1 files changed, 314 insertions, 0 deletions

diff --git a/apps/codecs/demac/libdemac/entropy.c b/apps/codecs/demac/libdemac/entropy.c
new file mode 100644
index 0000000000..2c60420250
--- /dev/null
+++ b/apps/codecs/demac/libdemac/entropy.c
@@ -0,0 +1,314 @@
+/*
+
+libdemac - A Monkey's Audio decoder
+
+$Id:$
+
+Copyright (C) Dave Chapman 2007
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
+
+*/
+
+#include <inttypes.h>
+#include <string.h>
+
+#include "parser.h"
+#include "entropy.h"
+#include "rangecoding.h"   /* Range-coding (static inline) functions */
+
+#define MODEL_ELEMENTS 64
+
+/*
+  The following counts arrays for use with the range decoder are
+  hard-coded in the Monkey's Audio decoder.
+*/
+
+static const int counts_3970[65] ICONST_ATTR =
+{
+        0,14824,28224,39348,47855,53994,58171,60926,
+    62682,63786,64463,64878,65126,65276,65365,65419,
+    65450,65469,65480,65487,65491,65493,65494,65495,
+    65496,65497,65498,65499,65500,65501,65502,65503,
+    65504,65505,65506,65507,65508,65509,65510,65511,
+    65512,65513,65514,65515,65516,65517,65518,65519,
+    65520,65521,65522,65523,65524,65525,65526,65527,
+    65528,65529,65530,65531,65532,65533,65534,65535,
+    65536
+};
+
+/* counts_diff_3970[i] = counts_3970[i+1] - counts_3970[i] */
+static const int counts_diff_3970[64] ICONST_ATTR =
+{
+    14824,13400,11124,8507,6139,4177,2755,1756,
+    1104,677,415,248,150,89,54,31,
+    19,11,7,4,2,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1
+};
+
+static const int counts_3980[65] ICONST_ATTR =
+{
+        0,19578,36160,48417,56323,60899,63265,64435,
+    64971,65232,65351,65416,65447,65466,65476,65482,
+    65485,65488,65490,65491,65492,65493,65494,65495,
+    65496,65497,65498,65499,65500,65501,65502,65503,
+    65504,65505,65506,65507,65508,65509,65510,65511,
+    65512,65513,65514,65515,65516,65517,65518,65519,
+    65520,65521,65522,65523,65524,65525,65526,65527,
+    65528,65529,65530,65531,65532,65533,65534,65535,
+    65536
+};
+
+/* counts_diff_3980[i] = counts_3980[i+1] - counts_3980[i] */
+
+static const int counts_diff_3980[64] ICONST_ATTR =
+{
+    19578,16582,12257,7906,4576,2366,1170,536,
+    261,119,65,31,19,10,6,3,
+    3,2,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1,
+    1,1,1,1,1,1,1,1
+};
+
+/*
+  range_get_symbol_* functions based on main decoding loop in simple_d.c from
+  http://www.compressconsult.com/rangecoder/rngcod13.zip
+  (c) Michael Schindler
+*/
+
+static inline int range_get_symbol_3980(void)
+{
+    int symbol, cf;
+
+    cf = range_decode_culshift(16);
+
+    /* figure out the symbol inefficiently; a binary search would be much better */
+    for (symbol = 0; counts_3980[symbol+1] <= cf; symbol++);
+
+    range_decode_update(counts_diff_3980[symbol],counts_3980[symbol]);
+
+    return symbol;
+}
+
+static inline int range_get_symbol_3970(void)
+{
+    int symbol, cf;
+
+    cf = range_decode_culshift(16);
+
+    /* figure out the symbol inefficiently; a binary search would be much better */
+    for (symbol = 0; counts_3970[symbol+1] <= cf; symbol++);
+
+    range_decode_update(counts_diff_3970[symbol],counts_3970[symbol]);
+
+    return symbol;
+}
+
+/* MAIN DECODING FUNCTIONS */
+
+struct rice_t
+{
+  uint32_t k;
+  uint32_t ksum;
+};
+
+static struct rice_t riceX IBSS_ATTR;
+static struct rice_t riceY IBSS_ATTR;
+
+static inline void update_rice(struct rice_t* rice, int x)
+{
+    rice->ksum += ((x + 1) / 2) - ((rice->ksum + 16) >> 5);
+
+    if (rice->k == 0) {
+        rice->k = 1;
+    } else if (rice->ksum < ((uint32_t)1 << (rice->k + 4))) {
+        rice->k--;
+    } else if (rice->ksum >= ((uint32_t)1 << (rice->k + 5))) {
+        rice->k++;
+    }
+}
+
+static inline int entropy_decode3980(struct rice_t* rice)
+{
+    int base, x, pivot, overflow;
+
+    pivot = rice->ksum >> 5;
+    if (pivot == 0) pivot=1;
+
+    overflow = range_get_symbol_3980();
+
+    if (overflow == (MODEL_ELEMENTS-1)) {
+        overflow = range_decode_short() << 16;
+        overflow |= range_decode_short();
+    }
+
+    if (pivot >= 0x10000) {
+        /* Codepath for 24-bit streams */
+        int nbits, lo_bits, base_hi, base_lo;
+
+        /* Count the number of bits in pivot */
+        nbits = 17; /* We know there must be at least 17 bits */
+        while ((pivot >> nbits) > 0) { nbits++; }
+
+        /* base_lo is the low (nbits-16) bits of base
+           base_hi is the high 16 bits of base
+        */
+        lo_bits = (nbits - 16);
+
+        base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
+        range_decode_update(1, base_hi);
+
+        base_lo = range_decode_culfreq(1 << lo_bits);
+        range_decode_update(1, base_lo);
+
+        base = (base_hi << lo_bits) + base_lo;
+    } else {
+        /* Codepath for 16-bit streams */
+        base = range_decode_culfreq(pivot);
+        range_decode_update(1, base);
+    }
+
+    x = base + (overflow * pivot);
+    update_rice(rice, x);
+
+    /* Convert to signed */
+    if (x & 1)
+        return (x >> 1) + 1;
+    else
+        return -(x >> 1);
+}
+
+
+static inline int entropy_decode3970(struct rice_t* rice)
+{
+    int x, tmpk;
+
+    int overflow = range_get_symbol_3970();
+
+    if (overflow == (MODEL_ELEMENTS - 1)) {
+        tmpk = range_decode_bits(5);
+        overflow = 0;
+    } else {
+        tmpk = (rice->k < 1) ? 0 : rice->k - 1;
+    }
+
+    if (tmpk <= 16) {
+        x = range_decode_bits(tmpk);
+    } else {
+        x = range_decode_short();
+        x |= (range_decode_bits(tmpk - 16) << 16);
+    }
+    x += (overflow << tmpk);
+
+    update_rice(rice, x);
+
+    /* Convert to signed */
+    if (x & 1)
+        return (x >> 1) + 1;
+    else
+        return -(x >> 1);
+}
+
+void init_entropy_decoder(struct ape_ctx_t* ape_ctx,
+                          unsigned char* inbuffer, int* firstbyte,
+                          int* bytesconsumed)
+{
+    bytebuffer = inbuffer;
+    bytebufferoffset = *firstbyte;
+
+    /* Read the CRC */
+    ape_ctx->CRC = read_byte();
+    ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
+    ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
+    ape_ctx->CRC = (ape_ctx->CRC << 8) | read_byte();
+
+    /* Read the frame flags if they exist */
+    ape_ctx->frameflags = 0;
+    if ((ape_ctx->fileversion > 3820) && (ape_ctx->CRC & 0x80000000)) {
+        ape_ctx->CRC &= ~0x80000000;
+
+        ape_ctx->frameflags = read_byte();
+        ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
+        ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
+        ape_ctx->frameflags = (ape_ctx->frameflags << 8) | read_byte();
+    }
+    /* Keep a count of the blocks decoded in this frame */
+    ape_ctx->blocksdecoded = 0;
+
+    /* Initialise the rice structs */
+    riceX.k = 10;
+    riceX.ksum = (1 << riceX.k) * 16;
+    riceY.k = 10;
+    riceY.ksum = (1 << riceY.k) * 16;
+
+    /* The first 8 bits of input are ignored. */
+    skip_byte();
+
+    range_start_decoding();
+
+    /* Return the new state of the buffer */
+    *bytesconsumed = (intptr_t)bytebuffer - (intptr_t)inbuffer;
+    *firstbyte = bytebufferoffset;
+}
+
+int entropy_decode(struct ape_ctx_t* ape_ctx,
+                   unsigned char* inbuffer, int* firstbyte,
+                   int* bytesconsumed,
+                   int32_t* decoded0, int32_t* decoded1,
+                   int blockstodecode)
+{
+    bytebuffer = inbuffer;
+    bytebufferoffset = *firstbyte;
+
+    ape_ctx->blocksdecoded += blockstodecode;
+
+    if (ape_ctx->frameflags & APE_FRAMECODE_STEREO_SILENCE) {
+        /* We are pure silence, just memset the output buffer. */
+        memset(decoded0, 0, blockstodecode * sizeof(int32_t));
+        memset(decoded1, 0, blockstodecode * sizeof(int32_t));
+    } else {
+        if (ape_ctx->fileversion > 3970) {
+            while (blockstodecode--) {
+                *(decoded0++) = entropy_decode3980(&riceY);
+                if (decoded1 != NULL)
+                    *(decoded1++) = entropy_decode3980(&riceX);
+            }
+        } else {
+            while (blockstodecode--) {
+                *(decoded0++) = entropy_decode3970(&riceY);
+                if (decoded1 != NULL)
+                    *(decoded1++) = entropy_decode3970(&riceX);
+            }
+        }
+    }
+
+    if (ape_ctx->blocksdecoded == ape_ctx->currentframeblocks)
+    {
+        range_done_decoding();
+    }
+
+    /* Return the new state of the buffer */
+    *bytesconsumed = bytebuffer - inbuffer;
+    *firstbyte = bytebufferoffset;
+
+    return(0);
+}