Ios const void类型的操作数，其中需要arihmetic或指针类型

为什么会出现错误： 如果类型为const void，则操作数，其中算术或指针类型需要到以下行：

//在文件中的特定位置插入数据

 NSData *chunk = chunkContainer; // some data
        NSUInteger insertPoint = chunkNo*512; // get the insertion point //
        // make sure the file exists, if it does, do the following //
        NSData *oldData = [NSData dataWithContentsOfFile:filePath];
        // error checking would be nice... if (oldData) ... blah //
        NSOutputStream *stream = [[NSOutputStream alloc] initToFileAtPath:filePath append:NO];
        [stream open];
        [stream write:(uint8_t *)[oldData bytes] maxLength:insertPoint]; // write the old data up to the insertion point //
        [stream write:(uint8_t *)[chunk bytes] maxLength:[chunk length]]; // write the new data //

//THE NEXT LINE IS THE LINE I AM GEETING THE ERROR AT 
  [stream write:(uint8_t *)[oldData bytes][insertPoint] maxLength:([oldData length] - insertionPoint)]; // write the rest of old data at the end of the file //
        [stream close];

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（（uint8_t*）[oldData bytes]）+插入点如何？
？为什么+？它现在显示错误：预期的标识符
+
是指针算术。它应该会起作用。问题解决了。我将查看此方法是否适用于在文件中插入值