If-Modified-Since header.

The If-Modified-Since header field The If-Modified-Since request-header field is used with a method to make it conditional: if the requested variant has not been modified since the time specified in this field, an entity will not be returned from the server; instead, a 304 (not modified) response will be returned without any message-body. More...

Defines
#define	HTTP_IF_MODIFIED_SINCE_INIT()
	Initializer for structure http_if_modified_since_t.
#define	HTTPTAG_IF_MODIFIED_SINCE(x)
	Tag list item for pointer to a If-Modified-Since header object.
#define	HTTPTAG_IF_MODIFIED_SINCE_STR(s)
	Tag list item for string with If-Modified-Since header value.
Typedefs
typedef http_date_t	http_if_modified_since_t
	The structure http_if_modified_since_t contains representation of If-Modified-Since header.
Enumerations
enum	{ http_if_modified_since_hash }
Functions
http_if_modified_since_t *	http_if_modified_since_init (http_if_modified_since_t x[1])
	Initialize a structure http_if_modified_since_t.
int	http_is_if_modified_since (http_header_t const *header)
	Test if header object is instance of http_if_modified_since_t.
http_if_modified_since_t *	http_if_modified_since_dup (su_home_t *home, http_if_modified_since_t const *hdr))
	Duplicate (deep copy) http_if_modified_since_t.
http_if_modified_since_t *	http_if_modified_since_copy (su_home_t *home, http_if_modified_since_t const *hdr))
	Copy a http_if_modified_since_t header structure.
http_if_modified_since_t *	http_if_modified_since_make (su_home_t *home, char const *s))
	Make a header structure http_if_modified_since_t.
http_if_modified_since_t *	http_if_modified_since_format (su_home_t *home, char const *fmt,...)))
	Make a If-Modified-Since header from formatting result.
Variables
msg_hclass_t	http_if_modified_since_class []
	Header class for HTTP If-Modified-Since header.
msg_parse_f	http_if_modified_since_d
	Decode (parse) a If-Modified-Since header.
msg_print_f	http_if_modified_since_e
	Encode (print) a If-Modified-Since header.

---

Detailed Description

The If-Modified-Since header field The If-Modified-Since request-header field is used with a method to make it conditional: if the requested variant has not been modified since the time specified in this field, an entity will not be returned from the server; instead, a 304 (not modified) response will be returned without any message-body.

Its syntax is defined in RFC 2616 secion 14.25 as follows:

    If-Modified-Since =  "If-Modified-Since" ":" HTTP-date

---

Define Documentation

#define HTTP_IF_MODIFIED_SINCE_INIT

(

)

Initializer for structure http_if_modified_since_t.

A static http_if_modified_since_t structure must be initialized with the HTTP_IF_MODIFIED_SINCE_INIT() macro. For instance,

  http_if_modified_since_t http_if_modified_since = HTTP_IF_MODIFIED_SINCE_INIT;

#define HTTPTAG_IF_MODIFIED_SINCE

(

x

)

Tag list item for pointer to a If-Modified-Since header object.

The HTTPTAG_IF_MODIFIED_SINCE() macro is used to include a tag item with a pointer to a http_if_modified_since_t object in a tag list.

Parameters:

x

pointer to a http_if_modified_since_t header structure, or NULL.

#define HTTPTAG_IF_MODIFIED_SINCE_STR

(

s

)

Tag list item for string with If-Modified-Since header value.

The HTTPTAG_IF_MODIFIED_SINCE_STR() macro is used to include a tag item with a string containing value of a http_if_modified_since_t header in a tag list.

Parameters:

s

pointer to a string containing http_if_modified_since_t value, or NULL.

The HTTPTAG_IF_MODIFIED_SINCE_STR string can be converted to a http_if_modified_since_t header structure by giving the string s has second argument to function http_if_modified_since_make().

---

Typedef Documentation

typedef struct http_if_modified_since_s http_if_modified_since_t

The structure http_if_modified_since_t contains representation of If-Modified-Since header.

The http_if_modified_since_t is defined as follows:

 typedef struct {
   msg_common_t    d_common[1];        // Common fragment info
   msg_error_t    *d_next;             // Link to next (dummy)
   http_time_t     d_time;             // Seconds since Jan 1, 1900
 } http_if_modified_since_t;

---

Enumeration Type Documentation

anonymous enum

Enumerator:

http_if_modified_since_hash

Hash of If-Modified-Since header.

---

Function Documentation

http_if_modified_since_t * http_if_modified_since_copy	(	su_home_t *	home,
		http_if_modified_since_t const *	hdr
	)			[inline]

Copy a http_if_modified_since_t header structure.

The function http_if_modified_since_copy() copies a header structure hdr. If the header structure hdr contains a reference (hdr->h_next) to a list of headers, all the headers in that list are copied, too. The function uses given memory home to allocate all the memory areas used to copy the header structure hdr.

Parameters:

	home	memory home used to allocate new structure
	hdr	pointer to the header structure to be duplicated

When copying, only the header structure and parameter lists attached to it are duplicated. The new header structure retains all the references to the strings within the old header, including the encoding of the old header, if present.

Example

   if_modified_since = http_if_modified_since_copy(home, http->http_if_modified_since);

Returns:

The function http_if_modified_since_copy() returns a pointer to newly copied header structure, or NULL upon an error.

http_if_modified_since_t * http_if_modified_since_dup	(	su_home_t *	home,
		http_if_modified_since_t const *	hdr
	)			[inline]

Duplicate (deep copy) http_if_modified_since_t.

The function http_if_modified_since_dup() duplicates a header structure hdr. If the header structure hdr contains a reference (hdr->x_next) to a list of headers, all the headers in the list are duplicated, too.

Parameters:

	home	memory home used to allocate new structure
	hdr	header structure to be duplicated

When duplicating, all parameter lists and non-constant strings attached to the header are copied, too. The function uses given memory home to allocate all the memory areas used to copy the header.

Example

   if_modified_since = http_if_modified_since_dup(home, http->http_if_modified_since);

Returns:

The function http_if_modified_since_dup() returns a pointer to the newly duplicated http_if_modified_since_t header structure, or NULL upon an error.

http_if_modified_since_t * http_if_modified_since_format	(	su_home_t *	home,
		char const *	fmt,
			...
	)			[inline]

Make a If-Modified-Since header from formatting result.

The function http_if_modified_since_format() makes a new If-Modified-Since header object using formatting result as its value. The function first prints the arguments according to the format fmt specified. Then it allocates a new header structure, and uses the formatting result as the header value.

Parameters:

	home	memory home used to allocate new header structure.
	fmt	string used as a printf()-style format
	...	argument list for format

Note:

This function is usually implemented as a macro calling msg_header_format().

Returns:

The function http_if_modified_since_format() returns a pointer to newly makes header structure, or NULL upon an error.

http_if_modified_since_t* http_if_modified_since_init

(

http_if_modified_since_t

x[1]

)

[inline]

Initialize a structure http_if_modified_since_t.

An http_if_modified_since_t structure can be initialized with the http_if_modified_since_init() function/macro. For instance,

  http_if_modified_since_t http_if_modified_since;

  http_if_modified_since_init(&http_if_modified_since);

http_if_modified_since_t * http_if_modified_since_make	(	su_home_t *	home,
		char const *	s
	)			[inline]

Make a header structure http_if_modified_since_t.

The function http_if_modified_since_make() makes a new http_if_modified_since_t header structure. It allocates a new header structure, and decodes the string s as the value of the structure.

Parameters:

	home	memory home used to allocate new header structure.
	s	string to be decoded as value of the new header structure

Note:

This function is usually implemented as a macro calling http_header_make().

Returns:

The function http_if_modified_since_make() returns a pointer to newly maked http_if_modified_since_t header structure, or NULL upon an error.

int http_is_if_modified_since

(

http_header_t const *

header

)

[inline]

Test if header object is instance of http_if_modified_since_t.

The function http_is_if_modified_since() returns true (nonzero) if the header class is an instance of If-Modified-Since header object and false (zero) otherwise.

Parameters:

header

pointer to the header structure to be tested

Returns:

The function http_is_xif_modified_since() returns true (nonzero) if the header object is an instance of header if_modified_since and false (zero) otherwise.

---

Variable Documentation

msg_hclass_t http_if_modified_since_class[]

Header class for HTTP If-Modified-Since header.

The header class http_if_modified_since_class defines how a HTTP If-Modified-Since header is parsed and printed. It also contains methods used by HTTP parser and other functions to manipulate the http_if_modified_since_t header structure.