void write_compression(unsigned char sigbits[255], unsigned long bitencodings[255], FILE * fphuff, FILE * fporig)
{//write the huffman compression to the output file
//compression variables
int readchar;
int numsignificant;
unsigned long encoding;
//1000 0000 0000 0000 0000 0000 0000 0000
unsigned long mask = 0x80000000;
bitspot = 0;
currentbyte = 0;
//write file
while (!feof(fporig))
{//read every character in the file until the EOF is found
readchar = fgetc(fporig);
if (readchar != EOF) //keeps the standard EOF file from being written, we must write our own pseudo EOF
{//save encoding, save amount of digits, shift the most significant bit to the far left
encoding = bitencodings[(int) readchar];
numsignificant = sigbits[(int) readchar];
encoding <<= (32 - numsignificant);
while (numsignificant > 0)
{//loop until we have used all of the significant bits in our encoding
if ((mask & encoding) == mask)
{//if the furthest left bit is 1, pack a 1
write_bit(fphuff, 1);
} else
{//if the furthest left bit is 0, pack a 0
write_bit(fphuff, 0);
}
//set up the next bit to write, decrement the number of bits still to write
encoding <<= 1;
--numsignificant;
}
}
}
//write the pseudo EOF character, using ASCII NULL = 0000 0000
encoding = bitencodings[0];
numsignificant = sigbits[0];
encoding <<= (32 - numsignificant);
//same as above, except dedicated to writing pseudo EOF
while (numsignificant > 0)
{
if ((mask & encoding) == mask)
{
write_bit(fphuff, 1);
} else
{
write_bit(fphuff, 0);
}
encoding <<= 1;
--numsignificant;
}
//finish off the byte with 0's and write it
pad_file(fphuff);
return;
}
int main(int argc, char * * argv)
{
int * weights = malloc(sizeof(int) * 256);
char * filename = argv[1];
int count;
int numNodes;
numchar = 0;
unsigned char sigbits[255] = {0};
unsigned long bitencodings[255] = {0};
Node * temp = NULL;
Node * head = NULL;
Node * root = NULL;
if (argc > 2)
{//error checking
fprintf(stderr, "\nERROR! TOO MANY INPUTS, huff.c ACCEPTS 1 INPUT: FILENAME.txt\n\n");
return (ERROR);
}
FILE * fp = fopen(filename, "r");
if (fp == NULL)
{//error checking
fprintf(stderr, "\nERROR! FILE COULD NOT BE OPENED.\n\n");
return (ERROR);
}
//counting the frequencies of chars in the file
weights = parse_file(weights, fp);
fclose(fp);
//generate linked list of non 0 weighted chars which are sorted in ascending order
for (count = 0, numNodes = 0; count < 256; ++count)
{
if (weights[count] != 0)
{//use all characters that showed up in the input file
temp = create_node((char) count, weights[count]);
if (head == NULL)
{//if its the first node, set it as the head
head = temp;
} else
{//insert the node into the list in ascending order
head = insert_node(head, temp);
}//keep track of the number of nodes in the list
++numNodes;
}
}
//adding pseudo-EOF node
temp = create_node((char) 0, 1);
head = insert_node(head, temp);
++numNodes;
//make huffman tree out of linked list
root = create_tree(head, numNodes);
//create sigbits and encodings from huffman tree
bits = 0;
countbits = 0;
generate_encodings(root, sigbits, bitencodings);
//file to read from
FILE * fporig = fopen(filename, "r");
rewind(fporig);
//file to write to
strcat(filename, ".huff");
FILE * fphuff = fopen(filename, "w");
if (fporig == NULL || fphuff == NULL)
{//error checking
fprintf(stderr, "\nERROR! FILE COULD NOT BE OPENED.\n\n");
return (ERROR);
}
//write header
bitspot = 0;
currentbyte = 0;
write_header(root, fphuff);
//write an extra 0 so that the header reader can reach the exit condition
write_bit(fphuff, 0);
//pad with zeroes
pad_file(fphuff);
//write the number of characters
fwrite(&numchar, sizeof(unsigned int), 1, fphuff);
//write a newline which will mark the end of the header
unsigned char newline = '\n';
fwrite(&newline, sizeof(unsigned char), 1, fphuff);
//write compressed data with pseudo EOF and necessary padding
write_compression(sigbits, bitencodings, fphuff, fporig);
//were done
fclose(fporig);
fclose(fphuff);
destroy_tree(root);
return (0);
}
int util_save_image(char *orig_file_name, char *save_file_name)
{
int origFd = -1, saveFd = -1;
char *start_data, *end_data, *start_text, *end_round;
struct exec old_hdr, new_hdr;
struct stat old_stat;
int n, page_size, length_text, length_data;
if ((origFd = open(orig_file_name, 0)) < 0) {
perror(orig_file_name);
(void) fprintf(stderr, "Cannot open original a.out file\n");
goto bad;
}
if (fstat(origFd, &old_stat) < 0) {
perror(orig_file_name);
(void) fprintf(stderr, "Cannot stat original a.out file\n");
goto bad;
}
/*
* Read the a.out header from the original file.
*/
if (read(origFd, (char *) &old_hdr, sizeof(old_hdr)) != sizeof(old_hdr)) {
perror(orig_file_name);
(void) fprintf(stderr, "Cannot read original a.out header\n");
goto bad;
}
if (N_BADMAG(old_hdr)) {
(void) fprintf(stderr, "File %s has a bad magic number (%o)\n",
orig_file_name, old_hdr.a_magic);
goto bad;
}
if (old_hdr.a_magic != ZMAGIC) {
(void) fprintf(stderr, "File %s is not demand-paged\n", orig_file_name);
goto bad;
}
/*
* Open the output file.
*/
if (access(save_file_name, /* F_OK */ 0) == 0) {
(void) unlink(save_file_name);
}
if ((saveFd = creat(save_file_name, 0777)) < 0) {
if (errno == ETXTBSY) {
(void) unlink(save_file_name);
saveFd = creat(save_file_name, 0777);
}
if (saveFd < 0) {
perror(save_file_name);
(void) fprintf(stderr, "Cannot create save file.\n");
goto bad;
}
}
/*
* Find out how far the data segment extends.
*/
new_hdr = old_hdr;
end_data = sbrk(0);
page_size = getpagesize();
n = ((((int) end_data) + page_size - 1) / page_size) * page_size;
end_round = (char *) n;
if (end_round > end_data) {
end_data = sbrk(end_round - end_data);
}
#ifdef vax
start_text = 0;
length_text = new_hdr.a_text;
start_data = (char *) old_hdr.a_text;
length_data = end_data - start_data;
#endif vax
#ifdef sun
start_text = (char *) N_TXTADDR(old_hdr) + sizeof(old_hdr);
length_text = old_hdr.a_text - sizeof(old_hdr);
start_data = (char *) N_DATADDR(old_hdr);
length_data = end_data - start_data;
#endif sun
new_hdr.a_data = end_data - start_data;
new_hdr.a_bss = 0;
/*
* First, the header plus enough pad to extend up to N_TXTOFF.
*/
if (write(saveFd, (char *) &new_hdr, (int) sizeof(new_hdr)) !=
sizeof(new_hdr)) {
perror("write");
(void) fprintf(stderr, "Error while copying header.\n");
goto bad;
}
if (! pad_file(saveFd, N_TXTOFF(old_hdr) - sizeof(new_hdr))) {
(void) fprintf(stderr, "Error while padding.\n");
goto bad;
}
/*
* Copy our text segment
*/
if (write(saveFd, start_text, length_text) != length_text) {
perror("write");
(void) fprintf(stderr, "Error while copying text segment.\n");
goto bad;
}
/*
* Copy our data segment
*/
if (write(saveFd, start_data, length_data) != length_data) {
perror("write");
(void) fprintf(stderr, "Error while copying data segment.\n");
goto bad;
}
/*
* Copy the symbol table and everything else.
* This takes us to the end of the original file.
*/
(void) lseek(origFd, (long) N_SYMOFF(old_hdr), 0);
if (! copy_file(origFd, saveFd, old_stat.st_size - N_SYMOFF(old_hdr))) {
(void) fprintf(stderr, "Error while copying symbol table.\n");
goto bad;
}
(void) close(origFd);
(void) close(saveFd);
return 1;
bad:
if (origFd >= 0) (void) close(origFd);
if (saveFd >= 0) (void) close(saveFd);
return 0;
}