W3C Sample Code Library libwww File Suffix Binding

# File Suffix Binding Manager

    /*
    **	(c) COPYRIGHT MIT 1995.
    **	Please first read the full copyright statement in the file COPYRIGH.
    */

The preferences that we described in section Request Preferences did not mention what libwww should do if it doesn't know the data format of a document. In many protocols this information is provided by the remote server. Typical examples are MIME like protocols where the metainformation such as the Content-Type and the Content-Language is provided together with the document. However, applications often have access to the local file system using file URLs which in general do not keep any or at least very little information of the file type. It is therefore required to have some kind of binding between the file system and the preferences registered in the Library which provides this mateinformation about the object.

Often files in a file system is classified by some sort of a suffix, for example, `GIF` files are often ending in .gif, text files in .txt etc. This binding is not static and it is therefore required to have a dynamic binding just like the preferences themselves. An example of the latter is HTML files which on most Unix systems end in .html whereas they on many MS-DOS based systems end in .htm.

This module provides a generic binding mechanism between a file and its representation internally in libwww. It is not limited to simple file suffix classification but can also be used in more advanced environments using data bases etc. However, at this point we are interested in how we can register bindings between file suffixes and for example content types, content languages etc. The Bind manager is born with a certain knowledge about the set of delimiters but more can be added to provide the functionality desired.

All the binding management could of course be replaced by a database interface.

This module is implemented by HTBind.c, and it is a part of the W3C Sample Code Library.

    #ifndef HTBIND_H
    #define HTBIND_H

    #include "HTFormat.h"
    #include "HTAnchor.h"

## Initialization of the Module

These functions must be called on startup and termination of the application. This is done automatically by HTLibInit() and HTLibTerminate().

    extern BOOL HTBind_init		(void);
    extern BOOL HTBind_deleteAll	(void);

## Case Sensitivity

Should the search for suffixes be case sensitive or not? The default value is case sensitive.

    extern void HTBind_caseSensitive	(BOOL sensitive);

## Suffix Delimiters

Change the set of suffix delimiters. The default is a platform dependent set defined in the tcp module.

    extern const char *HTBind_delimiters	(void);
    extern void HTBind_setDelimiters	(const char * new_suffixes);

## Set up Bindings Associated with a File Suffix

There are four types of bindings:

- Content Type (media type)
- Language
- Content Encoding
- Content Transfer Encoding

And the associated set of methods is defined as:

    extern BOOL HTBind_add		(const char *	suffix,
    				 const char *	representation,
    				 const char *	encoding,
    				 const char *	transfer,
    				 const char *	language,
    				 double		value);

    extern BOOL HTBind_addType	(const char *	suffix,
    				 const char *	format,
    				 double		value);

    extern BOOL HTBind_addEncoding	(const char *	suffix,
    				 const char *	encoding,
    				 double		value);

    extern BOOL HTBind_addTransfer	(const char *	suffix,
    				 const char *	transfer,
    				 double		value);

    extern BOOL HTBind_addLanguage	(const char *	suffix,
    				 const char *	language,
    				 double		value);

The first method is a "super" method for binding information to a file suffic. Any of the string values can be `NULL`. If filename suffix is already defined its previous definition is overridden or modified. For example, a `HTBind_setType` and `HTBind_setEncoding` can be called with the same suffix.

Calling this with suffix set to "*" will set the default representation. Calling this with suffix set to "*.*" will set the default representation for unknown suffix files which contain a "."

NOTE: The suffixes can contain characters that must be escaped in a URL. However, they should not be encoded when parsed as the `suffix` parameter.

## Determine a suitable suffix

Use the set of bindings to find a suitable suffix (or index) for a certain combination of language, media type and encoding given in the anchor. Returns a pointer to a suitable suffix string that must be freed by the caller. If more than one suffix is found they are all concatenated. If no suffix is found, NULL is returned.

    extern char * HTBind_getSuffix	(HTParentAnchor * anchor);

## Determine the content of an Anchor

Use the set of bindings to find the combination of language, media type and encoding of a given anchor. If more than one suffix is found they are all searched. The last suffix has highest priority, the first one lowest. Returns the HTAnchor object with the representations found. See also `HTBind_getFormat`

    extern BOOL HTBind_getAnchorBindings	(HTParentAnchor * anchor);

## Determine the content of a Response

Use the set of bindings to find the combination of language, media type and encoding of a given anchor. If more than one suffix is found they are all searched. The last suffix has highest priority, the first one lowest. Returns the HTResponse object with the representations found. See also `HTBind_getFormat`

    extern BOOL HTBind_getResponseBindings	(HTResponse * response,
                                             const char * url);

## Determine the content of File

Use the set of bindings to find the combination of language, media type and encoding of a given anchor. If more than one suffix is found they are all searched. The last suffix has highest priority, the first one lowest. Returns the format, encoding, and language found. See also `HTBind_getBindings`.

    extern BOOL HTBind_getFormat (const char *	filename,
    			      HTFormat *	format,
    			      HTEncoding *	enc,
    			      HTEncoding *	cte,
    			      HTLanguage *	lang,
    			      double *		quality);

End of declaration module

    #endif /* HTBIND_H */