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// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
#include "platform/utils.h"
#include "vm/allocation.h"
#include "vm/handles.h"
#include "vm/memory_region.h"
#include "vm/thread_state.h"
namespace dart {
// Zones support very fast allocation of small chunks of memory. The
// chunks cannot be deallocated individually, but instead zones
// support deallocating all chunks in one fast operation.
class Zone {
// Allocate an array sized to hold 'len' elements of type
// 'ElementType'. Checks for integer overflow when performing the
// size computation.
template <class ElementType>
inline ElementType* Alloc(intptr_t len);
// Allocates an array sized to hold 'len' elements of type
// 'ElementType'. The new array is initialized from the memory of
// 'old_array' up to 'old_len'.
template <class ElementType>
inline ElementType* Realloc(ElementType* old_array,
intptr_t old_len,
intptr_t new_len);
// Allocates 'size' bytes of memory in the zone; expands the zone by
// allocating new segments of memory on demand using 'new'.
// It is preferred to use Alloc<T>() instead, as that function can
// check for integer overflow. If you use AllocUnsafe, you are
// responsible for avoiding integer overflow yourself.
inline uword AllocUnsafe(intptr_t size);
// Make a copy of the string in the zone allocated area.
char* MakeCopyOfString(const char* str);
// Make a copy of the first n characters of a string in the zone
// allocated area.
char* MakeCopyOfStringN(const char* str, intptr_t len);
// Concatenate strings |a| and |b|. |a| may be NULL. If |a| is not NULL,
// |join| will be inserted between |a| and |b|.
char* ConcatStrings(const char* a, const char* b, char join = ',');
// TODO(zra): Remove these calls and replace them with calls to OS::SCreate
// and OS::VSCreate.
// These calls are deprecated. Do not add further calls to these functions.
// instead use OS::SCreate and OS::VSCreate.
// Make a zone-allocated string based on printf format and args.
char* PrintToString(const char* format, ...) PRINTF_ATTRIBUTE(2, 3);
char* VPrint(const char* format, va_list args);
// Compute the total size of this zone. This includes wasted space that is
// due to internal fragmentation in the segments.
uintptr_t SizeInBytes() const;
// Computes the amount of space used in the zone.
uintptr_t CapacityInBytes() const;
// Structure for managing handles allocation.
VMHandles* handles() { return &handles_; }
void VisitObjectPointers(ObjectPointerVisitor* visitor);
Zone* previous() const { return previous_; }
bool ContainsNestedZone(Zone* other) const {
while (other != NULL) {
if (this == other) return true;
other = other->previous_;
return false;
// All pointers returned from AllocateUnsafe() and New() have this alignment.
static const intptr_t kAlignment = kDoubleSize;
static void Init();
static void Cleanup();
static intptr_t Size() { return total_size_; }
~Zone(); // Delete all memory associated with the zone.
// Default initial chunk size.
static const intptr_t kInitialChunkSize = 1 * KB;
// Default segment size.
static const intptr_t kSegmentSize = 64 * KB;
// Zap value used to indicate deleted zone area (debug purposes).
static const unsigned char kZapDeletedByte = 0x42;
// Zap value used to indicate uninitialized zone area (debug purposes).
static const unsigned char kZapUninitializedByte = 0xab;
// Total size of current zone segments.
static RelaxedAtomic<intptr_t> total_size_;
// Expand the zone to accommodate an allocation of 'size' bytes.
uword AllocateExpand(intptr_t size);
// Allocate a large segment.
uword AllocateLargeSegment(intptr_t size);
// Insert zone into zone chain, after current_zone.
void Link(Zone* current_zone) { previous_ = current_zone; }
// Delete all objects and free all memory allocated in the zone.
void DeleteAll();
// Does not actually free any memory. Enables templated containers like
// BaseGrowableArray to use different allocators.
template <class ElementType>
void Free(ElementType* old_array, intptr_t len) {
#ifdef DEBUG
if (len > 0) {
ASSERT(old_array != nullptr);
memset(static_cast<void*>(old_array), kZapUninitializedByte,
len * sizeof(ElementType));
// Dump the current allocated sizes in the zone object.
void DumpZoneSizes();
// Overflow check (FATAL) for array length.
template <class ElementType>
static inline void CheckLength(intptr_t len);
// This buffer is used for allocation before any segments.
// This would act as the initial stack allocated chunk so that we don't
// end up calling malloc/free on zone scopes that allocate less than
// kChunkSize
COMPILE_ASSERT(kAlignment <= 8);
ALIGN8 uint8_t buffer_[kInitialChunkSize];
MemoryRegion initial_buffer_;
// The free region in the current (head) segment or the initial buffer is
// represented as the half-open interval [position, limit). The 'position'
// variable is guaranteed to be aligned as dictated by kAlignment.
uword position_;
uword limit_;
// Zone segments are internal data structures used to hold information
// about the memory segmentations that constitute a zone. The entire
// implementation is in
class Segment;
// Total size of all segments in [head_].
intptr_t small_segment_capacity_ = 0;
// The current head segment; may be NULL.
Segment* head_;
// List of large segments allocated in this zone; may be NULL.
Segment* large_segments_;
// Structure for managing handles allocation.
VMHandles handles_;
// Used for chaining zones in order to allow unwinding of stacks.
Zone* previous_;
friend class StackZone;
friend class ApiZone;
template <typename T, typename B, typename Allocator>
friend class BaseGrowableArray;
template <typename T, typename B, typename Allocator>
friend class BaseDirectChainedHashMap;
class StackZone : public StackResource {
// Create an empty zone and set is at the current zone for the Thread.
explicit StackZone(ThreadState* thread);
// Delete all memory associated with the zone.
virtual ~StackZone();
// Compute the total size of this zone. This includes wasted space that is
// due to internal fragmentation in the segments.
uintptr_t SizeInBytes() const { return zone_->SizeInBytes(); }
// Computes the used space in the zone.
intptr_t CapacityInBytes() const { return zone_->CapacityInBytes(); }
Zone* GetZone() { return zone_; }
Zone* zone_;
template <typename T>
friend class GrowableArray;
template <typename T>
friend class ZoneGrowableArray;
inline uword Zone::AllocUnsafe(intptr_t size) {
ASSERT(size >= 0);
// Round up the requested size to fit the alignment.
if (size > (kIntptrMax - kAlignment)) {
FATAL1("Zone::Alloc: 'size' is too large: size=%" Pd "", size);
size = Utils::RoundUp(size, kAlignment);
// Check if the requested size is available without expanding.
uword result;
intptr_t free_size = (limit_ - position_);
if (free_size >= size) {
result = position_;
position_ += size;
} else {
result = AllocateExpand(size);
// Check that the result has the proper alignment and return it.
ASSERT(Utils::IsAligned(result, kAlignment));
return result;
template <class ElementType>
inline void Zone::CheckLength(intptr_t len) {
const intptr_t kElementSize = sizeof(ElementType);
if (len > (kIntptrMax / kElementSize)) {
FATAL2("Zone::Alloc: 'len' is too large: len=%" Pd ", kElementSize=%" Pd,
len, kElementSize);
template <class ElementType>
inline ElementType* Zone::Alloc(intptr_t len) {
return reinterpret_cast<ElementType*>(AllocUnsafe(len * sizeof(ElementType)));
template <class ElementType>
inline ElementType* Zone::Realloc(ElementType* old_data,
intptr_t old_len,
intptr_t new_len) {
const intptr_t kElementSize = sizeof(ElementType);
uword old_end = reinterpret_cast<uword>(old_data) + (old_len * kElementSize);
// Resize existing allocation if nothing was allocated in between...
if (Utils::RoundUp(old_end, kAlignment) == position_) {
uword new_end =
reinterpret_cast<uword>(old_data) + (new_len * kElementSize);
// ...and there is sufficient space.
if (new_end <= limit_) {
ASSERT(new_len >= old_len);
position_ = Utils::RoundUp(new_end, kAlignment);
return old_data;
if (new_len <= old_len) {
return old_data;
ElementType* new_data = Alloc<ElementType>(new_len);
if (old_data != 0) {
reinterpret_cast<void*>(old_data), old_len * kElementSize);
return new_data;
} // namespace dart
#endif // RUNTIME_VM_ZONE_H_