OPC_READ_FLAGS enumeration (msopc.h)

  • Article

Describes the read settings for caching package components and validating them against ECMA-376 OpenXML, 1st Edition, Part 2: Open Packaging Conventions (OPC) conformance requirements.

Syntax

typedef enum __MIDL___MIDL_itf_msopc_0000_0002_0004 {
  OPC_READ_DEFAULT = 0,
  OPC_VALIDATE_ON_LOAD = 0x1,
  OPC_CACHE_ON_ACCESS = 0x2
} OPC_READ_FLAGS;

Constants

 
OPC_READ_DEFAULT
Value: 0
Validate a package component against OPC conformance requirements when the component is accessed. For more information about OPC conformance validation, see Remarks.

When validation is performed on access, OPC validation errors can be returned by any method.
OPC_VALIDATE_ON_LOAD
Value: 0x1
Validate all package components against OPC conformance requirements when a package is loaded. For more information about OPC conformance validation, see Remarks.

If this setting is enabled, performance costs for loading and validating package components are paid when the package is first loaded.
OPC_CACHE_ON_ACCESS
Value: 0x2
Cache decompressed package component data as a temp file when accessing the component for the first time. When a package component is accessed repeatedly, this caching reduces overhead because the component data is decompressed one time for the first read instead of once for every read operation.

Remarks

If both the OPC_CACHE_ON_ACCESS and OPC_VALIDATE_ON_LOAD read flags are set, all package components are decompressed and cached when a package is loaded.

The Packaging APIs do not use the OPC core properties feature; therefore, the core properties requirements listed in Table H-9 of the OPC are not validated by the Packaging APIs. For more information about OPC conformance requirements, see 1st edition, Part 2: Open Packaging Conventions in ECMA-376 OpenXML (https://www.ecma-international.org/publications-and-standards/standards/ecma-376/).

Important  Parts may be repeatedly read from the stream at any time, regardless of which read flags are set. For example, when a package is saved, previously accessed relationships in a Relationships part in the original package may be accessed again to preserve markup compatibility.
 

Requirements

Requirement Value
Header msopc.h

See also

ECMA-376 OpenXML standard

External Resources

Getting Started with the Packaging API

IOpcFactory::ReadPackageFromStream

Overviews

Packaging API Programming Guide

Packaging API Samples

Packaging Enumerations

Packaging Interfaces

Reference