129 lines
3.4 KiB
C
129 lines
3.4 KiB
C
#ifndef CACHE_H
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#define CACHE_H
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/**
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* \file cache.h
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* \brief cache related structures and functions
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* \details
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* - We store the metadata and the actual data separately in two
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* separate folders.
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*/
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#include <pthread.h>
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/**
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* \brief cache data type
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*/
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typedef struct Cache Cache;
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#include "link.h"
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/**
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* \brief Type definition for a cache segment
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*/
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typedef uint8_t Seg;
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/**
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* \brief cache data type in-memory data structure
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*/
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struct Cache {
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char *path; /**< the path to the file on the web server */
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Link *link; /**< the Link associated with this cache data set */
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long time; /**<the modified time of the file */
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off_t content_length; /**<the size of the file */
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pthread_t bgt; /**< background download pthread */
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pthread_mutex_t bgt_lock; /**< mutex for the background download thread */
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pthread_mutexattr_t bgt_lock_attr; /**< attributes for bgt_lock */
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off_t next_offset; /**<the offset of the next segment to be
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downloaded in background*/
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pthread_mutex_t rw_lock; /**< mutex for read/write operation */
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pthread_mutexattr_t rw_lock_attr; /**< attributes for rw_lock */
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FILE *dfp; /**< The FILE pointer for the data file*/
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FILE *mfp; /**< The FILE pointer for the metadata */
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int blksz; /**<the block size of the data file */
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long segbc; /**<segment array byte count */
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Seg *seg; /**< the detail of each segment */
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};
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/**
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* \brief whether the cache system is enabled
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*/
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extern int CACHE_SYSTEM_INIT;
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/**
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* \brief The size of each download segment
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*/
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extern int DATA_BLK_SZ;
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/**
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* \brief The maximum segment count for a single cache file
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*/
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extern int MAX_SEGBC;
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/**
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* \brief initialise the cache system directories
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* \details This function basically sets up the following variables:
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* - META_DIR
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* - DATA_DIR
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*
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* If these directories do not exist, they will be created.
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* \note Called by parse_arg_list(), verified to be working
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*/
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void CacheSystem_init(const char *path, int path_supplied);
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/**
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* \brief Create directories under the cache directory structure, if they do
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* not already exist
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* \return
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* - -1 failed to create metadata directory.
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* - -2 failed to create data directory.
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* - -3 failed to create both metadata and data directory.
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* \note Called by LinkTable_new()
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*/
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int CacheDir_create(const char *fn);
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/**
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* \brief open a cache file set
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* \note This function is called by fs_open()
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*/
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Cache *Cache_open(const char *fn);
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/**
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* \brief Close a cache data structure
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* \note This function is called by fs_release()
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*/
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void Cache_close(Cache *cf);
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/**
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* \brief create a cache file set if it doesn't exist already
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* \return
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* - 0, if the cache file already exists, or was created successfully.
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* - -1, otherwise
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* \note Called by fs_open()
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*/
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int Cache_create(Link *this_link);
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/**
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* \brief delete a cache file set
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* \note Called by fs_open()
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*/
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void Cache_delete(const char *fn);
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/**
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* \brief Intelligently read from the cache system
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* \details If the segment does not exist on the local hard disk, download from
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* the Internet
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* \param[in] cf the cache in-memory data structure
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* \param[out] output_buf the output buffer
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* \param[in] len the requested segment size
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* \param[in] offset the start of the segment
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* \return the length of the segment the cache system managed to obtain.
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* \note Called by fs_read(), verified to be working
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*/
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long Cache_read(Cache *cf, char *output_buf, off_t len, off_t offset);
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#endif
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