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Open an OLE compound file

Source: R/olereader.R
ole_open.Rd

Reads the header, the sector allocation tables and the directory of a Microsoft compound file (MS-CFB), also called OLE2 or structured storage. Stream contents are not read until you ask for them with ole_read(). Only reading is supported.

Usage

ole_open(path)

Arguments

path

Path to the file.

Value

An ole_file object: a list holding

  • path, version (3 or 4) and file_size, in bytes;

  • sector_size and mini_sector_size, in bytes, and n_sectors, the number of sectors after the header;

  • fat and minifat, which give for each sector or mini sector the 0-based number of the next sector in its chain, or a negative number marking the end of a chain or a free or reserved sector;

  • mini_chain, the 0-based sectors holding the mini stream, or the error met while following them;

  • dir, a data frame with one row per directory entry. Its columns are name; type (1 for a storage, 2 for a stream, 5 for the root); left, right and child, the 0-based IDs of the entry's siblings and first child, or -1 for none; start, its first sector; size, in bytes; parent, the row of the storage holding it, or 0 for the root and for entries not reached from it; and key, its name with the letters A to Z in lower case.

Details

The file is not kept open: each call to ole_read() reopens it. There is nothing to close.

The other functions also take a path in place of an ole_file object and call ole_open() on it themselves. A path is simpler for a single read, but the file is parsed again on every call, so open it once to read several streams.

Damaged files give an error rather than wrong data: a header or allocation table that does not fit the size of the file, a chain of sectors that loops, a directory entry that points past the end of the directory, or storages nested more than 64 levels deep.

See also

ole_streams(), ole_read(), ole_size(), ole_extract()

Examples

ole <- ole_open(system.file("extdata", "example.cfb", package = "olereader"))
ole
#> <ole_file> /home/runner/work/_temp/Library/olereader/extdata/example.cfb
#>   version 3, 512-byte sectors, 2 streams