Index: trunk/i386/boot2/lzss.c
===================================================================
--- trunk/i386/boot2/lzss.c	(revision 2342)
+++ trunk/i386/boot2/lzss.c	(revision 2343)
@@ -48,6 +48,22 @@
                            if match_length is greater than this */
 #define NIL       N     /* index for root of binary search trees */
 
+struct encode_state {
+    /*
+     * left & right children & parent. These constitute binary search trees.
+     */
+	int lchild[N + 1], rchild[N + 257], parent[N + 1];
+
+    /* ring buffer of size N, with extra F-1 bytes to aid string comparison */
+	u_int8_t text_buf[N + F - 1];
+
+    /*
+     * match_length of longest match.
+     * These are set by the insert_node() procedure.
+     */
+	int match_position, match_length;
+};
+
 int
 decompress_lzss(u_int8_t *dst, u_int8_t *src, u_int32_t srclen)
 {
@@ -90,3 +106,226 @@
     
     return dst - dststart;
 }
+
+/*
+ * initialize state, mostly the trees
+ *
+ * For i = 0 to N - 1, rchild[i] and lchild[i] will be the right and left
+ * children of node i. These nodes need not be initialized. Also, parent[i]
+ * is the parent of node i. These are initialized to NIL (= N), which stands
+ * for 'not used.' For i = 0 to 255, rchild[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. */
+static void init_state(struct encode_state *sp)
+{
+    int i;
+
+    bzero(sp, sizeof(*sp));
+
+    for (i = 0; i < N - F; i++)
+        sp->text_buf[i] = ' ';
+    for (i = N + 1; i <= N + 256; i++)
+        sp->rchild[i] = NIL;
+    for (i = 0; i < N; i++)
+        sp->parent[i] = NIL;
+}
+
+/*
+ * 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.
+ */
+static void insert_node(struct encode_state *sp, int r)
+{
+    int i, p, cmp;
+    u_int8_t *key;
+
+    cmp = 1;
+    key = &sp->text_buf[r];
+    p = N + 1 + key[0];
+    sp->rchild[r] = sp->lchild[r] = NIL;
+    sp->match_length = 0;
+    for ( ; ; ) {
+        if (cmp >= 0) {
+            if (sp->rchild[p] != NIL)
+                p = sp->rchild[p];
+            else {
+                sp->rchild[p] = r;
+                sp->parent[r] = p;
+                return;
+            }
+        } else {
+            if (sp->lchild[p] != NIL)
+                p = sp->lchild[p];
+            else {
+                sp->lchild[p] = r;
+                sp->parent[r] = p;
+                return;
+            }
+        }
+        for (i = 1; i < F; i++) {
+            if ((cmp = key[i] - sp->text_buf[p + i]) != 0)
+                break;
+        }
+        if (i > sp->match_length) {
+            sp->match_position = p;
+            if ((sp->match_length = i) >= F)
+                break;
+        }
+    }
+    sp->parent[r] = sp->parent[p];
+    sp->lchild[r] = sp->lchild[p];
+    sp->rchild[r] = sp->rchild[p];
+    sp->parent[sp->lchild[p]] = r;
+    sp->parent[sp->rchild[p]] = r;
+    if (sp->rchild[sp->parent[p]] == p)
+        sp->rchild[sp->parent[p]] = r;
+    else
+        sp->lchild[sp->parent[p]] = r;
+    sp->parent[p] = NIL; /* remove p */
+}
+
+/* deletes node p from tree */
+static void delete_node(struct encode_state *sp, int p)
+{
+    int q;
+
+    if (sp->parent[p] == NIL)
+        return; /* not in tree */
+    if (sp->rchild[p] == NIL)
+        q = sp->lchild[p];
+    else if (sp->lchild[p] == NIL)
+        q = sp->rchild[p];
+    else {
+        q = sp->lchild[p];
+        if (sp->rchild[q] != NIL) {
+            do {
+                q = sp->rchild[q];
+            } while (sp->rchild[q] != NIL);
+            sp->rchild[sp->parent[q]] = sp->lchild[q];
+            sp->parent[sp->lchild[q]] = sp->parent[q];
+            sp->lchild[q] = sp->lchild[p];
+            sp->parent[sp->lchild[p]] = q;
+        }
+        sp->rchild[q] = sp->rchild[p];
+        sp->parent[sp->rchild[p]] = q;
+    }
+    sp->parent[q] = sp->parent[p];
+    if (sp->rchild[sp->parent[p]] == p)
+        sp->rchild[sp->parent[p]] = q;
+    else
+        sp->lchild[sp->parent[p]] = q;
+    sp->parent[p] = NIL;
+}
+
+u_int8_t *compress_lzss(
+                        u_int8_t       * dst,
+                        u_int32_t        dstlen,
+                        u_int8_t       * src,
+                        u_int32_t        srclen)
+{
+    u_int8_t * result = NULL;
+    /* Encoding state, mostly tree but some current match stuff */
+    struct encode_state *sp;
+    int  i, c, len, r, s, last_match_length, code_buf_ptr;
+    u_int8_t code_buf[17], mask;
+    u_int8_t * srcend = src + srclen;
+    u_int8_t *dstend = dst + dstlen;
+    /* initialize trees */
+    sp = (struct encode_state *) malloc(sizeof(*sp));
+    if (!sp) goto finish;
+    init_state(sp);
+    /*
+     * 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[0] = 0;
+    code_buf_ptr = mask = 1;
+    /* Clear the buffer with any character that will appear often. */
+    s = 0;  r = N - F;
+    /* Read F bytes into the last F bytes of the buffer */
+    for (len = 0; len < F && src < srcend; len++)
+        sp->text_buf[r + len] = *src++;
+    if (!len)
+        goto finish;
+    /*
+     * 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.
+     */
+    for (i = 1; i <= F; i++)
+        insert_node(sp, r - i);
+    /*
+     * Finally, insert the whole string just read.
+     * The global variables match_length and match_position are set.
+     */
+    insert_node(sp, r);
+    do {
+        /* match_length may be spuriously long near the end of text. */
+        if (sp->match_length > len)
+            sp->match_length = len;
+        if (sp->match_length <= THRESHOLD) {
+            sp->match_length = 1;  /* Not long enough match.  Send one byte. */
+            code_buf[0] |= mask;  /* 'send one byte' flag */
+            code_buf[code_buf_ptr++] = sp->text_buf[r];  /* Send uncoded. */
+        } else {
+            /* Send position and length pair. Note match_length > THRESHOLD. */
+            code_buf[code_buf_ptr++] = (u_int8_t) sp->match_position;
+            code_buf[code_buf_ptr++] = (u_int8_t)
+            ( ((sp->match_position >> 4) & 0xF0)
+             |  (sp->match_length - (THRESHOLD + 1)) );
+        }
+        if ((mask <<= 1) == 0) {  /* Shift mask left one bit. */
+            /* Send at most 8 units of code together */
+            for (i = 0; i < code_buf_ptr; i++)
+                if (dst < dstend)
+                    *dst++ = code_buf[i];
+                else
+                    goto finish;
+            code_buf[0] = 0;
+            code_buf_ptr = mask = 1;
+        }
+        last_match_length = sp->match_length;
+        for (i = 0; i < last_match_length && src < srcend; i++) {
+            delete_node(sp, s);    /* Delete old strings and */
+            c = *src++;
+            sp->text_buf[s] = c;    /* read new bytes */
+            /*
+             * If the position is near the end of buffer, extend the buffer
+             * to make string comparison easier.
+             */
+            if (s < F - 1)
+                sp->text_buf[s + N] = c;
+            /* Since this is a ring buffer, increment the position modulo N. */
+            s = (s + 1) & (N - 1);
+            r = (r + 1) & (N - 1);
+            /* Register the string in text_buf[r..r+F-1] */
+            insert_node(sp, r);
+        }
+        while (i++ < last_match_length) {
+            delete_node(sp, s);
+            /* After the end of text, no need to read, */
+            s = (s + 1) & (N - 1);
+            r = (r + 1) & (N - 1);
+            /* but buffer may not be empty. */
+            if (--len)
+                insert_node(sp, r);
+        }
+    } 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++)
+            if (dst < dstend)
+                *dst++ = code_buf[i];
+            else
+                goto finish;
+    }
+    result = dst;
+finish:
+    if (sp) free(sp);
+    return result;
+}