diff --git a/manifest b/manifest
index 5071bf0aad..28598eff2e 100644
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Fix\ssome\smemory\sleaks\scaused\sby\sobscure\ssyntax\serrors\sin\sSQL.\s(CVS\s2882)
-D 2006-01-07T14:02:27
+C Enable\sredefinable\sI/O\sif\sthe\sSQLITE_ENABLE_REDEF_IO\smacro\sexists.\s(CVS\s2883)
+D 2006-01-07T16:06:07
 F Makefile.in c79fbdaa264c6afcd435f2fb492551de5a8cf80d
 F Makefile.linux-gcc aee18d8a05546dcf1888bd4547e442008a49a092
 F README 9c4e2d6706bdcc3efdd773ce752a8cdab4f90028
@@ -50,8 +50,8 @@ F src/insert.c 66f2e745bd3db551bed9756c7d7df191f7b72ba9
 F src/legacy.c 59757d857ab95fcbb0ac27692d3201e35f093dd7
 F src/main.c 8c2d64f1460200d79d7de4605a9489c0506be5fe
 F src/md5.c c5fdfa5c2593eaee2e32a5ce6c6927c986eaf217
-F src/os.c bdd3a2fd089777e7ad18b57c896f1141d5a0c1fd
-F src/os.h 6e61d5e901dfec761660707e892890f6760b5e63
+F src/os.c 1d1a61cdf150e9f9520a3bc787c8465148ea2e78
+F src/os.h 8710c0068f3386a73a37f8ad242b92c7580464df
 F src/os_common.h 78bcc34dded9b625b3c16d072b7e5b76d075a674
 F src/os_test.c 49833426101f99aee4bb5f6a44b7c4b2029fda1c
 F src/os_test.h 903c93554c23d88f34f667f1979e4a1cee792af3
@@ -72,7 +72,7 @@ F src/sqlite.h.in ba3a29daa6a16e054191ccb384a981964e882a1d
 F src/sqliteInt.h 40c3511c05df83c7c1c244d0432baa9497feee4d
 F src/table.c 486dcfce532685b53b5a2b5da8bba0ded6fb2316
 F src/tclsqlite.c 42151e6c78502277be77b88c00535d53ce89b917
-F src/test1.c 1171547fad57a104c716116695fb8c5c7ef43345
+F src/test1.c 53c6c0f86e280e739a9adfb56ba7d8b6e26cc16f
 F src/test2.c ca74a1d8aeb7d9606e8f6b762c5daf85c1a3f92b
 F src/test3.c 9742aa146eb750cab81c1d5605286c3a0eb88054
 F src/test4.c a8fd681e139e1c61f22a77d07fc3a99cb28fff3f
@@ -335,7 +335,7 @@ F www/tclsqlite.tcl bb0d1357328a42b1993d78573e587c6dcbc964b9
 F www/vdbe.tcl 87a31ace769f20d3627a64fa1fade7fed47b90d0
 F www/version3.tcl a99cf5f6d8bd4d5537584a2b342f0fb9fa601d8b
 F www/whentouse.tcl 97e2b5cd296f7d8057e11f44427dea8a4c2db513
-P 23b587b05b89727248805e6d9e5141e018cf2152
-R b9ef38eb9219972e18666035e7ca732b
-U danielk1977
-Z 5df6fea511267cf56eade3a5959a2ec5
+P 6593199a4d0d0e1f9cc2f48d30327b1c03a8170e
+R dca0e78f8894e9c4b7522be7f86ed95c
+U drh
+Z faf501161ea4c7faed845a75b2858bde
diff --git a/manifest.uuid b/manifest.uuid
index 25cb219226..77e0e8533f 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6593199a4d0d0e1f9cc2f48d30327b1c03a8170e
\ No newline at end of file
+e170e15766389e978991b42a0d2ec303162aaad6
\ No newline at end of file
diff --git a/src/os.c b/src/os.c
index 97036746a3..8c7aadbd91 100644
--- a/src/os.c
+++ b/src/os.c
@@ -13,6 +13,7 @@
 ** This file contains OS interface code that is common to all
 ** architectures.
 */
+#define _SQLITE_OS_C_ 1
 #include "sqliteInt.h"
 #include "os.h"
 
@@ -69,3 +70,18 @@ int sqlite3OsLockState(OsFile *id){
 int sqlite3OsCheckReservedLock(OsFile *id){
   return id->pMethod->xCheckReservedLock(id);
 }
+
+#ifdef SQLITE_ENABLE_REDEF_IO
+/*
+** A function to return a pointer to the virtual function table.
+** This routine really does not accomplish very much since the
+** virtual function table is a global variable and anybody who
+** can call this function can just as easily access the variable
+** for themselves.  Nevertheless, we include this routine for
+** backwards compatibility with an earlier redefinable I/O
+** interface design.
+*/
+struct sqlite3OsVtbl *sqlite3_os_switch(void){
+  return &sqlite3Os;
+}
+#endif
diff --git a/src/os.h b/src/os.h
index a132bc5e04..3123cba1b5 100644
--- a/src/os.h
+++ b/src/os.h
@@ -298,4 +298,143 @@ void *sqlite3OsRealloc(void *, int);
 void sqlite3OsFree(void *);
 int sqlite3OsAllocationSize(void *);
 
+/*
+** If the SQLITE_ENABLE_REDEF_IO macro is defined, then the OS-layer
+** interface routines are not called directly but are invoked using
+** pointers to functions.  This allows the implementation of various
+** OS-layer interface routines to be modified at run-time.  There are
+** obscure but legitimate reasons for wanting to do this.  But for
+** most users, a direct call to the underlying interface is preferable
+** so the the redefinable I/O interface is turned off by default.
+*/
+#ifdef SQLITE_ENABLE_REDEF_IO
+
+/*
+** When redefinable I/O is enabled, a single global instance of the
+** following structure holds pointers to the routines that SQLite 
+** uses to talk with the underlying operating system.  Modify this
+** structure (before using any SQLite API!) to accomodate perculiar
+** operating system interfaces or behaviors.
+*/
+struct sqlite3OsVtbl {
+  int (*xOpenReadWrite)(const char*, OsFile**, int*);
+  int (*xOpenExclusive)(const char*, OsFile**, int);
+  int (*xOpenReadOnly)(const char*, OsFile**);
+
+  int (*xDelete)(const char*);
+  int (*xFileExists)(const char*);
+  char *(*xFullPathname)(const char*);
+  int (*xIsDirWritable)(char*);
+  int (*xSyncDirectory)(const char*);
+  int (*xTempFileName)(char*);
+
+  int (*xRandomSeed)(char*);
+  int (*xSleep)(int ms);
+  int (*xCurrentTime)(double*);
+
+  void (*xEnterMutex)(void);
+  void (*xLeaveMutex)(void);
+  int (*xInMutex)(void);
+  void *(*xThreadSpecificData)(int);
+
+  void *(*xMalloc)(int);
+  void *(*xRealloc)(void *, int);
+  void (*xFree)(void *);
+  int (*xAllocationSize)(void *);
+};
+
+/* Macro used to comment out routines that do not exists when there is
+** no disk I/O 
+*/
+#ifdef SQLITE_OMIT_DISKIO
+# define IF_DISKIO(X)  0
+#else
+# define IF_DISKIO(X)  X
+#endif
+
+#ifdef _SQLITE_OS_C_
+  /*
+  ** The os.c file implements the global virtual function table.
+  */
+  struct sqlite3OsVtbl sqlite3Os = {
+    IF_DISKIO( sqlite3OsOpenReadWrite ),
+    IF_DISKIO( sqlite3OsOpenExclusive ),
+    IF_DISKIO( sqlite3OsOpenReadOnly ),
+    IF_DISKIO( sqlite3OsDelete ),
+    IF_DISKIO( sqlite3OsFileExists ),
+    IF_DISKIO( sqlite3OsFullPathname ),
+    IF_DISKIO( sqlite3OsIsDirWritable ),
+    IF_DISKIO( sqlite3OsSyncDirectory ),
+    IF_DISKIO( sqlite3OsTempFileName ),
+    sqlite3OsRandomSeed,
+    sqlite3OsSleep,
+    sqlite3OsCurrentTime,
+    sqlite3OsEnterMutex,
+    sqlite3OsLeaveMutex,
+    sqlite3OsInMutex,
+    sqlite3OsThreadSpecificData,
+    sqlite3OsMalloc,
+    sqlite3OsRealloc,
+    sqlite3OsFree,
+    sqlite3OsAllocationSize
+  };
+#else
+  /*
+  ** Files other than os.c just reference the global virtual function table. 
+  */
+  extern struct sqlite3OsVtbl sqlite3Os;
+#endif /* _SQLITE_OS_C_ */
+
+
+/* This additional API routine is available with redefinable I/O */
+struct sqlite3OsVtbl *sqlite3_os_switch(void);
+
+
+/*
+** Redefine the OS interface to go through the virtual function table
+** rather than calling routines directly.
+*/
+#undef sqlite3OsOpenReadWrite
+#undef sqlite3OsOpenExclusive
+#undef sqlite3OsOpenReadOnly
+#undef sqlite3OsDelete
+#undef sqlite3OsFileExists
+#undef sqlite3OsFullPathname
+#undef sqlite3OsIsDirWritable
+#undef sqlite3OsSyncDirectory
+#undef sqlite3OsTempFileName
+#undef sqlite3OsRandomSeed
+#undef sqlite3OsSleep
+#undef sqlite3OsCurrentTime
+#undef sqlite3OsEnterMutex
+#undef sqlite3OsLeaveMutex
+#undef sqlite3OsInMutex
+#undef sqlite3OsThreadSpecificData
+#undef sqlite3OsMalloc
+#undef sqlite3OsRealloc
+#undef sqlite3OsFree
+#undef sqlite3OsAllocationSize
+#define sqlite3OsOpenReadWrite      sqlite3Os.xOpenReadWrite
+#define sqlite3OsOpenExclusive      sqlite3Os.xOpenExclusive
+#define sqlite3OsOpenReadOnly       sqlite3Os.xOpenReadOnly
+#define sqlite3OsDelete             sqlite3Os.xDelete
+#define sqlite3OsFileExists         sqlite3Os.xFileExists
+#define sqlite3OsFullPathname       sqlite3Os.xFullPathname
+#define sqlite3OsIsDirWritable      sqlite3Os.xIsDirWritable
+#define sqlite3OsSyncDirectory      sqlite3Os.xSyncDirectory
+#define sqlite3OsTempFileName       sqlite3Os.xTempFileName
+#define sqlite3OsRandomSeed         sqlite3Os.xRandomSeed
+#define sqlite3OsSleep              sqlite3Os.xSleep
+#define sqlite3OsCurrentTime        sqlite3Os.xCurrentTime
+#define sqlite3OsEnterMutex         sqlite3Os.xEnterMutex
+#define sqlite3OsLeaveMutex         sqlite3Os.xLeaveMutex
+#define sqlite3OsInMutex            sqlite3Os.xInMutex
+#define sqlite3OsThreadSpecificData sqlite3Os.xThreadSpecificData
+#define sqlite3OsMalloc             sqlite3Os.xMalloc
+#define sqlite3OsRealloc            sqlite3Os.xRealloc
+#define sqlite3OsFree               sqlite3Os.xFree
+#define sqlite3OsAllocationSize     sqlite3Os.xAllocationSize
+
+#endif /* SQLITE_ENABLE_REDEF_IO */
+
 #endif /* _SQLITE_OS_H_ */
diff --git a/src/test1.c b/src/test1.c
index f981708f83..c86d3e6225 100644
--- a/src/test1.c
+++ b/src/test1.c
@@ -13,7 +13,7 @@
 ** is not included in the SQLite library.  It is used for automated
 ** testing of the SQLite library.
 **
-** $Id: test1.c,v 1.182 2006/01/06 21:52:50 drh Exp $
+** $Id: test1.c,v 1.183 2006/01/07 16:06:07 drh Exp $
 */
 #include "sqliteInt.h"
 #include "tcl.h"
@@ -3203,6 +3203,12 @@ static void set_options(Tcl_Interp *interp){
   Tcl_SetVar2(interp, "sqlite_options", "progress", "1", TCL_GLOBAL_ONLY);
 #endif
 
+#ifdef SQLITE_ENABLE_REDEF_IO
+  Tcl_SetVar2(interp, "sqlite_options", "redefio", "1", TCL_GLOBAL_ONLY);
+#else
+  Tcl_SetVar2(interp, "sqlite_options", "redefio", "0", TCL_GLOBAL_ONLY);
+#endif
+
 #ifdef SQLITE_OMIT_REINDEX
   Tcl_SetVar2(interp, "sqlite_options", "reindex", "0", TCL_GLOBAL_ONLY);
 #else