あっしゅくアルゴリズム
9781 ワード
#ifndef _JTC_COMPRESS_H__
#define _JTC_COMPRESS_H__
#include "Types.h"
#include <fstream>
using namespace std;
#define N 4096 /* size of ring buffer */
#define F 18 /* upper limit for match_length */
#define THRESHOLD 2 /* encode string into position and length
if match_length is greater than this */
#define NIL N /* index for root of binary search trees */
class CJtcCompress
{
private:
UInt32 textsize; /* text size counter */
UInt32 codesize; /* code size counter */
UInt32 printcount; /* counter for reporting progress every 1K bytes */
Byte text_buf[N + F - 1]; /* ring buffer of size N,
with extra F-1 bytes to facilitate string comparison */
int match_position;
int match_length; /* of longest match. These are set by the InsertNode() procedure. */
int lson[N + 1]; /* left & right children & parents -- These constitute binary search trees. */
int rson[N + 257];
int dad[N + 1];
private:
FILE * m_infile;
public:
CJtcCompress(const char * inFileName);
~CJtcCompress();
Byte * Decode(UInt32 & nFileLen); /* Just the reverse of Encode(). */
private:
void InitTree(); /* initialize trees */
void InsertNode(int r);
void DeleteNode(int p); /* deletes node p from tree */
//void Encode(void); //
};
#endif
#include "jtcCompress.h"
#define DELETE_FILE_IF(x) if(x != NULL){fclose(x); x=NULL;}
CJtcCompress::CJtcCompress(const char * inFileName)
{
textsize = 0;
codesize = 0;
printcount = 0;
m_infile = fopen(inFileName, "rb");
}
CJtcCompress::~CJtcCompress()
{
DELETE_FILE_IF(m_infile);
}
void CJtcCompress::InitTree() /* initialize trees */
{
int i;
/* For i = 0 to N - 1, rson[i] and lson[i] will be the right and
left children of node i. These nodes need not be initialized.
Also, dad[i] is the parent of node i. These are initialized to
NIL (= N), which stands for 'not used.'
For i = 0 to 255, rson[N + i + 1] is the root of the tree
for strings that begin with character i. These are initialized
to NIL. Note there are 256 trees. */
for (i = N + 1; i <= N + 256; i++) rson[i] = NIL;
for (i = 0; i < N; i++) dad[i] = NIL;
}
void CJtcCompress::InsertNode(int r)
/* Inserts string of length F, text_buf[r..r+F-1], into one of the
trees (text_buf[r]'th tree) and returns the longest-match position
and length via the global variables match_position and match_length.
If match_length = F, then removes the old node in favor of the new
one, because the old one will be deleted sooner.
Note r plays double role, as tree node and position in buffer. */
{
int i, p, cmp;
unsigned char *key;
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 > match_length) {
match_position = p;
if ((match_length = i) >= F) break;
}
}
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 CJtcCompress::DeleteNode(int p) /* deletes node p from tree */
{
int q;
if (dad[p] == NIL) return; /* not in tree */
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;
}
Byte * CJtcCompress::Decode(UInt32 & nFileLen) /* Just the reverse of Encode(). */
{
int i, j, k, r, c;
unsigned int flags;
Byte * pBuf = NULL;
fread(&nFileLen, 4, 1, m_infile);
pBuf = new Byte[nFileLen];
UInt32 offest = 0;
for (i = 0; i < N - F; i++) text_buf[i] = ' ';
r = N - F; flags = 0;
for ( ; ; ) {
if (((flags >>= 1) & 256) == 0) {
if ((c = getc(m_infile)) == EOF) break;
flags = c | 0xff00; /* uses higher byte cleverly */
} /* to count eight */
if (flags & 1) {
if ((c = getc(m_infile)) == EOF) break;
pBuf[offest] = c;
offest++;
text_buf[r++] = c;
r &= (N - 1);
} else {
if ((i = getc(m_infile)) == EOF) break;
if ((j = getc(m_infile)) == EOF) break;
i |= ((j & 0xf0) << 4); j = (j & 0x0f) + THRESHOLD;
for (k = 0; k <= j; k++) {
c = text_buf[(i + k) & (N - 1)];
pBuf[offest] = c;
offest++;
text_buf[r++] = c;
r &= (N - 1);
}
}
}
return pBuf;
}
//void Encode(void)
//{
// int i, c, len, r, s, last_match_length, code_buf_ptr;
// unsigned char code_buf[17], mask;
//
// InitTree(); /* initialize trees */
// code_buf[0] = 0; /* code_buf[1..16] saves eight units of code, and
// code_buf[0] works as eight flags, "1" representing that the unit
// is an unencoded letter (1 byte), "0" a position-and-length pair
// (2 bytes). Thus, eight units require at most 16 bytes of code. */
// code_buf_ptr = mask = 1;
// s = 0; r = N - F;
// for (i = s; i < r; i++) text_buf[i] = ' '; /* Clear the buffer with
// any character that will appear often. */
// for (len = 0; len < F && (c = getc(infile)) != EOF; len++)
// text_buf[r + len] = c; /* Read F bytes into the last F bytes of
// the buffer */
// if ((textsize = len) == 0) return; /* text of size zero */
// for (i = 1; i <= F; i++) InsertNode(r - i); /* Insert the F strings,
// each of which begins with one or more 'space' characters. Note
// the order in which these strings are inserted. This way,
// degenerate trees will be less likely to occur. */
// InsertNode(r); /* Finally, insert the whole string just read. The
// global variables match_length and match_position are set. */
// do {
// if (match_length > len) match_length = len; /* match_length
// may be spuriously long near the end of text. */
// if (match_length <= THRESHOLD) {
// match_length = 1; /* Not long enough match. Send one byte. */
// code_buf[0] |= mask; /* 'send one byte' flag */
// code_buf[code_buf_ptr++] = text_buf[r]; /* Send uncoded. */
// } else {
// code_buf[code_buf_ptr++] = (unsigned char) match_position;
// code_buf[code_buf_ptr++] = (unsigned char)
// (((match_position >> 4) & 0xf0)
// | (match_length - (THRESHOLD + 1))); /* Send position and
// length pair. Note match_length > THRESHOLD. */
// }
// if ((mask <<= 1) == 0) { /* Shift mask left one bit. */
// for (i = 0; i < code_buf_ptr; i++) /* Send at most 8 units of */
// putc(code_buf[i], outfile); /* code together */
// codesize += code_buf_ptr;
// code_buf[0] = 0; code_buf_ptr = mask = 1;
// }
// last_match_length = match_length;
// for (i = 0; i < last_match_length &&
// (c = getc(infile)) != EOF; i++) {
// DeleteNode(s); /* Delete old strings and */
// text_buf[s] = c; /* read new bytes */
// if (s < F - 1) text_buf[s + N] = c; /* If the position is
// near the end of buffer, extend the buffer to make
// string comparison easier. */
// s = (s + 1) & (N - 1); r = (r + 1) & (N - 1);
// /* Since this is a ring buffer, increment the position
// modulo N. */
// InsertNode(r); /* Register the string in text_buf[r..r+F-1] */
// }
// if ((textsize += i) > printcount) {
// printf("%12ld\r", textsize); printcount += 1024;
// /* Reports progress each time the textsize exceeds
// multiples of 1024. */
// }
// while (i++ < last_match_length) { /* After the end of text, */
// DeleteNode(s); /* no need to read, but */
// s = (s + 1) & (N - 1); r = (r + 1) & (N - 1);
// if (--len) InsertNode(r); /* buffer may not be empty. */
// }
// } while (len > 0); /* until length of string to be processed is zero */
// if (code_buf_ptr > 1) { /* Send remaining code. */
// for (i = 0; i < code_buf_ptr; i++) putc(code_buf[i], outfile);
// codesize += code_buf_ptr;
// }
// printf("In : %ld bytes
", textsize); /* Encoding is done. */
// printf("Out: %ld bytes
", codesize);
// printf("Out/In: %.3f
", (double)codesize / textsize);
//}