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httpdirfs/src/cache.c

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#include "cache.h"
#include "config.h"
#include "log.h"
#include "util.h"
#include <sys/stat.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
/*
* ---------------- External variables -----------------------
*/
int CACHE_SYSTEM_INIT = 0;
char *META_DIR;
/*
* ----------------- Static variables -----------------------
*/
/**
* \brief Cache file locking
* \details Ensure cache opening and cache closing is an atomic operation
*/
static pthread_mutex_t cf_lock;
/**
* \brief The data directory
*/
static char *DATA_DIR;
/**
* \brief Calculate cache system directory path
*/
static char *CacheSystem_calc_dir(const char *url)
{
char *xdg_cache_home = getenv("XDG_CACHE_HOME");
if (!xdg_cache_home) {
char *home = getenv("HOME");
char *xdg_cache_home_default = "/.cache";
xdg_cache_home = path_append(home, xdg_cache_home_default);
}
if (mkdir
(xdg_cache_home, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
char *cache_dir_root = path_append(xdg_cache_home, "/httpdirfs/");
if (mkdir
(cache_dir_root, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
char *fn = path_append(cache_dir_root, "/CACHEDIR.TAG");
FILE *fp = fopen(fn, "w");
if (fp) {
fprintf(fp, "Signature: 8a477f597d28d172789f06886806bc55\n\
# This file is a cache directory tag created by httpdirfs.\n\
# For information about cache directory tags, see:\n\
# http://www.brynosaurus.com/cachedir/\n");
} else {
lprintf(fatal, "fopen(%s): %s", fn, strerror(errno));
}
if (ferror(fp)) {
lprintf(fatal, "fwrite(): encountered error!\n");
}
if (fclose(fp)) {
lprintf(fatal, "fclose(%s): %s\n", fn, strerror(errno));
}
CURL *c = curl_easy_init();
char *escaped_url = curl_easy_escape(c, url, 0);
char *full_path = path_append(cache_dir_root, escaped_url);
if (mkdir(full_path, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
FREE(fn);
FREE(cache_dir_root);
curl_free(escaped_url);
curl_easy_cleanup(c);
return full_path;
}
void CacheSystem_init(const char *path, int url_supplied)
{
lprintf(cache_lock_debug,
"thread %x: initialise cf_lock;\n", pthread_self());
if (pthread_mutex_init(&cf_lock, NULL)) {
lprintf(fatal, "cf_lock initialisation failed!\n");
}
if (url_supplied) {
path = CacheSystem_calc_dir(path);
}
lprintf(debug, "%s\n", path);
META_DIR = path_append(path, "meta/");
DATA_DIR = path_append(path, "data/");
/*
* Check if directories exist, if not, create them
*/
if (mkdir(META_DIR, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
if (mkdir(DATA_DIR, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
if (CONFIG.mode == SONIC) {
char *sonic_path;
/*
* Create "rest" sub-directory for META_DIR
*/
sonic_path = path_append(META_DIR, "rest/");
if (mkdir
(sonic_path, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
FREE(sonic_path);
/*
* Create "rest" sub-directory for DATA_DIR
*/
sonic_path = path_append(DATA_DIR, "rest/");
if (mkdir
(sonic_path, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH)
&& (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
FREE(sonic_path);
}
CACHE_SYSTEM_INIT = 1;
}
/**
* \brief read a metadata file
* \return 0 on success, errno on error.
*/
static int Meta_read(Cache *cf)
{
FILE *fp = cf->mfp;
rewind(fp);
int nmemb = 0;
if (!fp) {
/*
* The metadata file does not exist
*/
lprintf(error, "fopen(): %s\n", strerror(errno));
return EIO;
}
if (sizeof(long) != fread(&cf->time, sizeof(long), 1, fp) ||
sizeof(off_t) != fread(&cf->content_length, sizeof(off_t), 1, fp) ||
sizeof(int) != fread(&cf->blksz, sizeof(int), 1, fp) ||
sizeof(long) != fread(&cf->segbc, sizeof(long), 1, fp) ||
ferror(fp)) {
lprintf(error, "error reading core metadata!\n");
return EIO;
}
/* These things really should not be zero!!! */
if (!cf->content_length || !cf->blksz || !cf->segbc) {
lprintf(error,
"corruption: content_length: %ld, blksz: %d, segbc: %ld\n",
cf->content_length, cf->blksz, cf->segbc);
return EBADMSG;
}
if (cf->blksz != CONFIG.data_blksz) {
lprintf(warning, "Warning: cf->blksz != CONFIG.data_blksz\n");
}
if (cf->segbc > CONFIG.max_segbc) {
lprintf(error, "Error: segbc: %ld\n", cf->segbc);
return EFBIG;
}
/*
* Allocate memory for all segments, and read them in
*/
cf->seg = CALLOC(cf->segbc, sizeof(Seg));
nmemb = fread(cf->seg, sizeof(Seg), cf->segbc, fp);
/*
* We shouldn't have gone past the end of the file
*/
if (feof(fp)) {
/*
* reached EOF
*/
lprintf(error, "attempted to read past the end of the \
file!\n");
return EBADMSG;
}
/*
* Error checking for fread
*/
if (ferror(fp)) {
lprintf(error, "error reading bitmap!\n");
return EIO;
}
/*
* Check for inconsistent metadata file
*/
if (nmemb != cf->segbc) {
lprintf(error, "corrupted metadata!\n");
return EBADMSG;
}
return 0;
}
/**
* \brief write a metadata file
* \return
* - -1 on error,
* - 0 on success
*/
static int Meta_write(Cache *cf)
{
FILE *fp = cf->mfp;
rewind(fp);
if (!fp) {
/*
* Cannot create the metadata file
*/
lprintf(error, "fopen(): %s\n", strerror(errno));
return -1;
}
/*
* These things really should not be zero!!!
*/
if (!cf->content_length || !cf->blksz || !cf->segbc) {
lprintf(error, "content_length: %ld, blksz: %d, segbc: %ld\n",
cf->content_length, cf->blksz, cf->segbc);
}
fwrite(&cf->time, sizeof(long), 1, fp);
fwrite(&cf->content_length, sizeof(off_t), 1, fp);
fwrite(&cf->blksz, sizeof(int), 1, fp);
fwrite(&cf->segbc, sizeof(long), 1, fp);
fwrite(cf->seg, sizeof(Seg), cf->segbc, fp);
/*
* Error checking for fwrite
*/
if (ferror(fp)) {
lprintf(error, "fwrite(): encountered error!\n");
return -1;
}
return 0;
}
/**
* \brief create a data file
* \details We use sparse creation here
* \return exit on failure
*/
static void Data_create(Cache *cf)
{
int fd;
int mode;
mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH;
char *datafn = path_append(DATA_DIR, cf->path);
fd = open(datafn, O_WRONLY | O_CREAT, mode);
FREE(datafn);
if (fd == -1) {
lprintf(fatal, "open(): %s\n", strerror(errno));
}
if (ftruncate(fd, cf->content_length)) {
lprintf(warning, "ftruncate(): %s\n", strerror(errno));
}
if (close(fd)) {
lprintf(fatal, "close:(): %s\n", strerror(errno));
}
}
/**
* \brief obtain the data file size
* \return file size on success, -1 on error
*/
static long Data_size(const char *fn)
{
char *datafn = path_append(DATA_DIR, fn);
struct stat st;
int s = stat(datafn, &st);
FREE(datafn);
if (!s) {
return st.st_size;
}
lprintf(error, "stat(): %s\n", strerror(errno));
return -1;
}
/**
* \brief read a data file
* \param[in] cf the pointer to the cache in-memory data structure
* \param[out] buf the output buffer
* \param[in] len the length of the segment
* \param[in] offset the offset of the segment
* \return
* - negative values on error,
* - otherwise, the number of bytes read.
*/
static long Data_read(Cache *cf, uint8_t *buf, off_t len, off_t offset)
{
if (len == 0) {
lprintf(error, "requested to read 0 byte!\n");
return -EINVAL;
}
lprintf(cache_lock_debug,
"thread %x: locking seek_lock;\n", pthread_self());
PTHREAD_MUTEX_LOCK(&cf->seek_lock);
long byte_read = 0;
/*
* Seek to the right location
*/
if (fseeko(cf->dfp, offset, SEEK_SET)) {
/*
* fseeko failed
*/
lprintf(error, "fseeko(): %s\n", strerror(errno));
byte_read = -EIO;
goto end;
}
/*
* Calculate how much to read
*/
if (offset + len > cf->content_length) {
len -= offset + len - cf->content_length;
if (len < 0) {
goto end;
}
}
byte_read = fread(buf, sizeof(uint8_t), len, cf->dfp);
if (byte_read != len) {
lprintf(debug,
"fread(): requested %ld, returned %ld!\n", len, byte_read);
if (feof(cf->dfp)) {
/*
* reached EOF
*/
lprintf(error, "fread(): reached the end of the file!\n");
}
if (ferror(cf->dfp)) {
/*
* filesystem error
*/
lprintf(error, "fread(): encountered error!\n");
}
}
end:
lprintf(cache_lock_debug,
"thread %x: unlocking seek_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->seek_lock);
return byte_read;
}
/**
* \brief write to a data file
* \param[in] cf the pointer to the cache in-memory data structure
* \param[in] buf the input buffer
* \param[in] len the length of the segment
* \param[in] offset the offset of the segment
* \return
* - -1 when the data file does not exist
* - otherwise, the number of bytes written.
*/
static long Data_write(Cache *cf, const uint8_t *buf, off_t len,
off_t offset)
{
if (len == 0) {
/*
* We should permit empty files
*/
return 0;
}
lprintf(cache_lock_debug,
"thread %x: locking seek_lock;\n", pthread_self());
PTHREAD_MUTEX_LOCK(&cf->seek_lock);
long byte_written = 0;
if (fseeko(cf->dfp, offset, SEEK_SET)) {
/*
* fseeko failed
*/
lprintf(error, "fseeko(): %s\n", strerror(errno));
byte_written = -EIO;
goto end;
}
byte_written = fwrite(buf, sizeof(uint8_t), len, cf->dfp);
if (byte_written != len) {
lprintf(error,
"fwrite(): requested %ld, returned %ld!\n",
len, byte_written);
}
if (ferror(cf->dfp)) {
/*
* filesystem error
*/
lprintf(error, "fwrite(): encountered error!\n");
}
end:
lprintf(cache_lock_debug,
"thread %x: unlocking seek_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->seek_lock);
return byte_written;
}
int CacheDir_create(const char *dirn)
{
char *metadirn = path_append(META_DIR, dirn);
char *datadirn = path_append(DATA_DIR, dirn);
int i;
i = -mkdir(metadirn, S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH);
if (i && (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
i |= -mkdir(datadirn,
S_IRWXU | S_IRGRP | S_IXGRP | S_IROTH | S_IXOTH) << 1;
if (i && (errno != EEXIST)) {
lprintf(fatal, "mkdir(): %s\n", strerror(errno));
}
FREE(datadirn);
FREE(metadirn);
return -i;
}
/**
* \brief Allocate a new cache data structure
*/
static Cache *Cache_alloc()
{
Cache *cf = CALLOC(1, sizeof(Cache));
if (pthread_mutex_init(&cf->seek_lock, NULL)) {
lprintf(fatal, "seek_lock initialisation failed!\n");
}
if (pthread_mutex_init(&cf->w_lock, NULL)) {
lprintf(fatal, "w_lock initialisation failed!\n");
}
if (pthread_mutexattr_init(&cf->bgt_lock_attr)) {
lprintf(fatal, "bgt_lock_attr initialisation failed!\n");
}
if (pthread_mutexattr_setpshared(&cf->bgt_lock_attr,
PTHREAD_PROCESS_SHARED)) {
lprintf(fatal, "could not set bgt_lock_attr!\n");
}
if (pthread_mutex_init(&cf->bgt_lock, &cf->bgt_lock_attr)) {
lprintf(fatal, "bgt_lock initialisation failed!\n");
}
return cf;
}
/**
* \brief free a cache data structure
*/
static void Cache_free(Cache *cf)
{
if (pthread_mutex_destroy(&cf->seek_lock)) {
lprintf(fatal, "could not destroy seek_lock!\n");
}
if (pthread_mutex_destroy(&cf->w_lock)) {
lprintf(fatal, "could not destroy w_lock!\n");
}
if (pthread_mutex_destroy(&cf->bgt_lock)) {
lprintf(fatal, "could not destroy bgt_lock!\n");
}
if (pthread_mutexattr_destroy(&cf->bgt_lock_attr)) {
lprintf(fatal, "could not destroy bgt_lock_attr!\n");
}
if (cf->path) {
FREE(cf->path);
}
if (cf->seg) {
FREE(cf->seg);
}
if (cf->fs_path) {
FREE(cf->fs_path);
}
FREE(cf);
}
/**
* \brief Check if both metadata and data file exist, otherwise perform cleanup.
* \details
* This function checks if both metadata file and the data file exist. If that
* is not the case, clean up is performed - the existing unpaired metadata file
* or data file is deleted.
* \return
* - 0, if both metadata and cache file exist
* - -1, otherwise
*/
static int Cache_exist(const char *fn)
{
char *metafn = path_append(META_DIR, fn);
char *datafn = path_append(DATA_DIR, fn);
/*
* access() returns 0 on success
*/
int no_meta = access(metafn, F_OK);
int no_data = access(datafn, F_OK);
if (no_meta ^ no_data) {
if (no_meta) {
lprintf(warning, "Cache file partially missing.\n");
if (unlink(datafn)) {
lprintf(error, "unlink(): %s\n", strerror(errno));
}
}
if (no_data) {
if (unlink(metafn)) {
lprintf(error, "unlink(): %s\n", strerror(errno));
}
}
}
FREE(metafn);
FREE(datafn);
return no_meta | no_data;
}
/**
* \brief delete a cache file set
*/
void Cache_delete(const char *fn)
{
if (CONFIG.mode == SONIC) {
Link *link = path_to_Link(fn);
fn = link->sonic.id;
}
char *metafn = path_append(META_DIR, fn);
char *datafn = path_append(DATA_DIR, fn);
if (!access(metafn, F_OK)) {
if (unlink(metafn)) {
lprintf(error, "unlink(): %s\n", strerror(errno));
}
}
if (!access(datafn, F_OK)) {
if (unlink(datafn)) {
lprintf(error, "unlink(): %s\n", strerror(errno));
}
}
FREE(metafn);
FREE(datafn);
}
/**
* \brief Open the data file of a cache data set
* \return
* - 0 on success
* - -1 on failure, with appropriate errno set.
*/
static int Data_open(Cache *cf)
{
char *datafn = path_append(DATA_DIR, cf->path);
cf->dfp = fopen(datafn, "r+");
if (!cf->dfp) {
/*
* Failed to open the data file
*/
lprintf(error, "fopen(%s): %s\n", datafn, strerror(errno));
FREE(datafn);
return -1;
}
FREE(datafn);
return 0;
}
/**
* \brief Open a metafile
* \return
* - 0 on success
* - -1 on failure, with appropriate errno set.
*/
static int Meta_open(Cache *cf)
{
char *metafn = path_append(META_DIR, cf->path);
cf->mfp = fopen(metafn, "r+");
if (!cf->mfp) {
/*
* Failed to open the data file
*/
lprintf(error, "fopen(%s): %s\n", metafn, strerror(errno));
FREE(metafn);
return -1;
}
FREE(metafn);
return 0;
}
/**
* \brief Create a metafile
* \return exit on error
*/
static void Meta_create(Cache *cf)
{
char *metafn = path_append(META_DIR, cf->path);
cf->mfp = fopen(metafn, "w");
if (!cf->mfp) {
/*
* Failed to open the data file
*/
lprintf(fatal, "fopen(%s): %s\n", metafn, strerror(errno));
}
if (fclose(cf->mfp)) {
lprintf(error,
"cannot close metadata after creation: %s.\n",
strerror(errno));
}
FREE(metafn);
}
int Cache_create(const char *path)
{
Link *this_link = path_to_Link(path);
char *fn = "__UNINITIALISED__";
if (CONFIG.mode == NORMAL) {
fn = curl_easy_unescape(NULL,
this_link->f_url + ROOT_LINK_OFFSET, 0,
NULL);
} else if (CONFIG.mode == SINGLE) {
fn = curl_easy_unescape(NULL, this_link->linkname, 0, NULL);
} else if (CONFIG.mode == SONIC) {
fn = this_link->sonic.id;
} else {
lprintf(fatal, "Invalid CONFIG.mode\n");
}
lprintf(debug, "Creating cache files for %s.\n", fn);
Cache *cf = Cache_alloc();
cf->path = strndup(fn, MAX_PATH_LEN);
cf->time = this_link->time;
cf->content_length = this_link->content_length;
cf->blksz = CONFIG.data_blksz;
cf->segbc = (cf->content_length / cf->blksz) + 1;
cf->seg = CALLOC(cf->segbc, sizeof(Seg));
Meta_create(cf);
if (Meta_open(cf)) {
Cache_free(cf);
lprintf(error, "cannot open metadata file, %s.\n", fn);
}
if (Meta_write(cf)) {
lprintf(error, "Meta_write() failed!\n");
}
if (fclose(cf->mfp)) {
lprintf(error,
"cannot close metadata after write, %s.\n",
strerror(errno));
}
Data_create(cf);
Cache_free(cf);
int res = Cache_exist(fn);
if (CONFIG.mode == NORMAL) {
curl_free(fn);
}
return res;
}
Cache *Cache_open(const char *fn)
{
/*
* Obtain the link structure memory pointer
*/
Link *link = path_to_Link(fn);
if (!link) {
/*
* There is no associated link to the path
*/
return NULL;
}
lprintf(cache_lock_debug,
"thread %x: locking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_LOCK(&cf_lock);
if (link->cache_ptr) {
link->cache_ptr->cache_opened++;
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return link->cache_ptr;
}
/*
* Check if both metadata and data file exist
*/
if (CONFIG.mode == NORMAL || CONFIG.mode == SINGLE) {
if (Cache_exist(fn)) {
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
} else if (CONFIG.mode == SONIC) {
if (Cache_exist(link->sonic.id)) {
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
} else {
lprintf(fatal, "Invalid CONFIG.mode\n");
}
/*
* Create the cache in-memory data structure
*/
Cache *cf = Cache_alloc();
/*
* Fill in the fs_path
*/
cf->fs_path = CALLOC(MAX_PATH_LEN + 1, sizeof(char));
strncpy(cf->fs_path, fn, MAX_PATH_LEN);
/*
* Set the path for the local cache file, if we are in sonic mode
*/
if (CONFIG.mode == SONIC) {
fn = link->sonic.id;
}
cf->path = strndup(fn, MAX_PATH_LEN);
/*
* Associate the cache structure with a link
*/
cf->link = link;
if (Meta_open(cf)) {
Cache_free(cf);
lprintf(error, "cannot open metadata file %s.\n", fn);
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
/*
* Corrupt metadata
*/
if (Meta_read(cf)) {
Cache_free(cf);
lprintf(error, "metadata error: %s.\n", fn);
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
/*
* Inconsistency between metadata and data file, note that on disk file
* size might be bigger than content_length, due to on-disk filesystem
* allocation policy.
*/
if (cf->content_length > Data_size(fn)) {
lprintf(error, "metadata inconsistency %s, \
cf->content_length: %ld, Data_size(fn): %ld.\n", fn, cf->content_length,
Data_size(fn));
Cache_free(cf);
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
/*
* Check if the cache files are not outdated
*/
if (cf->time != cf->link->time) {
lprintf(warning, "outdated cache file: %s.\n", fn);
Cache_free(cf);
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
if (Data_open(cf)) {
Cache_free(cf);
lprintf(error, "cannot open data file %s.\n", fn);
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return NULL;
}
cf->cache_opened = 1;
/*
* Yup, we just created a circular loop. ;)
*/
cf->link->cache_ptr = cf;
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return cf;
}
void Cache_close(Cache *cf)
{
lprintf(cache_lock_debug,
"thread %x: locking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_LOCK(&cf_lock);
cf->cache_opened--;
if (cf->cache_opened > 0) {
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return;
}
if (Meta_write(cf)) {
lprintf(error, "Meta_write() error.");
}
if (fclose(cf->mfp)) {
lprintf(error, "cannot close metadata: %s.\n", strerror(errno));
}
if (fclose(cf->dfp)) {
lprintf(error, "cannot close data file %s.\n", strerror(errno));
}
cf->link->cache_ptr = NULL;
lprintf(cache_lock_debug,
"thread %x: unlocking cf_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf_lock);
return Cache_free(cf);
}
/**
* \brief Check if a segment exists.
* \return 1 if the segment exists
*/
static int Seg_exist(Cache *cf, off_t offset)
{
off_t byte = offset / cf->blksz;
return cf->seg[byte];
}
/**
* \brief Set the existence of a segment
* \param[in] cf the cache in-memory data structure
* \param[in] offset the starting position of the segment.
* \param[in] i 1 for exist, 0 for doesn't exist
* \note Call this after downloading a segment.
*/
static void Seg_set(Cache *cf, off_t offset, int i)
{
off_t byte = offset / cf->blksz;
cf->seg[byte] = i;
}
/**
* \brief Background download function
* \details If we are requesting the data from the second half of the current
* segment, we can spawn a pthread using this function to download the next
* segment.
*/
static void *Cache_bgdl(void *arg)
{
Cache *cf = (Cache *) arg;
lprintf(cache_lock_debug, "thread %x: locking w_lock;\n",
pthread_self());
PTHREAD_MUTEX_LOCK(&cf->w_lock);
uint8_t *recv_buf = CALLOC(cf->blksz, sizeof(uint8_t));
lprintf(debug, "thread %x spawned.\n ", pthread_self());
long recv = Link_download(cf->link, (char *) recv_buf, cf->blksz,
cf->next_dl_offset);
if (recv < 0) {
lprintf(error, "thread %x received %ld bytes, \
which doesn't make sense\n", pthread_self(), recv);
}
if ((recv == cf->blksz) ||
(cf->next_dl_offset ==
(cf->content_length / cf->blksz * cf->blksz))) {
Data_write(cf, recv_buf, recv, cf->next_dl_offset);
Seg_set(cf, cf->next_dl_offset, 1);
} else {
lprintf(error, "received %ld rather than %ld, possible network \
error.\n", recv, cf->blksz);
}
FREE(recv_buf);
lprintf(cache_lock_debug,
"thread %x: unlocking bgt_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->bgt_lock);
lprintf(cache_lock_debug,
"thread %x: unlocking w_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->w_lock);
if (pthread_detach(pthread_self())) {
lprintf(error, "%s\n", strerror(errno));
};
pthread_exit(NULL);
}
long
Cache_read(Cache *cf, char *const output_buf, const off_t len,
const off_t offset_start)
{
long send;
/*
* The offset of the segment to be downloaded
*/
off_t dl_offset = (offset_start + len) / cf->blksz * cf->blksz;
/*
* ------------- Check if the segment already exists --------------
*/
if (Seg_exist(cf, dl_offset)) {
send = Data_read(cf, (uint8_t *) output_buf, len, offset_start);
goto bgdl;
} else {
/*
* Wait for any other download thread to finish
*/
lprintf(cache_lock_debug,
"thread %ld: locking w_lock;\n", pthread_self());
PTHREAD_MUTEX_LOCK(&cf->w_lock);
if (Seg_exist(cf, dl_offset)) {
/*
* The segment now exists - it was downloaded by another
* download thread. Send it off and unlock the I/O
*/
send =
Data_read(cf, (uint8_t *) output_buf, len, offset_start);
lprintf(cache_lock_debug,
"thread %x: unlocking w_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->w_lock);
goto bgdl;
}
}
/*
* ------------------ Download the segment ---------------------
*/
uint8_t *recv_buf = CALLOC(cf->blksz, sizeof(uint8_t));
lprintf(debug, "thread %x: spawned.\n ", pthread_self());
long recv = Link_download(cf->link, (char *) recv_buf, cf->blksz,
dl_offset);
if (recv < 0) {
lprintf(error, "thread %x received %ld bytes, \
which doesn't make sense\n", pthread_self(), recv);
}
/*
* check if we have received enough data, write it to the disk
*
* Condition 1: received the exact amount as the segment size.
* Condition 2: offset is the last segment
*/
if ((recv == cf->blksz) ||
(dl_offset == (cf->content_length / cf->blksz * cf->blksz))) {
Data_write(cf, recv_buf, recv, dl_offset);
Seg_set(cf, dl_offset, 1);
} else {
lprintf(error, "received %ld rather than %ld, possible network \
error.\n", recv, cf->blksz);
}
FREE(recv_buf);
send = Data_read(cf, (uint8_t *) output_buf, len, offset_start);
lprintf(cache_lock_debug,
"thread %x: unlocking w_lock;\n", pthread_self());
PTHREAD_MUTEX_UNLOCK(&cf->w_lock);
/*
* ----------- Download the next segment in background -----------------
*/
bgdl: {
}
off_t next_dl_offset = round_div(offset_start, cf->blksz) * cf->blksz;
if ((next_dl_offset > dl_offset) && !Seg_exist(cf, next_dl_offset)
&& next_dl_offset < cf->content_length) {
/*
* Stop the spawning of multiple background pthreads
*/
if (!pthread_mutex_trylock(&cf->bgt_lock)) {
lprintf(cache_lock_debug,
"thread %x: trylocked bgt_lock;\n", pthread_self());
cf->next_dl_offset = next_dl_offset;
if (pthread_create(&cf->bgt, NULL, Cache_bgdl, cf)) {
lprintf(error,
"Error creating background download thread\n");
}
}
}
return send;
}
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