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Problem in Huffman Encoding for Large files

ayu05ayu05 germanyPosts: 2Member

My program works fine for text files containing up to 3-4 lines.. But it has a problem encoding when there are more lines or characters. Please suggest me some solution. Here is my program:

#include <stdio.h>
#include <string.h>
#include<fstream>
#include<string> 
#include<iostream>

using namespace std;
typedef struct node_t {
    struct node_t *left, *right;
    int freq;
    char c;
} *node;

struct node_t pool[256] = {{0}};
node qqq[255], *q = qqq - 1;    
int n_nodes = 0, qend = 1;
char *code[128] = {0}, buf[1024];

node new_node(int freq, char c, node a, node b)
{
node n = pool + n_nodes++;
if (freq) n->c = c, n->freq = freq;
else {
    n->left = a, n->right = b;
    n->freq = a->freq + b->freq;
}
return n;
}

/* priority queue */
void qinsert(node n)
{
    int j, i = qend++;
    while ((j = i / 2)) {
    if (q[j]->freq <= n->freq) break;
    q[i] = q[j], i = j;
    }
    q[i] = n;
}   

node qremove()
{
    int i, l;
    node n = q[i = 1];

    if (qend < 2) return 0;
    qend--;
    while ((l = i * 2) < qend) {
        if (l + 1 < qend && q[l + 1]->freq < q[l]->freq) l++;
        q[i] = q[l], i = l;
    }
    q[i] = q[qend];
    return n;
}

/* walk the tree and put 0s and 1s */
void build_code(node n, char *s, int len)
{
    static char *out = buf;
    if (n->c) {
    s[len] = 0;
    strcpy(out, s);
    code[n->c] = out;
    out += len + 1;
    return;
    }

s[len] = '0'; build_code(n->left,  s, len + 1);
s[len] = '1'; build_code(n->right, s, len + 1);
}

void init(const char *s)
{
    int i, freq[128] = {0};
    char c[16];

while (*s) freq[(int)*s++]++;

for (i = 0; i < 128; i++)
    if (freq[i]) qinsert(new_node(freq[i], i, 0, 0));

while (qend > 2) 
    qinsert(new_node(0, 0, qremove(), qremove()));

build_code(q[1], c, 0);
}

void encode(const char *s, char *out)
{
    while (*s) {
    strcpy(out, code[*s]);
    out += strlen(code[*s++]);
    }
}

void decode(const char *s, node t)
{
    node n = t;
    while (*s) {
    if (*s++ == '0') n = n->left;
    else n = n->right;

    if (n->c) putchar(n->c), n = t;
    }

putchar('\n');putchar('\n');
if (t != n) printf("garbage input\n");
}

int main(void)
{
int i;

string filename;
ifstream myfile;
cout<<"Please Enter File Name that you want to Encode: ";
getline(cin,filename);
filename += ".txt";

myfile.open(filename.c_str());

std::string str;
str.assign( (std::istreambuf_iterator<char>(myfile) ),
            (std::istreambuf_iterator<char>()    ) );
std::cout<<"\n"<<str<<endl<<endl;

const char * c = str.c_str();
char buf[1024];

 init(c);
for (i = 0; i < 128; i++)
    if (code[i]) printf("'%c': %s\n", i, code[i]);

encode(c, buf);
ofstream binfile("binary.txt");
if(binfile.is_open())
{
    binfile<<buf;
    binfile.close();
}

printf("\nEncoded:\n%s\n", buf);

printf("\n\nDecoded:\n");
ifstream dfile("binary.txt");

while(getline(dfile,str))
    cout<<str<<endl<<endl;
const char * y = str.c_str();
decode(y, q[1]);

return 0;
}
Tagged:

Comments

  • Malcolm_McLeanMalcolm_McLean Posts: 251Member ✭✭

    There are quite a few errors in this. Encode is altering "out" but throwing the result away. The line orientated handling of binary.txt looks suspicious. Have you printed out your code list and checked that no code is a prefix to any other?

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