?? unhuf.c
字號(hào):
/*******************************************************************************
* *
* UNHUF.C by Shaun Case April 1991 *
* *
* Written in Borland C++ 2.0 under MS-DOS 3.3 *
* *
* Decompresses a single file encoded with companion program HUF, *
* which uses Huffman encoding. *
* *
* This program is in the public domain. *
* *
* atman%ecst.csuchico.edu@RELAY.CS.NET *
* *
* *
*******************************************************************************/
#include <stdio.h>
#include <math.h>
#define FALSE 0
#define TRUE !FALSE
#define MAX_DECODE_TABLE_SIZE 520 /* 512 should be enough */
/* uncomment the next line to see the decode table at runtime. */
/*
#define DEBUG
*/
/* uncomment the next line to only uncompress the exact number of bytes */
/* that were originally encoded. If it is not defined, the routine will */
/* faster, but will generate up to 8 extra bytes at the end of the */
/* decompressed data. */
#define EXACT
typedef struct decode_table_element { /* template for decode table element (wow) */
unsigned char letter; /* which character to decode to */
char spare; /* force 16-bit word alignment */
short left; /* index of lower left element from tree */
short right; /* index of lower right element from tree */
}decode_table_element;
short array_max_index; /* max number of elements in array (to be */
/* determined in create_decode_table() ) */
unsigned long total; /* total number of unencoded bytes */
FILE *infile; /* file ptr to SYSTEM.HUF (compressed) */
FILE *outfile; /* file ptr to SYSTEM.UNH (decompressed) */
char *infilename; /* name of the input file */
char origfilename[13]; /* name of the original file */
struct decode_table_element /* array implementation of huffman tree */
decode_table[MAX_DECODE_TABLE_SIZE];
/******
*
* Datafile: All 16/32 bit quantities in Intel byte ordering
*
* 13 bytes : original filename (8.3 + '\0')
* 16 bits : number of array elements needed, N (N == 511 means 512 array
* elements -> 0..511)
* 32 bits : size of uncompressed original data in bytes
* N * 6 bytes : Array elements in order 0 .. N
* struct decode_table_element {
* char letter; 8 bits
* char spare; 8 bits
* short left; 16 bits
* short right; 16 bits
* }
* <?> : compressed data, effectively a bit stream
*
******/
int main(int argc, char **argv)
{
short read_header(void); /* prototype */
void show_bit_sequences(short index); /* prototype */
short uncompress(void); /* prototype */
if (argc != 2) { /* check command line argument validity */
puts("'unhuf file' decodes file.");
return 1;
}
puts("Unhuf by Shaun Case, 1991, public domain");
infilename=argv[1];
if (read_header() != 0) /* read in file name, size, decode table */
return 1;
#ifdef DEBUG
show_bit_sequences(0);
#endif
if (uncompress() != 0) /* uncompress the data & write to file */
return 1;
fclose(infile);
return 0;
}
/*
* read in the original filename, size, and decode table
*
*/
short read_header(void)
{
if ((infile=fopen(infilename, "rb")) == NULL) /* open file */
{
printf("Unable to open %s\n", infilename);
return 1;
}
if ( /* get original name */
fread((void *)origfilename, 1, 13, infile)
< 13
)
{
printf("Unable to read original filename from %s\n", infilename);
fclose(infile);
return 1;
}
/* get length of decode table */
if (
fread((void *)&array_max_index, sizeof(short), 1, infile)
< 1
)
{
printf("Unable to read number of array elements from %s\n", infilename);
fclose(infile);
return 1;
}
if ( /* get filesize in bytes */
fread((void *)&total, sizeof(unsigned long), 1, infile)
< 1
)
{
printf("Unable to read original byte count from %s\n", infilename);
fclose(infile);
return 1;
}
printf("Decoding %ld bytes to %s.\n", total, origfilename);
printf("Decode table contains %d elements.\n",array_max_index + 1);
if ( /* get decode table */
fread((void *)decode_table, sizeof(decode_table_element), array_max_index + 1, infile)
< (array_max_index + 1)
)
{
printf("Unable to read decode table from %s\n", infilename);
fclose(infile);
return 1;
}
return 0;
}
#ifdef DEBUG
short seq_len=0; /* routine is recursive, needs global storage */
/* length of current bit sequence */
/* this should probably be static inside sbs() */
/*
* display the bit sequences that represent each character.
* useful for debugging.
*
*/
void show_bit_sequences(short index)
{
static short temp_index=0;
static char bit_sequence[16]; /* where to build the huffman bit sequence */
if (decode_table[index].left != 0) /* if we are not at a leaf, go left */
{
bit_sequence[seq_len++]='1';
show_bit_sequences(decode_table[index].left);
seq_len--;
}
/* returned from going left, now try right */
if (decode_table[index].right != 0)
{
bit_sequence[seq_len++]='0'; /* if we are not at a leaf, go right */
show_bit_sequences(decode_table[index].right);
seq_len--;
}
if (decode_table[index].left != NULL) /* we are at an interior node going back up */
return;
/* we are at a leaf, therefore we have a complete bit sequence built */
bit_sequence[seq_len] = 0; /* append teriminating NULL to string */
printf("[%3d] %3d == %16s == %3d\n", temp_index, decode_table[index].letter, bit_sequence, seq_len);
temp_index++;
}
#endif
/*
* all the fputc() calls are unrolled for speed.
*
*/
short uncompress(void)
{
/* tcc68 can assign 7 register variables */
register short index = 0; /* "ptr" to "node" in "tree" */
/* actually an array index */
register unsigned unsigned int buffer = 0; /* 8 bit buffer */
register unsigned short fastleft; /* fast ptr to next left element */
register unsigned short fastleft0; /* fast ptr to left of root */
register long running_total = 0L;
if ((outfile=fopen(origfilename, "wb")) == NULL) /* open file */
{
printf("Unable to open %s\n", origfilename);
return 1;
}
fastleft0 = decode_table[0].left; /* setup frequently used vars */
fastleft = fastleft0;
while (1)
{
buffer=fgetc(infile); /* get 8 bits */
/* branch left if current bit == 1, else branch right */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1; /* rotate next bit to test postion */
fastleft = decode_table[index].left; /* set up frequently used var */
if (fastleft == 0) /* if we have decoded a char */
{
if (
fputc((int)decode_table[index].letter, outfile) /* write it to output */
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0; /* set "ptr" to top of "tree" */
fastleft = fastleft0; /* set up freq. used variable */
#ifdef EXACT
if (++running_total == total) goto finished; /* if we are done, quit. */
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and do it again for 2nd bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and 3rd bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and 4th bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index=0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and 5th bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and 6th bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and 7th bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
/* and finally, the 8th bit. */
index = ( (buffer & 0x0080) ? fastleft : decode_table[index].right);
buffer <<= 1;
fastleft = decode_table[index].left;
if (fastleft == 0)
{
if (
fputc((int)decode_table[index].letter, outfile)
== EOF
)
{
puts("Error writing to output file, out of disk space?");
return 1;
}
index = 0;
fastleft = fastleft0;
#ifdef EXACT
if (++running_total == total) goto finished;
#endif EXACT
#ifndef EXACT
++running_total;
#endif EXACT
}
#ifndef EXACT
if (running_total >= total)
goto finished;
#endif EXACT
}
finished:
fclose(outfile);
printf("Decoded %ld bytes.", running_total);
return 0;
}
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