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GetChunks

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Desktop

POST /wopi/files/(file_id)

The GetChunks operation allows clients to download specific chunks from the host. Clients can pass a list of ChunkRange values to be returned.

In response to the request, the host returns the sequence number along with the chunk data.

If the file on the host changes while the client is downloading the chunks, the client can detect the change by reading an updated sequence number in the response header. The host returns the list of actual chunks being returned in the response body MessageJSON. If the file is updated on the host, some of the requested chunks might no longer be valid. The X-WOPI-SequenceNumber header must be provided to reflect the latest host state.

Parameters

  • file_id (string) – Required. A string that specifies a file ID of a file managed by the host. This string must be URL safe.

Query parameters

  • access_token (string) – Required. An access token that the host uses to determine whether the request is authorized.

Request headers

  • X-WOPI-Override (string) – Required. The string is GET_CHUNKS.

Request body

Sample message:

{
  "ContentFilters": [
    {
      "StreamId": "MainContent",
      "ChunkingScheme": "Zip",
      "ChunkRangesToReturn": [
        {
          "ChunkId": "ZZbM2oyjAXOFHEnVJ7Q2cg//",
          "Offset": 0,
          "Length": 4096
        },
        {
          "ChunkId": "--QQQbM2oyjAXOFHEnVJ7Q2cbb/",
          "Offset": 4096,
          "Length": -1
        }
      ]
    }
  ]
}

Note

Setting the Length value of ChunkRangeToReturn to -1 indicates that the client is requesting the chunk data from Offset to the end of the chunk.

Status codes

Response headers

  • X-WOPI-SequenceNumber (integer) – Required. An integer value that indicates the latest state of the file on the host. The value must be greater than 0, and should be increased if the host file is updated.
  • X-WOPI-ItemVersion (string) – Required. A string value that indicates the version of the file. Its value should be the same as the Version value in CheckFileInfo.
  • X-WOPI-FailureReason (string) – Optional. Used for logging purposes only. It should be set on non-200 OK responses.

Response body

Sample message:

{
  "ChunkRangeCollection": [
    {
      "StreamId": "MainContent",
      "ChunkIds": [
        "==QQQbM2oyjAXOFHEnVJ7Q2cbb/",
        "ZZbM2oyjAXOFHEnVJ7Q2cg//"
      ]
    }
  ]
}

The response body is composed of MessageJSON, several PartialChunk frames, and EndFrame. The ChunkId values of the chunks that are passed in subsequent PartialChunk frames are encoded in MessageJSON. This can facilitate asynchronous processing on the receiver. Chunk data is encoded in PartialChunk frames. Each frame contains the binary content for a chunk range. ChunkId, offset, length of a partial chunk, and flag (EndOfChunk) are stored in the extended header field, and data bytes are stored in the frame payload. The response body ends with EndFrame.

The response body encoding protocol is introduced in this section.

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