AS3处理任意大文件

你不能创建一个流,在给定的偏移量处读取一块字节,一次读取一块…所以:

function readPortionOfFile(starting:int, size:int):ByteArray
{
    var bytes:ByteArray ...
    var fileStream:FileStream ...    

    fileStream.open(myFile);
    fileStream.readBytes(bytes, starting, size);
    fileStream.close();

    return bytes;
}

然后根据需要重复。我不知道这是如何工作的,也没有测试过,但我觉得这是可行的。

可以使用filestream.readahead和filestream.position属性设置要读取的文件数据的数量以及要从文件中读取数据的位置。

假设您只想读取千兆字节文件的兆字节152。这样做; (千兆字节文件由1073741824字节组成) (兆字节152从158334976字节开始)

var _fileStream = new FileStream();
_fileStream.addEventListener(Event.COMPLETE, loadComplete);
_fileStream.addEventListener(ProgressEvent.PROGRESS, onBytesRead);
_fileStream.readAead = (1024 * 1024); // Read only 1 megabyte  
_fileStream.openAsync(myFile, FileMode.READ);
_fileStream.position = 158334976; // Read at this position in file  

var megabyte152:ByteArray = new ByteArray();

function onBytesRead(e:ProgressEvent)
{
    e.currentTarget.readBytes(megabyte152);
    if (megabyte152.length == (1024 * 1024))
    {
        chunkReady();
    }
}

function chunkReady()
{
    // 1 megabyte has been read successfully \\  
    // No more data from the hard drive file will be read unless _fileStream.position changes \\  
}