Data Transformation

COPYWRITE provides a feature to allow for the selection of which files are to be copied, and the transformation of the data being copied, for files being copied to a file system other than LIBRARY/MAINTENANCE.
For example, source files can be copied from the A-Series, and translated from EBCDIC to ASCII, and each record trimmed of trailing blanks, and a CR LF appended, so that they are suitable for Windows.
There are several intrinsic transformations provided, and they are selected using a shortcut.
The shortcuts select intrinsic transform functions, which are internal to COPYWRITE, to perform the data transformation. However, external transform functions can also be used by COPYWRITE.
A transform function is exported from an ALGOL LIBRARY, to which COPYWRITE links during a COPY. The definition of the transform interface is shown in the sample provided on the release CD.
The transform is specified to COPYWRITE by setting the TRANSFORM attribute of a file label equated to the COPY process, which has an INTNAME the same as the <destination volume> name. See Example 12.
The transform function is called in several different contexts, and the information provided depends on the context.

CWTr_OpenVolumeV	The Transform function is called from OpenCD, after the CD volume has been successfully opened. The attributes pertaining to the volume are valid in FileInfo.If the function does not return CWTr_OKV, the COPY is aborted, showing the Reason returned by the transform.
CWTr_StartOfFileV	The transform function is called from MetaMorphProlog, after the Disk File Header has been received, but before any data has arrived. If the file cannot be processed, for example, because there are rows missing, this call will not happen. The transform is provided with the disk file header. Many of the file attributes have already been extracted from the header and placed in FileInfo. Some attributes derived from the header are also available. Attributes can be extracted from the header using the MCP GetHeaderAttribute function, which is also used by COPYWRITE. If the transform returns CWTR_SkipFileV, the file is discarded. Typically the FILEKIND is used to decide whether or not to skip a file. Transforming A-Series codefiles into ASCII text files is not a common requirement. If the transform returns CWTr_OKV, the file is selected. If the transform returns CWTr_SelectFileAndChangeTitleV, the file is selected, and COPYWRITE expects to find a standardform filename in Record, which is the title of the file as it will exist in the destination volume. For example, the Windows95 shortcut, appends a ".TXT" to each filename, to avoid duplicate file and directory names.
CWTr_DataRecordV	This context is called from within MetaMorphWriteRecord. If the transform returns CWTR-OKV, the record is written to the volume, otherwise the record is skipped.
CWTr_EndOfFileV	This is called from MetaMorphEpilog. If CWTr_OKV is not returned, the COPY process terminates.
CWTr_CloseVolumeV	This context is called from within CloseCD, after all file systems have been written to the volume, and the volume has been locked on disk, and after the AUTOUNLOAD action has been completed.
CWTr_OpenFileSystemV	This is called from OpenFileSystem which is not yet called anywhere. The intention is to provide the transform notification of the start and end of a file system , during creation of a hybrid CD volume archive.
CWTr_CloseFileSystemV	This is called from CloseFileSystem, but not yet called.

The option does exist to add records at any point during the processing of the file. As yet this has not been tested. Any customer who intends to use this facilty should contact Metalogic.