2.3.41 FSCTL_OFFLOAD_READ Request
The FSCTL_OFFLOAD_READ Request message requests that the server perform an Offload Read operation to a specified portion of a file on a target volume. On the client side, this request is received, processed, and sent down to an intelligent storage subsystem that generates and returns a Token in an FSCTL_OFFLOAD_READ Reply (section 2.3.42) message. This Token logically represents the data to be read and can be used with an FSCTL_OFFLOAD_WRITE Request (section 2.3.43) and an FSCTL_OFFLOAD_WRITE Reply (section 2.3.44) pair to complete the data movement.<36>
The request message contains an FSCTL_OFFLOAD_READ_INPUT data element, as follows.
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Size |
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Flags |
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TokenTimeToLive |
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Reserved |
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FileOffset |
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... |
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CopyLength |
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Size (4 bytes): A 32-bit unsigned integer that indicates the size, in bytes, of this data element.
Flags (4 bytes): A 32-bit unsigned integer that indicates the flags to be set for this operation. Currently, no flags are defined. This field SHOULD be set to 0x00000000 and MUST be ignored.
TokenTimeToLive (4 bytes): A 32-bit unsigned integer that contains the requested Time to Live (TTL) value in milliseconds for the generated Token. This value MUST be greater than or equal to 0x00000000. A value of 0x00000000 represents a default TTL interval.<37>
Reserved (4 bytes): A 32-bit unsigned integer field that is reserved. This field SHOULD be set to 0x00000000 and MUST be ignored.
FileOffset (8 bytes): A 64-bit unsigned integer that contains the file offset, in bytes, of the start of a range of bytes in a file from which to generate the Token. The value of this field MUST be greater than or equal to 0x0000000000000000 and MUST be aligned to a logical sector boundary on the volume.
CopyLength (8 bytes): A 64-bit unsigned integer that contains the size, in bytes, of the requested range of the file from which to generate the Token. The value of this field MUST be greater than or equal to 0x0000000000000000 and MUST be aligned to a logical sector boundary on the volume.<38>