SYNOPSIS
#include <stdio>
#include <vistaio.h>
VistaIOAttrList VistaIOReadFile (file, filter)
- FILE *file; VistaIOReadFileFilterProc *filter;
ARGUMENTS
- file
- Specifies the open stream from which the data file should be read.
- filter
- May specify a function that determines which attributes' binary data is read from the file, or it may be NULL to indicate that all binary data should be read.
DESCRIPTION
VistaIOReadFile reads the contents of a Vista data file. It returns a list of the attributes found in the file. Attribute values in that list will have been converted to internal form, as described by VistaIOattribute(3) and VistaIOtype(3).With the filter argument you may supply a function that gets to decide for each attribute value that is an object whether or not that object's binary data should be read. This mechanism allows you to avoid the expense of reading binary data that is not of interest (e.g., image pixel values when images are not of concern). However, you need only supply a filter function if you are particularly concerned about efficiency. Your filter function should be declared:
- VistaIOBoolean MyFilter (bundle, repn)
- VistaIOBundle bundle; VistaIORepnKind repn;
Your filter function will be called once for each object encountered at any level in the file. It will be passed a VistaIOBundle representing the object (including its type name and attribute list, but not its binary data), and the repn value obtained by looking up its type name (i.e., the value returned by VistaIOLookupType(3) on the type name, which could be VistaIOUnknownRepn). The object's binary data will be read only if the filter function returns TRUE. If it returns FALSE, the object will be represented in the attribute list as a VistaIOBundle, without binary data --- it will not be converted to internal form (e.g., not to a VistaIOImage). If no filter function is supplied (i.e., filter is NULL), VistaIOReadFile will read all binary data associated with all objects.
For backwards compatibility VistaIOReadFile will recognize and read the contents of a UBC image file format (IFF) file. If the first character read from the stream is ``I'', VistaIOReadFile uses VistaIOReadUbcIff to read a single UBC IFF image. The image is returned as a VistaIOImage attribute value in a list containing a single attribute. In this case, the filter argument has no effect.
RETURN VALUE
VistaIOReadData returns an attribute list representing the file's contents, or NULL if an error is encountered. In the case of an error, the stream may not have been completely read.NOTES
Data is read from the stream sequentially, permitting the stream to be a pipe. No rewind is performed either before reading or after.DIAGNOSTIC
- ``EOF encountered in name attribute.''
- The end-of-file was encountered unexpectedly while reading the value of the named attribute.
- ``File continues beyond expected EOF.''
- The end-of-file wasn't encountered immediately after all expected binary data.
- ``Invalid name attribute.''
- The named attribute is encoded incorrectly in the stream. It may, for example, be missing the ``:'' that should separate its name and value.
- ``Missing {.''
- The ``{'' marking the start of an attribute list is missing.
- ``Missing }.''
- The ``}'' marking the end of an attribute list is missing.
- ``name attribute has data but not length.''
- The named attribute's value is an object whose attribute list contains a data attribute but not a length attribute. Both attributes must be present to specify binary data. (A similar diagnostic is produced if there is a length attribute but no data attribute.)
- ``name attribute's attr attribute incorrect.''
- The named attribute's value is an object whose attribute list indicates it has binary data. However, its data attribute specifies an offset too early in the binary data portion of the file, or its data or length attribute has a non-integer value.
- ``Read from stream failed.''
- An attempt to read a block of binary data failed, perhaps because of a premature end-of-file.
- ``Vista data file delimiter not found.''
- The FORMFEED NEWLINE sequence terminating the attribute list portion of the data file wasn't found.
- ``Vista data file isn't version 2.''
- The data file's header indicates a file format version other than 2, the current version.