decompress_unzip.c

busybox-1.5.1.tar.gz linux内核编译用到的工具

		}
		for (; i < 280; i++) {
			l[i] = 7;
		}
		for (; i < 288; i++) {	/* make a complete, but wrong code set */
			l[i] = 8;
		}
		bl = 7;
		i = huft_build(l, 288, 257, cplens, cplext, &tl, &bl);
		if (i != 0) {
			return i;
		}

		/* set up distance table */
		for (i = 0; i < 30; i++) {	/* make an incomplete code set */
			l[i] = 5;
		}
		bd = 5;
		i = huft_build(l, 30, 0, cpdist, cpdext, &td, &bd);
		if (i > 1) {
			huft_free(tl);
			return i;
		}

		/* decompress until an end-of-block code */
		inflate_codes_setup(PASS_STATE tl, td, bl, bd); // Setup inflate_codes

		/* huft_free code moved into inflate_codes */

		return -2;
	}
	case 2:			/* Inflate dynamic */
	{
		const int dbits = 6;	/* bits in base distance lookup table */
		const int lbits = 9;	/* bits in base literal/length lookup table */

		huft_t *tl;		/* literal/length code table */
		huft_t *td;		/* distance code table */
		unsigned i;			/* temporary variables */
		unsigned j;
		unsigned l;		/* last length */
		unsigned m;		/* mask for bit lengths table */
		unsigned n;		/* number of lengths to get */
		unsigned bl;			/* lookup bits for tl */
		unsigned bd;			/* lookup bits for td */
		unsigned nb;	/* number of bit length codes */
		unsigned nl;	/* number of literal/length codes */
		unsigned nd;	/* number of distance codes */

		unsigned ll[286 + 30];	/* literal/length and distance code lengths */
		unsigned b_dynamic;	/* bit buffer */
		unsigned k_dynamic;	/* number of bits in bit buffer */

		/* make local bit buffer */
		b_dynamic = gunzip_bb;
		k_dynamic = gunzip_bk;

		/* read in table lengths */
		b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 5);
		nl = 257 + ((unsigned) b_dynamic & 0x1f);	/* number of literal/length codes */

		b_dynamic >>= 5;
		k_dynamic -= 5;
		b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 5);
		nd = 1 + ((unsigned) b_dynamic & 0x1f);	/* number of distance codes */

		b_dynamic >>= 5;
		k_dynamic -= 5;
		b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 4);
		nb = 4 + ((unsigned) b_dynamic & 0xf);	/* number of bit length codes */

		b_dynamic >>= 4;
		k_dynamic -= 4;
		if (nl > 286 || nd > 30) {
			return 1;	/* bad lengths */
		}

		/* read in bit-length-code lengths */
		for (j = 0; j < nb; j++) {
			b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 3);
			ll[border[j]] = (unsigned) b_dynamic & 7;
			b_dynamic >>= 3;
			k_dynamic -= 3;
		}
		for (; j < 19; j++) {
			ll[border[j]] = 0;
		}

		/* build decoding table for trees--single level, 7 bit lookup */
		bl = 7;
		i = huft_build(ll, 19, 19, NULL, NULL, &tl, &bl);
		if (i != 0) {
			if (i == 1) {
				huft_free(tl);
			}
			return i;	/* incomplete code set */
		}

		/* read in literal and distance code lengths */
		n = nl + nd;
		m = mask_bits[bl];
		i = l = 0;
		while ((unsigned) i < n) {
			b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, (unsigned)bl);
			j = (td = tl + ((unsigned) b_dynamic & m))->b;
			b_dynamic >>= j;
			k_dynamic -= j;
			j = td->v.n;
			if (j < 16) {	/* length of code in bits (0..15) */
				ll[i++] = l = j;	/* save last length in l */
			} else if (j == 16) {	/* repeat last length 3 to 6 times */
				b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 2);
				j = 3 + ((unsigned) b_dynamic & 3);
				b_dynamic >>= 2;
				k_dynamic -= 2;
				if ((unsigned) i + j > n) {
					return 1;
				}
				while (j--) {
					ll[i++] = l;
				}
			} else if (j == 17) {	/* 3 to 10 zero length codes */
				b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 3);
				j = 3 + ((unsigned) b_dynamic & 7);
				b_dynamic >>= 3;
				k_dynamic -= 3;
				if ((unsigned) i + j > n) {
					return 1;
				}
				while (j--) {
					ll[i++] = 0;
				}
				l = 0;
			} else {	/* j == 18: 11 to 138 zero length codes */
				b_dynamic = fill_bitbuffer(PASS_STATE b_dynamic, &k_dynamic, 7);
				j = 11 + ((unsigned) b_dynamic & 0x7f);
				b_dynamic >>= 7;
				k_dynamic -= 7;
				if ((unsigned) i + j > n) {
					return 1;
				}
				while (j--) {
					ll[i++] = 0;
				}
				l = 0;
			}
		}

		/* free decoding table for trees */
		huft_free(tl);

		/* restore the global bit buffer */
		gunzip_bb = b_dynamic;
		gunzip_bk = k_dynamic;

		/* build the decoding tables for literal/length and distance codes */
		bl = lbits;

		i = huft_build(ll, nl, 257, cplens, cplext, &tl, &bl);
		if (i != 0) {
			if (i == 1) {
//shouldn't we propagate error?
				bb_error_msg_and_die("incomplete literal tree");
				/* huft_free(tl); */
			}
			return i;	/* incomplete code set */
		}

		bd = dbits;
		i = huft_build(ll + nl, nd, 0, cpdist, cpdext, &td, &bd);
		if (i != 0) {
			if (i == 1) {
//shouldn't we propagate error?
				bb_error_msg_and_die("incomplete distance tree");
				/* huft_free(td); */
			}
			huft_free(tl);
			return i;	/* incomplete code set */
		}

		/* decompress until an end-of-block code */
		inflate_codes_setup(PASS_STATE tl, td, bl, bd); // Setup inflate_codes

		/* huft_free code moved into inflate_codes */

		return -2;
	}
	default:
		/* bad block type */
//shouldn't we propagate error?
		bb_error_msg_and_die("bad block type %d", t);
	}
}

/* Two callsites, both in inflate_get_next_window */
static void calculate_gunzip_crc(STATE_PARAM_ONLY)
{
	int n;
	for (n = 0; n < gunzip_outbuf_count; n++) {
		gunzip_crc = gunzip_crc_table[((int) gunzip_crc ^ (gunzip_window[n])) & 0xff] ^ (gunzip_crc >> 8);
	}
	gunzip_bytes_out += gunzip_outbuf_count;
}

/* One callsite in inflate_unzip_internal */
static int inflate_get_next_window(STATE_PARAM_ONLY)
{
	gunzip_outbuf_count = 0;

	while (1) {
		int ret;

		if (need_another_block) {
			if (end_reached) {
				calculate_gunzip_crc(PASS_STATE_ONLY);
				end_reached = 0;
				need_another_block = 1;
				return 0; /* Last block */
			}
			method = inflate_block(PASS_STATE &end_reached);
			need_another_block = 0;
		}

		switch (method) {
		case -1:
			ret = inflate_stored(PASS_STATE_ONLY);
			break;
		case -2:
			ret = inflate_codes(PASS_STATE_ONLY);
			break;
		default:
//shouldn't we propagate error?
			bb_error_msg_and_die("inflate error %d", method);
		}

		if (ret == 1) {
			calculate_gunzip_crc(PASS_STATE_ONLY);
			return 1; // More data left
		}
		need_another_block = 1; // End of that block
	}
	/* Doesnt get here */
}


/* Called from inflate_gunzip() and inflate_unzip() */
/* NB: bytebuffer is allocated here but freeing it is left to the caller! */
static USE_DESKTOP(long long) int
inflate_unzip_internal(STATE_PARAM int in, int out)
{
	USE_DESKTOP(long long) int n = 0;
	ssize_t nwrote;

	/* Allocate all global buffers (for DYN_ALLOC option) */
	gunzip_window = xmalloc(GUNZIP_WSIZE);
	gunzip_outbuf_count = 0;
	gunzip_bytes_out = 0;
	gunzip_src_fd = in;

	/* initialize gunzip_window, bit buffer */
	gunzip_bk = 0;
	gunzip_bb = 0;

	/* Create the crc table */
	gunzip_crc_table = crc32_filltable(0);
	gunzip_crc = ~0;

	/* Allocate space for buffer */
	bytebuffer = xmalloc(bytebuffer_max);

	while (1) {
		int r = inflate_get_next_window(PASS_STATE_ONLY);
		nwrote = full_write(out, gunzip_window, gunzip_outbuf_count);
		if (nwrote != gunzip_outbuf_count) {
			bb_perror_msg("write");
			n = -1;
			goto ret;
		}
		USE_DESKTOP(n += nwrote;)
		if (r == 0) break;
	}

	/* Store unused bytes in a global buffer so calling applets can access it */
	if (gunzip_bk >= 8) {
		/* Undo too much lookahead. The next read will be byte aligned
		 * so we can discard unused bits in the last meaningful byte. */
		bytebuffer_offset--;
		bytebuffer[bytebuffer_offset] = gunzip_bb & 0xff;
		gunzip_bb >>= 8;
		gunzip_bk -= 8;
	}
 ret:
	/* Cleanup */
	free(gunzip_window);
	free(gunzip_crc_table);
	return n;
}


USE_DESKTOP(long long) int
inflate_unzip(inflate_unzip_result *res, unsigned bufsize, int in, int out)
{
	USE_DESKTOP(long long) int n;
	DECLARE_STATE;

	ALLOC_STATE;

	bytebuffer_max = bufsize + 8;
	bytebuffer_offset = 4;
	n = inflate_unzip_internal(PASS_STATE in, out);

	res->crc = gunzip_crc;
	res->bytes_out = gunzip_bytes_out;
	free(bytebuffer);
	DEALLOC_STATE;
	return n;
}


USE_DESKTOP(long long) int
inflate_gunzip(int in, int out)
{
	uint32_t stored_crc = 0;
	unsigned count;
	USE_DESKTOP(long long) int n;
	DECLARE_STATE;

	ALLOC_STATE;

	bytebuffer_max = 0x8000;
	n = inflate_unzip_internal(PASS_STATE in, out);

	if (n < 0) goto ret;

	/* top up the input buffer with the rest of the trailer */
	count = bytebuffer_size - bytebuffer_offset;
	if (count < 8) {
		xread(in, &bytebuffer[bytebuffer_size], 8 - count);
//shouldn't we propagate error?
		bytebuffer_size += 8 - count;
	}
	for (count = 0; count != 4; count++) {
		stored_crc |= (bytebuffer[bytebuffer_offset] << (count * 8));
		bytebuffer_offset++;
	}

	/* Validate decompression - crc */
	if (stored_crc != (~gunzip_crc)) {
		bb_error_msg("crc error");
		n = -1;
		goto ret;
	}

	/* Validate decompression - size */
	if (gunzip_bytes_out !=
		(bytebuffer[bytebuffer_offset] | (bytebuffer[bytebuffer_offset+1] << 8) |
		(bytebuffer[bytebuffer_offset+2] << 16) | (bytebuffer[bytebuffer_offset+3] << 24))
	) {
		bb_error_msg("incorrect length");
		n = -1;
	}
 ret:
	free(bytebuffer);
	DEALLOC_STATE;
	return n;
}