compr_lzari.c

jffs2源代码基于2。6内核

						if (op >= dstend) {
							*dstlen = written;
							return -1;
						}
						*(op++) = buffer;
						buffer = 0;
						mask = 128;
						written++;
						*srclen = read;
					}
					for ( ; shifts > 0; shifts--) {
						buffer |= mask;
						if ((mask >>= 1) == 0) {
							if (op >= dstend) {
								*dstlen = written;
								return -1;
							}
							*(op++) = buffer;
							buffer = 0;
							mask = 128;
							written++;
							*srclen = read;
						}
					}
				} else if (low >= Q2) {
					buffer |= mask;
					if ((mask >>= 1) == 0) {
						if (op >= dstend) {
							*dstlen = written;
							return -1;
						}
						*(op++) = buffer;
						buffer = 0;
						mask = 128;
						written++;
						*srclen = read;
					}
					for ( ; shifts > 0; shifts--) {
						if ((mask >>= 1) == 0) {
							if (op >= dstend) {
								*dstlen = written;
								return -1;
							}
							*(op++) = buffer;
							buffer = 0;
							mask = 128;
							written++;
							*srclen = read;
						}
					}
					low -= Q2;
					high -= Q2;
				} else if (low >= Q1 && high <= Q3) {
					shifts++;
					low -= Q1;
					high -= Q1;
				} else break;
				low += low;  high += high;
			}
			UpdateModel(sym);
			range = high - low;
			high = low + (range * position_cum[match_position - 1]) / position_cum[0];
			low +=       (range * position_cum[match_position    ]) / position_cum[0];
			for ( ; ; ) {
				if (high <= Q2) {
					if ((mask >>= 1) == 0) {
						if (op >= dstend) {
							*dstlen = written;
							return -1;
						}
						*(op++) = buffer;
						buffer = 0;
						mask = 128;
						written++;
						*srclen = read;
					}
					for ( ; shifts > 0; shifts--) {
						buffer |= mask;
						if ((mask >>= 1) == 0) {
							if (op >= dstend) {
								*dstlen = written;
								return -1;
							}
							*(op++) = buffer;
							buffer = 0;
							mask = 128;
							written++;
							*srclen = read;
						}
					}
				} else {
					if (low >= Q2) {
						buffer |= mask;
						if ((mask >>= 1) == 0) {
							if (op >= dstend) {
								*dstlen = written;
								return -1;
							}
							*(op++) = buffer;
							buffer = 0;
							mask = 128;
							written++;
							*srclen = read;
						}
						for ( ; shifts > 0; shifts--) {
							if ((mask >>= 1) == 0) {
								if (op >= dstend) {
									*dstlen = written;
									return -1;
								}
								*(op++) = buffer;
								buffer = 0;
								mask = 128;
								written++;
								*srclen = read;
							}
						}
						low -= Q2;
						high -= Q2;
					} else {
						if ((low >= Q1) && (high <= Q3)) {
							shifts++;
							low -= Q1;
							high -= Q1;
						} else {
							break;
						}
					}
				}
				low += low;
				high += high;
			}
		}
		last_match_length = match_length;
		for (i = 0; (i < last_match_length) && (ip < srcend); i++) {
			c = *(ip++);
			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);
		}
		read += i;
		while (i++ < last_match_length) {
			DeleteNode(s);
			s = (s + 1) & (N - 1);
			r = (r + 1) & (N - 1);
			if (--len) InsertNode(r);
		}
	} while (len > 0);
	shifts++;
	if (low < Q1) {
		if ((mask >>= 1) == 0) {
			if (op >= dstend) {
				*dstlen = written;
				return -1;
			}
			*(op++) = buffer;
			buffer = 0;
			mask = 128;
			written++;
			*srclen = read;
		}
		for ( ; shifts > 0; shifts--) {
			buffer |= mask;
			if ((mask >>= 1) == 0) {
				if (op >= dstend) {
					*dstlen = written;
					return -1;
				}
				*(op++) = buffer;
				buffer = 0;
				mask = 128;
				written++;
				*srclen = read;
			}
		}
	} else {
		buffer |= mask;
		if ((mask >>= 1) == 0) {
			if (op >= dstend) {
				*dstlen = written;
				return -1;
			}
			*(op++) = buffer;
			buffer = 0;
			mask = 128;
			written++;
			*srclen = read;
		}
		for ( ; shifts > 0; shifts--) {
			if ((mask >>= 1) == 0) {
				if (op >= dstend) {
					*dstlen = written;
					return -1;
				}
				*(op++) = buffer;
				buffer = 0;
				mask = 128;
				written++;
				*srclen = read;
			}
		}
	}
	for (i = 0; i < 7; i++) {
		if ((mask >>= 1) == 0) {
			if (op >= dstend) {
				*dstlen = written;
				return -1;
			}
			*(op++) = buffer;
			buffer = 0;
			mask = 128;
			written++;
			*srclen = read;
		}
	}
	*dstlen = written;
	return 0;
}

static int Decode(unsigned char *srcbuf, unsigned char *dstbuf, unsigned long srclen,
					unsigned long dstlen)	/* Just the reverse of Encode(). */
{
	unsigned long i, r, j, k, c, range, sym;
	unsigned char *ip, *op;
	unsigned char *srcend = srcbuf + srclen;
	unsigned char *dstend = dstbuf + dstlen;
	unsigned char buffer = 0;
	unsigned char mask = 0;
	unsigned long low = 0;
	unsigned long high = Q4;
	unsigned long value = 0;
	ip = srcbuf;
	op = dstbuf;
	for (i = 0; i < M + 2; i++) {
		value *= 2;
		if ((mask >>= 1) == 0) {
			buffer = (ip >= srcend) ? 0 : *(ip++);
			mask = 128;
		}
		value += ((buffer & mask) != 0);
	}
	StartModel();
	for (i = 0; i < N - F; i++) text_buf[i] = ' ';
	r = N - F;
	while (op < dstend) {
		range = high - low;
		sym = BinarySearchSym((unsigned long)
				(((value - low + 1) * sym_cum[0] - 1) / range));
		high = low + (range * sym_cum[sym - 1]) / sym_cum[0];
		low +=       (range * sym_cum[sym    ]) / sym_cum[0];
		for ( ; ; ) {
			if (low >= Q2) {
				value -= Q2;  low -= Q2;  high -= Q2;
			} else if (low >= Q1 && high <= Q3) {
				value -= Q1;  low -= Q1;  high -= Q1;
			} else if (high > Q2) break;
			low += low;  high += high;
			value *= 2;
			if ((mask >>= 1) == 0) {
				buffer = (ip >= srcend) ? 0 : *(ip++);
				mask = 128;
			}
			value += ((buffer & mask) != 0);
		}
		c = sym_to_char[sym];
		UpdateModel(sym);
		if (c < 256) {
			if (op >= dstend) return -1;
			*(op++) = c;
			text_buf[r++] = c;
			r &= (N - 1);
		} else {
			j = c - 255 + THRESHOLD;
			range = high - low;
			i = BinarySearchPos((unsigned long)
				(((value - low + 1) * position_cum[0] - 1) / range));
			high = low + (range * position_cum[i    ]) / position_cum[0];
			low +=       (range * position_cum[i + 1]) / position_cum[0];
			for ( ; ; ) {
				if (low >= Q2) {
					value -= Q2;  low -= Q2;  high -= Q2;
				} else if (low >= Q1 && high <= Q3) {
					value -= Q1;  low -= Q1;  high -= Q1;
				} else if (high > Q2) break;
				low += low;  high += high;
				value *= 2;
				if ((mask >>= 1) == 0) {
					buffer = (ip >= srcend) ? 0 : *(ip++);
					mask = 128;
				}
				value += ((buffer & mask) != 0);
			}
			i = (r - i - 1) & (N - 1);
			for (k = 0; k < j; k++) {
				c = text_buf[(i + k) & (N - 1)];
				if (op >= dstend) return -1;
				*(op++) = c;
				text_buf[r++] = c;
				r &= (N - 1);
			}		
		}
	}
	return 0;
}

/* interface to jffs2 follows */

#include "compr.h"
#include <linux/jffs2.h>

int jffs2_lzari_compress (unsigned char *input,
			unsigned char *output, uint32_t *sourcelen,
			uint32_t *dstlen, void *model);

int jffs2_lzari_decompress (unsigned char *input,
			  unsigned char *output, uint32_t sourcelen,
			  uint32_t dstlen, void *model);

struct jffs2_compressor jffs2_lzari_comp = {
	.priority = JFFS2_LZARI_PRIORITY,
	.name = "lzari",
	.compr = JFFS2_COMPR_LZARI,
	.compress = &jffs2_lzari_compress,
	.decompress = &jffs2_lzari_decompress,
#ifdef JFFS2_LZARI_DISABLED
	.disabled = 1,
#else
	.disabled = 0,
#endif
};

int jffs2_lzari_compress (unsigned char *input,
			unsigned char *output, uint32_t *sourcelen,
			uint32_t *dstlen, void *model)
{
	return Encode(input, output, (unsigned long *)sourcelen, (unsigned long *)dstlen);
}

int jffs2_lzari_decompress (unsigned char *input,
			  unsigned char *output, uint32_t sourcelen,
			  uint32_t dstlen, void *model)
{
    return Decode(input, output, sourcelen, dstlen);
}

int jffs2_lzari_init (void)
{
    return jffs2_register_compressor(&jffs2_lzari_comp);
}

void jffs2_lzari_exit (void)
{
    jffs2_unregister_compressor (&jffs2_lzari_comp);
}