Create huffman_decode.c

huffman_decode.c

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+/***************************************/
+/*     HUFFMAN DECODING PROGRAM        */
+/* CREATED BY ADEESHA SAVINDA DE SILVA */
+/*           12 June 2016              */
+/*     adeesha.savinda@gmail.com       */
+/***************************************/
+
+//Improved version with no buffer required.
+//i.e. .huffman file of any size can be decoded back
+#include <stdio.h>
+#include <string.h>
+
+//structure used to define a node
+typedef struct node_t {
+	struct node_t *left, *right;
+	int freq;
+	char c;
+} *node;
+
+//global variables
+int n_nodes = 0, qend = 1; 		//global variables for keep track of no.of nodes and end of the que
+struct node_t pool[256] = {{0}};        //pool of nodes
+node qqq[255], *q = qqq-1;      	//the priority que
+char buf[1024];				//a string array of the codes for each letter
+
+//function used to create a new node
+node new_node(int freq, char c, node a, node b)
+{
+	node n = pool + n_nodes++;
+	if (freq != 0){
+		n->c = c;			//assign the character 'c' to the character of the node (eventually a leaf)
+		n->freq = freq;			//assign frequency
+	}
+	else {
+		n->left = a, n->right = b;	//if there is no frequency provided with the invoking
+		n->freq = a->freq + b->freq;	//the removed nodes at the end of the que will be added to left and right
+	}
+	return n;
+}
+
+//function ued to insert a node into the priority que
+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;	//return the node
+}
+
+void import_table(FILE *fp_table, unsigned int *freq){
+	char c;						//temporary variable
+	int i = 0;
+
+	while((c=fgetc(fp_table))!=EOF){
+                freq[i++] = (unsigned char)c; 		//get the values from the .table file to update the huffman tree
+	}
+	for (i = 0; i < 128; i++)
+		if (freq[i]) qinsert(new_node(freq[i], i, 0, 0));	//insert new nodes into the que if there is a frequency
+	while (qend > 2)
+		qinsert(new_node(0, 0, qremove(), qremove()));		//build the tree
+}
+
+void decode(FILE *fp_huffman,FILE *fp_out){
+	int i=0,lim=0,j=0;
+	char c;
+	node n = q[1];
+
+	fscanf(fp_huffman,"%d",&lim);			//get the length of the bit stream from header
+	fseek(fp_huffman,1,SEEK_CUR);			//seek one position to avoid new line character of the header
+
+	printf("Decoded : \n");
+	for(i=0; i<lim; i++){
+		if(j==0)
+			c = fgetc(fp_huffman);
+		//if the anding of the character with b1000 0000 is true then,
+		if(c&128)	n = n->right;		//1 go right
+		else 		n = n->left;            //else go left
+                if(n->c){                               //until a leaf (node with a character) meets
+                        putchar(n->c);                  //spit that character out and
+                        fputc(n->c,fp_out);             //save the character in file
+                        n = q[1];                       //reset the que
+                }
+		c = c<<1;				//shift the character by 1
+		if(++j>7)
+			j = 0;
+	}
+
+	putchar('\n');
+	if (q[1] != n) printf("garbage input\n");	//the last node should end with a character which reset the que
+}
+
+int main(int argc, char* argv[]){
+	FILE *fp_table,*fp_huffman,*fp_out;		//FIFO pointers
+	char file_name[50]={0},temp[50]={0};		//file name
+	unsigned int freq[128] = {0};			//frequency of the letters
+
+	system("clear");
+	printf("**********************************************************************\n");
+	printf("                      COMMUNICATION  ENGINEERING\n");
+	printf("                                SHU M.Eng\n");
+	printf("                            -HUFFMAN DECODER-\n");
+	printf("**********************************************************************\n\n");
+
+
+	if( argc == 2 ) {
+		strcpy(file_name,argv[1]);				//commandline argument directly allows to compress the file
+		if(strstr(file_name,"huffman") == NULL){
+			printf("\nERROR:wrong file format!\n");
+			return 0;
+		}
+	}
+   	else if( argc > 2 ) {
+      		printf("Too many arguments supplied.\n");
+   	}
+   	else {
+		printf("Please enter the file to be compressed\t: "); 	//else a prompt comes to enter the file name
+		scanf("%s",file_name);
+		if(strstr(file_name,"huffman") == NULL){
+			printf("\nERROR:wrong file format!\n");
+			return 0;
+		}
+   	}
+
+	//import the frequency table and compressed from file and create the huffman tree
+	if((fp_huffman = fopen(file_name,"r"))==NULL){
+		printf("\nERROR: No such file\n");
+		return 0;
+	}
+	strcat(file_name,".table");			//file pointer for .table file
+	if((fp_table = fopen(file_name,"r"))==NULL){	//open the file stream
+		printf("\nERROR: Frequency table cannot be found\n");
+		return 0;
+	}
+	import_table(fp_table,freq);			//import the file and fills frequency array
+
+	*strstr(file_name,".huffman") = '\0';		//search for .huffman and remove it
+	strcpy(temp,"mkdir ");				//concatenating strings for the command
+	strcat(temp,file_name);				//to make a directory with the file name
+	system(strcat(temp,".decoded"));		//with .decoded at the end
+
+	strcpy(temp,"./");				//concatenating string to save the
+	strcat(temp,file_name);				//file with the original name in the .decoded derectory
+	strcat(temp,".decoded/");
+	if((fp_out = fopen(strcat(temp,file_name),"w"))==NULL){
+		printf("ERROR:Creating decoded file failed\n");	//if any error occured durig creating file; exit
+		return 0;
+	}
+	decode(fp_huffman,fp_out);			//decode the file and save
+
+	fclose(fp_huffman);				//close the file pointer for .huffman file
+	fclose(fp_table);				//close the file pointer for huffman frequency table file
+	fclose(fp_out);					//close file pointer for output file
+	return 0;
+}