type_manager

Product	Command Type
ClearCase®	data structure

Platform
UNIX®
Linux®
Windows®

Description

A type manager is a suite of programs that manipulates files with a particular data format; different type managers process files with different formats. A directory type manager provides programs that compare and/or merge versions of directory elements. ClearCase provides several type managers. On UNIX and Linux, users can create additional ones.

Several version-control methods for file elements are implemented in two phases:

Updating of the VOB database. This phase is independent of the element's data format and is handled directly by cleartool.
Manipulation of the element's data. In this phase, the data format is extremely significant, and so is handled by a particular type manager. The type manager is invoked as a separate program, rather than as a subroutine. This provides flexibility and openness, allowing users to integrate their own data-manipulation routines with ClearCase.

For example, checking in a text_file element involves the following:

Storing information in the VOB database about the creator of the new version, when it was created, and so on
Computing and storing the delta (incremental difference) between the new version and its predecessor.

For a different type of element—for example, a bitmap file—the delta is computed differently, or not at all, and so requires a different type manager.

Type managers

Following are descriptions of the type managers:

Manager	Function
whole_copy	Stores any data. Stores a whole copy of each version in a separate data container file.
z_whole_copy	Stores any data. Stores each version in a separate, compressed data container file using the ccgzip compression program. (ccgzip is a utility that implements IETF RFC 1951 + 1952 compression using zlib source code). Note that compressed files generally take more time to check in (because they must be compressed) and to reconstruct when first accessed (first cleartext fetch).
text_file_delta	Stores text files only (including those with multibyte text characters). Stores all versions in a single structured data container file. (On UNIX and Linux, similar to an SCCS s. file or an RCS ,v file.) Uses incremental file differences to reconstruct individual versions on the fly.
z_text_file_delta	Stores text files only. Stores all versions in a single structured data container file, in compressed format using both the ccgzip compression program and deltas.
binary_delta	Stores any data. Stores each branch's versions in a separate, structured compressed data container file using ccgzip. Uses incremental file differences to reconstruct individual versions on the fly. Version deltas are determined by comparing files on a per-byte basis.
_html	Stores HTML source. Stores information and reconstructs versions in the same way as the text_file_delta manager from which it is derived. Has its own compare, xcompare, merge and xmerge methods.
_html2	Same as the _html manager, except that _html2 is based on the binary_delta manager.
_ms_word	Stores Microsoft® Word documents. Stores information and reconstructs versions in the same way as the z_whole_copy manager from which it is derived. On Windows, has its own xcompare and xmerge methods.
_rftdef _rftmap _rftvp	Stores XDE™ Tester artifacts. Stores information and reconstructs versions in the same way as the binary_delta manager from which it is derived.
_rose	Stores IBM Rose artifacts. Stores information and reconstructs versions in the same way as the text_file_delta manager from which it is derived. On Windows, has its owncompare, xcompare, merge, and xmerge methods.
_rose2	Same as the _rose manager, except that _rose2 is based on the binary_delta manager.
_rosert	Stores IBM Rose RealTime artifacts. Stores information and reconstructs versions in the same way as the binary_delta manager from which it is derived. On Windows, has its own compare, xcompare, merge, and xmerge methods.
utf8_file_delta	Stores 8-bit Unicode Transformation Format source. The compare/merge functionality is similar to that of the text_file_delta type manager.
utf16be_file_delta	Stores 16-bit big-endian Unicode Transformation Format source. The compare/merge functionality is similar to that of the text_file_delta type manager.
utf16le_file_delta	Stores 16-bit little-endian Unicode Transformation Format source. The compare/merge functionality is similar to that of the text_file_delta type manager.
utf32be_file_delta	Stores 32-bit big-endian Unicode Transformation Format source. The compare/merge functionality is similar to that of the text_file_delta type manager.
utf32le_file_delta	Stores 32-bit little-endian Unicode Transformation Format source. The compare/merge functionality is similar to that of the text_file_delta type manager.
_xde	Stores IBM XDE artifacts. Stores information and reconstructs versions in the same way as the text_file_delta manager from which it is derived. On Windows, has its own merge, xmerge, compare, and xcompare methods.
_xde2	Same as the _xde manager, except that _xde2 is based on the binary_delta manager and it provides a context_merge method.
_xml	Stores XML source. Stores information and reconstructs versions in the same way as the text_file_delta manager from which it is derived. On Windows, has its own compare, xcompare, merge, and xmerge methods.
_xml2	Same as the _xml manager, except that _xml2 is based on the binary_delta manager.
directory	Not involved in storing or retrieving directory versions, which reside in the VOB database, not in a source storage pool. This type manager compares and merges versions of the same directory element.

Using a type manager

To have a given file element use a particular type manager, you need to associate the file element with an element type that is associated with that particular type manager. You can establish these connections as follows:

Verify that the VOB has an element type that is associated with the desired type manager. Use the lstype command to identify an existing element type. Alternatively, use the mkeltype –manager command to create a new element type that is associated with the desired type manager.
Create the file element, specifying the element type with the –eltype option. If the file element already exists, use the chtype command to change its element type.

You can automate the assignment of the new element type to newly created elements using the file-typing facility, driven by .magic files. For more information, see the cc.magic reference page.

Note that UTF element types are not created by default; you must create such types explicitly and associate them with UTF type managers.

Type manager structure

A type manager uses different methods to manipulate ClearCase data. Methods are invoked at the appropriate time by a version-control command.

On UNIX, and Linux a type manager is a collection of programs in a subdirectory of ccase-home-dir /lib/mgrs; the subdirectory name is the name by which the type manager is specified with the –manager option in a mkeltype command. Each program in a type manager subdirectory implements one method (data-manipulation operation). A method can be a compiled program, a shell script, or a link to an executable. It is invoked at the appropriate time by a ClearCase version-control command.

A type manager can include the following methods, which are invoked by a command or server process:

create_element	Invoked by mkelem to create an element's initial data container.
create_branch	Invoked by mkbranch to create a branch in an element's version tree.
create_version	Invoked by checkin to store a new version of an element.
annotate	Invoked by annotate to produce an annotated listing of a version's contents.
construct_version	Invoked by a view's view_server process when a file element is opened, from versions stored in delta or compressed format. This method constructs a readable, cleartext copy of a particular version. After the cleartext version is constructed, its line terminators may be adjusted by the view_server, according to the view's text mode. See the mkeltype and mkview reference pages.
context_merge
get_cont_info	Invoked by checkvob to determine the contents of a container. This method must be implemented to enable checkvob to fix container problems for the type manager.
delete_branches_versions	Invoked by rmver and rmbranch to delete versions of an element.
compare, xcompare	Invoked by diff to run a file-comparison program that is specific to the element's data format.
merge, xmerge	Invoked by merge to run a file-merge program that is specific to the element's data format.

A type manager need not implement every method. For example, a type manager for bitmap graphics images may omit the merge method, because the operation doesn't make sense for that file format. In this case, the command cleartool merge produces an error when invoked on an element that uses this type manager.

UNIX and Linux—Method inheritance and links

A type manager can use symbolic links to inherit one or more of its methods from another type manager. A typical use of symbolic links is to have individual methods be links to a master type manager program, which implements several (or all) of the methods. For an example, see directory ccase-home-dir/lib/mgrs/z_whole_copy.

A link to the cleardiff program can implement the compare and/or merge method for text files. Similarly, a link to the xcleardiff program can implement the xcompare and/or xmerge method. Again, see directory ccase-home-dir/lib/mgrs/z_whole_copy for an example.

Windows—The type manager map file

The map file, located in the ccase-home-dir\lib\mgrs directory, associates type manager methods with the programs that carry them out. A map file entry has three fields: type manager, method, and program. Below are some example entries from the map file:

Manager	Method	Implementing Program
text_file_delta	construct_version	..\..\bin\tfdmgr.exe
text_file_delta	compare	..\..\bin\cleardiff.exe
z_whole_copy	create_branch	..\..\bin\zmgr.exe
_rose	xmerge	HKEY_LOCAL_MACHINE\SOFTWARE \Software\Rose\AddIns\Rose Model Integrator \Install Path

When a type manager is invoked by a ClearCase command, it scans through the map file, finds the matching type manager and method in the first and second fields, and then runs the program specified in the third field. Note that the entry in the third field must be either a pathname relative to ccase-home-dir\lib\mgrs; for example, ..\..\bin\cleardiff.exe, a Windows Registry key under HKEY_LOCAL_MACHINE that points to an absolute pathname, or an absolute pathname.

Data containers

Type managers process data containers, each of which stores the actual data for one or more versions of some element. (Although growth may cause a container to split, versions never span container boundaries.) All data containers are files, and are stored in the VOB's source pools, which are directories. Only type managers deal with data containers directly; users always manipulate data using the names of elements and UNIX or Linux links.

Performing the data manipulation for a version-control operation involves several programs. For example, when ClearCase creates a new version of an element:

The pathname (within a source pool) is generated for a new data container.
On the VOB host (where the VOB storage area resides), a vob_server process creates an empty file at that pathname.
On the client host (where the user is working), the type manager fills the new data container with the data for the new version. (If the type manager implements deltas, it writes the data for one or more other versions to the new container, too.)
The vob_server changes the access mode of the new data container, making it unwritable.
The db_server updates the VOB database to reference the new container.
Using the MGR_DELETE_KEEP_JUST_NEW exit status returned by the type manager, the vob_server deletes the old data container.

Note: Even with a type manager that implements deltas, a new data container is created each time a new version is created. In this case, the old container (which may have stored 27 versions) is replaced by the new container (which stores 28 versions). A type manager must never write to an old container or delete a old container (it usually does not have rights to do so).

Source pool data container names

A container leaf name includes a type manager ID to aid checkvob in salvaging nonreferenced containers. Here is the format of a source pool data container name (in s/sdft, for example):

./nn/nn/type-mgr-id–orig-oid-str–xx

type-mrg-id is a one-, two-, or three-character string. One-character values correspond to the predefined type managers. Two-digit values correspond to type managers with names that begin with underscore (_), and three-digit values are computed by hashing user-defined type manager names.

Names of user-defined type managers must not begin with underscore.

UNIX and Linux files

ccase-home-dir/lib/mgrs/*
ccase-home-dir/lib/mgrs/mgr_info.h
ccase-home-dir/lib/mgrs/mgr_info.sh

Windows files

ccase-home-dir\lib\mgrs\map