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/*
FreeRDP: A Remote Desktop Protocol client.
RemoteFX Codec Library - RLGR
Copyright 2011 Vic Lee
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
/*
This implementation of RLGR refers to
[MS-RDPRFX] 3.1.8.1.7.3 RLGR1/RLGR3 Pseudocode
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "rfx_bitstream.h"
#include "rfx_rlgr.h"
/* Constants used within the RLGR1/RLGR3 algorithm */
#define KPMAX (80) /* max value for kp or krp */
#define LSGR (3) /* shift count to convert kp to k */
#define UP_GR (4) /* increase in kp after a zero run in RL mode */
#define DN_GR (6) /* decrease in kp after a nonzero symbol in RL mode */
#define UQ_GR (3) /* increase in kp after nonzero symbol in GR mode */
#define DQ_GR (3) /* decrease in kp after zero symbol in GR mode */
/* Gets (returns) the next nBits from the bitstream */
#define GetBits(nBits) rfx_bitstream_get_bits(bs, nBits)
/* From current output pointer, write "value", check and update buffer_size */
#define WriteValue(value) \
{ \
if (buffer_size > 0) \
*dst++ = (value); \
buffer_size--; \
}
/* From current output pointer, write next nZeroes terms with value 0, check and update buffer_size */
#define WriteZeroes(nZeroes) \
{ \
int nZeroesWritten = (nZeroes); \
if (nZeroesWritten > buffer_size) \
nZeroesWritten = buffer_size; \
if (nZeroesWritten > 0) \
{ \
memset(dst, 0, nZeroesWritten * sizeof(int)); \
dst += nZeroesWritten; \
} \
buffer_size -= (nZeroes); \
}
/* Returns the least number of bits required to represent a given value */
#define GetMinBits(_val, _nbits) \
{ \
uint32 _v = _val; \
_nbits = 0; \
while (_v) \
{ \
_v >>= 1; \
_nbits++; \
} \
} \
/* Converts from (2 * magnitude - sign) to integer */
#define GetIntFrom2MagSign(twoMs) (((twoMs) & 1) ? -1 * (int)(((twoMs) + 1) >> 1) : (int)((twoMs) >> 1))
/*
* Update the passed parameter and clamp it to the range [0, KPMAX]
* Return the value of parameter right-shifted by LSGR
*/
#define UpdateParam(_param, _deltaP, _k) \
{ \
_param += _deltaP; \
if (_param > KPMAX) \
_param = KPMAX; \
if (_param < 0) \
_param = 0; \
_k = (_param >> LSGR); \
}
/* Outputs the Golomb/Rice encoding of a non-negative integer */
#define GetGRCode(krp, kr) rfx_rlgr_get_gr_code(bs, krp, kr)
static uint32
rfx_rlgr_get_gr_code(RFX_BITSTREAM * bs, int * krp, int * kr)
{
int vk;
uint32 mag;
/* chew up/count leading 1s and escape 0 */
for (vk = 0; GetBits(1) == 1;)
vk++;
/* get next *kr bits, and combine with leading 1s */
mag = (vk << *kr) | GetBits(*kr);
/* adjust krp and kr based on vk */
if (!vk)
{
UpdateParam(*krp, -2, *kr);
}
else if (vk != 1)
{
/* at 1, no change! */
UpdateParam(*krp, vk, *kr);
}
return mag;
}
int
rfx_rlgr_decode(RLGR_MODE mode, const uint8 * data, int data_size, uint32 * buffer, int buffer_size)
{
int k;
int kp;
int kr;
int krp;
uint32 * dst;
RFX_BITSTREAM * bs;
bs = rfx_bitstream_new();
rfx_bitstream_put_buffer(bs, (uint8 *) data, data_size);
dst = buffer;
/* initialize the parameters */
k = 1;
kp = k << LSGR;
kr = 1;
krp = kr << LSGR;
while (!rfx_bitstream_eos(bs) && buffer_size > 0)
{
int run;
if (k)
{
int mag;
uint32 sign;
/* RL MODE */
while (!rfx_bitstream_eos(bs) && GetBits(1) == 0)
{
/* we have an RL escape "0", which translates to a run (1<<k) of zeros */
WriteZeroes(1 << k);
UpdateParam(kp, UP_GR, k); /* raise k and kp up because of zero run */
}
/* next k bits will contain remaining run or zeros */
run = GetBits(k);
WriteZeroes(run);
/* get nonzero value, starting with sign bit and then GRCode for magnitude -1 */
sign = GetBits(1);
/* magnitude - 1 was coded (because it was nonzero) */
mag = (int) GetGRCode(&krp, &kr) + 1;
WriteValue(sign ? -mag : mag);
UpdateParam(kp, -DN_GR, k); /* lower k and kp because of nonzero term */
}
else
{
uint32 mag;
uint32 nIdx;
uint32 val1;
uint32 val2;
/* GR (GOLOMB-RICE) MODE */
mag = GetGRCode(&krp, &kr); /* values coded are 2 * magnitude - sign */
if (mode == RLGR1)
{
if (!mag)
{
WriteValue(0);
UpdateParam(kp, UQ_GR, k); /* raise k and kp due to zero */
}
else
{
WriteValue(GetIntFrom2MagSign(mag));
UpdateParam(kp, -DQ_GR, k); /* lower k and kp due to nonzero */
}
}
else /* mode == RLGR3 */
{
/*
* In GR mode FOR RLGR3, we have encoded the
* sum of two (2 * mag - sign) values
*/
/* maximum possible bits for first term */
GetMinBits(mag, nIdx);
/* decode val1 is first term's (2 * mag - sign) value */
val1 = GetBits(nIdx);
/* val2 is second term's (2 * mag - sign) value */
val2 = mag - val1;
if (val1 && val2)
{
/* raise k and kp if both terms nonzero */
UpdateParam(kp, -2 * DQ_GR, k);
}
else if (!val1 && !val2)
{
/* lower k and kp if both terms zero */
UpdateParam(kp, 2 * UQ_GR, k);
}
WriteValue(GetIntFrom2MagSign(val1));
WriteValue(GetIntFrom2MagSign(val2));
}
}
}
rfx_bitstream_free(bs);
return (dst - buffer);
}
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