moves fraps huffman decoder to its own file, making it more generic

Originally committed as revision 10736 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/huffman.c

@@ -0,0 +1,103 @@
+/**
+ * @file huffman.c
+ * huffman tree builder and VLC generator
+ * Copyright (c) 2006 Konstantin Shishkov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "bitstream.h"
+#include "huffman.h"
+
+/* symbol for Huffman tree node */
+#define HNODE -1
+
+
+static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat, Node *nodes, int node, uint32_t pfx, int pl, int *pos)
+{
+    int s;
+
+    s = nodes[node].sym;
+    if(s != HNODE || !nodes[node].count){
+        bits[*pos] = pfx;
+        lens[*pos] = pl;
+        xlat[*pos] = s;
+        (*pos)++;
+    }else{
+        pfx <<= 1;
+        pl++;
+        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0, pfx, pl, pos);
+        pfx |= 1;
+        get_tree_codes(bits, lens, xlat, nodes, nodes[node].n0+1, pfx, pl, pos);
+    }
+}
+
+static int build_huff_tree(VLC *vlc, Node *nodes, int head)
+{
+    uint32_t bits[256];
+    int16_t lens[256];
+    uint8_t xlat[256];
+    int pos = 0;
+
+    get_tree_codes(bits, lens, xlat, nodes, head, 0, 0, &pos);
+    return init_vlc_sparse(vlc, 9, pos, lens, 2, 2, bits, 4, 4, xlat, 1, 1, 0);
+}
+
+
+/**
+ * first nb_codes nodes.count must be set
+ */
+int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
+                       Node nodes[2*nb_codes], huff_cmp_t cmp, int hnode_first)
+{
+    int i, j;
+    int cur_node;
+    int64_t sum = 0;
+
+    for(i = 0; i < nb_codes; i++){
+        nodes[i].sym = i;
+        nodes[i].n0 = -2;
+        sum += nodes[i].count;
+    }
+
+    if(sum >> 31) {
+        av_log(avctx, AV_LOG_ERROR, "Too high symbol frequencies. Tree construction is not possible\n");
+        return -1;
+    }
+    qsort(nodes, nb_codes, sizeof(Node), cmp);
+    cur_node = nb_codes;
+    for(i = 0; i < nb_codes*2-1; i += 2){
+        nodes[cur_node].sym = HNODE;
+        nodes[cur_node].count = nodes[i].count + nodes[i+1].count;
+        nodes[cur_node].n0 = i;
+        for(j = cur_node; j > 0; j--){
+            if(nodes[j].count > nodes[j-1].count ||
+               (nodes[j].count == nodes[j-1].count &&
+                (!hnode_first || nodes[j].n0==j-1 || nodes[j].n0==j-2 ||
+                 (nodes[j].sym!=HNODE && nodes[j-1].sym!=HNODE))))
+                break;
+            FFSWAP(Node, nodes[j], nodes[j-1]);
+        }
+        cur_node++;
+    }
+    if(build_huff_tree(vlc, nodes, nb_codes*2-2) < 0){
+        av_log(avctx, AV_LOG_ERROR, "Error building tree\n");
+        return -1;
+    }
+    return 0;
+}