/**************************************************************
        lzhuf.c
        written by Haruyasu Yoshizaki 11/20/1988
        some minor changes 4/6/1989
        comments translated by Haruhiko Okumura 4/7/1989
**************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

FILE  *infile, *outfile;
unsigned long int  textsize = 0, codesize = 0, printcount = 0;

char wterr[] = "Can't write.";

void Error(char *message)
{
        printf("\n%s\n", message);
        exit(EXIT_FAILURE);
}

/********** LZSS compression **********/

#define N               4096    /* buffer size */
#define F               60      /* lookahead buffer size */
#define THRESHOLD       2
#define NIL             N       /* leaf of tree */

unsigned char
                text_buf[N + F - 1];
int             match_position, match_length,
                lson[N + 1], rson[N + 257], dad[N + 1];

void InitTree(void)  /* initialize trees */
{
        int  i;

        for (i = N + 1; i <= N + 256; i++)
                rson[i] = NIL;                  /* root */
        for (i = 0; i < N; i++)
                dad[i] = NIL;                   /* node */
}

void InsertNode(int r)  /* insert to tree */
{
        int  i, p, cmp;
        unsigned char  *key;
        unsigned c;

        cmp = 1;
        key = &text_buf[r];
        p = N + 1 + key[0];
        rson[r] = lson[r] = NIL;
        match_length = 0;
        for ( ; ; ) {
                if (cmp >= 0) {
                        if (rson[p] != NIL)
                                p = rson[p];
                        else {
                                rson[p] = r;
                                dad[r] = p;
                                return;
                        }
                } else {
                        if (lson[p] != NIL)
                                p = lson[p];
                        else {
                                lson[p] = r;
                                dad[r] = p;
                                return;
                        }
                }
                for (i = 1; i < F; i++)
                        if ((cmp = key[i] - text_buf[p + i]) != 0)
                                break;
                if (i > THRESHOLD) {
                        if (i > match_length) {
                                match_position = ((r - p) & (N - 1)) - 1;
                                if ((match_length = i) >= F)
                                        break;
                        }
                        if (i == match_length) {
                                if ((c = ((r - p) & (N - 1)) - 1) < match_position) {
                                        match_position = c;
                                }
                        }
                }
        }
        dad[r] = dad[p];
        lson[r] = lson[p];
        rson[r] = rson[p];
        dad[lson[p]] = r;
        dad[rson[p]] = r;
        if (rson[dad[p]] == p)
                rson[dad[p]] = r;
        else
                lson[dad[p]] = r;
        dad[p] = NIL;  /* remove p */
}

void DeleteNode(int p)  /* remove from tree */
{
        int  q;

        if (dad[p] == NIL)
                return;                 /* not registered */
        if (rson[p] == NIL)
                q = lson[p];
        else
        if (lson[p] == NIL)
                q = rson[p];
        else {
                q = lson[p];
                if (rson[q] != NIL) {
                        do {
                                q = rson[q];
                        } while (rson[q] != NIL);
                        rson[dad[q]] = lson[q];
                        dad[lson[q]] = dad[q];
                        lson[q] = lson[p];
                        dad[lson[p]] = q;
                }
                rson[q] = rson[p];
                dad[rson[p]] = q;
        }
        dad[q] = dad[p];
        if (rson[dad[p]] == p)
                rson[dad[p]] = q;
        else
                lson[dad[p]] = q;
        dad[p] = NIL;
}

/* Huffman coding */

#define N_CHAR          (256 - THRESHOLD + F)
                                /* kinds of characters (character code = 0..N_CHAR-1) */
#define T               (N_CHAR * 2 - 1)        /* size of table */
#define R               (T - 1)                 /* position of root */
#define MAX_FREQ        0x8000          /* updates tree when the */
                                        /* root frequency comes to this value. */
typedef unsigned char uchar;


/* table for encoding and decoding the upper 6 bits of position */

/* for encoding */
uchar p_len[64] = {
        0x03, 0x04, 0x04, 0x04, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08
};

uchar p_code[64] = {
        0x00, 0x20, 0x30, 0x40, 0x50, 0x58, 0x60, 0x68,
        0x70, 0x78, 0x80, 0x88, 0x90, 0x94, 0x98, 0x9C,
        0xA0, 0xA4, 0xA8, 0xAC, 0xB0, 0xB4, 0xB8, 0xBC,
        0xC0, 0xC2, 0xC4, 0xC6, 0xC8, 0xCA, 0xCC, 0xCE,
        0xD0, 0xD2, 0xD4, 0xD6, 0xD8, 0xDA, 0xDC, 0xDE,
        0xE0, 0xE2, 0xE4, 0xE6, 0xE8, 0xEA, 0xEC, 0xEE,
        0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7,
        0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xFE, 0xFF
};

/* for decoding */
uchar d_code[256] = {
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
        0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01,
        0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,
        0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02, 0x02,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09, 0x09,
        0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A, 0x0A,
        0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B, 0x0B,
        0x0C, 0x0C, 0x0C, 0x0C, 0x0D, 0x0D, 0x0D, 0x0D,
        0x0E, 0x0E, 0x0E, 0x0E, 0x0F, 0x0F, 0x0F, 0x0F,
        0x10, 0x10, 0x10, 0x10, 0x11, 0x11, 0x11, 0x11,
        0x12, 0x12, 0x12, 0x12, 0x13, 0x13, 0x13, 0x13,
        0x14, 0x14, 0x14, 0x14, 0x15, 0x15, 0x15, 0x15,
        0x16, 0x16, 0x16, 0x16, 0x17, 0x17, 0x17, 0x17,
        0x18, 0x18, 0x19, 0x19, 0x1A, 0x1A, 0x1B, 0x1B,
        0x1C, 0x1C, 0x1D, 0x1D, 0x1E, 0x1E, 0x1F, 0x1F,
        0x20, 0x20, 0x21, 0x21, 0x22, 0x22, 0x23, 0x23,
        0x24, 0x24, 0x25, 0x25, 0x26, 0x26, 0x27, 0x27,
        0x28, 0x28, 0x29, 0x29, 0x2A, 0x2A, 0x2B, 0x2B,
        0x2C, 0x2C, 0x2D, 0x2D, 0x2E, 0x2E, 0x2F, 0x2F,
        0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
        0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
};

uchar d_len[256] = {
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03, 0x03,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05, 0x05,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06, 0x06,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07, 0x07,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
        0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
};

unsigned freq[T + 1];   /* frequency table */

int prnt[T + N_CHAR];   /* pointers to parent nodes, except for the */
                        /* elements [T..T + N_CHAR - 1] which are used to get */
                        /* the positions of leaves corresponding to the codes. */

int son[T];             /* pointers to child nodes (son[], son[] + 1) */

unsigned getbuf = 0;
uchar getlen = 0;

int GetBit(void)        /* get one bit */
{
        int i;
do {
                if ((i = getc(infile)) < 0) i = 0;
                getbuf |= i << (8 - getlen);
                getlen += 8;
 }       while (getlen <= 8);
        i = getbuf;
        getbuf <<= 1;
        getlen--;
        return (i < 0);
}

int GetByte(void)       /* get one byte */
{
        unsigned i;

        while (getlen <= 8) {
                if ((i = getc(infile)) >127)  i = 0;
                getbuf |= i << (8 - getlen);
                getlen += 8;
        }
        i = getbuf;
        getbuf <<= 8;
        getlen -= 8;
        return i >> 8;
}

unsigned putbuf = 0;
uchar putlen = 0;

void Putcode(int l, unsigned c)         /* output c bits of code */
{
        putbuf |= c >> putlen;
        if ((putlen += l) >= 8) {
                if (putc(putbuf >> 8, outfile) == EOF) {
                        Error(wterr);
                }
                if ((putlen -= 8) >= 8) {
                        if (putc(putbuf, outfile) == EOF) {
                                Error(wterr);
                        }
                        codesize += 2;
                        putlen -= 8;
                        putbuf = c << (l - putlen);
                } else {
                        putbuf <<= 8;
                        codesize++;
                }
        }
}


/* initialization of tree */

void StartHuff(void)
{
        int i, j;

        for (i = 0; i < N_CHAR; i++) {
                freq[i] = 1;
                son[i] = i + T;
                prnt[i + T] = i;
        }
        i = 0; j = N_CHAR;
        while (j <= R) {
                freq[j] = freq[i] + freq[i + 1];
                son[j] = i;
                prnt[i] = prnt[i + 1] = j;
                i += 2; j++;
        }
        freq[T] = 0xffff;
        prnt[R] = 0;
}


/* reconstruction of tree */

void reconst(void)
{
        int i, j, k;
        unsigned f, l;

        /* collect leaf nodes in the first half of the table */
        /* and replace the freq by (freq + 1) / 2. */
        j = 0;
        for (i = 0; i < T; i++) {
                if (son[i] >= T) {
                        freq[j] = (freq[i] + 1) / 2;
                        son[j] = son[i];
                        j++;
                }
        }
        /* begin constructing tree by connecting sons */
        for (i = 0, j = N_CHAR; j < T; i += 2, j++) {
                k = i + 1;
                f = freq[j] = freq[i] + freq[k];
                for (k = j - 1; f < freq[k]; k--);
                k++;
                l = (j - k) * 2;
                memmove(&freq[k + 1], &freq[k], l);
                freq[k] = f;
                memmove(&son[k + 1], &son[k], l);
                son[k] = i;
        }
        /* connect prnt */
        for (i = 0; i < T; i++) {
                if ((k = son[i]) >= T) {
                        prnt[k] = i;
                } else {
                        prnt[k] = prnt[k + 1] = i;
                }
        }
}


/* increment frequency of given code by one, and update tree */

void update(int c)
{
        int i, j, k, l;

        if (freq[R] == MAX_FREQ) {
                reconst();
        }
        c = prnt[c + T];
        do {
                k = ++freq[c];

                /* if the order is disturbed, exchange nodes */
                if (k > freq[l = c + 1]) {
                        while (k > freq[++l]);
                        l--;
                        freq[c] = freq[l];
                        freq[l] = k;

                        i = son[c];
                        prnt[i] = l;
                        if (i < T) prnt[i + 1] = l;

                        j = son[l];
                        son[l] = i;

                        prnt[j] = c;
                        if (j < T) prnt[j + 1] = c;
                        son[c] = j;

                        c = l;
                }
        } while ((c = prnt[c]) != 0);   /* repeat up to root */
}

unsigned code, len;

void EncodeChar(unsigned c)
{
        unsigned i;
        int j, k;

        i = 0;
        j = 0;
        k = prnt[c + T];

        /* travel from leaf to root */
        do {
                i >>= 1;

                /* if node's address is odd-numbered, choose bigger brother node */
                if (k & 1) i += 0x8000;

                j++;
        } while ((k = prnt[k]) != R);
        Putcode(j, i);
        code = i;
        len = j;
        update(c);
}

void EncodePosition(unsigned c)
{
        unsigned i;

        /* output upper 6 bits by table lookup */
        i = c >> 6;
        Putcode(p_len[i], (unsigned)p_code[i] << 8);

        /* output lower 6 bits verbatim */
        Putcode(6, (c & 0x3f) << 10);
}

void EncodeEnd(void)
{
        if (putlen) {
                if (putc(putbuf >> 8, outfile) == EOF) {
                        Error(wterr);
                }
                codesize++;
        }
}

int DecodeChar(void)
{
        unsigned c;

        c = son[R];

        /* travel from root to leaf, */
        /* choosing the smaller child node (son[]) if the read bit is 0, */
        /* the bigger (son[]+1} if 1 */
        while (c < T) {
                c += GetBit();
                c = son[c];
        }
        c -= T;
        update(c);
        return c;
}

int DecodePosition(void)
{
        unsigned i, j, c;

        /* recover upper 6 bits from table */
        i = GetByte();
        c = (unsigned)d_code[i] << 6;
        j = d_len[i];

        /* read lower 6 bits verbatim */
        j -= 2;
        while (j--) {
                i = (i << 1) + GetBit();
        }
        return c | (i & 0x3f);
}

/* compression */

void Encode(void)  /* compression */
{
        int  i, c, len, r, s, last_match_length;

        fseek(infile, 0L, 2);
        textsize = ftell(infile);
        if (fwrite(&textsize, sizeof textsize, 1, outfile) < 1)
                Error(wterr);   /* output size of text */
        if (textsize == 0)
                return;
        rewind(infile);
        textsize = 0;                   /* rewind and re-read */
        StartHuff();
        InitTree();
        s = 0;
        r = N - F;
        for (i = s; i < r; i++)
                text_buf[i] = ' ';
        for (len = 0; len < F && (c = getc(infile)) != EOF; len++)
                text_buf[r + len] = c;
        textsize = len;
        for (i = 1; i <= F; i++)
                InsertNode(r - i);
        InsertNode(r);
        do {
                if (match_length > len)
                        match_length = len;
                if (match_length <= THRESHOLD) {
                        match_length = 1;
                        EncodeChar(text_buf[r]);
                } else {
                        EncodeChar(255 - THRESHOLD + match_length);
                        EncodePosition(match_position);
                }
                last_match_length = match_length;
                for (i = 0; i < last_match_length &&
                                (c = getc(infile)) != EOF; i++) {
                        DeleteNode(s);
                        text_buf[s] = c;
                        if (s < F - 1)
                                text_buf[s + N] = c;
                        s = (s + 1) & (N - 1);
                        r = (r + 1) & (N - 1);
                        InsertNode(r);
                }
                if ((textsize += i) > printcount) {
                        printf("%12ld\r", textsize);
                        printcount += 1024;
                }
                while (i++ < last_match_length) {
                        DeleteNode(s);
                        s = (s + 1) & (N - 1);
                        r = (r + 1) & (N - 1);
                        if (--len) InsertNode(r);
                }
        } while (len > 0);
        EncodeEnd();
        printf("In : %ld bytes\n", textsize);
        printf("Out: %ld bytes\n", codesize);
        printf("Out/In: %.3f\n", (double)codesize / textsize);
}

void Decode(void)  /* recover */
{
        int  i, j, k, r, c;
        unsigned long int  count;

        if (fread(&textsize, sizeof textsize, 1, infile) < 1)
                Error("Can't read");  /* read size of text */
        if (textsize == 0)
                return;
        StartHuff();
        for (i = 0; i < N - F; i++)
                text_buf[i] = ' ';
        r = N - F;
        for (count = 0; count < textsize; ) {
                c = DecodeChar();
                if (c < 256) {
                        if (putc(c, outfile) == EOF) {
                                Error(wterr);
                        }
                        text_buf[r++] = c;
                        r &= (N - 1);
                        count++;
                } else {
                        i = (r - DecodePosition() - 1) & (N - 1);
                        j = c - 255 + THRESHOLD;
                        for (k = 0; k < j; k++) {
                                c = text_buf[(i + k) & (N - 1)];
                                if (putc(c, outfile) == EOF) {
                                        Error(wterr);
                                }
                                text_buf[r++] = c;
                                r &= (N - 1);
                                count++;
                        }
                }
                if (count > printcount) {
                        printf("%12ld\r", count);
                        printcount += 1024;
                }
        }
        printf("%12ld\n", count);
}

int main(int argc, char *argv[])
{
        char  *s;

        if (argc != 4) {
                printf("'lzhuf e file1 file2' encodes file1 into file2.\n"
                           "'lzhuf d file2 file1' decodes file2 into file1.\n");
                return EXIT_FAILURE;
        }
        if ((s = argv[1], s[1] || strpbrk(s, "DEde") == NULL)
         || (s = argv[2], (infile  = fopen(s, "rb")) == NULL)
         || (s = argv[3], (outfile = fopen(s, "wb")) == NULL)) {
                printf("??? %s\n", s);
                return EXIT_FAILURE;
        }
        if (toupper(*argv[1]) == 'E')
                Encode();
        else
                Decode();
        fclose(infile);
        fclose(outfile);
        return EXIT_SUCCESS;
}
