huffman: add ff_huff_gen_len_table

The function will be used by utvideo as well.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

configure

@@ -1376,6 +1376,7 @@ eatgq_decoder_select="aandcttables"
 eatqi_decoder_select="aandcttables error_resilience mpegvideo"
 ffv1_decoder_select="golomb rangecoder"
 ffv1_encoder_select="rangecoder"
+ffvhuff_encoder_select="huffman"
 flac_decoder_select="golomb"
 flac_encoder_select="golomb lpc"
 flashsv_decoder_select="zlib"
@@ -1397,6 +1398,7 @@ h264_dxva2_hwaccel_select="dxva2 h264_decoder"
 h264_vaapi_hwaccel_select="vaapi h264_decoder"
 h264_vda_hwaccel_select="vda h264_decoder"
 h264_vdpau_decoder_select="vdpau h264_decoder"
+huffyuv_encoder_select="huffman"
 iac_decoder_select="fft mdct sinewin"
 imc_decoder_select="fft mdct sinewin"
 jpegls_decoder_select="golomb"

libavcodec/huffman.c

 /*
  * Copyright (c) 2006 Konstantin Shishkov
+ * Copyright (c) 2007 Loren Merritt
  *
  * This file is part of Libav.
  *
@@ -30,6 +31,63 @@
 /* symbol for Huffman tree node */
 #define HNODE -1
 
+typedef struct {
+    uint64_t val;
+    int name;
+} HeapElem;
+
+static void heap_sift(HeapElem *h, int root, int size)
+{
+    while (root * 2 + 1 < size) {
+        int child = root * 2 + 1;
+        if (child < size - 1 && h[child].val > h[child+1].val)
+            child++;
+        if (h[root].val > h[child].val) {
+            FFSWAP(HeapElem, h[root], h[child]);
+            root = child;
+        } else
+            break;
+    }
+}
+
+void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats)
+{
+    HeapElem h[256];
+    int up[2*256];
+    int len[2*256];
+    int offset, i, next;
+    int size = 256;
+
+    for (offset = 1; ; offset <<= 1) {
+        for (i=0; i < size; i++) {
+            h[i].name = i;
+            h[i].val = (stats[i] << 8) + offset;
+        }
+        for (i = size / 2 - 1; i >= 0; i--)
+            heap_sift(h, i, size);
+
+        for (next = size; next < size * 2 - 1; next++) {
+            // merge the two smallest entries, and put it back in the heap
+            uint64_t min1v = h[0].val;
+            up[h[0].name] = next;
+            h[0].val = INT64_MAX;
+            heap_sift(h, 0, size);
+            up[h[0].name] = next;
+            h[0].name = next;
+            h[0].val += min1v;
+            heap_sift(h, 0, size);
+        }
+
+        len[2 * size - 2] = 0;
+        for (i = 2 * size - 3; i >= size; i--)
+            len[i] = len[up[i]] + 1;
+        for (i = 0; i < size; i++) {
+            dst[i] = len[up[i]] + 1;
+            if (dst[i] >= 32) break;
+        }
+        if (i==size) break;
+    }
+}
 
 static void get_tree_codes(uint32_t *bits, int16_t *lens, uint8_t *xlat,
                            Node *nodes, int node,

libavcodec/huffman.h

@@ -42,4 +42,6 @@ typedef int (*HuffCmp)(const void *va, const void *vb);
 int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int nb_codes,
                        Node *nodes, HuffCmp cmp, int flags);
 
+void ff_huff_gen_len_table(uint8_t *dst, const uint64_t *stats);
+
 #endif /* AVCODEC_HUFFMAN_H */

libavcodec/huffyuv.c

@@ -33,6 +33,7 @@
 #include "put_bits.h"
 #include "dsputil.h"
 #include "thread.h"
+#include "huffman.h"
 
 #define VLC_BITS 11
 
@@ -223,66 +224,6 @@ static int generate_bits_table(uint32_t *dst, const uint8_t *len_table)
     return 0;
 }
 
-#if CONFIG_HUFFYUV_ENCODER || CONFIG_FFVHUFF_ENCODER
-typedef struct {
-    uint64_t val;
-    int name;
-} HeapElem;
-
-static void heap_sift(HeapElem *h, int root, int size)
-{
-    while (root * 2 + 1 < size) {
-        int child = root * 2 + 1;
-        if (child < size - 1 && h[child].val > h[child + 1].val)
-            child++;
-        if (h[root].val > h[child].val) {
-            FFSWAP(HeapElem, h[root], h[child]);
-            root = child;
-        } else
-            break;
-    }
-}
-
-static void generate_len_table(uint8_t *dst, const uint64_t *stats)
-{
-    HeapElem h[256];
-    int up[2*256];
-    int len[2*256];
-    int offset, i, next;
-    int size = 256;
-
-    for (offset = 1; ; offset <<= 1) {
-        for (i = 0; i < size; i++) {
-            h[i].name = i;
-            h[i].val = (stats[i] << 8) + offset;
-        }
-        for (i = size / 2 - 1; i >= 0; i--)
-            heap_sift(h, i, size);
-
-        for (next = size; next < size * 2 - 1; next++) {
-            // merge the two smallest entries, and put it back in the heap
-            uint64_t min1v = h[0].val;
-            up[h[0].name] = next;
-            h[0].val = INT64_MAX;
-            heap_sift(h, 0, size);
-            up[h[0].name] = next;
-            h[0].name = next;
-            h[0].val += min1v;
-            heap_sift(h, 0, size);
-        }
-
-        len[2 * size - 2] = 0;
-        for (i = 2 * size - 3; i >= size; i--)
-            len[i] = len[up[i]] + 1;
-        for (i = 0; i < size; i++) {
-            dst[i] = len[up[i]] + 1;
-            if (dst[i] >= 32) break;
-        }
-        if (i==size) break;
-    }
-}
-#endif /* CONFIG_HUFFYUV_ENCODER || CONFIG_FFVHUFF_ENCODER */
-
 static void generate_joint_tables(HYuvContext *s)
 {
     uint16_t symbols[1 << VLC_BITS];
@@ -697,7 +638,7 @@ static av_cold int encode_init(AVCodecContext *avctx)
     }
 
     for (i = 0; i < 3; i++) {
-        generate_len_table(s->len[i], s->stats[i]);
+        ff_huff_gen_len_table(s->len[i], s->stats[i]);
 
         if (generate_bits_table(s->bits[i], s->len[i]) < 0) {
             return -1;
@@ -1307,7 +1248,7 @@ static int encode_frame(AVCodecContext *avctx, AVPacket *pkt,
 
     if (s->context) {
         for (i = 0; i < 3; i++) {
-            generate_len_table(s->len[i], s->stats[i]);
+            ff_huff_gen_len_table(s->len[i], s->stats[i]);
             if (generate_bits_table(s->bits[i], s->len[i]) < 0)
                 return -1;
             size += store_table(s, s->len[i], &pkt->data[size]);