7zip Assembly

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IInArchive ​

IInArchive is the interface the plugin archive format must implement to be able to Open and Extract the archive. We will utilize the CMyUnknownImpl with Z7_IFACES_IMP_UNK_1 macro to 'hide' boilerplate 'COM' code:

C++
class SzInArchive : public CMyUnknownImp, public IInArchive {
public:
  Z7_IFACES_IMP_UNK_1(IInArchive);
};
class SzInArchive : public CMyUnknownImp, public IInArchive {
public:
  Z7_IFACES_IMP_UNK_1(IInArchive);
};

Open ​

C++
HRESULT IInArchive::Open(
    IInStream *stream,
    const UInt64 *maxCheckStartPosition,
    IArchiveOpenCallback *openCallback
) noexcept;
HRESULT IInArchive::Open(
    IInStream *stream,
    const UInt64 *maxCheckStartPosition,
    IArchiveOpenCallback *openCallback
) noexcept;

Function invoked when plugin host will find the fitting archive to open. Usually it is not mandatory to read all archive in memory. Most archives read only head(table) section of the archive. This gives basic understanding of the properties of the archive that can be queried later on.

[in] stream

The file stream that was opened upon reading the archive file.

[in] maxCheckStartPosition

If NULL, the handler can try to search archive start in stream. If *0, the handler must check only current position as archive start

[in] openCallback

The callback to report the progress of opening the archive. See IArchiveOpenCallback.

Close ​

C++
HRESULT IInArchive::Close() noexcept;
HRESULT IInArchive::Close() noexcept;

Function called to close the archive. Dispose the resources allocated in Open function.

GetNumberOfItems ​

C++
HRESULT IInArchive::GetNumberOfItems(
    UInt32 *numItems
) noexcept;
HRESULT IInArchive::GetNumberOfItems(
    UInt32 *numItems
) noexcept;

[out] numItems

Return the number of items(files, dirs) stored in archive. The index of the item will be used later to extract it or to get metadata about it.

GetProperty ​

C++
HRESULT IInArchive::GetProperty(
    UInt32 index,
    PROPID propID,
    PROPVARIANT *value
) noexcept;
HRESULT IInArchive::GetProperty(
    UInt32 index,
    PROPID propID,
    PROPVARIANT *value
) noexcept;

This function must return the property of the particular item. Item is indexed using GetNumberOfItems function.

[in] index

Index of the item which property will be returned.

[in] propID

The id of the property. See props defined in ProgID.h for details.

[out] value

The value of the property to return.

Extract ​

C++
HRESULT IInArchive::Extract(
    const UInt32 *indices,
    UInt32 numItems,
    Int32 testMode,
    IArchiveExtractCallback *extractCallback
) noexcept;
HRESULT IInArchive::Extract(
    const UInt32 *indices,
    UInt32 numItems,
    Int32 testMode,
    IArchiveExtractCallback *extractCallback
) noexcept;

Extract the items indexed by indices. Use extract callback to query for the stream to write to.

[in] indices

The array of the items to extract.

[in] numItems

The size of the indices array.

[in] testMode

Indicates that archive must test the ability to extract the given items, without doing so. See IArchiveExtractCallback

[in] extractCallback

The callback to report the progress of extracting the items. Also, this callback can be used to query for the stream to write to.

GetArchiveProperty ​

C++
HRESULT IInArchive::GetArchiveProperty(
    PROPID propID,
    PROPVARIANT *value
) noexcept;
HRESULT IInArchive::GetArchiveProperty(
    PROPID propID,
    PROPVARIANT *value
) noexcept;

Gets general archive properties like PhysicalSize or Readonly or error properties if to check if there was any error during Open.

[in] propID

The id of the property to query. Properties enum can be found in ProgID.h.

[out] value

The value to the property to required to return.

GetNumberOfProperties ​

C++
HRESULT IInArchive::GetNumberOfProperties(
    UInt32 *numProps
) noexcept;
HRESULT IInArchive::GetNumberOfProperties(
    UInt32 *numProps
) noexcept;

Gets the number of properties in the archive.

[out] numProps

Return the number of the properties that will later on by queried using GetPropertyInfo.

TIP 1

If you return 0 rest 3 functions can safely return E_NOTIMPL.

TIP 2

It is easy to confuse the GetPropertyInfo and GetProperty functions. So, GetNumberOfProperties is used for GetPropertyInfo, and GetPropertyInfo is used for the display(like giving names to the column in FileManager) and GetProperty is used by the plugin host to correctly work with files depending of their metadata.

GetPropertyInfo ​

C++
HRESULT IInArchive::GetPropertyInfo(
    UInt32 index,
    BSTR *name,
    PROPID *propID,
    VARTYPE *varType
) noexcept;
HRESULT IInArchive::GetPropertyInfo(
    UInt32 index,
    BSTR *name,
    PROPID *propID,
    VARTYPE *varType
) noexcept;

Assigns names to the properties of the archive items.

[in] index

The index of the property to get info about.

[out] name

Assign the name of the property that will be displayed.

[out] propID

The corresponding property id from GetProperty to link with the given name.

[out] varType

The variant type(short) of the property.

GetNumberOfArchiveProperties ​

C++
HRESULT IInArchive::GetNumberOfArchiveProperties(
    UInt32 *numProps
) noexcept;
HRESULT IInArchive::GetNumberOfArchiveProperties(
    UInt32 *numProps
) noexcept;

[out] numProps

Return the number of the names properties you want display for the archive.

GetArchivePropertyInfo ​

C++
HRESULT IInArchive::GetArchivePropertyInfo(
    PROPID propID,
    BSTR *name,
    PROPID *propID,
    VARTYPE *varType
) noexcept;
HRESULT IInArchive::GetArchivePropertyInfo(
    PROPID propID,
    BSTR *name,
    PROPID *propID,
    VARTYPE *varType
) noexcept;

Assign the name to the archive properties.

[in] propID

The property id of the archive, indexed with the help of GetNumberOfArchiveProperties

[out] name

The name to assign to the archive property.

[out] propID

The property id from GetArchiveProperty to associate with the names property.

[out] varType

The variant type(short) of the property.