h_mgr.cpp

Go to the documentation of this file.

/* Copyright (c) 2013 Wildfire Games
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

/*
 * handle manager for resources.
 */

#include "precompiled.h"
#include "h_mgr.h"

#include <boost/unordered_map.hpp>

#include <limits.h> // CHAR_BIT
#include <string.h>
#include <stdlib.h>
#include <new>      // std::bad_alloc

#include "lib/fnv_hash.h"
#include "lib/allocators/overrun_protector.h"
#include "lib/allocators/pool.h"
#include "lib/module_init.h"
#include "lib/posix/posix_pthread.h"


namespace ERR {
static const Status H_IDX_INVALID   = -120000;  // totally invalid
static const Status H_IDX_UNUSED    = -120001;  // beyond current cap
static const Status H_TAG_MISMATCH  = -120003;
static const Status H_TYPE_MISMATCH = -120004;
static const Status H_ALREADY_FREED = -120005;
}
static const StatusDefinition hStatusDefinitions[] = {
    { ERR::H_IDX_INVALID,   L"Handle index completely out of bounds" },
    { ERR::H_IDX_UNUSED,    L"Handle index exceeds high-water mark" },
    { ERR::H_TAG_MISMATCH,  L"Handle tag mismatch (stale reference?)" },
    { ERR::H_TYPE_MISMATCH, L"Handle type mismatch" },
    { ERR::H_ALREADY_FREED, L"Handle already freed" }
};
STATUS_ADD_DEFINITIONS(hStatusDefinitions);



// rationale
//
// why fixed size control blocks, instead of just allocating dynamically?
// it is expected that resources be created and freed often. this way is
// much nicer to the memory manager. defining control blocks larger than
// the allotted space is caught by h_alloc (made possible by the vtbl builder
// storing control block size). it is also efficient to have all CBs in an
// more or less contiguous array (see below).
//
// why a manager, instead of a simple pool allocator?
// we need a central list of resources for freeing at exit, checking if a
// resource has already been loaded (for caching), and when reloading.
// may as well keep them in an array, rather than add a list and index.



//
// handle
//

// 0 = invalid handle value
// < 0 is an error code (we assume < 0 <==> MSB is set - 
//     true for 1s and 2s complement and sign-magnitude systems)

// fields:
// (shift value = # bits between LSB and field LSB.
//  may be larger than the field type - only shift Handle vars!)

// - index (0-based) of control block in our array.
//   (field width determines maximum currently open handles)
#define IDX_BITS 16
static const u64 IDX_MASK = (1l << IDX_BITS) - 1;

// - tag (1-based) ensures the handle references a certain resource instance.
//   (field width determines maximum unambiguous resource allocs)
typedef i64 Tag;
#define TAG_BITS 48
static const u64 TAG_MASK = 0xFFFFFFFF; // safer than (1 << 32) - 1

// make sure both fields fit within a Handle variable
cassert(IDX_BITS + TAG_BITS <= sizeof(Handle)*CHAR_BIT);


// return the handle's index field (always non-negative).
// no error checking!
static inline size_t h_idx(const Handle h)
{
    return (size_t)(h & IDX_MASK) - 1;
}

// return the handle's tag field.
// no error checking!
static inline Tag h_tag(Handle h)
{
    return h >> IDX_BITS;
}

// build a handle from index and tag.
// can't fail.
static inline Handle handle(size_t idx, u64 tag)
{
    const size_t idxPlusOne = idx+1;
    ENSURE(idxPlusOne <= IDX_MASK);
    ENSURE((tag & IDX_MASK) == 0);
    Handle h = tag | idxPlusOne;
    ENSURE(h > 0);
    return h;
}


//
// internal per-resource-instance data
//

// chosen so that all current resource structs are covered.
static const size_t HDATA_USER_SIZE = 100;


struct HDATA
{
    // we only need the tag, because it is trivial to compute
    // &HDATA from idx and vice versa. storing the entire handle
    // avoids needing to extract the tag field.
    Handle h;   // NB: will be overwritten by pool_free

    uintptr_t key;

    intptr_t refs;

    // smaller bit fields combined into 1
    // .. if set, do not actually release the resource (i.e. call dtor)
    //    when the handle is h_free-d, regardless of the refcount.
    //    set by h_alloc; reset on exit and by housekeeping.
    u32 keep_open : 1;
    // .. HACK: prevent adding to h_find lookup index if flags & RES_UNIQUE
    //    (because those handles might have several instances open,
    //    which the index can't currently handle)
    u32 unique : 1;
    u32 disallow_reload : 1;

    H_Type type;

    // for statistics
    size_t num_derefs;

    // storing PIVFS here is not a good idea since this often isn't
    // `freed' due to caching (and there is no dtor), so
    // the VFS reference count would never reach zero.
    VfsPath pathname;

    u8 user[HDATA_USER_SIZE];
};


// max data array entries. compared to last_in_use => signed.
static const ssize_t hdata_cap = (1ul << IDX_BITS)/4;

// pool of fixed-size elements allows O(1) alloc and free;
// there is a simple mapping between HDATA address and index.
static Pool hpool;


// error checking strategy:
// all handles passed in go through h_data(Handle, Type)


// get a (possibly new) array entry.
//
// fails if idx is out of bounds.
static Status h_data_from_idx(ssize_t idx, HDATA*& hd)
{
    // don't check if idx is beyond the current high-water mark, because
    // we might be allocating a new entry. subsequent tag checks protect
    // against using unallocated entries.
    if(size_t(idx) >= size_t(hdata_cap))    // also detects negative idx
        WARN_RETURN(ERR::H_IDX_INVALID);

    hd = (HDATA*)(hpool.da.base + idx*hpool.el_size);
    hd->num_derefs++;
    return INFO::OK;
}

static ssize_t h_idx_from_data(HDATA* hd)
{
    if(!pool_contains(&hpool, hd))
        WARN_RETURN(ERR::INVALID_POINTER);
    return (uintptr_t(hd) - uintptr_t(hpool.da.base))/hpool.el_size;
}


// get HDATA for the given handle.
// only uses (and checks) the index field.
// used by h_force_close (which must work regardless of tag).
static inline Status h_data_no_tag(const Handle h, HDATA*& hd)
{
    ssize_t idx = (ssize_t)h_idx(h);
    RETURN_STATUS_IF_ERR(h_data_from_idx(idx, hd));
    // need to verify it's in range - h_data_from_idx can only verify that
    // it's < maximum allowable index.
    if(uintptr_t(hd) > uintptr_t(hpool.da.base)+hpool.da.pos)
        WARN_RETURN(ERR::H_IDX_UNUSED);
    return INFO::OK;
}


static bool ignoreDoubleFree = false;

// get HDATA for the given handle.
// also verifies the tag field.
// used by functions callable for any handle type, e.g. h_filename.
static inline Status h_data_tag(Handle h, HDATA*& hd)
{
    RETURN_STATUS_IF_ERR(h_data_no_tag(h, hd));

    if(hd->key == 0)    // HDATA was wiped out and hd->h overwritten by pool_free
    {
        if(ignoreDoubleFree)
            return ERR::H_ALREADY_FREED;    // NOWARN (see ignoreDoubleFree)
        else
            WARN_RETURN(ERR::H_ALREADY_FREED);
    }

    if(h != hd->h)
        WARN_RETURN(ERR::H_TAG_MISMATCH);

    return INFO::OK;
}


// get HDATA for the given handle.
// also verifies the type.
// used by most functions accessing handle data.
static Status h_data_tag_type(const Handle h, const H_Type type, HDATA*& hd)
{
    RETURN_STATUS_IF_ERR(h_data_tag(h, hd));

    // h_alloc makes sure type isn't 0, so no need to check that here.
    if(hd->type != type)
    {
        debug_printf(L"h_mgr: expected type %ls, got %ls\n", hd->type->name, type->name);
        WARN_RETURN(ERR::H_TYPE_MISMATCH);
    }

    return INFO::OK;
}


//-----------------------------------------------------------------------------
// lookup data structure
//-----------------------------------------------------------------------------

// speed up h_find (called every h_alloc)
// multimap, because we want to add handles of differing type but same key
// (e.g. a VFile and Tex object for the same underlying filename hash key)
//
// store index because it's smaller and Handle can easily be reconstructed
//
//
// note: there may be several RES_UNIQUE handles of the same type and key
// (e.g. sound files - several instances of a sound definition file).
// that wasn't foreseen here, so we'll just refrain from adding to the index.
// that means they won't be found via h_find - no biggie.

typedef boost::unordered_multimap<uintptr_t, ssize_t> Key2Idx;
typedef Key2Idx::iterator It;
static OverrunProtector<Key2Idx> key2idx_wrapper;

enum KeyRemoveFlag { KEY_NOREMOVE, KEY_REMOVE };

static Handle key_find(uintptr_t key, H_Type type, KeyRemoveFlag remove_option = KEY_NOREMOVE)
{
    Key2Idx* key2idx = key2idx_wrapper.get();
    if(!key2idx)
        WARN_RETURN(ERR::NO_MEM);

    // initial return value: "not found at all, or it's of the
    // wrong type". the latter happens when called by h_alloc to
    // check if e.g. a Tex object already exists; at that time,
    // only the corresponding VFile exists.
    Handle ret = -1;

    std::pair<It, It> range = key2idx->equal_range(key);
    for(It it = range.first; it != range.second; ++it)
    {
        ssize_t idx = it->second;
        HDATA* hd;
        if(h_data_from_idx(idx, hd) != INFO::OK)
            continue;
        if(hd->type != type || hd->key != key)
            continue;

        // found a match
        if(remove_option == KEY_REMOVE)
            key2idx->erase(it);
        ret = hd->h;
        break;
    }

    key2idx_wrapper.lock();
    return ret;
}


static void key_add(uintptr_t key, Handle h)
{
    Key2Idx* key2idx = key2idx_wrapper.get();
    if(!key2idx)
        return;

    const ssize_t idx = h_idx(h);
    // note: MSDN documentation of stdext::hash_multimap is incorrect;
    // there is no overload of insert() that returns pair<iterator, bool>.
    (void)key2idx->insert(std::make_pair(key, idx));

    key2idx_wrapper.lock();
}


static void key_remove(uintptr_t key, H_Type type)
{
    Handle ret = key_find(key, type, KEY_REMOVE);
    ENSURE(ret > 0);
}


//----------------------------------------------------------------------------
// h_alloc
//----------------------------------------------------------------------------

static void warn_if_invalid(HDATA* hd)
{
#ifndef NDEBUG
    H_VTbl* vtbl = hd->type;

    // validate HDATA
    // currently nothing to do; <type> is checked by h_alloc and
    // the others have no invariants we could check.

    // have the resource validate its user_data
    Status err = vtbl->validate(hd->user);
    ENSURE(err == INFO::OK);

    // make sure empty space in control block isn't touched
    // .. but only if we're not storing a filename there
    const u8* start = hd->user + vtbl->user_size;
    const u8* end   = hd->user + HDATA_USER_SIZE;
    for(const u8* p = start; p < end; p++)
        ENSURE(*p == 0);    // else: handle user data was overrun!
#else
    UNUSED2(hd);
#endif
}


static Status type_validate(H_Type type)
{
    if(!type)
        WARN_RETURN(ERR::INVALID_PARAM);
    if(type->user_size > HDATA_USER_SIZE)
        WARN_RETURN(ERR::LIMIT);
    if(type->name == 0)
        WARN_RETURN(ERR::INVALID_PARAM);

    return INFO::OK;
}


static Tag gen_tag()
{
    static Tag tag;
    tag += (1ull << IDX_BITS);
    // it's not easy to detect overflow, because compilers
    // are allowed to assume it'll never happen. however,
    // pow(2, 64-IDX_BITS) is "enough" anyway.
    return tag;
}


static Handle reuse_existing_handle(uintptr_t key, H_Type type, size_t flags)
{
    if(flags & RES_NO_CACHE)
        return 0;

    // object of specified key and type doesn't exist yet
    Handle h = h_find(type, key);
    if(h <= 0)
        return 0;

    HDATA* hd;
    RETURN_STATUS_IF_ERR(h_data_tag_type(h, type, hd)); // h_find means this won't fail

    hd->refs += 1;

    // we are reactivating a closed but cached handle.
    // need to generate a new tag so that copies of the
    // previous handle can no longer access the resource.
    // (we don't need to reset the tag in h_free, because
    // use before this fails due to refs > 0 check in h_user_data).
    if(hd->refs == 1)
    {
        const Tag tag = gen_tag();
        h = handle(h_idx(h), tag);  // can't fail
        hd->h = h;
    }

    return h;
}


static Status call_init_and_reload(Handle h, H_Type type, HDATA* hd, const PIVFS& vfs, const VfsPath& pathname, va_list* init_args)
{
    Status err = INFO::OK;
    H_VTbl* vtbl = type;    // exact same thing but for clarity

    // init
    if(vtbl->init)
        vtbl->init(hd->user, *init_args);

    // reload
    if(vtbl->reload)
    {
        // catch exception to simplify reload funcs - let them use new()
        try
        {
            err = vtbl->reload(hd->user, vfs, pathname, h);
            if(err == INFO::OK)
                warn_if_invalid(hd);
        }
        catch(std::bad_alloc&)
        {
            err  = ERR::NO_MEM;
        }
    }

    return err;
}


static Handle alloc_new_handle(H_Type type, const PIVFS& vfs, const VfsPath& pathname, uintptr_t key, size_t flags, va_list* init_args)
{
    HDATA* hd = (HDATA*)pool_alloc(&hpool, 0);
    if(!hd)
        WARN_RETURN(ERR::NO_MEM);
    new(&hd->pathname) VfsPath;

    ssize_t idx = h_idx_from_data(hd);
    RETURN_STATUS_IF_ERR(idx);

    // (don't want to do this before the add-reference exit,
    // so as not to waste tags for often allocated handles.)
    const Tag tag = gen_tag();
    Handle h = handle(idx, tag);    // can't fail.

    hd->h = h;
    hd->key  = key;
    hd->type = type;
    hd->refs = 1;
    if(!(flags & RES_NO_CACHE))
        hd->keep_open = 1;
    if(flags & RES_DISALLOW_RELOAD)
        hd->disallow_reload = 1;
    hd->unique = (flags & RES_UNIQUE) != 0;
    hd->pathname = pathname;

    if(key && !hd->unique)
        key_add(key, h);

    Status err = call_init_and_reload(h, type, hd, vfs, pathname, init_args);
    if(err < 0)
        goto fail;

    return h;

fail:
    // reload failed; free the handle
    hd->keep_open = 0;  // disallow caching (since contents are invalid)
    (void)h_free(h, type);  // (h_free already does WARN_IF_ERR)

    // note: since some uses will always fail (e.g. loading sounds if
    // g_Quickstart), do not complain here.
    return (Handle)err;
}


static pthread_mutex_t h_mutex;
// (the same class is defined in vfs.cpp, but it is easier to
// just duplicate it to avoid having to specify the mutex.
// such a class exists in ps/ThreadUtil.h, but we can't
// take a dependency on that module here.)
struct H_ScopedLock
{
    H_ScopedLock() { pthread_mutex_lock(&h_mutex); }
    ~H_ScopedLock() { pthread_mutex_unlock(&h_mutex); }
};


// any further params are passed to type's init routine
Handle h_alloc(H_Type type, const PIVFS& vfs, const VfsPath& pathname, size_t flags, ...)
{
    H_ScopedLock s;

    RETURN_STATUS_IF_ERR(type_validate(type));

    const uintptr_t key = fnv_hash(pathname.string().c_str(), pathname.string().length()*sizeof(pathname.string()[0]));

    // see if we can reuse an existing handle
    Handle h = reuse_existing_handle(key, type, flags);
    RETURN_STATUS_IF_ERR(h);
    // .. successfully reused the handle; refcount increased
    if(h > 0)
        return h;
    // .. need to allocate a new one:
    va_list args;
    va_start(args, flags);
    h = alloc_new_handle(type, vfs, pathname, key, flags, &args);
    va_end(args);
    return h;   // alloc_new_handle already does WARN_RETURN_STATUS_IF_ERR
}


//-----------------------------------------------------------------------------

static void h_free_hd(HDATA* hd)
{
    if(hd->refs > 0)
        hd->refs--;

    // still references open or caching requests it stays - do not release.
    if(hd->refs > 0 || hd->keep_open)
        return;

    // actually release the resource (call dtor, free control block).

    // h_alloc makes sure type != 0; if we get here, it still is
    H_VTbl* vtbl = hd->type;

    // call its destructor
    // note: H_TYPE_DEFINE currently always defines a dtor, but play it safe
    if(vtbl->dtor)
        vtbl->dtor(hd->user);

    if(hd->key && !hd->unique)
        key_remove(hd->key, hd->type);

#ifndef NDEBUG
    // to_string is slow for some handles, so avoid calling it if unnecessary
    if(debug_filter_allows(L"H_MGR|"))
    {
        wchar_t buf[H_STRING_LEN];
        if(vtbl->to_string(hd->user, buf) < 0)
            wcscpy_s(buf, ARRAY_SIZE(buf), L"(error)");
        debug_printf(L"H_MGR| free %ls %ls accesses=%lu %ls\n", hd->type->name, hd->pathname.string().c_str(), (unsigned long)hd->num_derefs, buf);
    }
#endif

    hd->pathname.~VfsPath();    // FIXME: ugly hack, but necessary to reclaim memory
    memset(hd, 0, sizeof(*hd));
    pool_free(&hpool, hd);
}


Status h_free(Handle& h, H_Type type)
{
    H_ScopedLock s;

    // 0-initialized or an error code; don't complain because this
    // happens often and is harmless.
    if(h <= 0)
        return INFO::OK;

    // wipe out the handle to prevent reuse but keep a copy for below.
    const Handle h_copy = h;
    h = 0;

    HDATA* hd;
    RETURN_STATUS_IF_ERR(h_data_tag_type(h_copy, type, hd));

    h_free_hd(hd);
    return INFO::OK;
}


//----------------------------------------------------------------------------
// remaining API

void* h_user_data(const Handle h, const H_Type type)
{
    HDATA* hd;
    if(h_data_tag_type(h, type, hd) != INFO::OK)
        return 0;

    if(!hd->refs)
    {
        // note: resetting the tag is not enough (user might pass in its value)
        DEBUG_WARN_ERR(ERR::LOGIC); // no references to resource (it's cached, but someone is accessing it directly)
        return 0;
    }

    warn_if_invalid(hd);
    return hd->user;
}


VfsPath h_filename(const Handle h)
{
    // don't require type check: should be usable for any handle,
    // even if the caller doesn't know its type.
    HDATA* hd;
    if(h_data_tag(h, hd) != INFO::OK)
        return VfsPath();
    return hd->pathname;
}


// TODO: what if iterating through all handles is too slow?
Status h_reload(const PIVFS& vfs, const VfsPath& pathname)
{
    H_ScopedLock s;

    const u32 key = fnv_hash(pathname.string().c_str(), pathname.string().length()*sizeof(pathname.string()[0]));

    // destroy (note: not free!) all handles backed by this file.
    // do this before reloading any of them, because we don't specify reload
    // order (the parent resource may be reloaded first, and load the child,
    // whose original data would leak).
    for(HDATA* hd = (HDATA*)hpool.da.base; hd < (HDATA*)(hpool.da.base + hpool.da.pos); hd = (HDATA*)(uintptr_t(hd)+hpool.el_size))
    {
        if(hd->key == 0 || hd->key != key || hd->disallow_reload)
            continue;
        hd->type->dtor(hd->user);
    }

    Status ret = INFO::OK;

    // now reload all affected handles
    size_t i = 0;
    for(HDATA* hd = (HDATA*)hpool.da.base; hd < (HDATA*)(hpool.da.base + hpool.da.pos); hd = (HDATA*)(uintptr_t(hd)+hpool.el_size), i++)
    {
        if(hd->key == 0 || hd->key != key || hd->disallow_reload)
            continue;

        Status err = hd->type->reload(hd->user, vfs, hd->pathname, hd->h);
        // don't stop if an error is encountered - try to reload them all.
        if(err < 0)
        {
            h_free(hd->h, hd->type);
            if(ret == 0)    // don't overwrite first error
                ret = err;
        }
        else
            warn_if_invalid(hd);
    }

    return ret;
}


Handle h_find(H_Type type, uintptr_t key)
{
    H_ScopedLock s;
    return key_find(key, type);
}



// force the resource to be freed immediately, even if cached.
// tag is not checked - this allows the first Handle returned
// (whose tag will change after being 'freed', but remaining in memory)
// to later close the object.
// this is used when reinitializing the sound engine -
// at that point, all (cached) OpenAL resources must be freed.
Status h_force_free(Handle h, H_Type type)
{
    H_ScopedLock s;

    // require valid index; ignore tag; type checked below.
    HDATA* hd;
    RETURN_STATUS_IF_ERR(h_data_no_tag(h, hd));
    if(hd->type != type)
        WARN_RETURN(ERR::H_TYPE_MISMATCH);
    hd->keep_open = 0;
    hd->refs = 0;
    h_free_hd(hd);
    return INFO::OK;
}


// increment Handle <h>'s reference count.
// only meant to be used for objects that free a Handle in their dtor,
// so that they are copy-equivalent and can be stored in a STL container.
// do not use this to implement refcounting on top of the Handle scheme,
// e.g. loading a Handle once and then passing it around. instead, have each
// user load the resource; refcounting is done under the hood.
void h_add_ref(Handle h)
{
    HDATA* hd;
    if(h_data_tag(h, hd) != INFO::OK)
        return;

    ENSURE(hd->refs);   // if there are no refs, how did the caller manage to keep a Handle?!
    hd->refs++;
}


// retrieve the internal reference count or a negative error code.
// background: since h_alloc has no way of indicating whether it
// allocated a new handle or reused an existing one, counting references
// within resource control blocks is impossible. since that is sometimes
// necessary (always wrapping objects in Handles is excessive), we
// provide access to the internal reference count.
intptr_t h_get_refcnt(Handle h)
{
    HDATA* hd;
    RETURN_STATUS_IF_ERR(h_data_tag(h, hd));

    ENSURE(hd->refs);   // if there are no refs, how did the caller manage to keep a Handle?!
    return hd->refs;
}


static ModuleInitState initState;

static Status Init()
{
    // lock must be recursive (e.g. h_alloc calls h_find)
    pthread_mutexattr_t attr;
    int err;
    err = pthread_mutexattr_init(&attr);
    ENSURE(err == 0);
    err = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
    ENSURE(err == 0);
    err = pthread_mutex_init(&h_mutex, &attr);
    ENSURE(err == 0);
    err = pthread_mutexattr_destroy(&attr);
    ENSURE(err == 0);

    RETURN_STATUS_IF_ERR(pool_create(&hpool, hdata_cap*sizeof(HDATA), sizeof(HDATA)));
    return INFO::OK;
}

static void Shutdown()
{
    debug_printf(L"H_MGR| shutdown. any handle frees after this are leaks!\n");
    // objects that store handles to other objects are destroyed before their
    // children, so the subsequent forced destruction of the child here will
    // raise a double-free warning unless we ignore it. (#860, #915, #920)
    ignoreDoubleFree = true;

    H_ScopedLock s;

    // forcibly close all open handles
    for(HDATA* hd = (HDATA*)hpool.da.base; hd < (HDATA*)(hpool.da.base + hpool.da.pos); hd = (HDATA*)(uintptr_t(hd)+hpool.el_size))
    {
        // it's already been freed; don't free again so that this
        // doesn't look like an error.
        if(hd->key == 0)
            continue;

        // disable caching; we need to release the resource now.
        hd->keep_open = 0;
        hd->refs = 0;

        h_free_hd(hd);
    }

    pool_destroy(&hpool);
}

void h_mgr_free_type(const H_Type type)
{
    ignoreDoubleFree = true;

    H_ScopedLock s;

    // forcibly close all open handles of the specified type
    for(HDATA* hd = (HDATA*)hpool.da.base; hd < (HDATA*)(hpool.da.base + hpool.da.pos); hd = (HDATA*)(uintptr_t(hd)+hpool.el_size))
    {
        // free if not previously freed and only free the proper type
        if (hd->key == 0 || hd->type != type)
            continue;

        // disable caching; we need to release the resource now.
        hd->keep_open = 0;
        hd->refs = 0;

        h_free_hd(hd);
    }
}

void h_mgr_init()
{
    ModuleInit(&initState, Init);
}

void h_mgr_shutdown()
{
    ModuleShutdown(&initState, Shutdown);
}