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fscache.c
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fscache.c
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#include "../../cache.h"
#include "../../hashmap.h"
#include "../win32.h"
#include "fscache.h"
#include "../../dir.h"
static int initialized;
static volatile long enabled;
static struct hashmap map;
static CRITICAL_SECTION mutex;
static struct trace_key trace_fscache = TRACE_KEY_INIT(FSCACHE);
/*
* An entry in the file system cache. Used for both entire directory listings
* and file entries.
*/
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wpedantic"
struct fsentry {
struct hashmap_entry ent;
mode_t st_mode;
/* Pointer to the directory listing, or NULL for the listing itself. */
struct fsentry *list;
/* Pointer to the next file entry of the list. */
struct fsentry *next;
union {
/* Reference count of the directory listing. */
volatile long refcnt;
/* Handle to wait on the loading thread. */
HANDLE hwait;
struct {
/* More stat members (only used for file entries). */
off64_t st_size;
struct timespec st_atim;
struct timespec st_mtim;
struct timespec st_ctim;
} s;
} u;
/* Length of name. */
unsigned short len;
/*
* Name of the entry. For directory listings: relative path of the
* directory, without trailing '/' (empty for cwd()). For file entries:
* name of the file. Typically points to the end of the structure if
* the fsentry is allocated on the heap (see fsentry_alloc), or to a
* local variable if on the stack (see fsentry_init).
*/
struct dirent dirent;
};
#pragma GCC diagnostic pop
struct heap_fsentry {
union {
struct fsentry ent;
char dummy[sizeof(struct fsentry) + MAX_PATH];
} u;
};
/*
* Compares the paths of two fsentry structures for equality.
*/
static int fsentry_cmp(void *unused_cmp_data,
const struct fsentry *fse1, const struct fsentry *fse2,
void *unused_keydata)
{
int res;
if (fse1 == fse2)
return 0;
/* compare the list parts first */
if (fse1->list != fse2->list &&
(res = fsentry_cmp(NULL, fse1->list ? fse1->list : fse1,
fse2->list ? fse2->list : fse2, NULL)))
return res;
/* if list parts are equal, compare len and name */
if (fse1->len != fse2->len)
return fse1->len - fse2->len;
return fspathncmp(fse1->dirent.d_name, fse2->dirent.d_name, fse1->len);
}
/*
* Calculates the hash code of an fsentry structure's path.
*/
static unsigned int fsentry_hash(const struct fsentry *fse)
{
unsigned int hash = fse->list ? fse->list->ent.hash : 0;
return hash ^ memihash(fse->dirent.d_name, fse->len);
}
/*
* Initialize an fsentry structure for use by fsentry_hash and fsentry_cmp.
*/
static void fsentry_init(struct fsentry *fse, struct fsentry *list,
const char *name, size_t len)
{
fse->list = list;
if (len > MAX_PATH)
BUG("Trying to allocate fsentry for long path '%.*s'",
(int)len, name);
memcpy(fse->dirent.d_name, name, len);
fse->dirent.d_name[len] = 0;
fse->len = len;
hashmap_entry_init(&fse->ent, fsentry_hash(fse));
}
/*
* Allocate an fsentry structure on the heap.
*/
static struct fsentry *fsentry_alloc(struct fsentry *list, const char *name,
size_t len)
{
/* overallocate fsentry and copy the name to the end */
struct fsentry *fse = xmalloc(sizeof(struct fsentry) + len + 1);
/* init the rest of the structure */
fsentry_init(fse, list, name, len);
fse->next = NULL;
fse->u.refcnt = 1;
return fse;
}
/*
* Add a reference to an fsentry.
*/
inline static void fsentry_addref(struct fsentry *fse)
{
if (fse->list)
fse = fse->list;
InterlockedIncrement(&(fse->u.refcnt));
}
/*
* Release the reference to an fsentry, frees the memory if its the last ref.
*/
static void fsentry_release(struct fsentry *fse)
{
if (fse->list)
fse = fse->list;
if (InterlockedDecrement(&(fse->u.refcnt)))
return;
while (fse) {
struct fsentry *next = fse->next;
free(fse);
fse = next;
}
}
/*
* Allocate and initialize an fsentry from a WIN32_FIND_DATA structure.
*/
static struct fsentry *fseentry_create_entry(struct fsentry *list,
const WIN32_FIND_DATAW *fdata)
{
char buf[MAX_PATH * 3];
int len;
struct fsentry *fse;
len = xwcstoutf(buf, fdata->cFileName, ARRAY_SIZE(buf));
fse = fsentry_alloc(list, buf, len);
fse->st_mode = file_attr_to_st_mode(fdata->dwFileAttributes);
fse->dirent.d_type = S_ISDIR(fse->st_mode) ? DT_DIR : DT_REG;
fse->u.s.st_size = (((off64_t) (fdata->nFileSizeHigh)) << 32)
| fdata->nFileSizeLow;
filetime_to_timespec(&(fdata->ftLastAccessTime), &(fse->u.s.st_atim));
filetime_to_timespec(&(fdata->ftLastWriteTime), &(fse->u.s.st_mtim));
filetime_to_timespec(&(fdata->ftCreationTime), &(fse->u.s.st_ctim));
return fse;
}
/*
* Create an fsentry-based directory listing (similar to opendir / readdir).
* Dir should not contain trailing '/'. Use an empty string for the current
* directory (not "."!).
*/
static struct fsentry *fsentry_create_list(const struct fsentry *dir,
int *dir_not_found)
{
wchar_t pattern[MAX_PATH + 2]; /* + 2 for '/' '*' */
WIN32_FIND_DATAW fdata;
HANDLE h;
int wlen;
struct fsentry *list, **phead;
DWORD err;
*dir_not_found = 0;
/* convert name to UTF-16 and check length < MAX_PATH */
if ((wlen = xutftowcsn(pattern, dir->dirent.d_name, MAX_PATH,
dir->len)) < 0) {
if (errno == ERANGE)
errno = ENAMETOOLONG;
return NULL;
}
/* append optional '/' and wildcard '*' */
if (wlen)
pattern[wlen++] = '/';
pattern[wlen++] = '*';
pattern[wlen] = 0;
/* open find handle */
h = FindFirstFileW(pattern, &fdata);
if (h == INVALID_HANDLE_VALUE) {
err = GetLastError();
*dir_not_found = 1; /* or empty directory */
errno = (err == ERROR_DIRECTORY) ? ENOTDIR : err_win_to_posix(err);
trace_printf_key(&trace_fscache, "fscache: error(%d) '%s'\n",
errno, dir->dirent.d_name);
return NULL;
}
/* allocate object to hold directory listing */
list = fsentry_alloc(NULL, dir->dirent.d_name, dir->len);
list->st_mode = S_IFDIR;
list->dirent.d_type = DT_DIR;
/* walk directory and build linked list of fsentry structures */
phead = &list->next;
do {
*phead = fseentry_create_entry(list, &fdata);
phead = &(*phead)->next;
} while (FindNextFileW(h, &fdata));
/* remember result of last FindNextFile, then close find handle */
err = GetLastError();
FindClose(h);
/* return the list if we've got all the files */
if (err == ERROR_NO_MORE_FILES)
return list;
/* otherwise free the list and return error */
fsentry_release(list);
errno = err_win_to_posix(err);
return NULL;
}
/*
* Adds a directory listing to the cache.
*/
static void fscache_add(struct fsentry *fse)
{
if (fse->list)
fse = fse->list;
for (; fse; fse = fse->next)
hashmap_add(&map, &fse->ent);
}
/*
* Clears the cache.
*/
static void fscache_clear(void)
{
hashmap_clear_and_free(&map, struct fsentry, ent);
hashmap_init(&map, (hashmap_cmp_fn)fsentry_cmp, NULL, 0);
}
/*
* Checks if the cache is enabled for the given path.
*/
int fscache_enabled(const char *path)
{
return enabled > 0 && !is_absolute_path(path);
}
/*
* Looks up a cache entry, waits if its being loaded by another thread.
* The mutex must be owned by the calling thread.
*/
static struct fsentry *fscache_get_wait(struct fsentry *key)
{
struct fsentry *fse = hashmap_get_entry(&map, key, ent, NULL);
/* return if its a 'real' entry (future entries have refcnt == 0) */
if (!fse || fse->list || fse->u.refcnt)
return fse;
/* create an event and link our key to the future entry */
key->u.hwait = CreateEvent(NULL, TRUE, FALSE, NULL);
key->next = fse->next;
fse->next = key;
/* wait for the loading thread to signal us */
LeaveCriticalSection(&mutex);
WaitForSingleObject(key->u.hwait, INFINITE);
CloseHandle(key->u.hwait);
EnterCriticalSection(&mutex);
/* repeat cache lookup */
return hashmap_get_entry(&map, key, ent, NULL);
}
/*
* Looks up or creates a cache entry for the specified key.
*/
static struct fsentry *fscache_get(struct fsentry *key)
{
struct fsentry *fse, *future, *waiter;
int dir_not_found;
EnterCriticalSection(&mutex);
/* check if entry is in cache */
fse = fscache_get_wait(key);
if (fse) {
if (fse->st_mode)
fsentry_addref(fse);
else
fse = NULL; /* non-existing directory */
LeaveCriticalSection(&mutex);
return fse;
}
/* if looking for a file, check if directory listing is in cache */
if (!fse && key->list) {
fse = fscache_get_wait(key->list);
if (fse) {
LeaveCriticalSection(&mutex);
/*
* dir entry without file entry, or dir does not
* exist -> file doesn't exist
*/
errno = ENOENT;
return NULL;
}
}
/* add future entry to indicate that we're loading it */
future = key->list ? key->list : key;
future->next = NULL;
future->u.refcnt = 0;
hashmap_add(&map, &future->ent);
/* create the directory listing (outside mutex!) */
LeaveCriticalSection(&mutex);
fse = fsentry_create_list(future, &dir_not_found);
EnterCriticalSection(&mutex);
/* remove future entry and signal waiting threads */
hashmap_remove(&map, &future->ent, NULL);
waiter = future->next;
while (waiter) {
HANDLE h = waiter->u.hwait;
waiter = waiter->next;
SetEvent(h);
}
/* leave on error (errno set by fsentry_create_list) */
if (!fse) {
if (dir_not_found && key->list) {
/*
* Record that the directory does not exist (or is
* empty, which for all practical matters is the same
* thing as far as fscache is concerned).
*/
fse = fsentry_alloc(key->list->list,
key->list->dirent.d_name,
key->list->len);
fse->st_mode = 0;
hashmap_add(&map, &fse->ent);
}
LeaveCriticalSection(&mutex);
return NULL;
}
/* add directory listing to the cache */
fscache_add(fse);
/* lookup file entry if requested (fse already points to directory) */
if (key->list)
fse = hashmap_get_entry(&map, key, ent, NULL);
if (fse && !fse->st_mode)
fse = NULL; /* non-existing directory */
/* return entry or ENOENT */
if (fse)
fsentry_addref(fse);
else
errno = ENOENT;
LeaveCriticalSection(&mutex);
return fse;
}
/*
* Enables or disables the cache. Note that the cache is read-only, changes to
* the working directory are NOT reflected in the cache while enabled.
*/
int fscache_enable(int enable)
{
int result;
if (!initialized) {
/* allow the cache to be disabled entirely */
if (!core_fscache)
return 0;
InitializeCriticalSection(&mutex);
hashmap_init(&map, (hashmap_cmp_fn) fsentry_cmp, NULL, 0);
initialized = 1;
}
result = enable ? InterlockedIncrement(&enabled)
: InterlockedDecrement(&enabled);
if (enable && result == 1) {
/* redirect opendir and lstat to the fscache implementations */
opendir = fscache_opendir;
lstat = fscache_lstat;
} else if (!enable && !result) {
/* reset opendir and lstat to the original implementations */
opendir = dirent_opendir;
lstat = mingw_lstat;
EnterCriticalSection(&mutex);
fscache_clear();
LeaveCriticalSection(&mutex);
}
trace_printf_key(&trace_fscache, "fscache: enable(%d)\n", enable);
return result;
}
/*
* Lstat replacement, uses the cache if enabled, otherwise redirects to
* mingw_lstat.
*/
int fscache_lstat(const char *filename, struct stat *st)
{
int dirlen, base, len;
struct heap_fsentry key[2];
struct fsentry *fse;
if (!fscache_enabled(filename))
return mingw_lstat(filename, st);
/* split filename into path + name */
len = strlen(filename);
if (len && is_dir_sep(filename[len - 1]))
len--;
base = len;
while (base && !is_dir_sep(filename[base - 1]))
base--;
dirlen = base ? base - 1 : 0;
/* lookup entry for path + name in cache */
fsentry_init(&key[0].u.ent, NULL, filename, dirlen);
fsentry_init(&key[1].u.ent, &key[0].u.ent, filename + base, len - base);
fse = fscache_get(&key[1].u.ent);
if (!fse) {
errno = ENOENT;
return -1;
}
/* copy stat data */
st->st_ino = 0;
st->st_gid = 0;
st->st_uid = 0;
st->st_dev = 0;
st->st_rdev = 0;
st->st_nlink = 1;
st->st_mode = fse->st_mode;
st->st_size = fse->u.s.st_size;
st->st_atim = fse->u.s.st_atim;
st->st_mtim = fse->u.s.st_mtim;
st->st_ctim = fse->u.s.st_ctim;
/* don't forget to release fsentry */
fsentry_release(fse);
return 0;
}
typedef struct fscache_DIR {
struct DIR base_dir; /* extend base struct DIR */
struct fsentry *pfsentry;
struct dirent *dirent;
} fscache_DIR;
/*
* Readdir replacement.
*/
static struct dirent *fscache_readdir(DIR *base_dir)
{
fscache_DIR *dir = (fscache_DIR*) base_dir;
struct fsentry *next = dir->pfsentry->next;
if (!next)
return NULL;
dir->pfsentry = next;
dir->dirent = &next->dirent;
return dir->dirent;
}
/*
* Closedir replacement.
*/
static int fscache_closedir(DIR *base_dir)
{
fscache_DIR *dir = (fscache_DIR*) base_dir;
fsentry_release(dir->pfsentry);
free(dir);
return 0;
}
/*
* Opendir replacement, uses a directory listing from the cache if enabled,
* otherwise calls original dirent implementation.
*/
DIR *fscache_opendir(const char *dirname)
{
struct heap_fsentry key;
struct fsentry *list;
fscache_DIR *dir;
int len;
if (!fscache_enabled(dirname))
return dirent_opendir(dirname);
/* prepare name (strip trailing '/', replace '.') */
len = strlen(dirname);
if ((len == 1 && dirname[0] == '.') ||
(len && is_dir_sep(dirname[len - 1])))
len--;
/* get directory listing from cache */
fsentry_init(&key.u.ent, NULL, dirname, len);
list = fscache_get(&key.u.ent);
if (!list)
return NULL;
/* alloc and return DIR structure */
dir = (fscache_DIR*) xmalloc(sizeof(fscache_DIR));
dir->base_dir.preaddir = fscache_readdir;
dir->base_dir.pclosedir = fscache_closedir;
dir->pfsentry = list;
return (DIR*) dir;
}