Fix the build for cases when pread()/pwrite() are not available.

FossilOrigin-Name: 7d67d876b70c7a4199697c5b112d809c600e140e

manifest

@@ -1,5 +1,5 @@
-C Update\sthe\sconfigure\sscript\sto\sdetect\spread/pwrite\sand\supdate\sos_unix.c\sto\nuse\sthose\sroutines\sif\sthey\sare\savailable.
-D 2016-03-04T02:38:00.565
+C Fix\sthe\sbuild\sfor\scases\swhen\spread()/pwrite()\sare\snot\savailable.
+D 2016-03-04T03:02:06.930
 F Makefile.in e335453db0b16da00c884ad51bb56d1c091a74de
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc dbd4621ecc585c2ef0c2aa0874698c54675754f1
@@ -333,7 +333,7 @@ F src/os.c ca9a104b677328ee037cfdf1a54a16fd1805e8c9
 F src/os.h 3e57a24e2794a94d3cf2342c6d9a884888cd96bf
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
-F src/os_unix.c a1aaf2d8d253138e63d2a8a972693f9f624f885d
+F src/os_unix.c 14a28aeb3b77102a90ed645534a8d319b8ac6082
 F src/os_win.c f0d7aa603eb6262143d7169a222aea07c4fca91d
 F src/os_win.h eb7a47aa17b26b77eb97e4823f20a00b8bda12ca
 F src/pager.c d034c69b958c01289eb8070cbf902e1a68cd7e0b
@@ -1453,7 +1453,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 16fbf2e19c22df9441aef5c8b7f5670adc38a6b6
-R 8390ec5e0d9e5eb3999e5eee0cb5ce81
+P 2cffb9e50bed77d1079603f5b4a71b7559de7294
+R 340d2ced6d6364f0299bbd36b34b2f41
 U drh
-Z b764ac5f33b779f6bf5d09a763220c12
+Z a704f390d3e95dbf657db754d417ef5a

manifest.uuid

@@ -1 +1 @@
-2cffb9e50bed77d1079603f5b4a71b7559de7294
+7d67d876b70c7a4199697c5b112d809c600e140e

src/os_unix.c

@@ -84,7 +84,6 @@
 # define USE_PWRITE64 1
 #endif
 
-
 /*
 ** standard include files.
 */
@@ -214,9 +213,6 @@ struct unixFile {
   const char *zPath;                  /* Name of the file */
   unixShm *pShm;                      /* Shared memory segment information */
   int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
-#if !defined(USE_PREAD) && !defined(USE_PREAD64)
-  off64_t iOfst;                      /* Current offset */
-#endif
 #if SQLITE_MAX_MMAP_SIZE>0
   int nFetchOut;                      /* Number of outstanding xFetch refs */
   sqlite3_int64 mmapSize;             /* Usable size of mapping at pMapRegion */
@@ -3114,6 +3110,9 @@ static int nfsUnlock(sqlite3_file *id, int eFileLock){
 static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
   int got;
   int prior = 0;
+#if (!defined(USE_PREAD) && !defined(USE_PREAD64))
+  i64 newOffset;
+#endif
   TIMER_START;
   assert( cnt==(cnt&0x1ffff) );
   assert( id->h>2 );
@@ -3125,15 +3124,13 @@ static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
     got = osPread64(id->h, pBuf, cnt, offset);
     SimulateIOError( got = -1 );
 #else
-    if( offset!=id->iOfst ){
-      id->iOfst = lseek(id->h, offset, SEEK_SET);
-      SimulateIOError( id->iOfst = -1 );
-      if( id->iOfst<0 ){
-        storeLastErrno((unixFile*)id, errno);
-        return -1;
-      }
-      got = osRead(id->h, pBuf, cnt);
-      if( got>=0 ) id->iOfst += got;
+    newOffset = lseek(id->h, offset, SEEK_SET);
+    SimulateIOError( newOffset = -1 );
+    if( newOffset<0 ){
+      storeLastErrno((unixFile*)id, errno);
+      return -1;
+    }
+    got = osRead(id->h, pBuf, cnt);
 #endif
     if( got==cnt ) break;
     if( got<0 ){
@@ -3239,7 +3236,6 @@ static int seekAndWriteFd(
   do{ rc = (int)osPwrite64(fd, pBuf, nBuf, iOff);}while( rc<0 && errno==EINTR);
 #else
   do{
-    if( iOff!=fd
     i64 iSeek = lseek(fd, iOff, SEEK_SET);
     SimulateIOError( iSeek = -1 );
     if( iSeek<0 ){