If the read() system call in unix returns fewer bytes than expected, retry

it until it either returns zero or an error.

FossilOrigin-Name: 72256634773f6cba0aabaa3c953cd5daefd50e67

manifest

@@ -1,5 +1,5 @@
-C Version\s3.7.9
-D 2011-11-01T00:52:41.132
+C If\sthe\sread()\ssystem\scall\sin\sunix\sreturns\sfewer\sbytes\sthan\sexpected,\sretry\nit\suntil\sit\seither\sreturns\szero\sor\san\serror.
+D 2011-11-01T15:45:28.858
 F Makefile.arm-wince-mingw32ce-gcc d6df77f1f48d690bd73162294bbba7f59507c72f
 F Makefile.in a162fe39e249b8ed4a65ee947c30152786cfe897
 F Makefile.linux-gcc 91d710bdc4998cb015f39edf3cb314ec4f4d7e23
@@ -166,7 +166,7 @@ F src/os.c 5d9b02782ed36345348d6fe21d7762ed3a9cfd2a
 F src/os.h 9dbed8c2b9c1f2f2ebabc09e49829d4777c26bf9
 F src/os_common.h 92815ed65f805560b66166e3583470ff94478f04
 F src/os_os2.c 4a75888ba3dfc820ad5e8177025972d74d7f2440
-F src/os_unix.c ddda0b1c5ae536669634d7bff31b3f8f4d654866
+F src/os_unix.c 82e71071198c2474d89f421076e524e2c4f3fda4
 F src/os_win.c 49d418916428a59d773f39993db0ecde56ab4c37
 F src/pager.c ad62daa0c21e27ae332b3ceb4f579a2a97046ddc
 F src/pager.h 9f81b08efb06db4ba8be69446e10b005c351373d
@@ -974,8 +974,10 @@ F tool/tostr.awk e75472c2f98dd76e06b8c9c1367f4ab07e122d06
 F tool/vdbe-compress.tcl d70ea6d8a19e3571d7ab8c9b75cba86d1173ff0f
 F tool/warnings-clang.sh 9f406d66e750e8ac031c63a9ef3248aaa347ef2a
 F tool/warnings.sh fbc018d67fd7395f440c28f33ef0f94420226381
-P 6635cd9a7714b681dd8aa96e90be462a40d10178
-R b059ff356abfc5b4524a9b548916f43e
-T +sym-version-3.7.9 *
+P c7c6050ef060877ebe77b41d959e9df13f8c9b5e
+R 168a5dade3c3abfe1d87f94e8b5ca421
+T *branch * retry-short-reads
+T *sym-retry-short-reads *
+T -sym-trunk *
 U drh
-Z a9ecbb5c487c786a176874d979505217
+Z 20b068a5313402ed91403f5e74abce9f

manifest.uuid

@@ -1 +1 @@
-c7c6050ef060877ebe77b41d959e9df13f8c9b5e
+72256634773f6cba0aabaa3c953cd5daefd50e67

src/os_unix.c

@@ -2944,35 +2944,44 @@ static int nfsUnlock(sqlite3_file *id, int eFileLock){
 */
 static int seekAndRead(unixFile *id, sqlite3_int64 offset, void *pBuf, int cnt){
   int got;
+  int total = 0;
 #if (!defined(USE_PREAD) && !defined(USE_PREAD64))
   i64 newOffset;
 #endif
   TIMER_START;
+  while( cnt>0 ){
 #if defined(USE_PREAD)
-  do{ got = osPread(id->h, pBuf, cnt, offset); }while( got<0 && errno==EINTR );
-  SimulateIOError( got = -1 );
+    do{ got = osPread(id->h, pBuf, cnt, offset); }while(got<0 && errno==EINTR);
+    SimulateIOError( got = -1 );
 #elif defined(USE_PREAD64)
-  do{ got = osPread64(id->h, pBuf, cnt, offset); }while( got<0 && errno==EINTR);
-  SimulateIOError( got = -1 );
+    do{ got = osPread64(id->h, pBuf,cnt,offset); }while(got<0 && errno==EINTR);
+    SimulateIOError( got = -1 );
 #else
-  newOffset = lseek(id->h, offset, SEEK_SET);
-  SimulateIOError( newOffset-- );
-  if( newOffset!=offset ){
-    if( newOffset == -1 ){
-      ((unixFile*)id)->lastErrno = errno;
-    }else{
-      ((unixFile*)id)->lastErrno = 0;			
+    newOffset = lseek(id->h, offset, SEEK_SET);
+    SimulateIOError( newOffset-- );
+    if( newOffset!=offset ){
+      if( newOffset == -1 ){
+        ((unixFile*)id)->lastErrno = errno;
+      }else{
+        ((unixFile*)id)->lastErrno = 0;			
+      }
+      return -1;
     }
-    return -1;
-  }
-  do{ got = osRead(id->h, pBuf, cnt); }while( got<0 && errno==EINTR );
+    do{ got = osRead(id->h, pBuf, cnt); }while( got<0 && errno==EINTR );
 #endif
+    if( got<=0 ) break;
+    total += got;
+    cnt -= got;
+    offset += got;
+    pBuf = (void*)(got + (char*)pBuf);
+  }
   TIMER_END;
   if( got<0 ){
     ((unixFile*)id)->lastErrno = errno;
+    total = got;
   }
-  OSTRACE(("READ    %-3d %5d %7lld %llu\n", id->h, got, offset, TIMER_ELAPSED));
-  return got;
+  OSTRACE(("READ    %-3d %5d %7lld %llu\n", id->h,total,offset,TIMER_ELAPSED));
+  return total;
 }
 
 /*