Add experimental unix-only file-control to grow and truncate the database file by a configurable chunk size.

FossilOrigin-Name: 7cf0e851d4c5e826ea22ed08291b7c91d7b1abc7

src/os_unix.c

@@ -210,6 +210,7 @@ struct unixFile {
   int fileFlags;                      /* Miscellanous flags */
   const char *zPath;                  /* Name of the file */
   unixShm *pShm;                      /* Shared memory segment information */
+  int szChunk;                        /* Configured by FCNTL_CHUNK_SIZE */
 #if SQLITE_ENABLE_LOCKING_STYLE
   int openFlags;                      /* The flags specified at open() */
 #endif
@@ -2763,6 +2764,43 @@ static int unixWrite(
   }
   SimulateIOError(( wrote=(-1), amt=1 ));
   SimulateDiskfullError(( wrote=0, amt=1 ));
+
+  /* If the user has configured a chunk-size for this file, it could be
+  ** that the file needs to be extended at this point. 
+  */
+  if( pFile->szChunk && amt==0 ){
+    i64 nSize;                    /* Required file size */
+    struct stat buf;              /* Used to hold return values of fstat() */
+    int rc = fstat(pFile->h, &buf);
+    if( rc!=0 ) return SQLITE_IOERR_FSTAT;
+    nSize = ((offset+amt+pFile->szChunk-1) / pFile->szChunk) * pFile->szChunk;
+    if( nSize>(i64)buf.st_size ){
+#ifdef HAVE_POSIX_FALLOCATE
+      if( posix_fallocate(pFile->h, buf.st_size, nSize-buf.st_size) ){
+        return SQLITE_IOERR_WRITE;
+      }
+#else
+      /* If the OS does not have posix_fallocate(), fake it. First use
+      ** ftruncate() to set the file size, then write a single byte to
+      ** the last byte in each block within the extended region.
+      */
+      int nBlk = buf.st_blksize;  /* File-system block size */
+      i64 iWrite;                 /* Next offset to write to */
+
+      if( ftruncate(pFile->h, nSize) ){
+	pFile->lastErrno = errno;
+	return SQLITE_IOERR_TRUNCATE;
+      }
+      iWrite = ((buf.st_size + 2*nBlk - 1)/nBlk)*nBlk-1;
+      do {
+	wrote = seekAndWrite(pFile, iWrite, "", 1);
+	iWrite += nBlk;
+      } while( wrote==1 && iWrite<nSize );
+      if( wrote!=1 ) amt = 1;
+#endif
+    }
+  }
+
   if( amt>0 ){
     if( wrote<0 ){
       /* lastErrno set by seekAndWrite */
@@ -2772,6 +2810,7 @@ static int unixWrite(
       return SQLITE_FULL;
     }
   }
+
   return SQLITE_OK;
 }
 
@@ -2973,12 +3012,23 @@ static int unixSync(sqlite3_file *id, int flags){
 ** Truncate an open file to a specified size
 */
 static int unixTruncate(sqlite3_file *id, i64 nByte){
+  unixFile *pFile = (unixFile *)id;
   int rc;
-  assert( id );
+  assert( pFile );
   SimulateIOError( return SQLITE_IOERR_TRUNCATE );
-  rc = ftruncate(((unixFile*)id)->h, (off_t)nByte);
+
+  /* If the user has configured a chunk-size for this file, truncate the
+  ** file so that it consists of an integer number of chunks (i.e. the
+  ** actual file size after the operation may be larger than the requested
+  ** size).
+  */
+  if( pFile->szChunk ){
+    nByte = ((nByte + pFile->szChunk - 1)/pFile->szChunk) * pFile->szChunk;
+  }
+
+  rc = ftruncate(pFile->h, (off_t)nByte);
   if( rc ){
-    ((unixFile*)id)->lastErrno = errno;
+    pFile->lastErrno = errno;
     return SQLITE_IOERR_TRUNCATE;
   }else{
 #ifndef NDEBUG
@@ -2989,8 +3039,8 @@ static int unixTruncate(sqlite3_file *id, i64 nByte){
     ** when restoring a database using the backup API from a zero-length
     ** source.
     */
-    if( ((unixFile*)id)->inNormalWrite && nByte==0 ){
-      ((unixFile*)id)->transCntrChng = 1;
+    if( pFile->inNormalWrite && nByte==0 ){
+      pFile->transCntrChng = 1;
     }
 #endif
 
@@ -3047,6 +3097,10 @@ static int unixFileControl(sqlite3_file *id, int op, void *pArg){
       *(int*)pArg = ((unixFile*)id)->lastErrno;
       return SQLITE_OK;
     }
+    case SQLITE_FCNTL_CHUNK_SIZE: {
+      ((unixFile*)id)->szChunk = *(int *)pArg;
+      return SQLITE_OK;				    
+    }
     case SQLITE_FCNTL_SIZE_HINT: {
 #if 0 /* No performance advantage seen on Linux */
       sqlite3_int64 szFile = *(sqlite3_int64*)pArg;

src/sqlite.h.in

@@ -696,6 +696,7 @@ struct sqlite3_io_methods {
 #define SQLITE_SET_LOCKPROXYFILE      3
 #define SQLITE_LAST_ERRNO             4
 #define SQLITE_FCNTL_SIZE_HINT        5
+#define SQLITE_FCNTL_CHUNK_SIZE       6
 
 /*
 ** CAPI3REF: Mutex Handle

src/test1.c

@@ -4613,6 +4613,44 @@ static int file_control_lasterrno_test(
   return TCL_OK;  
 }
 
+/*
+** tclcmd:   file_control_chunksize_test DB DBNAME SIZE
+**
+** This TCL command runs the sqlite3_file_control interface and
+** verifies correct operation of the SQLITE_GET_LOCKPROXYFILE and
+** SQLITE_SET_LOCKPROXYFILE verbs.
+*/
+static int file_control_chunksize_test(
+  ClientData clientData, /* Pointer to sqlite3_enable_XXX function */
+  Tcl_Interp *interp,    /* The TCL interpreter that invoked this command */
+  int objc,              /* Number of arguments */
+  Tcl_Obj *CONST objv[]  /* Command arguments */
+){
+  int nSize;                      /* New chunk size */
+  char *zDb;                      /* Db name ("main", "temp" etc.) */
+  sqlite3 *db;                    /* Database handle */
+  int rc;                         /* file_control() return code */
+
+  if( objc!=4 ){
+    Tcl_WrongNumArgs(interp, 1, objv, "DB DBNAME SIZE");
+    return TCL_ERROR;
+  }
+  if( getDbPointer(interp, Tcl_GetString(objv[1]), &db) 
+   || Tcl_GetIntFromObj(interp, objv[3], &nSize)
+  ){
+   return TCL_ERROR;
+  }
+  zDb = Tcl_GetString(objv[2]);
+  if( zDb[0]=='\0' ) zDb = NULL;
+
+  rc = sqlite3_file_control(db, zDb, SQLITE_FCNTL_CHUNK_SIZE, (void *)&nSize);
+  if( rc ){
+    Tcl_SetResult(interp, (char *)sqlite3TestErrorName(rc), TCL_STATIC);
+    return TCL_ERROR;
+  }
+  return TCL_OK;
+}
+
 /*
 ** tclcmd:   file_control_lockproxy_test DB PWD
 **
@@ -5106,6 +5144,7 @@ int Sqlitetest1_Init(Tcl_Interp *interp){
      { "file_control_test",          file_control_test,   0   },
      { "file_control_lasterrno_test", file_control_lasterrno_test,  0   },
      { "file_control_lockproxy_test", file_control_lockproxy_test,  0   },
+     { "file_control_chunksize_test", file_control_chunksize_test,  0   },
      { "sqlite3_vfs_list",           vfs_list,     0   },
 
      /* Functions from os.h */