From b60e53d27ff399f5ad9d38f9a64622b04a0ef895 Mon Sep 17 00:00:00 2001
From: amiconn <amiconn@a1c6a512-1295-4272-9138-f99709370657>
Date: Tue, 4 Nov 2008 23:46:04 +0000
Subject: [PATCH] Some entropy decoder tweaks. Also removed unnecessary 'tmp'
 variables.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@19008 a1c6a512-1295-4272-9138-f99709370657
---
 apps/codecs/demac/libdemac/entropy.c     | 13 ++++++++-----
 apps/codecs/demac/libdemac/rangecoding.h | 28 +++++++++-------------------
 2 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/apps/codecs/demac/libdemac/entropy.c b/apps/codecs/demac/libdemac/entropy.c
index 1ef5bc4dc..86ea06d38 100644
--- a/apps/codecs/demac/libdemac/entropy.c
+++ b/apps/codecs/demac/libdemac/entropy.c
@@ -141,10 +141,13 @@ static inline void update_rice(struct rice_t* rice, int x)
 
     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++;
+    } else {
+        uint32_t lim = 1 << (rice->k + 4);
+        if (rice->ksum < lim) {
+            rice->k--;
+        } else if (rice->ksum >= 2 * lim) {
+            rice->k++;
+        }
     }
 }
 
@@ -178,7 +181,7 @@ static inline int entropy_decode3980(struct rice_t* rice)
         base_hi = range_decode_culfreq((pivot >> lo_bits) + 1);
         range_decode_update(1, base_hi);
 
-        base_lo = range_decode_culfreq(1 << lo_bits);
+        base_lo = range_decode_culshift(lo_bits);
         range_decode_update(1, base_lo);
 
         base = (base_hi << lo_bits) + base_lo;
diff --git a/apps/codecs/demac/libdemac/rangecoding.h b/apps/codecs/demac/libdemac/rangecoding.h
index 9c26344ec..c96886e32 100644
--- a/apps/codecs/demac/libdemac/rangecoding.h
+++ b/apps/codecs/demac/libdemac/rangecoding.h
@@ -62,12 +62,9 @@ static int bytebufferoffset IBSS_ATTR;
 
 static inline void skip_byte(void)
 {
-    if (bytebufferoffset) {
-        bytebufferoffset--;
-    } else {
-        bytebufferoffset = 3;
-        bytebuffer += 4;
-    }
+    bytebufferoffset--;
+    bytebuffer += bytebufferoffset & 4;
+    bytebufferoffset &= 3;
 }
 
 static inline int read_byte(void)
@@ -122,23 +119,17 @@ static inline void range_dec_normalize(void)
 /* or: totf is (code_value)1<<shift                                      */
 /* returns the culmulative frequency                         */
 static inline int range_decode_culfreq(int tot_f)
-{   int tmp;
-
+{
     range_dec_normalize();
-
     rc.help = rc.range / tot_f;
-    tmp = rc.low / rc.help;
-
-    return tmp;
+    return rc.low / rc.help;
 }
 
 static inline int range_decode_culshift(int shift)
 {
-    int tmp;
     range_dec_normalize();
-    rc.help = rc.range>>shift;
-    tmp = rc.low/rc.help;
-    return tmp;
+    rc.help = rc.range >> shift;
+    return rc.low / rc.help;
 }
 
 
@@ -146,9 +137,8 @@ static inline int range_decode_culshift(int shift)
 /* sy_f is the interval length (frequency of the symbol)     */
 /* lt_f is the lower end (frequency sum of < symbols)        */
 static inline void range_decode_update(int sy_f, int lt_f)
-{   int tmp;
-    tmp = rc.help * lt_f;
-    rc.low -= tmp;
+{
+    rc.low -= rc.help * lt_f;
     rc.range = rc.help * sy_f;
 }
 
-- 
2.11.4.GIT