# DocumentSpec¶

class DocumentSpec

A descriptor that refers to a particular version of a document. This includes the URL of the document and its identity tag and last-modified dates.

The DocumentSpec may also be used to request a newer document than a particular one if available, for instance to refresh a cached document.

Inheritance diagram

enum CacheControl
enumerator CC_allow_cache = 0
enumerator CC_revalidate = 1
enumerator CC_no_cache = 2
enum RequestMode
enumerator RM_any = 0
enumerator RM_equal = 1
enumerator RM_newer = 2
enumerator RM_equal_or_newer = 3
DocumentSpec(void)
DocumentSpec(std::string const &url)
DocumentSpec(URLSpec const &url)
DocumentSpec(DocumentSpec const &copy)
void clear_date(void)

Removes the last-modified date associated with the DocumentSpec, if there is one.

void clear_tag(void)

Removes the identity tag associated with the DocumentSpec, if there is one.

int compare_to(DocumentSpec const &other) const
CacheControl get_cache_control(void) const

Returns the request mode of this DocumentSpec. See set_cache_control().

HTTPDate const &get_date(void) const

Returns the last-modified date associated with the DocumentSpec, if there is one. It is an error to call this if has_date() returns false.

RequestMode get_request_mode(void) const

Returns the request mode of this DocumentSpec. See set_request_mode().

HTTPEntityTag const &get_tag(void) const

Returns the identity tag associated with the DocumentSpec, if there is one. It is an error to call this if has_tag() returns false.

The identity tag is set by the HTTP server to uniquely refer to a particular version of a document.

URLSpec const &get_url(void) const

Retrieves the URL of the DocumentSpec.

bool has_date(void) const

Returns true if a last-modified date is associated with the DocumentSpec.

bool has_tag(void) const

Returns true if an identity tag is associated with the DocumentSpec.

bool input(std::istream &in)

Can be used to read in the DocumentSpec from a stream generated either by output() or write(). Returns true on success, false on failure.

void output(std::ostream &out) const
void set_cache_control(DocumentSpec::CacheControl cache_control)

Specifies what kind of cached value is acceptable for this document. Warning: some HTTP proxies may not respect this setting and may return a cached result anyway.

CC_allow_cache: the normal HTTP behavior; the server may return a cached value if it believes it is valid.

CC_revalidate: a proxy is forced to contact the origin server and verify that is cached value is in fact still valid before it returns it.

CC_no_cache: a proxy must not return its cached value at all, but is forced to go all the way back to the origin server for the official document.

The default mode is CC_allow_cache.

void set_date(HTTPDate const &date)

Changes the last-modified date associated with the DocumentSpec.

void set_request_mode(DocumentSpec::RequestMode request_mode)

Sets the request mode of this DocumentSpec. This is only relevant when using the DocumentSpec to generate a request (for instance, in HTTPChannel). This specifies whether the document request will ask the server for a newer version than the indicated version, or the exact version, neither, or either.

The possible values are:

RM_any: ignore date and tag (if specified), and retrieve any document that matches the URL. For a subrange request, if the document matches the version indicated exactly, retrieve the subrange only; otherwise, retrieve the entire document.

RM_equal: request only the precise version of the document that matches the particular date and/or tag exactly, if specified; fail if this version is not available.

RM_newer: request any document that is newer than the version indicated by the particular date and/or tag; fail if only that version (or older versions) are available.

RM_newer_or_equal: request any document that matches the version indicated by the particular date and/or tag, or is a newer version; fail if only older versions are available.

In any of the above, you may specify either or both of the last-modified date and the identity tag, whichever is known to the client.

The default mode is RM_any.

void set_tag(HTTPEntityTag const &tag)

Changes the identity tag associated with the DocumentSpec.

void set_url(URLSpec const &url)

Changes the URL of the DocumentSpec without modifying its other properties. Normally this would be a strange thing to do, because the tag and date are usually strongly associated with the URL. To get a DocumentSpec pointing to a new URL, you would normally create a new DocumentSpec object.

void write(std::ostream &out, int indent_level = 0) const