usaa21/sk2a/compressor.c

#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "compressor.h"
#define BUFSIZE 1024

int basic_string = 0;


char *rotateString(char *str, int count) {

    size_t len = strlen(str);
    int counter;

    for(counter=0;counter < len;counter++) {
        int value = (int)str[counter];

        if((char)value != ' ') {
            value = value + count;
            str[counter] = value;
        }
    }

    return str;
}

char* bwt_compress(char buffer[BUFSIZE * 2]){
    char* encoded = (char*) calloc(BUFSIZE *2, sizeof(char));
    char* rotation[strlen(buffer)];

    char* temp = (char*) calloc(BUFSIZE * 2, sizeof(char));

    for(int i = 0; i < strlen(buffer); i++){
        rotation[i] = (char*) calloc(BUFSIZE * 2, sizeof(char));
    }

    for(int i = 0; i < strlen(buffer); i++){
        strcpy(rotation[i], rotateString(buffer, -1));
    }


    for(int i = 0; i < strlen(buffer); i++){
        for(int j = 0; j < strlen(buffer); j++){
            if(strcmp(rotation[j], rotation[j+1]) > 0){
                strcpy(temp, rotation[j]);
                strcpy(rotation[j], rotation[j+1]);
                strcpy(rotation[j+1], temp);
            }
        }
    }

    for(int i = 0; i < strlen(buffer); i++){
        strncat(encoded, &rotation[i][strlen(rotation[i])], 1);
        if(strcmp(rotation[i], buffer) == 0){
            basic_string = i;
        }
    }

    return encoded;
}

char* run_length(char buffer[BUFSIZE]){
    char* encoded = (char*) calloc(BUFSIZE * 2, sizeof(char));
    int counter = 1;
    int i = 1;

    while(i < strlen(buffer)+1){
        for(; i < strlen(buffer)+1; i++){
            if(buffer[i] == buffer[i-1])
                counter++;
            else {
                char* temp = (char*) calloc(5, sizeof(char));
                sprintf(temp, "%d", counter);
                strncat(encoded, temp, strlen(temp));
                strncat(encoded, &buffer[i-1], 1);
                i++;
                counter = 1;
                break;
            }
        }
    }

    return encoded;
}


void compress(FILE* infile,FILE* outfile){
    char buffer[BUFSIZE];
    memset(buffer,0,BUFSIZE);
    while(1) {
        int insize = (int) fread(buffer, sizeof(char), BUFSIZE, infile);
        if (insize == 0) {
            if (feof(infile)) {
                // end of file
                break;
            }
            assert(!ferror(infile));
        }

        char outbuf[BUFSIZE*2];
        strncpy(outbuf, run_length(bwt_compress(buffer)), BUFSIZE*2-1);

        fwrite(outbuf,sizeof(char), strlen(outbuf),outfile);
    }
}

char* bwt_decompress(char buffer[BUFSIZE * 2]){
    char* rotation[strlen(buffer)];

    for(int i = 0; i < strlen(buffer); i++){
        rotation[i] = (char*) calloc(BUFSIZE * 2, sizeof(char));
    }

    for(int i = 0; i < strlen(buffer); i++){
        for(int j = 0; j < strlen(buffer); j++){
            rotation[j][i] = buffer[strlen(buffer) - 1 -j];
        }

        char* temp = (char*) calloc(BUFSIZE * 2, sizeof(char));

        for(int iterator = 0; iterator < strlen(buffer); iterator++){
            for(int j = 0; j < strlen(buffer); j++){
                if(strcmp(rotation[j], rotation[j+1]) > 0){
                    strcpy(temp, rotation[j]);
                    strcpy(rotation[j], rotation[j+1]);
                    strcpy(rotation[j+1], temp);
                }
            }
        }
    }

    return rotation[basic_string];
}

char* run_length_decompress(char buffer[BUFSIZE * 2]){
    char* decoded = (char*) calloc(BUFSIZE, sizeof(char));
    int i = 0;

    while(i < strlen(buffer)){
        char* temp = (char*) calloc(5, sizeof(char));
        for(; i < strlen(buffer); i++){
            if(isdigit(buffer[i])){
                strncat(temp, &buffer[i], 1);
            }
            else{
                for(int j = 0; j < atoi(temp); j++)
                    strncat(decoded, &buffer[i], 1);
                i++;
                break;
            }
        }
        memset(temp, '\0', 5);
    }

    return decoded;
}

void decompress(FILE* infile,FILE* outfile){
    char buffer[BUFSIZE * 2];
    memset(buffer, 0, BUFSIZE*2);
    while(1){
        int insize = (int)fread(buffer,sizeof(char),BUFSIZE * 2,infile);
        if (insize == 0){
            if (feof(infile)){
                // end of file
                break;
            }
            assert(!ferror(infile));
        }
        char outbuf[BUFSIZE];
        strncpy(outbuf, bwt_decompress(run_length_decompress(buffer)), BUFSIZE-1);

        fwrite(outbuf,sizeof(char), strlen(outbuf),outfile);
    }
}