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authorroot <root>2002-06-09 22:41:34 +0000
committerroot <root>2002-06-09 22:41:34 +0000
commitdb8367fa234d20d6e8e07901398fd45e23058d7b (patch)
treec0c635ca63d515c33e69cb051bb56ed565f4c2ca /lzf_c.c
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diff --git a/lzf_c.c b/lzf_c.c
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+/*
+ * Copyright (c) 2000 Marc Alexander Lehmann <pcg@goof.com>
+ *
+ * Redistribution and use in source and binary forms, with or without modifica-
+ * tion, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * 3. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
+ * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
+ * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
+ * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
+ * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
+ * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
+ * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "lzfP.h"
+
+#define HSIZE (1 << (HLOG))
+
+/*
+ * don't play with this unless you benchmark!
+ * decompression is not dependent on the hash function
+ * the hashing function might seem strange, just believe me
+ * it works ;)
+ */
+#define FRST(p) (((p[0]) << 8) + p[1])
+#define NEXT(v,p) (((v) << 8) + p[2])
+#define IDX(h) ((((h ^ (h << 4)) >> (3*8 - HLOG)) + h*3) & (HSIZE - 1))
+/*
+ * IDX works because it is very similar to a multiplicative hash, e.g.
+ * (h * 57321 >> (3*8 - HLOG))
+ * the next one is also quite good, albeit slow ;)
+ * (int)(cos(h & 0xffffff) * 1e6)
+ */
+
+#if 0
+/* original lzv-like hash function */
+# define FRST(p) (p[0] << 5) ^ p[1]
+# define NEXT(v,p) (v << 5) ^ p[2]
+# define IDX(h) (h) & (HSIZE - 1)
+#endif
+
+#define MAX_LIT (1 << 5)
+#define MAX_OFF (1 << 13)
+#define MAX_REF ((1 << 8) + (1 << 3))
+
+/*
+ * compressed format
+ *
+ * 000LLLLL <L+1> ; literal
+ * LLLOOOOO oooooooo ; backref L
+ * 111OOOOO LLLLLLLL oooooooo ; backref L+7
+ *
+ */
+
+unsigned int
+lzf_compress (const void *const in_data, unsigned int in_len,
+ void *out_data, unsigned int out_len)
+{
+ const u8 *htab[HSIZE];
+ const u8 **hslot;
+ const u8 *ip = in_data;
+ u8 *op = out_data;
+ const u8 *in_end = ip + in_len;
+ u8 *out_end = op + out_len;
+ const u8 *ref;
+
+ unsigned int hval = FRST (ip);
+ unsigned long off;
+ int lit = 0;
+
+#if INIT_HTAB
+# if USE_MEMCPY
+ memset (htab, 0, sizeof (htab));
+# else
+ for (hslot = htab; hslot < htab + HSIZE; hslot++)
+ *hslot++ = ip;
+# endif
+#endif
+
+ do
+ {
+ hval = NEXT (hval, ip);
+ hslot = htab + IDX (hval);
+ ref = *hslot; *hslot = ip;
+
+ if (1
+#if INIT_HTAB && !USE_MEMCPY
+ && ref < ip /* the next test will actually take care of this, but it is faster */
+#endif
+ && (off = ip - ref - 1) < MAX_OFF
+ && ip + 4 < in_end
+ && ref > (u8 *)in_data
+#if STRICT_ALIGN
+ && ref[0] == ip[0]
+ && ref[1] == ip[1]
+ && ref[2] == ip[2]
+#else
+ && *(u16 *)ref == *(u16 *)ip
+ && ref[2] == ip[2]
+#endif
+ )
+ {
+ /* match found at *ref++ */
+ unsigned int len = 2;
+ unsigned int maxlen = in_end - ip - len;
+ maxlen = maxlen > MAX_REF ? MAX_REF : maxlen;
+
+ do
+ len++;
+ while (len < maxlen && ref[len] == ip[len]);
+
+ if (op + lit + 1 + 3 >= out_end)
+ return 0;
+
+ if (lit)
+ {
+ *op++ = lit - 1;
+ lit = -lit;
+ do
+ *op++ = ip[lit];
+ while (++lit);
+ }
+
+ len -= 2;
+ ip++;
+
+ if (len < 7)
+ {
+ *op++ = (off >> 8) + (len << 5);
+ }
+ else
+ {
+ *op++ = (off >> 8) + ( 7 << 5);
+ *op++ = len - 7;
+ }
+
+ *op++ = off;
+
+#if ULTRA_FAST
+ ip += len;
+ hval = FRST (ip);
+ hval = NEXT (hval, ip);
+ htab[IDX (hval)] = ip;
+ ip++;
+#else
+ do
+ {
+ hval = NEXT (hval, ip);
+ htab[IDX (hval)] = ip;
+ ip++;
+ }
+ while (len--);
+#endif
+ }
+ else
+ {
+ /* one more literal byte we must copy */
+ lit++;
+ ip++;
+
+ if (lit == MAX_LIT)
+ {
+ if (op + 1 + MAX_LIT >= out_end)
+ return 0;
+
+ *op++ = MAX_LIT - 1;
+#if USE_MEMCPY
+ memcpy (op, ip - MAX_LIT, MAX_LIT);
+ op += MAX_LIT;
+ lit = 0;
+#else
+ lit = -lit;
+ do
+ *op++ = ip[lit];
+ while (++lit);
+#endif
+ }
+ }
+ }
+ while (ip < in_end);
+
+ if (lit)
+ {
+ if (op + lit + 1 >= out_end)
+ return 0;
+
+ *op++ = lit - 1;
+ lit = -lit;
+ do
+ *op++ = ip[lit];
+ while (++lit);
+ }
+
+ return op - (u8 *) out_data;
+}