c-basic/huffman/huffman.c

#include <errno.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

off_t fsize(const char *filename) {
    struct stat st;

    if (stat(filename, &st) == 0)
        return st.st_size;

    fprintf(stderr, "Cannot determine size of %s: %s\n", filename,
            strerror(errno));

    return -1;
}

void helper() {
    printf("huffman compression algorithm implementation for educational "
            "purposes.\n\nSyntax:\nhuffman -f fileToCompress\t\tcompress the "
            "given file\nhuffman -xf fileToDecompress\t\tdecompress the given "
            "file\nhuffman -h\t\t\t\tshow this help\nhuffman -v\t\t\t\tverbose\n");
}

int main(int argc, char *argv[]) {
    int opt;
    bool extract_mode = false;
    bool verbose = false;
    bool debug = false;
    char *filestring = NULL;
    uint64_t filelen;

    FILE *fptrR = NULL; 	// file pointer for reading
    FILE *fptrW = NULL; 	// file pointer for writing

    while ((opt = getopt(argc, argv, "dvxhf:")) != -1) {
        if (debug)
            printf("optarg is: %s\n", optarg);
        switch (opt) {
            case 'v':
                verbose = true;
                break;
            case 'd':
                debug = true;
                break;
            case 'f':
                filestring = optarg;
                break;
            case 'h':
                helper();
                exit(0);
                break;
            case 'x':
                extract_mode = true;
                break;
            default:
                fprintf(stderr, "Usage: %s [-dvhx -f] [file]\n", argv[0]);
                exit(EXIT_FAILURE);
        }
    }

    // Now optind (declared extern int by <unistd.h>) is the index of the first
    // non-option argument. If it is >= argc, there were no non-option arguments.

    if (verbose)
        printf("selected file: %s\n", filestring);

    if (filestring) {
        if(debug)
            printf("[DEBUG]processing given file argument.\n");
        // open the given file in binary mode, I want this to work with any files,
        // not just textfiles.
        fptrR = fopen(filestring, "rb");
        if (fptrR == NULL) {
            fprintf(stderr, "The given file does not exist or is unavailable.\n");
            exit(EXIT_FAILURE);
        }
        // causes bugs.
        fseek(fptrR, 0L, SEEK_END);
        filelen = ftell(fptrR);
        fseek(fptrR, 0L, SEEK_SET);
    } 
    else {
        // empty filestring or filestring is NULL
        fprintf(stderr, "Usage: %s [-dvhx -f] [file]\n", argv[0]);
        exit(EXIT_FAILURE);
    }

    // TODO check file size and spit a "what the heck im not a 10x dev, do a
    if(verbose)
        printf("filesize: %ldB\n", filelen);

    if (extract_mode) {
        printf("extracting is not yet implemented.\n");
        // decompress the file
    }

    else {
        // compress the file
        if (verbose)
            printf("compressing file...\n");

        // frequency analysis

        uint8_t buf[512];

        // dump start of file if debugging
        // FIXME add conditions if the part to print is smaller than 512B
        if(debug){
            printf("[DEBUG]First 512 bytes are:\n");
            fread(buf, 1, 512, fptrR);
            for(int i=0;i<512;i++){
                if(i%16==0)
                    printf("%08x\t", i);
                printf("%02x ", buf[i]);
                if(i%16==7)
                    printf(" ");
                if(i%16==15){
                    printf("\n");
                }
            }
        }

        uint64_t occurences[256];
        for(int i=0;i<256;i++){
            occurences[i]=0;    
        }
        // FIXME doesnt loop through full file! only 50% for larger files
        // Backup occurence counting algorithm
        /*
           while(!feof(fptrR)){
           fseek(fptrR, 512, SEEK_CUR);
           if(fread(buf, 1, 512, fptrR)){
           for(int i=0;i<512;i++){
           occurences[buf[i]]++;
           }
           }
           else{
           fprintf(stderr, "Error when processing file.\n");
           exit(EXIT_FAILURE);
           }

        // advance filepointer 512 bytes foreward. If not possible, set endOfFile flag.
        // FIXME
        offset += 512;
        }
        */
        // backup
        while(1){
            fseek(fptrR, 512, SEEK_CUR);	// this line seems the be making the most problems

            //	On  success, fread() and fwri)te() return the number of items read or written.  
            //	This number equals the number of bytes transferred only when size is
            //	1.  If an error occurs, or the end of the file is reached, the return value is a short item count (or zero).
            //	fread() does not distinguish between end-of-file and error, and callers must use feof(3) and ferror(3) to determine which occurred.

            // FIXME )This is a buggy mess
            if(512 == fread(buf, 1, 512, fptrR)){
                for(int i=0;i<512;i++){
                    occurences[buf[i]]++;
                }
            }
            else if(0 == fread(buf, 1, 512, fptrR)){
                if(debug)
                    printf("[DEBUG]fread returned 0! ftell for current position is %lu\n", ftell(fptrR));
                break;
            }
            else{
                fprintf(stderr, "Error when processing file: %lu, At offset %lu\n",fread(buf, 1, 512, fptrR), ftell(fptrR));
                exit(EXIT_FAILURE);
            }
            if(ftell(fptrR) > filelen) {
                // ??? unknown error
                fprintf(stderr, "tried reading further than the file is long somehow?\n");
                exit(EXIT_FAILURE);
            }
        }
        // ALMOST WORKS! ~200 bytes lost for a 10M file!!!
        uint8_t bufMini[1];
        //        while(1){
        //            if(fread(bufMini, 1, 1, fptrR)){
        //                occurences[buf[0]]++;	
        //            }
        //            else{
        //                if(ferror(fptrR)){
        //                    fprintf(stderr, "encountered error when reading file.\n");
        //                    exit(EXIT_FAILURE);
        //                }
        //            }
        //            fseek(fptrR, 1, SEEK_SET);
        //            if(ferror(fptrR)){
        //                fprintf(stderr, "encountered error when reading file.\n");
        //                exit(EXIT_FAILURE);
        //            }
        //            else if(feof(fptrR)){
        //                break;
        //            }
        //        }
        if(debug){
            printf("Occurences (Hex):\n");
            for(int i=0;i<256;i++){
                if(i%4==0)
                    printf("\n");
                printf("0x%02x: %016lx\t", i, occurences[i]);
            }
            printf("\n\nfile length(by pointer):\t\t%luB\n", filelen);
            long long int addedUpOccurences = 0; // FIXME might not be enough storage for larger files!
            for(int i=0;i<256;i++){
                addedUpOccurences += occurences[i];
            }
            printf("file length(added up occurences):\t%lldB\n", addedUpOccurences);
        }

        if(verbose)
            printf("\n\nDone calculating occurences of bytes.\n");

        // TODO
        // calculate the frequencies of the bytes.
        double frequencies[256];
        for(int i=0;i<256;i++){
            frequencies[i]=((double)occurences[i]/(double)filelen)*100;	// calculate frequencies of bytes in percent (example: 05.23 (%))
        }
        if(debug){
            printf("Frequencies:\n");
            for(int i=0;i<256;i++){
                if(i%8==0)
                    printf("\n");
                printf("0x%02x: %05.02f%%\t", i, frequencies[i]);
            }
            double addedUpFrequencies = 0; 
            for(int i=0;i<256;i++){
                addedUpFrequencies += frequencies[i];
            }
            printf("\n\nadded up frequencies: %05.02f%%\n",addedUpFrequencies);
        }
    } 
    fclose(fptrR);
    printf("\n");
    exit(EXIT_SUCCESS);
}