From ecbc8847c41ce2c207ab614717755385a603c87f Mon Sep 17 00:00:00 2001
From: jkeil <jkeil@b3059339-0415-0410-9bf9-f77b7e298cf2>
Date: Sat, 14 Jul 2001 16:52:09 +0000
Subject: mp3 audio decoding didn't work on big-endian architectures

git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@1319 b3059339-0415-0410-9bf9-f77b7e298cf2
---
 mp3lib/decod386.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 44 insertions(+), 2 deletions(-)

(limited to 'mp3lib/decod386.c')

diff --git a/mp3lib/decod386.c b/mp3lib/decod386.c
index fc88ae2851..f5ca8940c0 100644
--- a/mp3lib/decod386.c
+++ b/mp3lib/decod386.c
@@ -11,17 +11,59 @@
  */
 
 
-
+#include "../config.h"
+
+#if 0
+ /* old WRITE_SAMPLE */
+   /* is portable */
+#define WRITE_SAMPLE(samples,sum,clip) {			\
+  if( (sum) > 32767.0) { *(samples) = 0x7fff; (clip)++; }	\
+  else if( (sum) < -32768.0) { *(samples) = -0x8000; (clip)++; }\
+  else { *(samples) = sum;  }					\
+}
+#else
  /* new WRITE_SAMPLE */
+
+/*
+ * should be the same as the "old WRITE_SAMPLE" macro above, but uses
+ * some tricks to avoid double->int conversions and floating point compares.
+ *
+ * Here's how it works:
+ * ((((65536.0 * 65536.0 * 16)+(65536.0 * 0.5))* 65536.0)) is
+ * 0x0010000080000000LL in hex.  It computes 0x0010000080000000LL + sum
+ * as a double IEEE fp value and extracts the low-order 32-bits from the
+ * IEEE fp representation stored in memory.  The 2^56 bit in the constant
+ * is intended to force the bits of "sum" into the least significant bits
+ * of the double mantissa.  After an integer substraction of 0x80000000
+ * we have the original double value "sum" converted to an 32-bit int value.
+ *
+ * (Is that really faster than the clean and simple old version of the macro?)
+ */
+
+/*
+ * On a SPARC cpu, we fetch the low-order 32-bit from the second 32-bit
+ * word of the double fp value stored in memory.  On an x86 cpu, we fetch it
+ * from the first 32-bit word.
+ * I'm not sure if the WORDS_BIGENDIAN feature test covers all possible memory
+ * layouts of double floating point values an all cpu architectures.  If
+ * it doesn't work for you, just enable the "old WRITE_SAMPLE" macro.
+ */
+#if WORDS_BIGENDIAN
+#define	MANTISSA_OFFSET	1
+#else
+#define	MANTISSA_OFFSET	0
+#endif
+
    /* sizeof(int) == 4 */
 #define WRITE_SAMPLE(samples,sum,clip) { \
   double dtemp; long v;                  \
   dtemp = ((((65536.0 * 65536.0 * 16)+(65536.0 * 0.5))* 65536.0)) + (sum);\
-  v = ((*(int *)&dtemp) - 0x80000000); \
+  v = (((int *)&dtemp)[MANTISSA_OFFSET] - 0x80000000); \
   if( v > 32767) { *(samples) = 0x7fff; (clip)++; } \
   else if( v < -32768) { *(samples) = -0x8000; (clip)++; } \
   else { *(samples) = v; } \
 }
+#endif
 
 
 /*
-- 
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