#include <HTTPCacheTable.h>

Collaboration diagram for libdap::HTTPCacheTable:

Classes
struct	CacheEntry

Public Types
using	CacheEntries = std::vector<CacheEntry *>

using	CacheTable = std::vector<CacheEntries>

Public Member Functions
void	delete_by_hits (int hits)
	Delete all the entries in the cache that have fewer than `hits` hits.

void	delete_by_size (unsigned long size)
	Delete all the entries in the cache that are larger than `size` bytes.

void	delete_expired_entries (time_t time=0)
	Delete all the expired entries in the cache.

unsigned int	get_block_size () const

std::string	get_cache_root () const

unsigned long	get_current_size () const

int	get_new_entries () const

	HTTPCacheTable ()=delete

	HTTPCacheTable (const HTTPCacheTable &)=delete

	HTTPCacheTable (const std::string &cache_root, int block_size)

void	increment_new_entries ()

HTTPCacheTable &	operator= (const HTTPCacheTable &)=delete

void	set_block_size (unsigned int sz)

void	set_cache_root (const std::string &cr)

void	set_current_size (unsigned long sz)

virtual	~HTTPCacheTable ()

Friends
class	HTTPCacheTest

Methods to manipulate instances of CacheEntry.
void	delete_all_entries ()

void	add_entry_to_cache_table (CacheEntry *entry)

void	remove_entry_from_cache_table (const std::string &url)

CacheEntry *	get_read_locked_entry_from_cache_table (const std::string &url)

CacheEntry *	get_write_locked_entry_from_cache_table (const std::string &url)

void	calculate_time (HTTPCacheTable::CacheEntry *entry, int default_expiration, time_t request_time)

void	parse_headers (HTTPCacheTable::CacheEntry *entry, unsigned long max_entry_size, const std::vector< std::string > &headers)

void	bind_entry_to_data (CacheEntry entry, FILE body)

void	uncouple_entry_from_data (FILE *body)

bool	is_locked_read_responses () const

Cache Index
These methods manage the cache's index file. Each cache holds an index file named .index which stores the cache's state information.
void	create_location (CacheEntry *entry)

void	cache_index_write ()

Detailed Description

The table of entries in the client-side cache. This class maintains a table of CacheEntries, where one instance of CacheEntry is made for each item in the cache. When an item is accessed it is either locked for reading or writing. When locked for reading the entry is recorded on a list of read-locked entries. The caller must explicitly free the entry for it to be removed from this list (which is the only way it can be opened for writing). An entry can be accessed by multiple readers but only one writer.

Note: The CacheEntry class used to contain a lock that was used to ensure that the entry was locked during any changes to any of its fields. That has been removed - its now the responsibility of the caller. This change was made because it's likely the caller will need to lock all of the methods that operate on a CacheEntry anyway, so the CacheEntry-specific lock was redundant.

Definition at line 66 of file HTTPCacheTable.h.

Member Typedef Documentation

◆ CacheEntries

using libdap::HTTPCacheTable::CacheEntries = std::vector<CacheEntry *>

Definition at line 178 of file HTTPCacheTable.h.

◆ CacheTable

using libdap::HTTPCacheTable::CacheTable = std::vector<CacheEntries>

Definition at line 179 of file HTTPCacheTable.h.

Constructor & Destructor Documentation

◆ HTTPCacheTable() [1/3]

libdap::HTTPCacheTable::HTTPCacheTable	(	const std::string &	cache_root,
		int	block_size )

Definition at line 65 of file HTTPCacheTable.cc.

◆ HTTPCacheTable() [2/3]

libdap::HTTPCacheTable::HTTPCacheTable ( const HTTPCacheTable & )

delete

◆ HTTPCacheTable() [3/3]

libdap::HTTPCacheTable::HTTPCacheTable ( )

delete

◆ ~HTTPCacheTable()

libdap::HTTPCacheTable::~HTTPCacheTable ( )

virtual

Definition at line 74 of file HTTPCacheTable.cc.

Member Function Documentation

◆ add_entry_to_cache_table()

void libdap::HTTPCacheTable::add_entry_to_cache_table ( CacheEntry * entry )

Add a CacheEntry to the cache table. As each entry is read, load it into the in-memory cache table and update the HTTPCache's current_size. The later is used by the garbage collection method.

Parameters

entry The CacheEntry instance to add.

Definition at line 380 of file HTTPCacheTable.cc.

◆ bind_entry_to_data()

void libdap::HTTPCacheTable::bind_entry_to_data	(	HTTPCacheTable::CacheEntry *	entry,
		FILE *	body )

Definition at line 622 of file HTTPCacheTable.cc.

◆ cache_index_write()

void libdap::HTTPCacheTable::cache_index_write ( )

Walk through the list of cached objects and write the cache index file to disk. If the file does not exist, it is created. If the file does exist, it is overwritten. As a side effect, zero the new_entries counter.

A private method.

Exceptions

Error Thrown if the index file cannot be opened for writing.

Note: The HTTPCache destructor calls this method and silently ignores this exception.

Definition at line 260 of file HTTPCacheTable.cc.

◆ calculate_time()

void libdap::HTTPCacheTable::calculate_time	(	HTTPCacheTable::CacheEntry *	entry,
		int	default_expiration,
		time_t	request_time )

Calculate the corrected_initial_age of the object. We use the time when this function is called as the response_time as this is when we have received the complete response. This may cause a delay if the response header is very big but should not cause any incorrect behavior.

A private method.

Parameters

entry	The CacheEntry object.
default_expiration	The default value of the cached object's expiration time.
request_time	When was the request made? I think this value must be passed into the method that calls this method...

Definition at line 530 of file HTTPCacheTable.cc.

◆ create_location()

void libdap::HTTPCacheTable::create_location ( HTTPCacheTable::CacheEntry * entry )

Create the directory for this url (using the hash value from get_hash()) and a file within that directory to hold the response's information. The cache name and cache_body_fd fields of entry are updated.

mkstemp opens the file it creates, which is a good thing but it makes tracking resources hard for the HTTPCache object (because an exception might cause a file descriptor resource leak). So I close that file descriptor here.

A private method.

Parameters

entry The cache entry object to operate on.

Exceptions

Error If the file for the response's body cannot be created.

Definition at line 339 of file HTTPCacheTable.cc.

◆ delete_all_entries()

void libdap::HTTPCacheTable::delete_all_entries ( )

Definition at line 501 of file HTTPCacheTable.cc.

◆ delete_by_hits()

void libdap::HTTPCacheTable::delete_by_hits ( int hits )

Delete all the entries in the cache that have fewer than hits hits.

Parameters

hits

Definition at line 111 of file HTTPCacheTable.cc.

◆ delete_by_size()

void libdap::HTTPCacheTable::delete_by_size ( unsigned long size )

Delete all the entries in the cache that are larger than size bytes.

Parameters

size

Definition at line 131 of file HTTPCacheTable.cc.

◆ delete_expired_entries()

void libdap::HTTPCacheTable::delete_expired_entries ( time_t t = 0 )

Delete all the expired entries in the cache.

Parameters

t	Time to use as the base for the expiration check. If 0, use Now.

Definition at line 87 of file HTTPCacheTable.cc.

◆ get_block_size()

unsigned int libdap::HTTPCacheTable::get_block_size ( ) const

inline

Definition at line 215 of file HTTPCacheTable.h.

◆ get_cache_root()

std::string libdap::HTTPCacheTable::get_cache_root ( ) const

inline

Definition at line 223 of file HTTPCacheTable.h.

◆ get_current_size()

unsigned long libdap::HTTPCacheTable::get_current_size ( ) const

inline

Definition at line 211 of file HTTPCacheTable.h.

◆ get_new_entries()

int libdap::HTTPCacheTable::get_new_entries ( ) const

inline

Definition at line 219 of file HTTPCacheTable.h.

◆ get_read_locked_entry_from_cache_table()

HTTPCacheTable::CacheEntry * libdap::HTTPCacheTable::get_read_locked_entry_from_cache_table ( const std::string & url )

Get a pointer to a CacheEntry from the cache table.

Parameters

url	Look for this URL.

Definition at line 400 of file HTTPCacheTable.cc.

◆ get_write_locked_entry_from_cache_table()

HTTPCacheTable::CacheEntry * libdap::HTTPCacheTable::get_write_locked_entry_from_cache_table ( const std::string & url )

Get a pointer to a CacheEntry from the cache table. Providing a way to pass the hash code into this method makes it easier to test for correct behavior when two entries collide. 10/07/02 jhrg

Note: The caller must unlock the entry when it is done with it.

Parameters

url	Look for this URL.

Returns: The matching CacheEntry instance or NULL if none was found.

Definition at line 441 of file HTTPCacheTable.cc.

◆ increment_new_entries()

void libdap::HTTPCacheTable::increment_new_entries ( )

inline

Definition at line 221 of file HTTPCacheTable.h.

◆ is_locked_read_responses()

bool libdap::HTTPCacheTable::is_locked_read_responses ( ) const

Definition at line 639 of file HTTPCacheTable.cc.

◆ operator=()

HTTPCacheTable & libdap::HTTPCacheTable::operator= ( const HTTPCacheTable & )

delete

◆ parse_headers()

void libdap::HTTPCacheTable::parse_headers	(	HTTPCacheTable::CacheEntry *	entry,
		unsigned long	max_entry_size,
		const std::vector< std::string > &	headers )

Parse various headers from the vector (which can be retrieved from libcurl once a response is received) and load the CacheEntry object with values. This method should only be called with headers from a response (it should not be used to parse request headers).

A private method.

Parameters

entry	Store values from the headers here.
max_entry_size	DO not cache entries larger than this.
headers	A vector of header lines.

Definition at line 569 of file HTTPCacheTable.cc.

◆ remove_entry_from_cache_table()

void libdap::HTTPCacheTable::remove_entry_from_cache_table ( const std::string & url )

Find the CacheEntry for the given url and remove both its information in the persistent store and the entry in d_cache_table. If url is not in the cache, this method does nothing.

Parameters

url	Remove this URL's entry.

Exceptions

InternalErr Thrown if the CacheEntry for url is locked.

Definition at line 485 of file HTTPCacheTable.cc.

◆ set_block_size()

void libdap::HTTPCacheTable::set_block_size ( unsigned int sz )

inline

Definition at line 217 of file HTTPCacheTable.h.

◆ set_cache_root()

void libdap::HTTPCacheTable::set_cache_root ( const std::string & cr )

inline

Definition at line 225 of file HTTPCacheTable.h.

◆ set_current_size()

void libdap::HTTPCacheTable::set_current_size ( unsigned long sz )

inline

Definition at line 213 of file HTTPCacheTable.h.

◆ uncouple_entry_from_data()

void libdap::HTTPCacheTable::uncouple_entry_from_data ( FILE * body )

Definition at line 627 of file HTTPCacheTable.cc.

Friends And Related Symbol Documentation

◆ HTTPCacheTest

friend class HTTPCacheTest

friend

Definition at line 181 of file HTTPCacheTable.h.

The documentation for this class was generated from the following files:

Classes

Public Types

Public Member Functions

Friends

Methods to manipulate instances of CacheEntry.

Cache Index

Detailed Description

Member Typedef Documentation

◆ CacheEntries

◆ CacheTable

Constructor & Destructor Documentation

◆ HTTPCacheTable() [1/3]

◆ HTTPCacheTable() [2/3]

◆ HTTPCacheTable() [3/3]

◆ ~HTTPCacheTable()

Member Function Documentation

◆ add_entry_to_cache_table()

◆ bind_entry_to_data()

◆ cache_index_write()

◆ calculate_time()

◆ create_location()

◆ delete_all_entries()

◆ delete_by_hits()

◆ delete_by_size()

◆ delete_expired_entries()

◆ get_block_size()

◆ get_cache_root()

◆ get_current_size()

◆ get_new_entries()

◆ get_read_locked_entry_from_cache_table()

◆ get_write_locked_entry_from_cache_table()

◆ increment_new_entries()

◆ is_locked_read_responses()

◆ operator=()

◆ parse_headers()

◆ remove_entry_from_cache_table()

◆ set_block_size()

◆ set_cache_root()

◆ set_current_size()

◆ uncouple_entry_from_data()

Friends And Related Symbol Documentation

◆ HTTPCacheTest