("file length(added up occurences):\t%lldB\n", addedUpOccurences);
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}
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if(verbose)
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printf("\n\nDone calculating occurences of bytes.\n");
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// TODO
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// calculate the frequencies of the bytes.
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double frequencies[256];
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for(int i=0;i<256;i++){
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frequencies[i]=((double)occurences[i]/(double)filelen)*100; // calculate frequencies of bytes in percent (example: 05.23 (%))
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}
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if(debug){
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printf("Frequencies:\n");
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for(int i=0;i<256;i++){
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if(i%8==0)
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printf("\n");
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printf("0x%02x: %05.02f%%\t", i, frequencies[i]);
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}
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double addedUpFrequencies = 0;
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for(int i=0;i<256;i++){
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addedUpFrequencies += frequencies[i];
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}
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printf("\n\nadded up frequencies: %05.02f%%\n",addedUpFrequencies);
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}
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}
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fclose(fptrR);
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printf("\n");
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exit(EXIT_SUCCESS);
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}
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