Question

使用Windows Azure存储客户端库，CloudBlob.OpenRead（）方法只读取4 MB的数据。如何使用OpenRead方法读取完整流。

CloudBlob blob = container.GetBlobReference(filename);
Stream stream = blob.OpenRead();

我必须使用OpenRead方法。无法使用DownloadToFile或DownloadToStream。

编辑： 超出我的范围的消费者代码调用

stream.CopyTo(readIntoStream);

CopyTo是一种扩展方法。

public static int CopyTo(this Stream source, Stream destination)
        {
            byte[] buffer = new byte[BUFFER_SIZE];
            int bytesRead;
            int bytesCopied = 0;

            do
            {
                bytesRead = source.Read(buffer, 0, BUFFER_SIZE);
                if (bytesRead > 0)
                    destination.Write(buffer, 0, bytesRead);
                bytesCopied += bytesRead;
            }
            while (bytesRead > 0);

            return bytesCopied;
        }

编辑2：

我观察到当使用blob.UploadText（）方法上传文件时，它工作正常但是当使用OpenWrite方法上传blob时，如下面的代码示例所示，OpenRead方法只读取4194304字节（4 mb）。 / p>

using(var input = File.OpenRead(@"C:\testFile.txt")) //5000000 bytes
using (var output = blob.OpenWrite())
{
       input.CopyTo(output);
}

编辑3：

在我的最后产生问题的完整代码。

 static void Main(string[] args)
    {
        var blobContainer = GetContainer("tier1");
        blobContainer.CreateIfNotExist();

        var containerPermissions = new BlobContainerPermissions();
        containerPermissions.PublicAccess = BlobContainerPublicAccessType.Blob;
        blobContainer.SetPermissions(containerPermissions);
        var blob = blobContainer.GetBlobReference("testfileWithOpenWrite1.txt");

        using (var input = File.OpenRead(@"C:\testFile.txt")) //5000000 bytes
        using (var output = blob.OpenWrite(new BlobRequestOptions()))
            input.CopyTo(output);

        Console.WriteLine("uploaded");

        int bytesDownloaded = 0;
        byte[] buffer = new byte[65536];

        using (BlobStream bs = blob.OpenRead())
        {
            int chunkLength;
            do
            {
                chunkLength = bs.Read(buffer, 0, buffer.Length);
                bytesDownloaded += chunkLength;
            } while (chunkLength > 0);
        }

        Console.WriteLine(bytesDownloaded);
    }

    public static int CopyTo(this Stream source, Stream destination)
    {
        int BUFFER_SIZE = 65536;
        byte[] buffer = new byte[BUFFER_SIZE];
        int bytesRead;
        int bytesCopied = 0;

        do
        {
            bytesRead = source.Read(buffer, 0, BUFFER_SIZE);
            if (bytesRead > 0)
                destination.Write(buffer, 0, bytesRead);
            bytesCopied += bytesRead;
        }
        while (bytesRead > 0);

        return bytesCopied;
    }

编辑4 - 结论：

这可能是SDK v1.2附带的Microsoft.WindowsAzure.StorageClient.dll（程序集版本6.0.6002.17043）中的错误。它适用于最新的Microsoft.WindowsAzure.StorageClient.dll（程序集版本6.0.6002.18312 - SDK v1.4）。

谢谢smarx：）

Answer 1

我无法重现你所看到的。事情似乎按预期发挥作用：

static void Main(string[] args)
{
    // I also tried a real cloud storage account. Same result.
    var container = CloudStorageAccount.DevelopmentStorageAccount.CreateCloudBlobClient().GetContainerReference("testcontainer");
    container.CreateIfNotExist();

    var blob = container.GetBlobReference("testblob.txt");

    blob.UploadText(new String('x', 5000000));

    var source = blob.OpenRead();

    int BUFFER_SIZE = 4000000;
    byte[] buffer = new byte[BUFFER_SIZE];
    int bytesRead;
    int bytesCopied = 0;
    do
    {
        bytesRead = source.Read(buffer, 0, BUFFER_SIZE);
        bytesCopied += bytesRead;
    } while (bytesRead > 0);

    Console.WriteLine(bytesCopied); // prints 5000000
}

编辑：

我也（响应编辑过的问题）现在尝试使用OpenWrite上传blob，结果是一样的。（我得到了完整的blob。）我使用这段代码代替blob.UploadText（...）：

using (var input = File.OpenRead(@"testblob.txt")) //5000000 bytes
using (var output = blob.OpenWrite())
{
    input.CopyTo(output);
}

最终的WriteLine仍会打印5000000。

编辑2：

这有点令人厌烦。将BUFFER_SIZE更改为65536并未更改任何内容。结果似乎对我来说仍然是正确的。这是我的完整比较应用程序：

static void Main(string[] args)
{
    // I also tried a real cloud storage account. Same result.
    var container = CloudStorageAccount.DevelopmentStorageAccount.CreateCloudBlobClient().GetContainerReference("testcontainer");
    container.CreateIfNotExist();

    var blob = container.GetBlobReference("testblob.txt");

    using (var input = File.OpenRead(@"testblob.txt")) //5000000 bytes
    using (var output = blob.OpenWrite())
    {
        input.CopyTo(output);
    }

    var source = blob.OpenRead();

    int BUFFER_SIZE = 65536;
    byte[] buffer = new byte[BUFFER_SIZE];
    int bytesRead;
    int bytesCopied = 0;
    do
    {
        bytesRead = source.Read(buffer, 0, BUFFER_SIZE);
        bytesCopied += bytesRead;
    } while (bytesRead > 0);

    Console.WriteLine(bytesCopied); // prints 5000000
}

CloudBlob.OpenRead（）不读取所有数据

1 个答案: