From 60d09a712cf2253f243683dae32fe0958d6c87fc Mon Sep 17 00:00:00 2001
From: drh <drh@noemail.net>
Date: Thu, 30 Aug 2007 15:05:08 +0000
Subject: [PATCH] Fix the SQLITE_MIXED_ENDIAN_64BIT_FLOAT option so that it
 works on goofy linux kernels that employ CONFIG_FPE_FASTFPE.  Patch from
 Frank van Vugt. (CVS 4339)

FossilOrigin-Name: 71ab92e900512ad01047b46f734bd5f65998ecf9
---
 manifest      | 12 ++++++------
 manifest.uuid |  2 +-
 src/vdbeaux.c | 27 ++++++++++++++++++++-------
 3 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/manifest b/manifest
index 7760fe718a..344a2fdb01 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\sa\sref-count\sproblem\sin\sthe\sTCL\sbindings.\s\sTicket\s#2597.\s(CVS\s4338)
-D 2007-08-30T14:58:20
+C Fix\sthe\sSQLITE_MIXED_ENDIAN_64BIT_FLOAT\soption\sso\sthat\sit\sworks\son\ngoofy\slinux\skernels\sthat\semploy\sCONFIG_FPE_FASTFPE.\s\sPatch\sfrom\nFrank\svan\sVugt.\s(CVS\s4339)
+D 2007-08-30T15:05:08
 F Makefile.in bfcc303429a5d9dcd552d807ee016c77427418c3
 F Makefile.linux-gcc 65241babba6faf1152bf86574477baab19190499
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -166,7 +166,7 @@ F src/vdbe.c d2f156bbb6b636e9b4a3648c38454bf472668a86
 F src/vdbe.h 03a0fa17f6753a24d6cb585d7a362944a2c115aa
 F src/vdbeInt.h 630145b9bfaa19190ab491f52658a7db550f2247
 F src/vdbeapi.c 9c2d681b75e4b90c28b9dd01a3f2e5905267f884
-F src/vdbeaux.c 0e92ed38fe905131f1a95011d67cea67cd973ff2
+F src/vdbeaux.c e35c851e3c1d18a7b90dbe35ae5e0fc9419a4ed4
 F src/vdbeblob.c 82f51cdf9b0c0af729732fde48c824e498c0a1ca
 F src/vdbefifo.c 334c838c8f42d61a94813d136019ee566b5dc2f6
 F src/vdbemem.c 246d434fa60bde6553490eb686adfd86adcd6712
@@ -568,7 +568,7 @@ F www/tclsqlite.tcl 8be95ee6dba05eabcd27a9d91331c803f2ce2130
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl 890248cf7b70e60c383b0e84d77d5132b3ead42b
 F www/whentouse.tcl fc46eae081251c3c181bd79c5faef8195d7991a5
-P 5a22d8695b49cf7bc2eee382b66a98d29adb9e6e
-R e8bf3e9d6844747dd965b50d2cb26b45
+P 18a5babb72102f9a82cb24757612a8b683a3f995
+R 8fce7bfd868038e0cdf6352f204f8e03
 U drh
-Z 936d6ea52e3c08696df033234951ad71
+Z a486c2c7c2c9dc221c09c07a8a467098
diff --git a/manifest.uuid b/manifest.uuid
index c635013750..4af2d4186d 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-18a5babb72102f9a82cb24757612a8b683a3f995
\ No newline at end of file
+71ab92e900512ad01047b46f734bd5f65998ecf9
\ No newline at end of file
diff --git a/src/vdbeaux.c b/src/vdbeaux.c
index 4af63d2fc6..ac347c50a5 100644
--- a/src/vdbeaux.c
+++ b/src/vdbeaux.c
@@ -1852,11 +1852,24 @@ int sqlite3VdbeSerialTypeLen(u32 serial_type){
 ** application using -DSQLITE_DEBUG=1 at least once.  With DEBUG
 ** enabled, some asserts below will ensure that the byte order of
 ** floating point values is correct.
+**
+** (2007-08-30)  Frank van Vugt has studied this problem closely
+** and has send his findings to the SQLite developers.  Frank
+** writes that some Linux kernels offer floating point hardware
+** emulation that uses only 32-bit mantissas instead of a full 
+** 48-bits as required by the IEEE standard.  (This is the
+** CONFIG_FPE_FASTFPE option.)  On such systems, floating point
+** byte swapping becomes very complicated.  To avoid problems,
+** the necessary byte swapping is carried out using a 64-bit integer
+** rather than a 64-bit float.  Frank assures us that the code here
+** works for him.  We, the developers, have no way to independently
+** verify this, but Frank seems to know what he is talking about
+** so we trust him.
 */
 #ifdef SQLITE_MIXED_ENDIAN_64BIT_FLOAT
-static double floatSwap(double in){
+static u64 floatSwap(u64 in){
   union {
-    double r;
+    u64 r;
     u32 i[2];
   } u;
   u32 t;
@@ -1900,8 +1913,8 @@ int sqlite3VdbeSerialPut(u8 *buf, int nBuf, Mem *pMem, int file_format){
     int i;
     if( serial_type==7 ){
       assert( sizeof(v)==sizeof(pMem->r) );
-      swapMixedEndianFloat(pMem->r);
       memcpy(&v, &pMem->r, sizeof(v));
+      swapMixedEndianFloat(v);
     }else{
       v = pMem->u.i;
     }
@@ -1991,9 +2004,9 @@ int sqlite3VdbeSerialGet(
       */
       static const u64 t1 = ((u64)0x3ff00000)<<32;
       static const double r1 = 1.0;
-      double r2 = r1;
-      swapMixedEndianFloat(r2);
-      assert( sizeof(r2)==sizeof(t1) && memcmp(&r2, &t1, sizeof(r1))==0 );
+      u64 t2 = t1;
+      swapMixedEndianFloat(t2);
+      assert( sizeof(r1)==sizeof(t2) && memcmp(&r1, &t2, sizeof(r1))==0 );
 #endif
 
       x = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
@@ -2004,8 +2017,8 @@ int sqlite3VdbeSerialGet(
         pMem->flags = MEM_Int;
       }else{
         assert( sizeof(x)==8 && sizeof(pMem->r)==8 );
+        swapMixedEndianFloat(x);
         memcpy(&pMem->r, &x, sizeof(x));
-        swapMixedEndianFloat(pMem->r);
         pMem->flags = MEM_Real;
       }
       return 8;
-- 
2.47.3