NAME¶
VistaIOReadFile - read a Vista data file
SYNOPSIS¶
#include <stdio>
#include <vistaio.h>
VistaIOAttrList VistaIOReadFile ( file, filter)
FILE * file;
VistaIOReadFileFilterProc * filter;
typedef VistaIOBoolean VistaIOReadFileFilterProc (VistaIOBundle, VistaIORepnKind);
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.
SEE ALSO¶
VistaIOReadObjects(3),
VistaIOReadUbcIff(3),
stdio(3),
VistaIOBundle(3),
VistaIOattribute(3),
VistaIOtype(3)
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.
AUTHOR¶
Art Pope <pope@cs.ubc.ca>
Adaption to vistaio: Gert Wollny <gw.fossdev@gmail.com>
