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harfbuzz/src/hb-machinery.hh
Behdad Esfahbod f398097529 More static constexpr
2019-01-25 16:08:25 +01:00

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/*
* Copyright © 2007,2008,2009,2010 Red Hat, Inc.
* Copyright © 2012,2018 Google, Inc.
*
* This is part of HarfBuzz, a text shaping library.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and its documentation for any purpose, provided that the
* above copyright notice and the following two paragraphs appear in
* all copies of this software.
*
* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
* Red Hat Author(s): Behdad Esfahbod
* Google Author(s): Behdad Esfahbod
*/
#ifndef HB_MACHINERY_HH
#define HB_MACHINERY_HH
#include "hb.hh"
#include "hb-blob.hh"
#include "hb-array.hh"
#include "hb-vector.hh"
/*
* Casts
*/
/* Cast to struct T, reference to reference */
template<typename Type, typename TObject>
static inline const Type& CastR(const TObject &X)
{ return reinterpret_cast<const Type&> (X); }
template<typename Type, typename TObject>
static inline Type& CastR(TObject &X)
{ return reinterpret_cast<Type&> (X); }
/* Cast to struct T, pointer to pointer */
template<typename Type, typename TObject>
static inline const Type* CastP(const TObject *X)
{ return reinterpret_cast<const Type*> (X); }
template<typename Type, typename TObject>
static inline Type* CastP(TObject *X)
{ return reinterpret_cast<Type*> (X); }
/* StructAtOffset<T>(P,Ofs) returns the struct T& that is placed at memory
* location pointed to by P plus Ofs bytes. */
template<typename Type>
static inline const Type& StructAtOffset(const void *P, unsigned int offset)
{ return * reinterpret_cast<const Type*> ((const char *) P + offset); }
template<typename Type>
static inline Type& StructAtOffset(void *P, unsigned int offset)
{ return * reinterpret_cast<Type*> ((char *) P + offset); }
template<typename Type>
static inline const Type& StructAtOffsetUnaligned(const void *P, unsigned int offset)
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
return * reinterpret_cast<Type*> ((char *) P + offset);
#pragma GCC diagnostic pop
}
template<typename Type>
static inline Type& StructAtOffsetUnaligned(void *P, unsigned int offset)
{
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wcast-align"
return * reinterpret_cast<Type*> ((char *) P + offset);
#pragma GCC diagnostic pop
}
/* StructAfter<T>(X) returns the struct T& that is placed after X.
* Works with X of variable size also. X must implement get_size() */
template<typename Type, typename TObject>
static inline const Type& StructAfter(const TObject &X)
{ return StructAtOffset<Type>(&X, X.get_size()); }
template<typename Type, typename TObject>
static inline Type& StructAfter(TObject &X)
{ return StructAtOffset<Type>(&X, X.get_size()); }
/*
* Size checking
*/
/* Check _assertion in a method environment */
#define _DEFINE_INSTANCE_ASSERTION1(_line, _assertion) \
void _instance_assertion_on_line_##_line () const \
{ static_assert ((_assertion), ""); }
# define _DEFINE_INSTANCE_ASSERTION0(_line, _assertion) _DEFINE_INSTANCE_ASSERTION1 (_line, _assertion)
# define DEFINE_INSTANCE_ASSERTION(_assertion) _DEFINE_INSTANCE_ASSERTION0 (__LINE__, _assertion)
/* Check that _code compiles in a method environment */
#define _DEFINE_COMPILES_ASSERTION1(_line, _code) \
void _compiles_assertion_on_line_##_line () const \
{ _code; }
# define _DEFINE_COMPILES_ASSERTION0(_line, _code) _DEFINE_COMPILES_ASSERTION1 (_line, _code)
# define DEFINE_COMPILES_ASSERTION(_code) _DEFINE_COMPILES_ASSERTION0 (__LINE__, _code)
#define DEFINE_SIZE_STATIC(size) \
DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size)) \
unsigned int get_size () const { return (size); } \
static constexpr unsigned null_size = (size); \
static constexpr unsigned min_size = (size); \
static constexpr unsigned static_size = (size)
#define DEFINE_SIZE_UNION(size, _member) \
DEFINE_COMPILES_ASSERTION ((void) this->u._member.static_size) \
DEFINE_INSTANCE_ASSERTION (sizeof(this->u._member) == (size)) \
static constexpr unsigned null_size = (size); \
static constexpr unsigned min_size = (size)
#define DEFINE_SIZE_MIN(size) \
DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
static constexpr unsigned null_size = (size); \
static constexpr unsigned min_size = (size)
#define DEFINE_SIZE_UNBOUNDED(size) \
DEFINE_INSTANCE_ASSERTION (sizeof (*this) >= (size)) \
static constexpr unsigned min_size = (size)
#define DEFINE_SIZE_ARRAY(size, array) \
DEFINE_COMPILES_ASSERTION ((void) (array)[0].static_size) \
DEFINE_INSTANCE_ASSERTION (sizeof (*this) == (size) + VAR * sizeof ((array)[0])) \
static constexpr unsigned null_size = (size); \
static constexpr unsigned min_size = (size)
#define DEFINE_SIZE_ARRAY_SIZED(size, array) \
unsigned int get_size () const { return (size - (array).min_size + (array).get_size ()); } \
DEFINE_SIZE_ARRAY(size, array)
/*
* Dispatch
*/
template <typename Context, typename Return, unsigned int MaxDebugDepth>
struct hb_dispatch_context_t
{
static constexpr unsigned max_debug_depth = MaxDebugDepth;
typedef Return return_t;
template <typename T, typename F>
bool may_dispatch (const T *obj HB_UNUSED, const F *format HB_UNUSED) { return true; }
static return_t no_dispatch_return_value () { return Context::default_return_value (); }
static bool stop_sublookup_iteration (const return_t r HB_UNUSED) { return false; }
};
/*
* Sanitize
*
*
* === Introduction ===
*
* The sanitize machinery is at the core of our zero-cost font loading. We
* mmap() font file into memory and create a blob out of it. Font subtables
* are returned as a readonly sub-blob of the main font blob. These table
* blobs are then sanitized before use, to ensure invalid memory access does
* not happen. The toplevel sanitize API use is like, eg. to load the 'head'
* table:
*
* hb_blob_t *head_blob = hb_sanitize_context_t ().reference_table<OT::head> (face);
*
* The blob then can be converted to a head table struct with:
*
* const head *head_table = head_blob->as<head> ();
*
* What the reference_table does is, to call hb_face_reference_table() to load
* the table blob, sanitize it and return either the sanitized blob, or empty
* blob if sanitization failed. The blob->as() function returns the null
* object of its template type argument if the blob is empty. Otherwise, it
* just casts the blob contents to the desired type.
*
* Sanitizing a blob of data with a type T works as follows (with minor
* simplification):
*
* - Cast blob content to T*, call sanitize() method of it,
* - If sanitize succeeded, return blob.
* - Otherwise, if blob is not writable, try making it writable,
* or copy if cannot be made writable in-place,
* - Call sanitize() again. Return blob if sanitize succeeded.
* - Return empty blob otherwise.
*
*
* === The sanitize() contract ===
*
* The sanitize() method of each object type shall return true if it's safe to
* call other methods of the object, and false otherwise.
*
* Note that what sanitize() checks for might align with what the specification
* describes as valid table data, but does not have to be. In particular, we
* do NOT want to be pedantic and concern ourselves with validity checks that
* are irrelevant to our use of the table. On the contrary, we want to be
* lenient with error handling and accept invalid data to the extent that it
* does not impose extra burden on us.
*
* Based on the sanitize contract, one can see that what we check for depends
* on how we use the data in other table methods. Ie. if other table methods
* assume that offsets do NOT point out of the table data block, then that's
* something sanitize() must check for (GSUB/GPOS/GDEF/etc work this way). On
* the other hand, if other methods do such checks themselves, then sanitize()
* does not have to bother with them (glyf/local work this way). The choice
* depends on the table structure and sanitize() performance. For example, to
* check glyf/loca offsets in sanitize() would cost O(num-glyphs). We try hard
* to avoid such costs during font loading. By postponing such checks to the
* actual glyph loading, we reduce the sanitize cost to O(1) and total runtime
* cost to O(used-glyphs). As such, this is preferred.
*
* The same argument can be made re GSUB/GPOS/GDEF, but there, the table
* structure is so complicated that by checking all offsets at sanitize() time,
* we make the code much simpler in other methods, as offsets and referenced
* objects do not need to be validated at each use site.
*/
/* This limits sanitizing time on really broken fonts. */
#ifndef HB_SANITIZE_MAX_EDITS
#define HB_SANITIZE_MAX_EDITS 32
#endif
#ifndef HB_SANITIZE_MAX_OPS_FACTOR
#define HB_SANITIZE_MAX_OPS_FACTOR 8
#endif
#ifndef HB_SANITIZE_MAX_OPS_MIN
#define HB_SANITIZE_MAX_OPS_MIN 16384
#endif
#ifndef HB_SANITIZE_MAX_OPS_MAX
#define HB_SANITIZE_MAX_OPS_MAX 0x3FFFFFFF
#endif
struct hb_sanitize_context_t :
hb_dispatch_context_t<hb_sanitize_context_t, bool, HB_DEBUG_SANITIZE>
{
hb_sanitize_context_t () :
debug_depth (0),
start (nullptr), end (nullptr),
max_ops (0),
writable (false), edit_count (0),
blob (nullptr),
num_glyphs (65536),
num_glyphs_set (false) {}
const char *get_name () { return "SANITIZE"; }
template <typename T, typename F>
bool may_dispatch (const T *obj HB_UNUSED, const F *format)
{ return format->sanitize (this); }
template <typename T>
return_t dispatch (const T &obj) { return obj.sanitize (this); }
static return_t default_return_value () { return true; }
static return_t no_dispatch_return_value () { return false; }
bool stop_sublookup_iteration (const return_t r) const { return !r; }
void init (hb_blob_t *b)
{
this->blob = hb_blob_reference (b);
this->writable = false;
}
void set_num_glyphs (unsigned int num_glyphs_)
{
num_glyphs = num_glyphs_;
num_glyphs_set = true;
}
unsigned int get_num_glyphs () { return num_glyphs; }
void set_max_ops (int max_ops_) { max_ops = max_ops_; }
template <typename T>
void set_object (const T *obj)
{
reset_object ();
if (!obj) return;
const char *obj_start = (const char *) obj;
if (unlikely (obj_start < this->start || this->end <= obj_start))
this->start = this->end = nullptr;
else
{
this->start = obj_start;
this->end = obj_start + MIN<uintptr_t> (this->end - obj_start, obj->get_size ());
}
}
void reset_object ()
{
this->start = this->blob->data;
this->end = this->start + this->blob->length;
assert (this->start <= this->end); /* Must not overflow. */
}
void start_processing ()
{
reset_object ();
this->max_ops = MAX ((unsigned int) (this->end - this->start) * HB_SANITIZE_MAX_OPS_FACTOR,
(unsigned) HB_SANITIZE_MAX_OPS_MIN);
this->edit_count = 0;
this->debug_depth = 0;
DEBUG_MSG_LEVEL (SANITIZE, start, 0, +1,
"start [%p..%p] (%lu bytes)",
this->start, this->end,
(unsigned long) (this->end - this->start));
}
void end_processing ()
{
DEBUG_MSG_LEVEL (SANITIZE, this->start, 0, -1,
"end [%p..%p] %u edit requests",
this->start, this->end, this->edit_count);
hb_blob_destroy (this->blob);
this->blob = nullptr;
this->start = this->end = nullptr;
}
bool check_range (const void *base,
unsigned int len) const
{
const char *p = (const char *) base;
bool ok = this->start <= p &&
p <= this->end &&
(unsigned int) (this->end - p) >= len &&
this->max_ops-- > 0;
DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
"check_range [%p..%p] (%d bytes) in [%p..%p] -> %s",
p, p + len, len,
this->start, this->end,
ok ? "OK" : "OUT-OF-RANGE");
return likely (ok);
}
template <typename T>
bool check_range (const T *base,
unsigned int a,
unsigned int b) const
{
return !hb_unsigned_mul_overflows (a, b) &&
this->check_range (base, a * b);
}
template <typename T>
bool check_range (const T *base,
unsigned int a,
unsigned int b,
unsigned int c) const
{
return !hb_unsigned_mul_overflows (a, b) &&
this->check_range (base, a * b, c);
}
template <typename T>
bool check_array (const T *base, unsigned int len) const
{
return this->check_range (base, len, hb_static_size (T));
}
template <typename T>
bool check_array (const T *base,
unsigned int a,
unsigned int b) const
{
return this->check_range (base, a, b, hb_static_size (T));
}
template <typename Type>
bool check_struct (const Type *obj) const
{ return likely (this->check_range (obj, obj->min_size)); }
bool may_edit (const void *base, unsigned int len)
{
if (this->edit_count >= HB_SANITIZE_MAX_EDITS)
return false;
const char *p = (const char *) base;
this->edit_count++;
DEBUG_MSG_LEVEL (SANITIZE, p, this->debug_depth+1, 0,
"may_edit(%u) [%p..%p] (%d bytes) in [%p..%p] -> %s",
this->edit_count,
p, p + len, len,
this->start, this->end,
this->writable ? "GRANTED" : "DENIED");
return this->writable;
}
template <typename Type, typename ValueType>
bool try_set (const Type *obj, const ValueType &v)
{
if (this->may_edit (obj, hb_static_size (Type)))
{
hb_assign (* const_cast<Type *> (obj), v);
return true;
}
return false;
}
template <typename Type>
hb_blob_t *sanitize_blob (hb_blob_t *blob)
{
bool sane;
init (blob);
retry:
DEBUG_MSG_FUNC (SANITIZE, start, "start");
start_processing ();
if (unlikely (!start))
{
end_processing ();
return blob;
}
Type *t = CastP<Type> (const_cast<char *> (start));
sane = t->sanitize (this);
if (sane)
{
if (edit_count)
{
DEBUG_MSG_FUNC (SANITIZE, start, "passed first round with %d edits; going for second round", edit_count);
/* sanitize again to ensure no toe-stepping */
edit_count = 0;
sane = t->sanitize (this);
if (edit_count) {
DEBUG_MSG_FUNC (SANITIZE, start, "requested %d edits in second round; FAILLING", edit_count);
sane = false;
}
}
}
else
{
if (edit_count && !writable) {
start = hb_blob_get_data_writable (blob, nullptr);
end = start + blob->length;
if (start)
{
writable = true;
/* ok, we made it writable by relocating. try again */
DEBUG_MSG_FUNC (SANITIZE, start, "retry");
goto retry;
}
}
}
end_processing ();
DEBUG_MSG_FUNC (SANITIZE, start, sane ? "PASSED" : "FAILED");
if (sane)
{
hb_blob_make_immutable (blob);
return blob;
}
else
{
hb_blob_destroy (blob);
return hb_blob_get_empty ();
}
}
template <typename Type>
hb_blob_t *reference_table (const hb_face_t *face, hb_tag_t tableTag = Type::tableTag)
{
if (!num_glyphs_set)
set_num_glyphs (hb_face_get_glyph_count (face));
return sanitize_blob<Type> (hb_face_reference_table (face, tableTag));
}
mutable unsigned int debug_depth;
const char *start, *end;
mutable int max_ops;
private:
bool writable;
unsigned int edit_count;
hb_blob_t *blob;
unsigned int num_glyphs;
bool num_glyphs_set;
};
struct hb_sanitize_with_object_t
{
template <typename T>
hb_sanitize_with_object_t (hb_sanitize_context_t *c,
const T& obj) : c (c)
{ c->set_object (obj); }
~hb_sanitize_with_object_t ()
{ c->reset_object (); }
private:
hb_sanitize_context_t *c;
};
/*
* Serialize
*/
struct hb_serialize_context_t
{
hb_serialize_context_t (void *start_, unsigned int size)
{
this->start = (char *) start_;
this->end = this->start + size;
reset ();
}
bool in_error () const { return !this->successful; }
void reset ()
{
this->successful = true;
this->head = this->start;
this->debug_depth = 0;
}
bool propagate_error (bool e)
{ return this->successful = this->successful && e; }
template <typename T> bool propagate_error (const T &obj)
{ return this->successful = this->successful && !obj.in_error (); }
template <typename T> bool propagate_error (const T *obj)
{ return this->successful = this->successful && !obj->in_error (); }
template <typename T1, typename T2> bool propagate_error (T1 &o1, T2 &o2)
{ return propagate_error (o1) && propagate_error (o2); }
template <typename T1, typename T2> bool propagate_error (T1 *o1, T2 *o2)
{ return propagate_error (o1) && propagate_error (o2); }
template <typename T1, typename T2, typename T3>
bool propagate_error (T1 &o1, T2 &o2, T3 &o3)
{ return propagate_error (o1) && propagate_error (o2, o3); }
template <typename T1, typename T2, typename T3>
bool propagate_error (T1 *o1, T2 *o2, T3 *o3)
{ return propagate_error (o1) && propagate_error (o2, o3); }
/* To be called around main operation. */
template <typename Type>
Type *start_serialize ()
{
DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, +1,
"start [%p..%p] (%lu bytes)",
this->start, this->end,
(unsigned long) (this->end - this->start));
return start_embed<Type> ();
}
void end_serialize ()
{
DEBUG_MSG_LEVEL (SERIALIZE, this->start, 0, -1,
"end [%p..%p] serialized %d bytes; %s",
this->start, this->end,
(int) (this->head - this->start),
this->successful ? "successful" : "UNSUCCESSFUL");
}
unsigned int length () const { return this->head - this->start; }
void align (unsigned int alignment)
{
unsigned int l = length () % alignment;
if (l)
allocate_size<void> (alignment - l);
}
template <typename Type>
Type *start_embed (const Type *_ HB_UNUSED = nullptr) const
{
Type *ret = reinterpret_cast<Type *> (this->head);
return ret;
}
template <typename Type>
Type *allocate_size (unsigned int size)
{
if (unlikely (!this->successful || this->end - this->head < ptrdiff_t (size))) {
this->successful = false;
return nullptr;
}
memset (this->head, 0, size);
char *ret = this->head;
this->head += size;
return reinterpret_cast<Type *> (ret);
}
template <typename Type>
Type *allocate_min ()
{
return this->allocate_size<Type> (Type::min_size);
}
template <typename Type>
Type *embed (const Type &obj)
{
unsigned int size = obj.get_size ();
Type *ret = this->allocate_size<Type> (size);
if (unlikely (!ret)) return nullptr;
memcpy (ret, &obj, size);
return ret;
}
template <typename Type>
hb_serialize_context_t &operator << (const Type &obj) { embed (obj); return *this; }
template <typename Type>
Type *extend_size (Type &obj, unsigned int size)
{
assert (this->start <= (char *) &obj);
assert ((char *) &obj <= this->head);
assert ((char *) &obj + size >= this->head);
if (unlikely (!this->allocate_size<Type> (((char *) &obj) + size - this->head))) return nullptr;
return reinterpret_cast<Type *> (&obj);
}
template <typename Type>
Type *extend_min (Type &obj) { return extend_size (obj, obj.min_size); }
template <typename Type>
Type *extend (Type &obj) { return extend_size (obj, obj.get_size ()); }
/* Output routines. */
template <typename Type>
Type *copy () const
{
assert (this->successful);
unsigned int len = this->head - this->start;
void *p = malloc (len);
if (p)
memcpy (p, this->start, len);
return reinterpret_cast<Type *> (p);
}
hb_bytes_t copy_bytes () const
{
assert (this->successful);
unsigned int len = this->head - this->start;
void *p = malloc (len);
if (p)
memcpy (p, this->start, len);
else
return hb_bytes_t ();
return hb_bytes_t ((char *) p, len);
}
hb_blob_t *copy_blob () const
{
assert (this->successful);
return hb_blob_create (this->start,
this->head - this->start,
HB_MEMORY_MODE_DUPLICATE,
nullptr, nullptr);
}
public:
unsigned int debug_depth;
char *start, *end, *head;
bool successful;
};
/*
* Big-endian integers.
*/
template <typename Type, int Bytes> struct BEInt;
template <typename Type>
struct BEInt<Type, 1>
{
public:
void set (Type V) { v = V; }
operator Type () const { return v; }
private: uint8_t v;
};
template <typename Type>
struct BEInt<Type, 2>
{
public:
void set (Type V)
{
v[0] = (V >> 8) & 0xFF;
v[1] = (V ) & 0xFF;
}
operator Type () const
{
#if ((defined(__GNUC__) && __GNUC__ >= 5) || defined(__clang__)) && \
defined(__BYTE_ORDER) && \
(__BYTE_ORDER == __LITTLE_ENDIAN || __BYTE_ORDER == __BIG_ENDIAN)
/* Spoon-feed the compiler a big-endian integer with alignment 1.
* https://github.com/harfbuzz/harfbuzz/pull/1398 */
struct __attribute__((packed)) packed_uint16_t { uint16_t v; };
#if __BYTE_ORDER == __LITTLE_ENDIAN
return __builtin_bswap16 (((packed_uint16_t *) this)->v);
#else /* __BYTE_ORDER == __BIG_ENDIAN */
return ((packed_uint16_t *) this)->v;
#endif
#endif
return (v[0] << 8)
+ (v[1] );
}
private: uint8_t v[2];
};
template <typename Type>
struct BEInt<Type, 3>
{
public:
void set (Type V)
{
v[0] = (V >> 16) & 0xFF;
v[1] = (V >> 8) & 0xFF;
v[2] = (V ) & 0xFF;
}
operator Type () const
{
return (v[0] << 16)
+ (v[1] << 8)
+ (v[2] );
}
private: uint8_t v[3];
};
template <typename Type>
struct BEInt<Type, 4>
{
public:
typedef Type type;
void set (Type V)
{
v[0] = (V >> 24) & 0xFF;
v[1] = (V >> 16) & 0xFF;
v[2] = (V >> 8) & 0xFF;
v[3] = (V ) & 0xFF;
}
operator Type () const
{
return (v[0] << 24)
+ (v[1] << 16)
+ (v[2] << 8)
+ (v[3] );
}
private: uint8_t v[4];
};
/*
* Lazy loaders.
*/
template <typename Data, unsigned int WheresData>
struct hb_data_wrapper_t
{
static_assert (WheresData > 0, "");
Data * get_data () const
{ return *(((Data **) (void *) this) - WheresData); }
bool is_inert () const { return !get_data (); }
template <typename Stored, typename Subclass>
Stored * call_create () const { return Subclass::create (get_data ()); }
};
template <>
struct hb_data_wrapper_t<void, 0>
{
bool is_inert () const { return false; }
template <typename Stored, typename Funcs>
Stored * call_create () const { return Funcs::create (); }
};
template <typename T1, typename T2> struct hb_non_void_t { typedef T1 value; };
template <typename T2> struct hb_non_void_t<void, T2> { typedef T2 value; };
template <typename Returned,
typename Subclass = void,
typename Data = void,
unsigned int WheresData = 0,
typename Stored = Returned>
struct hb_lazy_loader_t : hb_data_wrapper_t<Data, WheresData>
{
typedef typename hb_non_void_t<Subclass,
hb_lazy_loader_t<Returned,Subclass,Data,WheresData,Stored>
>::value Funcs;
void init0 () {} /* Init, when memory is already set to 0. No-op for us. */
void init () { instance.set_relaxed (nullptr); }
void fini () { do_destroy (instance.get ()); }
void free_instance ()
{
retry:
Stored *p = instance.get ();
if (unlikely (p && !cmpexch (p, nullptr)))
goto retry;
do_destroy (p);
}
static void do_destroy (Stored *p)
{
if (p && p != const_cast<Stored *> (Funcs::get_null ()))
Funcs::destroy (p);
}
const Returned * operator -> () const { return get (); }
const Returned & operator * () const { return *get (); }
explicit_operator bool () const
{ return get_stored () != Funcs::get_null (); }
template <typename C> operator const C * () const { return get (); }
Stored * get_stored () const
{
retry:
Stored *p = this->instance.get ();
if (unlikely (!p))
{
if (unlikely (this->is_inert ()))
return const_cast<Stored *> (Funcs::get_null ());
p = this->template call_create<Stored, Funcs> ();
if (unlikely (!p))
p = const_cast<Stored *> (Funcs::get_null ());
if (unlikely (!cmpexch (nullptr, p)))
{
do_destroy (p);
goto retry;
}
}
return p;
}
Stored * get_stored_relaxed () const
{
return this->instance.get_relaxed ();
}
bool cmpexch (Stored *current, Stored *value) const
{
/* This *must* be called when there are no other threads accessing. */
return this->instance.cmpexch (current, value);
}
const Returned * get () const { return Funcs::convert (get_stored ()); }
const Returned * get_relaxed () const { return Funcs::convert (get_stored_relaxed ()); }
Returned * get_unconst () const { return const_cast<Returned *> (Funcs::convert (get_stored ())); }
/* To be possibly overloaded by subclasses. */
static Returned* convert (Stored *p) { return p; }
/* By default null/init/fini the object. */
static const Stored* get_null () { return &Null(Stored); }
static Stored *create (Data *data)
{
Stored *p = (Stored *) calloc (1, sizeof (Stored));
if (likely (p))
p->init (data);
return p;
}
static Stored *create ()
{
Stored *p = (Stored *) calloc (1, sizeof (Stored));
if (likely (p))
p->init ();
return p;
}
static void destroy (Stored *p)
{
p->fini ();
free (p);
}
// private:
/* Must only have one pointer. */
hb_atomic_ptr_t<Stored *> instance;
};
/* Specializations. */
template <typename T, unsigned int WheresFace>
struct hb_face_lazy_loader_t : hb_lazy_loader_t<T,
hb_face_lazy_loader_t<T, WheresFace>,
hb_face_t, WheresFace> {};
template <typename T, unsigned int WheresFace>
struct hb_table_lazy_loader_t : hb_lazy_loader_t<T,
hb_table_lazy_loader_t<T, WheresFace>,
hb_face_t, WheresFace,
hb_blob_t>
{
static hb_blob_t *create (hb_face_t *face)
{ return hb_sanitize_context_t ().reference_table<T> (face); }
static void destroy (hb_blob_t *p) { hb_blob_destroy (p); }
static const hb_blob_t *get_null ()
{ return hb_blob_get_empty (); }
static const T* convert (const hb_blob_t *blob)
{ return blob->as<T> (); }
hb_blob_t* get_blob () const { return this->get_stored (); }
};
template <typename Subclass>
struct hb_font_funcs_lazy_loader_t : hb_lazy_loader_t<hb_font_funcs_t, Subclass>
{
static void destroy (hb_font_funcs_t *p)
{ hb_font_funcs_destroy (p); }
static const hb_font_funcs_t *get_null ()
{ return hb_font_funcs_get_empty (); }
};
template <typename Subclass>
struct hb_unicode_funcs_lazy_loader_t : hb_lazy_loader_t<hb_unicode_funcs_t, Subclass>
{
static void destroy (hb_unicode_funcs_t *p)
{ hb_unicode_funcs_destroy (p); }
static const hb_unicode_funcs_t *get_null ()
{ return hb_unicode_funcs_get_empty (); }
};
#endif /* HB_MACHINERY_HH */
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