From 85aa3a8d381ac980b49699d49234e4df051813e5 Mon Sep 17 00:00:00 2001
From: Dave Chapman <dave@dchapman.com>
Date: Mon, 9 Jul 2007 10:53:56 +0000
Subject: Code reorganisation - move the vlc functions back to
 common.c/common.h (where they originally were in the ffmpeg source).  This
 code is still identical to the ffmpeg source.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@13830 a1c6a512-1295-4272-9138-f99709370657
---
 apps/codecs/libwma/common.c | 161 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 161 insertions(+)

(limited to 'apps/codecs/libwma/common.c')

diff --git a/apps/codecs/libwma/common.c b/apps/codecs/libwma/common.c
index 619ce47197..b4577a4c74 100644
--- a/apps/codecs/libwma/common.c
+++ b/apps/codecs/libwma/common.c
@@ -105,3 +105,164 @@ int check_marker(GetBitContext *s, const char *msg)
     return bit;
 }
 
+/* VLC decoding */
+
+//#define DEBUG_VLC
+
+#define GET_DATA(v, table, i, wrap, size) \
+{\
+    const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
+    switch(size) {\
+    case 1:\
+        v = *(const uint8_t *)ptr;\
+        break;\
+    case 2:\
+        v = *(const uint16_t *)ptr;\
+        break;\
+    default:\
+        v = *(const uint32_t *)ptr;\
+        break;\
+    }\
+}
+
+static int alloc_table(VLC *vlc, int size)
+{
+    int index;
+    index = vlc->table_size;
+    vlc->table_size += size;
+    if (vlc->table_size > vlc->table_allocated) {
+        vlc->table_allocated += (1 << vlc->bits);
+        if (!vlc->table)
+            return -1;
+    }
+    return index;
+}
+
+static int build_table(VLC *vlc, int table_nb_bits,
+                int nb_codes,
+                const void *bits, int bits_wrap, int bits_size,
+                const void *codes, int codes_wrap, int codes_size,
+                uint32_t code_prefix, int n_prefix)
+{
+    int i, j, k, n, table_size, table_index, nb, n1, index;
+    uint32_t code;
+    VLC_TYPE (*table)[2];
+
+    table_size = 1 << table_nb_bits;
+    table_index = alloc_table(vlc, table_size);
+    if (table_index < 0)
+        return -1;
+    table = &vlc->table[table_index];
+
+    for(i=0;i<table_size;i++)
+    {
+        table[i][1] = 0; //bits
+        table[i][0] = -1; //codes
+    }
+
+    /* first pass: map codes and compute auxillary table sizes */
+    for(i=0;i<nb_codes;i++)
+    {
+        GET_DATA(n, bits, i, bits_wrap, bits_size);
+        GET_DATA(code, codes, i, codes_wrap, codes_size);
+        /* we accept tables with holes */
+        if (n <= 0)
+            continue;
+        /* if code matches the prefix, it is in the table */
+        n -= n_prefix;
+        if (n > 0 && (code >> n) == code_prefix)
+        {
+            if (n <= table_nb_bits)
+            {
+                /* no need to add another table */
+                j = (code << (table_nb_bits - n)) & (table_size - 1);
+                nb = 1 << (table_nb_bits - n);
+                for(k=0;k<nb;k++)
+                {
+                    if (table[j][1] /*bits*/ != 0)
+                    {
+                        // PJJ exit(-1);
+                    }
+                    table[j][1] = n; //bits
+                    table[j][0] = i; //code
+                    j++;
+                }
+            }
+            else
+            {
+                n -= table_nb_bits;
+                j = (code >> n) & ((1 << table_nb_bits) - 1);
+                /* compute table size */
+                n1 = -table[j][1]; //bits
+                if (n > n1)
+                    n1 = n;
+                table[j][1] = -n1; //bits
+            }
+        }
+    }
+
+    /* second pass : fill auxillary tables recursively */
+    for(i=0;i<table_size;i++)
+    {
+        n = table[i][1]; //bits
+        if (n < 0)
+        {
+            n = -n;
+            if (n > table_nb_bits)
+            {
+                n = table_nb_bits;
+                table[i][1] = -n; //bits
+            }
+            index = build_table(vlc, n, nb_codes,
+                                bits, bits_wrap, bits_size,
+                                codes, codes_wrap, codes_size,
+                                (code_prefix << table_nb_bits) | i,
+                                n_prefix + table_nb_bits);
+            if (index < 0)
+                return -1;
+            /* note: realloc has been done, so reload tables */
+            table = &vlc->table[table_index];
+            table[i][0] = index; //code
+        }
+    }
+    return table_index;
+}
+
+/* Build VLC decoding tables suitable for use with get_vlc().
+
+   'nb_bits' set thee decoding table size (2^nb_bits) entries. The
+   bigger it is, the faster is the decoding. But it should not be too
+   big to save memory and L1 cache. '9' is a good compromise.
+
+   'nb_codes' : number of vlcs codes
+
+   'bits' : table which gives the size (in bits) of each vlc code.
+
+   'codes' : table which gives the bit pattern of of each vlc code.
+
+   'xxx_wrap' : give the number of bytes between each entry of the
+   'bits' or 'codes' tables.
+
+   'xxx_size' : gives the number of bytes of each entry of the 'bits'
+   or 'codes' tables.
+
+   'wrap' and 'size' allows to use any memory configuration and types
+   (byte/word/long) to store the 'bits' and 'codes' tables.
+*/
+int init_vlc(VLC *vlc, int nb_bits, int nb_codes,
+             const void *bits, int bits_wrap, int bits_size,
+             const void *codes, int codes_wrap, int codes_size)
+{
+    vlc->bits = nb_bits;
+    vlc->table_size = 0;
+
+    if (build_table(vlc, nb_bits, nb_codes,
+                    bits, bits_wrap, bits_size,
+                    codes, codes_wrap, codes_size,
+                    0, 0) < 0)
+    {
+
+        return -1;
+    }
+    return 0;
+}
-- 
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