Simplification to the read and write primatives in the unix VFS.

FossilOrigin-Name: 9eefa449792f03c4c149edcbc6b9b7692617994c

manifest

@@ -1,5 +1,5 @@
-C Add\sthe\sSQLITE_PRINTF_PRECISION_LIMIT\scompile-time\soption.
-D 2015-11-30T22:52:14.011
+C Simplification\sto\sthe\sread\sand\swrite\sprimatives\sin\sthe\sunix\sVFS.
+D 2015-12-01T16:21:35.045
 F Makefile.in d828db6afa6c1fa060d01e33e4674408df1942a1
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc e928e68168df69b353300ac87c10105206653a03
@@ -323,7 +323,7 @@ F src/os.c 8fd25588eeba74068d41102d26810e216999b6c8
 F src/os.h 3e57a24e2794a94d3cf2342c6d9a884888cd96bf
 F src/os_common.h abdb9a191a367793268fe553d25bab894e986a0e
 F src/os_setup.h c9d4553b5aaa6f73391448b265b89bed0b890faa
-F src/os_unix.c 88d9fd1da4f3d26c64ef954fb32cce583605eba0
+F src/os_unix.c 7d56433ac85e77423d2d613fd5e53db08c5868ed
 F src/os_win.c 386fba30419e8458b13209781c2af5590eab2811
 F src/os_win.h eb7a47aa17b26b77eb97e4823f20a00b8bda12ca
 F src/pager.c f92aacd5216d8815136c9e0190041783c602641a
@@ -1406,7 +1406,7 @@ F tool/vdbe_profile.tcl 246d0da094856d72d2c12efec03250d71639d19f
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P bb1e2c4df0b81327923f121dd6c002845486a314
-R d3b18adc3009f6c25adcd36c4f052eab
+P ecad75d69e0d5c83dd3584d363e557e84b65f7f2
+R bca4975588f4da52a9a8fe0cd42dc56d
 U drh
-Z 7ba0fba490eff520c14229730eb61dd8
+Z 462bb50cf4ea1a0b7483c62da14af105

manifest.uuid

@@ -1 +1 @@
-ecad75d69e0d5c83dd3584d363e557e84b65f7f2
+9eefa449792f03c4c149edcbc6b9b7692617994c

src/os_unix.c

@@ -3086,13 +3086,9 @@ static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
     SimulateIOError( got = -1 );
 #else
     newOffset = lseek(id->h, offset, SEEK_SET);
-    SimulateIOError( newOffset-- );
-    if( newOffset!=offset ){
-      if( newOffset == -1 ){
-        storeLastErrno((unixFile*)id, errno);
-      }else{
-        storeLastErrno((unixFile*)id, 0);
-      }
+    SimulateIOError( newOffset = -1 );
+    if( newOffset<0 ){
+      storeLastErrno((unixFile*)id, errno);
       return -1;
     }
     got = osRead(id->h, pBuf, cnt);
@@ -3191,6 +3187,7 @@ static int seekAndWriteFd(
 
   assert( nBuf==(nBuf&0x1ffff) );
   assert( fd>2 );
+  assert( piErrno!=0 );
   nBuf &= 0x1ffff;
   TIMER_START;
 
@@ -3201,11 +3198,10 @@ static int seekAndWriteFd(
 #else
   do{
     i64 iSeek = lseek(fd, iOff, SEEK_SET);
-    SimulateIOError( iSeek-- );
-
-    if( iSeek!=iOff ){
-      if( piErrno ) *piErrno = (iSeek==-1 ? errno : 0);
-      return -1;
+    SimulateIOError( iSeek = -1 );
+    if( iSeek<0 ){
+      rc = -1;
+      break;
     }
     rc = osWrite(fd, pBuf, nBuf);
   }while( rc<0 && errno==EINTR );
@@ -3214,7 +3210,7 @@ static int seekAndWriteFd(
   TIMER_END;
   OSTRACE(("WRITE   %-3d %5d %7lld %llu\n", fd, rc, iOff, TIMER_ELAPSED));
 
-  if( rc<0 && piErrno ) *piErrno = errno;
+  if( rc<0 ) *piErrno = errno;
   return rc;
 }
 
@@ -4410,7 +4406,8 @@ static int unixShmMap(
           /* Write to the last byte of each newly allocated or extended page */
           assert( (nByte % pgsz)==0 );
           for(iPg=(sStat.st_size/pgsz); iPg<(nByte/pgsz); iPg++){
-            if( seekAndWriteFd(pShmNode->h, iPg*pgsz + pgsz-1, "", 1, 0)!=1 ){
+            int x = 0;
+            if( seekAndWriteFd(pShmNode->h, iPg*pgsz + pgsz-1, "", 1, &x)!=1 ){
               const char *zFile = pShmNode->zFilename;
               rc = unixLogError(SQLITE_IOERR_SHMSIZE, "write", zFile);
               goto shmpage_out;