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Diffstat (limited to 'mozglue/baseprofiler/public/ProfileChunkedBuffer.h')
| -rw-r--r-- | mozglue/baseprofiler/public/ProfileChunkedBuffer.h | 1872 |
1 files changed, 1872 insertions, 0 deletions
diff --git a/mozglue/baseprofiler/public/ProfileChunkedBuffer.h b/mozglue/baseprofiler/public/ProfileChunkedBuffer.h new file mode 100644 index 0000000000..d4d55eafcb --- /dev/null +++ b/mozglue/baseprofiler/public/ProfileChunkedBuffer.h @@ -0,0 +1,1872 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim: set ts=8 sts=2 et sw=2 tw=80: */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +#ifndef ProfileChunkedBuffer_h +#define ProfileChunkedBuffer_h + +#include "mozilla/BaseProfilerDetail.h" +#include "mozilla/NotNull.h" +#include "mozilla/ProfileBufferChunkManager.h" +#include "mozilla/ProfileBufferChunkManagerSingle.h" +#include "mozilla/ProfileBufferEntrySerialization.h" +#include "mozilla/RefCounted.h" +#include "mozilla/RefPtr.h" +#include "mozilla/ScopeExit.h" +#include "mozilla/Unused.h" + +#include <cstdio> +#include <utility> + +namespace mozilla { + +namespace detail { + +// Internal accessor pointing at a position inside a chunk. +// It can handle two groups of chunks (typically the extant chunks stored in +// the store manager, and the current chunk). +// The main operations are: +// - ReadEntrySize() to read an entry size, 0 means failure. +// - operator+=(Length) to skip a number of bytes. +// - EntryReader() creates an entry reader at the current position for a given +// size (it may fail with an empty reader), and skips the entry. +// Note that there is no "past-the-end" position -- as soon as InChunkPointer +// reaches the end, it becomes effectively null. +class InChunkPointer { + public: + using Byte = ProfileBufferChunk::Byte; + using Length = ProfileBufferChunk::Length; + + // Nullptr-like InChunkPointer, may be used as end iterator. + InChunkPointer() + : mChunk(nullptr), mNextChunkGroup(nullptr), mOffsetInChunk(0) {} + + // InChunkPointer over one or two chunk groups, pointing at the given + // block index (if still in range). + // This constructor should only be used with *trusted* block index values! + InChunkPointer(const ProfileBufferChunk* aChunk, + const ProfileBufferChunk* aNextChunkGroup, + ProfileBufferBlockIndex aBlockIndex) + : mChunk(aChunk), mNextChunkGroup(aNextChunkGroup) { + if (mChunk) { + mOffsetInChunk = mChunk->OffsetFirstBlock(); + Adjust(); + } else if (mNextChunkGroup) { + mChunk = mNextChunkGroup; + mNextChunkGroup = nullptr; + mOffsetInChunk = mChunk->OffsetFirstBlock(); + Adjust(); + } else { + mOffsetInChunk = 0; + } + + // Try to advance to given position. + if (!AdvanceToGlobalRangePosition(aBlockIndex)) { + // Block does not exist anymore (or block doesn't look valid), reset the + // in-chunk pointer. + mChunk = nullptr; + mNextChunkGroup = nullptr; + } + } + + // InChunkPointer over one or two chunk groups, will start at the first + // block (if any). This may be slow, so avoid using it too much. + InChunkPointer(const ProfileBufferChunk* aChunk, + const ProfileBufferChunk* aNextChunkGroup, + ProfileBufferIndex aIndex = ProfileBufferIndex(0)) + : mChunk(aChunk), mNextChunkGroup(aNextChunkGroup) { + if (mChunk) { + mOffsetInChunk = mChunk->OffsetFirstBlock(); + Adjust(); + } else if (mNextChunkGroup) { + mChunk = mNextChunkGroup; + mNextChunkGroup = nullptr; + mOffsetInChunk = mChunk->OffsetFirstBlock(); + Adjust(); + } else { + mOffsetInChunk = 0; + } + + // Try to advance to given position. + if (!AdvanceToGlobalRangePosition(aIndex)) { + // Block does not exist anymore, reset the in-chunk pointer. + mChunk = nullptr; + mNextChunkGroup = nullptr; + } + } + + // Compute the current position in the global range. + // 0 if null (including if we're reached the end). + [[nodiscard]] ProfileBufferIndex GlobalRangePosition() const { + if (IsNull()) { + return 0; + } + return mChunk->RangeStart() + mOffsetInChunk; + } + + // Move InChunkPointer forward to the block at the given global block + // position, which is assumed to be valid exactly -- but it may be obsolete. + // 0 stays where it is (if valid already). + // MOZ_ASSERTs if the index is invalid. + [[nodiscard]] bool AdvanceToGlobalRangePosition( + ProfileBufferBlockIndex aBlockIndex) { + if (IsNull()) { + // Pointer is null already. (Not asserting because it's acceptable.) + return false; + } + if (!aBlockIndex) { + // Special null position, just stay where we are. + return ShouldPointAtValidBlock(); + } + if (aBlockIndex.ConvertToProfileBufferIndex() < GlobalRangePosition()) { + // Past the requested position, stay where we are (assuming the current + // position was valid). + return ShouldPointAtValidBlock(); + } + for (;;) { + if (aBlockIndex.ConvertToProfileBufferIndex() < + mChunk->RangeStart() + mChunk->OffsetPastLastBlock()) { + // Target position is in this chunk's written space, move to it. + mOffsetInChunk = + aBlockIndex.ConvertToProfileBufferIndex() - mChunk->RangeStart(); + return ShouldPointAtValidBlock(); + } + // Position is after this chunk, try next chunk. + GoToNextChunk(); + if (IsNull()) { + return false; + } + // Skip whatever block tail there is, we don't allow pointing in the + // middle of a block. + mOffsetInChunk = mChunk->OffsetFirstBlock(); + if (aBlockIndex.ConvertToProfileBufferIndex() < GlobalRangePosition()) { + // Past the requested position, meaning that the given position was in- + // between blocks -> Failure. + MOZ_ASSERT(false, "AdvanceToGlobalRangePosition - In-between blocks"); + return false; + } + } + } + + // Move InChunkPointer forward to the block at or after the given global + // range position. + // 0 stays where it is (if valid already). + [[nodiscard]] bool AdvanceToGlobalRangePosition( + ProfileBufferIndex aPosition) { + if (aPosition == 0) { + // Special position '0', just stay where we are. + // Success if this position is already valid. + return !IsNull(); + } + for (;;) { + ProfileBufferIndex currentPosition = GlobalRangePosition(); + if (currentPosition == 0) { + // Pointer is null. + return false; + } + if (aPosition <= currentPosition) { + // At or past the requested position, stay where we are. + return true; + } + if (aPosition < mChunk->RangeStart() + mChunk->OffsetPastLastBlock()) { + // Target position is in this chunk's written space, move to it. + for (;;) { + // Skip the current block. + mOffsetInChunk += ReadEntrySize(); + if (mOffsetInChunk >= mChunk->OffsetPastLastBlock()) { + // Reached the end of the chunk, this can happen for the last + // block, let's just continue to the next chunk. + break; + } + if (aPosition <= mChunk->RangeStart() + mOffsetInChunk) { + // We're at or after the position, return at this block position. + return true; + } + } + } + // Position is after this chunk, try next chunk. + GoToNextChunk(); + if (IsNull()) { + return false; + } + // Skip whatever block tail there is, we don't allow pointing in the + // middle of a block. + mOffsetInChunk = mChunk->OffsetFirstBlock(); + } + } + + [[nodiscard]] Byte ReadByte() { + MOZ_ASSERT(!IsNull()); + MOZ_ASSERT(mOffsetInChunk < mChunk->OffsetPastLastBlock()); + Byte byte = mChunk->ByteAt(mOffsetInChunk); + if (MOZ_UNLIKELY(++mOffsetInChunk == mChunk->OffsetPastLastBlock())) { + Adjust(); + } + return byte; + } + + // Read and skip a ULEB128-encoded size. + // 0 means failure (0-byte entries are not allowed.) + // Note that this doesn't guarantee that there are actually that many bytes + // available to read! (EntryReader() below may gracefully fail.) + [[nodiscard]] Length ReadEntrySize() { + ULEB128Reader<Length> reader; + if (IsNull()) { + return 0; + } + for (;;) { + const bool isComplete = reader.FeedByteIsComplete(ReadByte()); + if (MOZ_UNLIKELY(IsNull())) { + // End of chunks, so there's no actual entry after this anyway. + return 0; + } + if (MOZ_LIKELY(isComplete)) { + if (MOZ_UNLIKELY(reader.Value() > mChunk->BufferBytes())) { + // Don't allow entries larger than a chunk. + return 0; + } + return reader.Value(); + } + } + } + + InChunkPointer& operator+=(Length aLength) { + MOZ_ASSERT(!IsNull()); + mOffsetInChunk += aLength; + Adjust(); + return *this; + } + + [[nodiscard]] ProfileBufferEntryReader EntryReader(Length aLength) { + if (IsNull() || aLength == 0) { + return ProfileBufferEntryReader(); + } + + MOZ_ASSERT(mOffsetInChunk < mChunk->OffsetPastLastBlock()); + + // We should be pointing at the entry, past the entry size. + const ProfileBufferIndex entryIndex = GlobalRangePosition(); + // Verify that there's enough space before for the size (starting at index + // 1 at least). + MOZ_ASSERT(entryIndex >= 1u + ULEB128Size(aLength)); + + const Length remaining = mChunk->OffsetPastLastBlock() - mOffsetInChunk; + Span<const Byte> mem0 = mChunk->BufferSpan(); + mem0 = mem0.From(mOffsetInChunk); + if (aLength <= remaining) { + // Move to the end of this block, which could make this null if we have + // reached the end of all buffers. + *this += aLength; + return ProfileBufferEntryReader( + mem0.To(aLength), + // Block starts before the entry size. + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + entryIndex - ULEB128Size(aLength)), + // Block ends right after the entry (could be null for last entry). + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + GlobalRangePosition())); + } + + // We need to go to the next chunk for the 2nd part of this block. + GoToNextChunk(); + if (IsNull()) { + return ProfileBufferEntryReader(); + } + + Span<const Byte> mem1 = mChunk->BufferSpan(); + const Length tail = aLength - remaining; + MOZ_ASSERT(tail <= mChunk->BufferBytes()); + MOZ_ASSERT(tail == mChunk->OffsetFirstBlock()); + // We are in the correct chunk, move the offset to the end of the block. + mOffsetInChunk = tail; + // And adjust as needed, which could make this null if we have reached the + // end of all buffers. + Adjust(); + return ProfileBufferEntryReader( + mem0, mem1.To(tail), + // Block starts before the entry size. + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + entryIndex - ULEB128Size(aLength)), + // Block ends right after the entry (could be null for last entry). + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + GlobalRangePosition())); + } + + [[nodiscard]] bool IsNull() const { return !mChunk; } + + [[nodiscard]] bool operator==(const InChunkPointer& aOther) const { + if (IsNull() || aOther.IsNull()) { + return IsNull() && aOther.IsNull(); + } + return mChunk == aOther.mChunk && mOffsetInChunk == aOther.mOffsetInChunk; + } + + [[nodiscard]] bool operator!=(const InChunkPointer& aOther) const { + return !(*this == aOther); + } + + [[nodiscard]] Byte operator*() const { + MOZ_ASSERT(!IsNull()); + MOZ_ASSERT(mOffsetInChunk < mChunk->OffsetPastLastBlock()); + return mChunk->ByteAt(mOffsetInChunk); + } + + InChunkPointer& operator++() { + MOZ_ASSERT(!IsNull()); + MOZ_ASSERT(mOffsetInChunk < mChunk->OffsetPastLastBlock()); + if (MOZ_UNLIKELY(++mOffsetInChunk == mChunk->OffsetPastLastBlock())) { + mOffsetInChunk = 0; + GoToNextChunk(); + Adjust(); + } + return *this; + } + + private: + void GoToNextChunk() { + MOZ_ASSERT(!IsNull()); + const ProfileBufferIndex expectedNextRangeStart = + mChunk->RangeStart() + mChunk->BufferBytes(); + + mChunk = mChunk->GetNext(); + if (!mChunk) { + // Reached the end of the current chunk group, try the next one (which + // may be null too, especially on the 2nd try). + mChunk = mNextChunkGroup; + mNextChunkGroup = nullptr; + } + + if (mChunk && mChunk->RangeStart() == 0) { + // Reached a chunk without a valid (non-null) range start, assume there + // are only unused chunks from here on. + mChunk = nullptr; + } + + MOZ_ASSERT(!mChunk || mChunk->RangeStart() == expectedNextRangeStart, + "We don't handle discontinuous buffers (yet)"); + // Non-DEBUG fallback: Stop reading past discontinuities. + // (They should be rare, only happening on temporary OOMs.) + // TODO: Handle discontinuities (by skipping over incomplete blocks). + if (mChunk && mChunk->RangeStart() != expectedNextRangeStart) { + mChunk = nullptr; + } + } + + // We want `InChunkPointer` to always point at a valid byte (or be null). + // After some operations, `mOffsetInChunk` may point past the end of the + // current `mChunk`, in which case we need to adjust our position to be inside + // the appropriate chunk. E.g., if we're 10 bytes after the end of the current + // chunk, we should end up at offset 10 in the next chunk. + // Note that we may "fall off" the last chunk and make this `InChunkPointer` + // effectively null. + void Adjust() { + while (mChunk && mOffsetInChunk >= mChunk->OffsetPastLastBlock()) { + // TODO: Try to adjust offset between chunks relative to mRangeStart + // differences. But we don't handle discontinuities yet. + if (mOffsetInChunk < mChunk->BufferBytes()) { + mOffsetInChunk -= mChunk->BufferBytes(); + } else { + mOffsetInChunk -= mChunk->OffsetPastLastBlock(); + } + GoToNextChunk(); + } + } + + // Check if the current position is likely to point at a valid block. + // (Size should be reasonable, and block should fully fit inside buffer.) + // MOZ_ASSERTs on failure, to catch incorrect uses of block indices (which + // should only point at valid blocks if still in range). Non-asserting build + // fallback should still be handled. + [[nodiscard]] bool ShouldPointAtValidBlock() const { + if (IsNull()) { + // Pointer is null, no blocks here. + MOZ_ASSERT(false, "ShouldPointAtValidBlock - null pointer"); + return false; + } + // Use a copy, so we don't modify `*this`. + InChunkPointer pointer = *this; + // Try to read the entry size. + Length entrySize = pointer.ReadEntrySize(); + if (entrySize == 0) { + // Entry size of zero means we read 0 or a way-too-big value. + MOZ_ASSERT(false, "ShouldPointAtValidBlock - invalid size"); + return false; + } + // See if the last byte of the entry is still inside the buffer. + pointer += entrySize - 1; + MOZ_ASSERT(!IsNull(), "ShouldPointAtValidBlock - past end of buffer"); + return !IsNull(); + } + + const ProfileBufferChunk* mChunk; + const ProfileBufferChunk* mNextChunkGroup; + Length mOffsetInChunk; +}; + +} // namespace detail + +// Thread-safe buffer that can store blocks of different sizes during defined +// sessions, using Chunks (from a ChunkManager) as storage. +// +// Each *block* contains an *entry* and the entry size: +// [ entry_size | entry ] [ entry_size | entry ] ... +// +// *In-session* is a period of time during which `ProfileChunkedBuffer` allows +// reading and writing. +// *Out-of-session*, the `ProfileChunkedBuffer` object is still valid, but +// contains no data, and gracefully denies accesses. +// +// To write an entry, the buffer reserves a block of sufficient size (to contain +// user data of predetermined size), writes the entry size, and lets the caller +// fill the entry contents using a ProfileBufferEntryWriter. E.g.: +// ``` +// ProfileChunkedBuffer cb(...); +// cb.ReserveAndPut([]() { return sizeof(123); }, +// [&](Maybe<ProfileBufferEntryWriter>& aEW) { +// if (aEW) { aEW->WriteObject(123); } +// }); +// ``` +// Other `Put...` functions may be used as shortcuts for simple entries. +// The objects given to the caller's callbacks should only be used inside the +// callbacks and not stored elsewhere, because they keep their own references to +// chunk memory and therefore should not live longer. +// Different type of objects may be serialized into an entry, see +// `ProfileBufferEntryWriter::Serializer` for more information. +// +// When reading data, the buffer iterates over blocks (it knows how to read the +// entry size, and therefore move to the next block), and lets the caller read +// the entry inside of each block. E.g.: +// ``` +// cb.ReadEach([](ProfileBufferEntryReader& aER) { +// /* Use ProfileBufferEntryReader functions to read serialized objects. */ +// int n = aER.ReadObject<int>(); +// }); +// ``` +// Different type of objects may be deserialized from an entry, see +// `ProfileBufferEntryReader::Deserializer` for more information. +// +// Writers may retrieve the block index corresponding to an entry +// (`ProfileBufferBlockIndex` is an opaque type preventing the user from easily +// modifying it). That index may later be used with `ReadAt` to get back to the +// entry in that particular block -- if it still exists. +class ProfileChunkedBuffer { + public: + using Byte = ProfileBufferChunk::Byte; + using Length = ProfileBufferChunk::Length; + + enum class ThreadSafety { WithoutMutex, WithMutex }; + + // Default constructor starts out-of-session (nothing to read or write). + explicit ProfileChunkedBuffer(ThreadSafety aThreadSafety) + : mMutex(aThreadSafety != ThreadSafety::WithoutMutex) {} + + // Start in-session with external chunk manager. + ProfileChunkedBuffer(ThreadSafety aThreadSafety, + ProfileBufferChunkManager& aChunkManager) + : mMutex(aThreadSafety != ThreadSafety::WithoutMutex) { + SetChunkManager(aChunkManager); + } + + // Start in-session with owned chunk manager. + ProfileChunkedBuffer(ThreadSafety aThreadSafety, + UniquePtr<ProfileBufferChunkManager>&& aChunkManager) + : mMutex(aThreadSafety != ThreadSafety::WithoutMutex) { + SetChunkManager(std::move(aChunkManager)); + } + + ~ProfileChunkedBuffer() { + // Do proper clean-up by resetting the chunk manager. + ResetChunkManager(); + } + + // This cannot change during the lifetime of this buffer, so there's no need + // to lock. + [[nodiscard]] bool IsThreadSafe() const { return mMutex.IsActivated(); } + + [[nodiscard]] bool IsInSession() const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return !!mChunkManager; + } + + // Stop using the current chunk manager. + // If we own the current chunk manager, it will be destroyed. + // This will always clear currently-held chunks, if any. + void ResetChunkManager() { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + Unused << ResetChunkManager(lock); + } + + // Set the current chunk manager. + // The caller is responsible for keeping the chunk manager alive as along as + // it's used here (until the next (Re)SetChunkManager, or + // ~ProfileChunkedBuffer). + void SetChunkManager(ProfileBufferChunkManager& aChunkManager) { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + Unused << ResetChunkManager(lock); + SetChunkManager(aChunkManager, lock); + } + + // Set the current chunk manager, and keep ownership of it. + void SetChunkManager(UniquePtr<ProfileBufferChunkManager>&& aChunkManager) { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + Unused << ResetChunkManager(lock); + mOwnedChunkManager = std::move(aChunkManager); + if (mOwnedChunkManager) { + SetChunkManager(*mOwnedChunkManager, lock); + } + } + + // Stop using the current chunk manager, and return it if owned here. + [[nodiscard]] UniquePtr<ProfileBufferChunkManager> ExtractChunkManager() { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return ResetChunkManager(lock); + } + + // Clear the contents of this buffer, ready to receive new chunks. + // Note that memory is not freed: No chunks are destroyed, they are all + // receycled. + // Also the range doesn't reset, instead it continues at some point after the + // previous range. This may be useful if the caller may be keeping indexes + // into old chunks that have now been cleared, using these indexes will fail + // gracefully (instead of potentially pointing into new data). + void Clear() { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return; + } + + mRangeStart = mRangeEnd = mNextChunkRangeStart; + mPushedBlockCount = 0; + mClearedBlockCount = 0; + mFailedPutBytes = 0; + + // Recycle all released chunks as "next" chunks. This will reduce the number + // of future allocations. Also, when using ProfileBufferChunkManagerSingle, + // this retrieves the one chunk if it was released. + UniquePtr<ProfileBufferChunk> releasedChunks = + mChunkManager->GetExtantReleasedChunks(); + if (releasedChunks) { + // Released chunks should be in the "Done" state, they need to be marked + // "recycled" before they can be reused. + for (ProfileBufferChunk* chunk = releasedChunks.get(); chunk; + chunk = chunk->GetNext()) { + chunk->MarkRecycled(); + } + mNextChunks = ProfileBufferChunk::Join(std::move(mNextChunks), + std::move(releasedChunks)); + } + + if (mCurrentChunk) { + // We already have a current chunk (empty or in-use), mark it "done" and + // then "recycled", ready to be reused. + mCurrentChunk->MarkDone(); + mCurrentChunk->MarkRecycled(); + } else { + if (!mNextChunks) { + // No current chunk, and no next chunks to recycle, nothing more to do. + // The next "Put" operation will try to allocate a chunk as needed. + return; + } + + // No current chunk, take a next chunk. + mCurrentChunk = std::exchange(mNextChunks, mNextChunks->ReleaseNext()); + } + + // Here, there was already a current chunk, or one has just been taken. + // Make sure it's ready to receive new entries. + InitializeCurrentChunk(lock); + } + + // Buffer maximum length in bytes. + Maybe<size_t> BufferLength() const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (!mChunkManager) { + return Nothing{}; + } + return Some(mChunkManager->MaxTotalSize()); + } + + [[nodiscard]] size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return SizeOfExcludingThis(aMallocSizeOf, lock); + } + + [[nodiscard]] size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf, lock); + } + + // Snapshot of the buffer state. + struct State { + // Index to/before the first block. + ProfileBufferIndex mRangeStart = 1; + + // Index past the last block. Equals mRangeStart if empty. + ProfileBufferIndex mRangeEnd = 1; + + // Number of blocks that have been pushed into this buffer. + uint64_t mPushedBlockCount = 0; + + // Number of blocks that have been removed from this buffer. + // Note: Live entries = pushed - cleared. + uint64_t mClearedBlockCount = 0; + + // Number of bytes that could not be put into this buffer. + uint64_t mFailedPutBytes = 0; + }; + + // Get a snapshot of the current state. + // When out-of-session, mFirstReadIndex==mNextWriteIndex, and + // mPushedBlockCount==mClearedBlockCount==0. + // Note that these may change right after this thread-safe call, so they + // should only be used for statistical purposes. + [[nodiscard]] State GetState() const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return {mRangeStart, mRangeEnd, mPushedBlockCount, mClearedBlockCount, + mFailedPutBytes}; + } + + [[nodiscard]] bool IsEmpty() const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return mRangeStart == mRangeEnd; + } + + // True if this buffer is already locked on this thread. + // This should be used if some functions may call an already-locked buffer, + // e.g.: Put -> memory hook -> profiler_add_native_allocation_marker -> Put. + [[nodiscard]] bool IsThreadSafeAndLockedOnCurrentThread() const { + return mMutex.IsActivatedAndLockedOnCurrentThread(); + } + + // Lock the buffer mutex and run the provided callback. + // This can be useful when the caller needs to explicitly lock down this + // buffer, but not do anything else with it. + template <typename Callback> + auto LockAndRun(Callback&& aCallback) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return std::forward<Callback>(aCallback)(); + } + + // Reserve a block that can hold an entry of the given `aCallbackEntryBytes()` + // size, write the entry size (ULEB128-encoded), and invoke and return + // `aCallback(Maybe<ProfileBufferEntryWriter>&)`. + // Note: `aCallbackEntryBytes` is a callback instead of a simple value, to + // delay this potentially-expensive computation until after we're checked that + // we're in-session; use `Put(Length, Callback)` below if you know the size + // already. + template <typename CallbackEntryBytes, typename Callback> + auto ReserveAndPut(CallbackEntryBytes&& aCallbackEntryBytes, + Callback&& aCallback) + -> decltype(std::forward<Callback>(aCallback)( + std::declval<Maybe<ProfileBufferEntryWriter>&>())) { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + + // This can only be read in the 2nd lambda below after it has been written + // by the first lambda. + Length entryBytes; + + return ReserveAndPutRaw( + [&]() { + entryBytes = std::forward<CallbackEntryBytes>(aCallbackEntryBytes)(); + MOZ_ASSERT(entryBytes != 0, "Empty entries are not allowed"); + return ULEB128Size(entryBytes) + entryBytes; + }, + [&](Maybe<ProfileBufferEntryWriter>& aMaybeEntryWriter) { + if (aMaybeEntryWriter.isSome()) { + aMaybeEntryWriter->WriteULEB128(entryBytes); + MOZ_ASSERT(aMaybeEntryWriter->RemainingBytes() == entryBytes); + } + return std::forward<Callback>(aCallback)(aMaybeEntryWriter); + }, + lock); + } + + template <typename Callback> + auto Put(Length aEntryBytes, Callback&& aCallback) { + return ReserveAndPut([aEntryBytes]() { return aEntryBytes; }, + std::forward<Callback>(aCallback)); + } + + // Add a new entry copied from the given buffer, return block index. + ProfileBufferBlockIndex PutFrom(const void* aSrc, Length aBytes) { + return ReserveAndPut( + [aBytes]() { return aBytes; }, + [aSrc, aBytes](Maybe<ProfileBufferEntryWriter>& aMaybeEntryWriter) { + if (aMaybeEntryWriter.isNothing()) { + return ProfileBufferBlockIndex{}; + } + aMaybeEntryWriter->WriteBytes(aSrc, aBytes); + return aMaybeEntryWriter->CurrentBlockIndex(); + }); + } + + // Add a new single entry with *all* given object (using a Serializer for + // each), return block index. + template <typename... Ts> + ProfileBufferBlockIndex PutObjects(const Ts&... aTs) { + static_assert(sizeof...(Ts) > 0, + "PutObjects must be given at least one object."); + return ReserveAndPut( + [&]() { return ProfileBufferEntryWriter::SumBytes(aTs...); }, + [&](Maybe<ProfileBufferEntryWriter>& aMaybeEntryWriter) { + if (aMaybeEntryWriter.isNothing()) { + return ProfileBufferBlockIndex{}; + } + aMaybeEntryWriter->WriteObjects(aTs...); + return aMaybeEntryWriter->CurrentBlockIndex(); + }); + } + + // Add a new entry copied from the given object, return block index. + template <typename T> + ProfileBufferBlockIndex PutObject(const T& aOb) { + return PutObjects(aOb); + } + + // Get *all* chunks related to this buffer, including extant chunks in its + // ChunkManager, and yet-unused new/recycled chunks. + // We don't expect this buffer to be used again, though it's still possible + // and will allocate the first buffer when needed. + [[nodiscard]] UniquePtr<ProfileBufferChunk> GetAllChunks() { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return nullptr; + } + UniquePtr<ProfileBufferChunk> chunks = + mChunkManager->GetExtantReleasedChunks(); + Unused << HandleRequestedChunk_IsPending(lock); + if (MOZ_LIKELY(!!mCurrentChunk)) { + mCurrentChunk->MarkDone(); + chunks = + ProfileBufferChunk::Join(std::move(chunks), std::move(mCurrentChunk)); + } + chunks = + ProfileBufferChunk::Join(std::move(chunks), std::move(mNextChunks)); + mChunkManager->ForgetUnreleasedChunks(); + mRangeStart = mRangeEnd = mNextChunkRangeStart; + return chunks; + } + + class Reader; + + // Class that can iterate through blocks and provide + // `ProfileBufferEntryReader`s. + // Created through `Reader`, lives within a lock guard lifetime. + class BlockIterator { + public: +#ifdef DEBUG + ~BlockIterator() { + // No BlockIterator should live outside of a mutexed call. + mBuffer->mMutex.AssertCurrentThreadOwns(); + } +#endif // DEBUG + + // Comparison with other iterator, mostly used in range-for loops. + [[nodiscard]] bool operator==(const BlockIterator& aRhs) const { + MOZ_ASSERT(mBuffer == aRhs.mBuffer); + return mCurrentBlockIndex == aRhs.mCurrentBlockIndex; + } + [[nodiscard]] bool operator!=(const BlockIterator& aRhs) const { + MOZ_ASSERT(mBuffer == aRhs.mBuffer); + return mCurrentBlockIndex != aRhs.mCurrentBlockIndex; + } + + // Advance to next BlockIterator. + BlockIterator& operator++() { + mBuffer->mMutex.AssertCurrentThreadOwns(); + mCurrentBlockIndex = + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mNextBlockPointer.GlobalRangePosition()); + mCurrentEntry = + mNextBlockPointer.EntryReader(mNextBlockPointer.ReadEntrySize()); + return *this; + } + + // Dereferencing creates a `ProfileBufferEntryReader` object for the entry + // inside this block. + // (Note: It would be possible to return a `const + // ProfileBufferEntryReader&`, but not useful in practice, because in most + // case the user will want to read, which is non-const.) + [[nodiscard]] ProfileBufferEntryReader operator*() const { + return mCurrentEntry; + } + + // True if this iterator is just past the last entry. + [[nodiscard]] bool IsAtEnd() const { + return mCurrentEntry.RemainingBytes() == 0; + } + + // Can be used as reference to come back to this entry with `GetEntryAt()`. + [[nodiscard]] ProfileBufferBlockIndex CurrentBlockIndex() const { + return mCurrentBlockIndex; + } + + // Index past the end of this block, which is the start of the next block. + [[nodiscard]] ProfileBufferBlockIndex NextBlockIndex() const { + MOZ_ASSERT(!IsAtEnd()); + return ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mNextBlockPointer.GlobalRangePosition()); + } + + // Index of the first block in the whole buffer. + [[nodiscard]] ProfileBufferBlockIndex BufferRangeStart() const { + mBuffer->mMutex.AssertCurrentThreadOwns(); + return ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mBuffer->mRangeStart); + } + + // Index past the last block in the whole buffer. + [[nodiscard]] ProfileBufferBlockIndex BufferRangeEnd() const { + mBuffer->mMutex.AssertCurrentThreadOwns(); + return ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mBuffer->mRangeEnd); + } + + private: + // Only a Reader can instantiate a BlockIterator. + friend class Reader; + + BlockIterator(const ProfileChunkedBuffer& aBuffer, + const ProfileBufferChunk* aChunks0, + const ProfileBufferChunk* aChunks1, + ProfileBufferBlockIndex aBlockIndex) + : mNextBlockPointer(aChunks0, aChunks1, aBlockIndex), + mCurrentBlockIndex( + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mNextBlockPointer.GlobalRangePosition())), + mCurrentEntry( + mNextBlockPointer.EntryReader(mNextBlockPointer.ReadEntrySize())), + mBuffer(WrapNotNull(&aBuffer)) { + // No BlockIterator should live outside of a mutexed call. + mBuffer->mMutex.AssertCurrentThreadOwns(); + } + + detail::InChunkPointer mNextBlockPointer; + + ProfileBufferBlockIndex mCurrentBlockIndex; + + ProfileBufferEntryReader mCurrentEntry; + + // Using a non-null pointer instead of a reference, to allow copying. + // This BlockIterator should only live inside one of the thread-safe + // ProfileChunkedBuffer functions, for this reference to stay valid. + NotNull<const ProfileChunkedBuffer*> mBuffer; + }; + + // Class that can create `BlockIterator`s (e.g., for range-for), or just + // iterate through entries; lives within a lock guard lifetime. + class MOZ_RAII Reader { + public: + Reader(const Reader&) = delete; + Reader& operator=(const Reader&) = delete; + Reader(Reader&&) = delete; + Reader& operator=(Reader&&) = delete; + +#ifdef DEBUG + ~Reader() { + // No Reader should live outside of a mutexed call. + mBuffer.mMutex.AssertCurrentThreadOwns(); + } +#endif // DEBUG + + // Index of the first block in the whole buffer. + [[nodiscard]] ProfileBufferBlockIndex BufferRangeStart() const { + mBuffer.mMutex.AssertCurrentThreadOwns(); + return ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mBuffer.mRangeStart); + } + + // Index past the last block in the whole buffer. + [[nodiscard]] ProfileBufferBlockIndex BufferRangeEnd() const { + mBuffer.mMutex.AssertCurrentThreadOwns(); + return ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + mBuffer.mRangeEnd); + } + + // Iterators to the first and past-the-last blocks. + // Compatible with range-for (see `ForEach` below as example). + [[nodiscard]] BlockIterator begin() const { + return BlockIterator(mBuffer, mChunks0, mChunks1, nullptr); + } + // Note that a `BlockIterator` at the `end()` should not be dereferenced, as + // there is no actual block there! + [[nodiscard]] BlockIterator end() const { + return BlockIterator(mBuffer, nullptr, nullptr, nullptr); + } + + // Get a `BlockIterator` at the given `ProfileBufferBlockIndex`, clamped to + // the stored range. Note that a `BlockIterator` at the `end()` should not + // be dereferenced, as there is no actual block there! + [[nodiscard]] BlockIterator At(ProfileBufferBlockIndex aBlockIndex) const { + if (aBlockIndex < BufferRangeStart()) { + // Anything before the range (including null ProfileBufferBlockIndex) is + // clamped at the beginning. + return begin(); + } + // Otherwise we at least expect the index to be valid (pointing exactly at + // a live block, or just past the end.) + return BlockIterator(mBuffer, mChunks0, mChunks1, aBlockIndex); + } + + // Run `aCallback(ProfileBufferEntryReader&)` on each entry from first to + // last. Callback should not store `ProfileBufferEntryReader`, as it may + // become invalid after this thread-safe call. + template <typename Callback> + void ForEach(Callback&& aCallback) const { + for (ProfileBufferEntryReader reader : *this) { + aCallback(reader); + } + } + + // If this reader only points at one chunk with some data, this data will be + // exposed as a single entry. + [[nodiscard]] ProfileBufferEntryReader SingleChunkDataAsEntry() { + const ProfileBufferChunk* onlyNonEmptyChunk = nullptr; + for (const ProfileBufferChunk* chunkList : {mChunks0, mChunks1}) { + for (const ProfileBufferChunk* chunk = chunkList; chunk; + chunk = chunk->GetNext()) { + if (chunk->OffsetFirstBlock() != chunk->OffsetPastLastBlock()) { + if (onlyNonEmptyChunk) { + // More than one non-empty chunk. + return ProfileBufferEntryReader(); + } + onlyNonEmptyChunk = chunk; + } + } + } + if (!onlyNonEmptyChunk) { + // No non-empty chunks. + return ProfileBufferEntryReader(); + } + // Here, we have found one chunk that had some data. + return ProfileBufferEntryReader( + onlyNonEmptyChunk->BufferSpan().FromTo( + onlyNonEmptyChunk->OffsetFirstBlock(), + onlyNonEmptyChunk->OffsetPastLastBlock()), + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + onlyNonEmptyChunk->RangeStart()), + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + onlyNonEmptyChunk->RangeStart() + + (onlyNonEmptyChunk->OffsetPastLastBlock() - + onlyNonEmptyChunk->OffsetFirstBlock()))); + } + + private: + friend class ProfileChunkedBuffer; + + explicit Reader(const ProfileChunkedBuffer& aBuffer, + const ProfileBufferChunk* aChunks0, + const ProfileBufferChunk* aChunks1) + : mBuffer(aBuffer), mChunks0(aChunks0), mChunks1(aChunks1) { + // No Reader should live outside of a mutexed call. + mBuffer.mMutex.AssertCurrentThreadOwns(); + } + + // This Reader should only live inside one of the thread-safe + // ProfileChunkedBuffer functions, for this reference to stay valid. + const ProfileChunkedBuffer& mBuffer; + const ProfileBufferChunk* mChunks0; + const ProfileBufferChunk* mChunks1; + }; + + // In in-session, call `aCallback(ProfileChunkedBuffer::Reader&)` and return + // true. Callback should not store `Reader`, because it may become invalid + // after this call. + // If out-of-session, return false (callback is not invoked). + template <typename Callback> + [[nodiscard]] auto Read(Callback&& aCallback) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return std::forward<Callback>(aCallback)(static_cast<Reader*>(nullptr)); + } + return mChunkManager->PeekExtantReleasedChunks( + [&](const ProfileBufferChunk* aOldestChunk) { + Reader reader(*this, aOldestChunk, mCurrentChunk.get()); + return std::forward<Callback>(aCallback)(&reader); + }); + } + + // Invoke `aCallback(ProfileBufferEntryReader& [, ProfileBufferBlockIndex])` + // on each entry, it must read or at least skip everything. Either/both chunk + // pointers may be null. + template <typename Callback> + static void ReadEach(const ProfileBufferChunk* aChunks0, + const ProfileBufferChunk* aChunks1, + Callback&& aCallback) { + static_assert(std::is_invocable_v<Callback, ProfileBufferEntryReader&> || + std::is_invocable_v<Callback, ProfileBufferEntryReader&, + ProfileBufferBlockIndex>, + "ReadEach callback must take ProfileBufferEntryReader& and " + "optionally a ProfileBufferBlockIndex"); + detail::InChunkPointer p{aChunks0, aChunks1}; + while (!p.IsNull()) { + // The position right before an entry size *is* a block index. + const ProfileBufferBlockIndex blockIndex = + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + p.GlobalRangePosition()); + Length entrySize = p.ReadEntrySize(); + if (entrySize == 0) { + return; + } + ProfileBufferEntryReader entryReader = p.EntryReader(entrySize); + if (entryReader.RemainingBytes() == 0) { + return; + } + MOZ_ASSERT(entryReader.RemainingBytes() == entrySize); + if constexpr (std::is_invocable_v<Callback, ProfileBufferEntryReader&, + ProfileBufferBlockIndex>) { + aCallback(entryReader, blockIndex); + } else { + Unused << blockIndex; + aCallback(entryReader); + } + MOZ_ASSERT(entryReader.RemainingBytes() == 0); + } + } + + // Invoke `aCallback(ProfileBufferEntryReader& [, ProfileBufferBlockIndex])` + // on each entry, it must read or at least skip everything. + template <typename Callback> + void ReadEach(Callback&& aCallback) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return; + } + mChunkManager->PeekExtantReleasedChunks( + [&](const ProfileBufferChunk* aOldestChunk) { + ReadEach(aOldestChunk, mCurrentChunk.get(), + std::forward<Callback>(aCallback)); + }); + } + + // Call `aCallback(Maybe<ProfileBufferEntryReader>&&)` on the entry at + // the given ProfileBufferBlockIndex; The `Maybe` will be `Nothing` if + // out-of-session, or if that entry doesn't exist anymore, or if we've reached + // just past the last entry. Return whatever `aCallback` returns. Callback + // should not store `ProfileBufferEntryReader`, because it may become invalid + // after this call. + // Either/both chunk pointers may be null. + template <typename Callback> + [[nodiscard]] static auto ReadAt(ProfileBufferBlockIndex aMinimumBlockIndex, + const ProfileBufferChunk* aChunks0, + const ProfileBufferChunk* aChunks1, + Callback&& aCallback) { + static_assert( + std::is_invocable_v<Callback, Maybe<ProfileBufferEntryReader>&&>, + "ReadAt callback must take a Maybe<ProfileBufferEntryReader>&&"); + Maybe<ProfileBufferEntryReader> maybeEntryReader; + if (detail::InChunkPointer p{aChunks0, aChunks1}; !p.IsNull()) { + // If the pointer position is before the given position, try to advance. + if (p.GlobalRangePosition() >= + aMinimumBlockIndex.ConvertToProfileBufferIndex() || + p.AdvanceToGlobalRangePosition( + aMinimumBlockIndex.ConvertToProfileBufferIndex())) { + MOZ_ASSERT(p.GlobalRangePosition() >= + aMinimumBlockIndex.ConvertToProfileBufferIndex()); + // Here we're pointing at the start of a block, try to read the entry + // size. (Entries cannot be empty, so 0 means failure.) + if (Length entrySize = p.ReadEntrySize(); entrySize != 0) { + maybeEntryReader.emplace(p.EntryReader(entrySize)); + if (maybeEntryReader->RemainingBytes() == 0) { + // An empty entry reader means there was no complete block at the + // given index. + maybeEntryReader.reset(); + } else { + MOZ_ASSERT(maybeEntryReader->RemainingBytes() == entrySize); + } + } + } + } +#ifdef DEBUG + auto assertAllRead = MakeScopeExit([&]() { + MOZ_ASSERT(!maybeEntryReader || maybeEntryReader->RemainingBytes() == 0); + }); +#endif // DEBUG + return std::forward<Callback>(aCallback)(std::move(maybeEntryReader)); + } + + // Call `aCallback(Maybe<ProfileBufferEntryReader>&&)` on the entry at + // the given ProfileBufferBlockIndex; The `Maybe` will be `Nothing` if + // out-of-session, or if that entry doesn't exist anymore, or if we've reached + // just past the last entry. Return whatever `aCallback` returns. Callback + // should not store `ProfileBufferEntryReader`, because it may become invalid + // after this call. + template <typename Callback> + [[nodiscard]] auto ReadAt(ProfileBufferBlockIndex aBlockIndex, + Callback&& aCallback) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return std::forward<Callback>(aCallback)(Nothing{}); + } + return mChunkManager->PeekExtantReleasedChunks( + [&](const ProfileBufferChunk* aOldestChunk) { + return ReadAt(aBlockIndex, aOldestChunk, mCurrentChunk.get(), + std::forward<Callback>(aCallback)); + }); + } + + // Append the contents of another ProfileChunkedBuffer to this one. + ProfileBufferBlockIndex AppendContents(const ProfileChunkedBuffer& aSrc) { + ProfileBufferBlockIndex firstBlockIndex; + // If we start failing, we'll stop writing. + bool failed = false; + aSrc.ReadEach([&](ProfileBufferEntryReader& aER) { + if (failed) { + return; + } + failed = + !Put(aER.RemainingBytes(), [&](Maybe<ProfileBufferEntryWriter>& aEW) { + if (aEW.isNothing()) { + return false; + } + if (!firstBlockIndex) { + firstBlockIndex = aEW->CurrentBlockIndex(); + } + aEW->WriteFromReader(aER, aER.RemainingBytes()); + return true; + }); + }); + return failed ? nullptr : firstBlockIndex; + } + +#ifdef DEBUG + void Dump(std::FILE* aFile = stdout) const { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + fprintf(aFile, + "ProfileChunkedBuffer[%p] State: range %u-%u pushed=%u cleared=%u " + "(live=%u) failed-puts=%u bytes", + this, unsigned(mRangeStart), unsigned(mRangeEnd), + unsigned(mPushedBlockCount), unsigned(mClearedBlockCount), + unsigned(mPushedBlockCount) - unsigned(mClearedBlockCount), + unsigned(mFailedPutBytes)); + if (MOZ_UNLIKELY(!mChunkManager)) { + fprintf(aFile, " - Out-of-session\n"); + return; + } + fprintf(aFile, " - chunks:\n"); + bool hasChunks = false; + mChunkManager->PeekExtantReleasedChunks( + [&](const ProfileBufferChunk* aOldestChunk) { + for (const ProfileBufferChunk* chunk = aOldestChunk; chunk; + chunk = chunk->GetNext()) { + fprintf(aFile, "R "); + chunk->Dump(aFile); + hasChunks = true; + } + }); + if (mCurrentChunk) { + fprintf(aFile, "C "); + mCurrentChunk->Dump(aFile); + hasChunks = true; + } + for (const ProfileBufferChunk* chunk = mNextChunks.get(); chunk; + chunk = chunk->GetNext()) { + fprintf(aFile, "N "); + chunk->Dump(aFile); + hasChunks = true; + } + switch (mRequestedChunkHolder->GetState()) { + case RequestedChunkRefCountedHolder::State::Unused: + fprintf(aFile, " - No request pending.\n"); + break; + case RequestedChunkRefCountedHolder::State::Requested: + fprintf(aFile, " - Request pending.\n"); + break; + case RequestedChunkRefCountedHolder::State::Fulfilled: + fprintf(aFile, " - Request fulfilled.\n"); + break; + } + if (!hasChunks) { + fprintf(aFile, " No chunks.\n"); + } + } +#endif // DEBUG + + private: + // Used to de/serialize a ProfileChunkedBuffer (e.g., containing a backtrace). + friend ProfileBufferEntryWriter::Serializer<ProfileChunkedBuffer>; + friend ProfileBufferEntryReader::Deserializer<ProfileChunkedBuffer>; + friend ProfileBufferEntryWriter::Serializer<UniquePtr<ProfileChunkedBuffer>>; + friend ProfileBufferEntryReader::Deserializer< + UniquePtr<ProfileChunkedBuffer>>; + + [[nodiscard]] UniquePtr<ProfileBufferChunkManager> ResetChunkManager( + const baseprofiler::detail::BaseProfilerMaybeAutoLock&) { + UniquePtr<ProfileBufferChunkManager> chunkManager; + if (mChunkManager) { + mRequestedChunkHolder = nullptr; + mChunkManager->ForgetUnreleasedChunks(); +#ifdef DEBUG + mChunkManager->DeregisteredFrom(this); +#endif + mChunkManager = nullptr; + chunkManager = std::move(mOwnedChunkManager); + if (mCurrentChunk) { + mCurrentChunk->MarkDone(); + mCurrentChunk = nullptr; + } + mNextChunks = nullptr; + mNextChunkRangeStart = mRangeEnd; + mRangeStart = mRangeEnd; + mPushedBlockCount = 0; + mClearedBlockCount = 0; + mFailedPutBytes = 0; + } + return chunkManager; + } + + void SetChunkManager( + ProfileBufferChunkManager& aChunkManager, + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + MOZ_ASSERT(!mChunkManager); + mChunkManager = &aChunkManager; +#ifdef DEBUG + mChunkManager->RegisteredWith(this); +#endif + + mChunkManager->SetChunkDestroyedCallback( + [this](const ProfileBufferChunk& aChunk) { + for (;;) { + ProfileBufferIndex rangeStart = mRangeStart; + if (MOZ_LIKELY(rangeStart <= aChunk.RangeStart())) { + if (MOZ_LIKELY(mRangeStart.compareExchange( + rangeStart, + aChunk.RangeStart() + aChunk.BufferBytes()))) { + break; + } + } + } + mClearedBlockCount += aChunk.BlockCount(); + }); + + // We start with one chunk right away, and request a following one now + // so it should be available before the current chunk is full. + SetAndInitializeCurrentChunk(mChunkManager->GetChunk(), aLock); + mRequestedChunkHolder = MakeRefPtr<RequestedChunkRefCountedHolder>(); + RequestChunk(aLock); + } + + [[nodiscard]] size_t SizeOfExcludingThis( + MallocSizeOf aMallocSizeOf, + const baseprofiler::detail::BaseProfilerMaybeAutoLock&) const { + if (MOZ_UNLIKELY(!mChunkManager)) { + // Out-of-session. + return 0; + } + size_t size = mChunkManager->SizeOfIncludingThis(aMallocSizeOf); + if (mCurrentChunk) { + size += mCurrentChunk->SizeOfIncludingThis(aMallocSizeOf); + } + if (mNextChunks) { + size += mNextChunks->SizeOfIncludingThis(aMallocSizeOf); + } + return size; + } + + void InitializeCurrentChunk( + const baseprofiler::detail::BaseProfilerMaybeAutoLock&) { + MOZ_ASSERT(!!mCurrentChunk); + mCurrentChunk->SetRangeStart(mNextChunkRangeStart); + mNextChunkRangeStart += mCurrentChunk->BufferBytes(); + Unused << mCurrentChunk->ReserveInitialBlockAsTail(0); + } + + void SetAndInitializeCurrentChunk( + UniquePtr<ProfileBufferChunk>&& aChunk, + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + mCurrentChunk = std::move(aChunk); + if (mCurrentChunk) { + InitializeCurrentChunk(aLock); + } + } + + void RequestChunk( + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + if (HandleRequestedChunk_IsPending(aLock)) { + // There is already a pending request, don't start a new one. + return; + } + + // Ensure the `RequestedChunkHolder` knows we're starting a request. + mRequestedChunkHolder->StartRequest(); + + // Request a chunk, the callback carries a `RefPtr` of the + // `RequestedChunkHolder`, so it's guaranteed to live until it's invoked, + // even if this `ProfileChunkedBuffer` changes its `ChunkManager` or is + // destroyed. + mChunkManager->RequestChunk( + [requestedChunkHolder = RefPtr<RequestedChunkRefCountedHolder>( + mRequestedChunkHolder)](UniquePtr<ProfileBufferChunk> aChunk) { + requestedChunkHolder->AddRequestedChunk(std::move(aChunk)); + }); + } + + [[nodiscard]] bool HandleRequestedChunk_IsPending( + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + MOZ_ASSERT(!!mChunkManager); + MOZ_ASSERT(!!mRequestedChunkHolder); + + if (mRequestedChunkHolder->GetState() == + RequestedChunkRefCountedHolder::State::Unused) { + return false; + } + + // A request is either in-flight or fulfilled. + Maybe<UniquePtr<ProfileBufferChunk>> maybeChunk = + mRequestedChunkHolder->GetChunkIfFulfilled(); + if (maybeChunk.isNothing()) { + // Request is still pending. + return true; + } + + // Since we extracted the provided chunk, the holder should now be unused. + MOZ_ASSERT(mRequestedChunkHolder->GetState() == + RequestedChunkRefCountedHolder::State::Unused); + + // Request has been fulfilled. + UniquePtr<ProfileBufferChunk>& chunk = *maybeChunk; + if (chunk) { + // Try to use as current chunk if needed. + if (!mCurrentChunk) { + SetAndInitializeCurrentChunk(std::move(chunk), aLock); + // We've just received a chunk and made it current, request a next chunk + // for later. + MOZ_ASSERT(!mNextChunks); + RequestChunk(aLock); + return true; + } + + if (!mNextChunks) { + mNextChunks = std::move(chunk); + } else { + mNextChunks->InsertNext(std::move(chunk)); + } + } + + return false; + } + + // Get a pointer to the next chunk available + [[nodiscard]] ProfileBufferChunk* GetOrCreateCurrentChunk( + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + ProfileBufferChunk* current = mCurrentChunk.get(); + if (MOZ_UNLIKELY(!current)) { + // No current chunk ready. + MOZ_ASSERT(!mNextChunks, + "There shouldn't be next chunks when there is no current one"); + // See if a request has recently been fulfilled, ignore pending status. + Unused << HandleRequestedChunk_IsPending(aLock); + current = mCurrentChunk.get(); + if (MOZ_UNLIKELY(!current)) { + // There was no pending chunk, try to get one right now. + // This may still fail, but we can't do anything else about it, the + // caller must handle the nullptr case. + // Attempt a request for later. + SetAndInitializeCurrentChunk(mChunkManager->GetChunk(), aLock); + current = mCurrentChunk.get(); + } + } + return current; + } + + // Get a pointer to the next chunk available + [[nodiscard]] ProfileBufferChunk* GetOrCreateNextChunk( + const baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock) { + MOZ_ASSERT(!!mCurrentChunk, + "Why ask for a next chunk when there isn't even a current one?"); + ProfileBufferChunk* next = mNextChunks.get(); + if (MOZ_UNLIKELY(!next)) { + // No next chunk ready, see if a request has recently been fulfilled, + // ignore pending status. + Unused << HandleRequestedChunk_IsPending(aLock); + next = mNextChunks.get(); + if (MOZ_UNLIKELY(!next)) { + // There was no pending chunk, try to get one right now. + mNextChunks = mChunkManager->GetChunk(); + next = mNextChunks.get(); + // This may still fail, but we can't do anything else about it, the + // caller must handle the nullptr case. + if (MOZ_UNLIKELY(!next)) { + // Attempt a request for later. + RequestChunk(aLock); + } + } + } + return next; + } + + // Reserve a block of `aCallbackBlockBytes()` size, and invoke and return + // `aCallback(Maybe<ProfileBufferEntryWriter>&)`. Note that this is the "raw" + // version that doesn't write the entry size at the beginning of the block. + // Note: `aCallbackBlockBytes` is a callback instead of a simple value, to + // delay this potentially-expensive computation until after we're checked that + // we're in-session; use `Put(Length, Callback)` below if you know the size + // already. + template <typename CallbackBlockBytes, typename Callback> + auto ReserveAndPutRaw(CallbackBlockBytes&& aCallbackBlockBytes, + Callback&& aCallback, + baseprofiler::detail::BaseProfilerMaybeAutoLock& aLock, + uint64_t aBlockCount = 1) { + // The entry writer that will point into one or two chunks to write + // into, empty by default (failure). + Maybe<ProfileBufferEntryWriter> maybeEntryWriter; + + // The current chunk will be filled if we need to write more than its + // remaining space. + bool currentChunkFilled = false; + + // If the current chunk gets filled, we may or may not initialize the next + // chunk! + bool nextChunkInitialized = false; + + if (MOZ_LIKELY(mChunkManager)) { + // In-session. + + const Length blockBytes = + std::forward<CallbackBlockBytes>(aCallbackBlockBytes)(); + + if (ProfileBufferChunk* current = GetOrCreateCurrentChunk(aLock); + MOZ_LIKELY(current)) { + if (blockBytes <= current->RemainingBytes()) { + // Block fits in current chunk with only one span. + currentChunkFilled = blockBytes == current->RemainingBytes(); + const auto [mem0, blockIndex] = current->ReserveBlock(blockBytes); + MOZ_ASSERT(mem0.LengthBytes() == blockBytes); + maybeEntryWriter.emplace( + mem0, blockIndex, + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + blockIndex.ConvertToProfileBufferIndex() + blockBytes)); + MOZ_ASSERT(maybeEntryWriter->RemainingBytes() == blockBytes); + mRangeEnd += blockBytes; + mPushedBlockCount += aBlockCount; + } else { + // Block doesn't fit fully in current chunk, it needs to overflow into + // the next one. + // Whether or not we can write this entry, the current chunk is now + // considered full, so it will be released. (Otherwise we could refuse + // this entry, but later accept a smaller entry into this chunk, which + // would be somewhat inconsistent.) + currentChunkFilled = true; + // Make sure the next chunk is available (from a previous request), + // otherwise create one on the spot. + if (ProfileBufferChunk* next = GetOrCreateNextChunk(aLock); + MOZ_LIKELY(next)) { + // Here, we know we have a current and a next chunk. + // Reserve head of block at the end of the current chunk. + const auto [mem0, blockIndex] = + current->ReserveBlock(current->RemainingBytes()); + MOZ_ASSERT(mem0.LengthBytes() < blockBytes); + MOZ_ASSERT(current->RemainingBytes() == 0); + // Set the next chunk range, and reserve the needed space for the + // tail of the block. + next->SetRangeStart(mNextChunkRangeStart); + mNextChunkRangeStart += next->BufferBytes(); + const auto mem1 = next->ReserveInitialBlockAsTail( + blockBytes - mem0.LengthBytes()); + MOZ_ASSERT(next->RemainingBytes() != 0); + nextChunkInitialized = true; + // Block is split in two spans. + maybeEntryWriter.emplace( + mem0, mem1, blockIndex, + ProfileBufferBlockIndex::CreateFromProfileBufferIndex( + blockIndex.ConvertToProfileBufferIndex() + blockBytes)); + MOZ_ASSERT(maybeEntryWriter->RemainingBytes() == blockBytes); + mRangeEnd += blockBytes; + mPushedBlockCount += aBlockCount; + } else { + // Cannot get a new chunk. Record put failure. + mFailedPutBytes += blockBytes; + } + } + } else { + // Cannot get a current chunk. Record put failure. + mFailedPutBytes += blockBytes; + } + } // end of `if (MOZ_LIKELY(mChunkManager))` + + // Here, we either have a `Nothing` (failure), or a non-empty entry writer + // pointing at the start of the block. + + // After we invoke the callback and return, we may need to handle the + // current chunk being filled. + auto handleFilledChunk = MakeScopeExit([&]() { + // If the entry writer was not already empty, the callback *must* have + // filled the full entry. + MOZ_ASSERT(!maybeEntryWriter || maybeEntryWriter->RemainingBytes() == 0); + + if (currentChunkFilled) { + // Extract current (now filled) chunk. + UniquePtr<ProfileBufferChunk> filled = std::move(mCurrentChunk); + + if (mNextChunks) { + // Cycle to the next chunk. + mCurrentChunk = + std::exchange(mNextChunks, mNextChunks->ReleaseNext()); + + // Make sure it is initialized (it is now the current chunk). + if (!nextChunkInitialized) { + InitializeCurrentChunk(aLock); + } + } + + // And finally mark filled chunk done and release it. + filled->MarkDone(); + mChunkManager->ReleaseChunk(std::move(filled)); + + // Request another chunk if needed. + // In most cases, here we should have one current chunk and no next + // chunk, so we want to do a request so there hopefully will be a next + // chunk available when the current one gets filled. + // But we also for a request if we don't even have a current chunk (if + // it's too late, it's ok because the next `ReserveAndPutRaw` wil just + // allocate one on the spot.) + // And if we already have a next chunk, there's no need for more now. + if (!mCurrentChunk || !mNextChunks) { + RequestChunk(aLock); + } + } + }); + + return std::forward<Callback>(aCallback)(maybeEntryWriter); + } + + // Reserve a block of `aBlockBytes` size, and invoke and return + // `aCallback(Maybe<ProfileBufferEntryWriter>&)`. Note that this is the "raw" + // version that doesn't write the entry size at the beginning of the block. + template <typename Callback> + auto ReserveAndPutRaw(Length aBlockBytes, Callback&& aCallback, + uint64_t aBlockCount) { + baseprofiler::detail::BaseProfilerMaybeAutoLock lock(mMutex); + return ReserveAndPutRaw([aBlockBytes]() { return aBlockBytes; }, + std::forward<Callback>(aCallback), lock, + aBlockCount); + } + + // Mutex guarding the following members. + mutable baseprofiler::detail::BaseProfilerMaybeMutex mMutex; + + // Pointer to the current Chunk Manager (or null when out-of-session.) + // It may be owned locally (see below) or externally. + ProfileBufferChunkManager* mChunkManager = nullptr; + + // Only non-null when we own the current Chunk Manager. + UniquePtr<ProfileBufferChunkManager> mOwnedChunkManager; + + UniquePtr<ProfileBufferChunk> mCurrentChunk; + + UniquePtr<ProfileBufferChunk> mNextChunks; + + // Class used to transfer requested chunks from a `ChunkManager` to a + // `ProfileChunkedBuffer`. + // It needs to be ref-counted because the request may be fulfilled + // asynchronously, and either side may be destroyed during the request. + // It cannot use the `ProfileChunkedBuffer` mutex, because that buffer and its + // mutex could be destroyed during the request. + class RequestedChunkRefCountedHolder + : public external::AtomicRefCounted<RequestedChunkRefCountedHolder> { + public: + MOZ_DECLARE_REFCOUNTED_TYPENAME(RequestedChunkRefCountedHolder) + + enum class State { Unused, Requested, Fulfilled }; + + // Get the current state. Note that it may change after the function + // returns, so it should be used carefully, e.g., `ProfileChunkedBuffer` can + // see if a request is pending or fulfilled, to avoid starting another + // request. + [[nodiscard]] State GetState() const { + baseprofiler::detail::BaseProfilerAutoLock lock(mRequestMutex); + return mState; + } + + // Must be called by `ProfileChunkedBuffer` when it requests a chunk. + // There cannot be more than one request in-flight. + void StartRequest() { + baseprofiler::detail::BaseProfilerAutoLock lock(mRequestMutex); + MOZ_ASSERT(mState == State::Unused, "Already requested or fulfilled"); + mState = State::Requested; + } + + // Must be called by the `ChunkManager` with a chunk. + // If the `ChunkManager` cannot provide a chunk (because of memory limits, + // or it gets destroyed), it must call this anyway with a nullptr. + void AddRequestedChunk(UniquePtr<ProfileBufferChunk>&& aChunk) { + baseprofiler::detail::BaseProfilerAutoLock lock(mRequestMutex); + MOZ_ASSERT(mState == State::Requested); + mState = State::Fulfilled; + mRequestedChunk = std::move(aChunk); + } + + // The `ProfileChunkedBuffer` can try to extract the provided chunk after a + // request: + // - Nothing -> Request is not fulfilled yet. + // - Some(nullptr) -> The `ChunkManager` was not able to provide a chunk. + // - Some(chunk) -> Requested chunk. + [[nodiscard]] Maybe<UniquePtr<ProfileBufferChunk>> GetChunkIfFulfilled() { + Maybe<UniquePtr<ProfileBufferChunk>> maybeChunk; + baseprofiler::detail::BaseProfilerAutoLock lock(mRequestMutex); + MOZ_ASSERT(mState == State::Requested || mState == State::Fulfilled); + if (mState == State::Fulfilled) { + mState = State::Unused; + maybeChunk.emplace(std::move(mRequestedChunk)); + } + return maybeChunk; + } + + private: + // Mutex guarding the following members. + mutable baseprofiler::detail::BaseProfilerMutex mRequestMutex; + State mState = State::Unused; + UniquePtr<ProfileBufferChunk> mRequestedChunk; + }; + + // Requested-chunk holder, kept alive when in-session, but may also live + // longer if a request is in-flight. + RefPtr<RequestedChunkRefCountedHolder> mRequestedChunkHolder; + + // Range start of the next chunk to become current. Starting at 1 because + // 0 is a reserved index similar to nullptr. + ProfileBufferIndex mNextChunkRangeStart = 1; + + // Index to the first block. + // Atomic because it may be increased when a Chunk is destroyed, and the + // callback may be invoked from anywhere, including from inside one of our + // locked section, so we cannot protect it with a mutex. + Atomic<ProfileBufferIndex, MemoryOrdering::ReleaseAcquire> mRangeStart{1}; + + // Index past the last block. Equals mRangeStart if empty. + ProfileBufferIndex mRangeEnd = 1; + + // Number of blocks that have been pushed into this buffer. + uint64_t mPushedBlockCount = 0; + + // Number of blocks that have been removed from this buffer. + // Note: Live entries = pushed - cleared. + // Atomic because it may be updated when a Chunk is destroyed, and the + // callback may be invoked from anywhere, including from inside one of our + // locked section, so we cannot protect it with a mutex. + Atomic<uint64_t, MemoryOrdering::ReleaseAcquire> mClearedBlockCount{0}; + + // Number of bytes that could not be put into this buffer. + uint64_t mFailedPutBytes = 0; +}; + +// ---------------------------------------------------------------------------- +// ProfileChunkedBuffer serialization + +// A ProfileChunkedBuffer can hide another one! +// This will be used to store marker backtraces; They can be read back into a +// UniquePtr<ProfileChunkedBuffer>. +// Format: len (ULEB128) | start | end | buffer (len bytes) | pushed | cleared +// len==0 marks an out-of-session buffer, or empty buffer. +template <> +struct ProfileBufferEntryWriter::Serializer<ProfileChunkedBuffer> { + static Length Bytes(const ProfileChunkedBuffer& aBuffer) { + return aBuffer.Read([&](ProfileChunkedBuffer::Reader* aReader) { + if (!aReader) { + // Out-of-session, we only need 1 byte to store a length of 0. + return ULEB128Size<Length>(0); + } + ProfileBufferEntryReader reader = aReader->SingleChunkDataAsEntry(); + const ProfileBufferIndex start = + reader.CurrentBlockIndex().ConvertToProfileBufferIndex(); + const ProfileBufferIndex end = + reader.NextBlockIndex().ConvertToProfileBufferIndex(); + MOZ_ASSERT(end - start <= std::numeric_limits<Length>::max()); + const Length len = static_cast<Length>(end - start); + if (len == 0) { + // In-session but empty, also store a length of 0. + return ULEB128Size<Length>(0); + } + // In-session. + return static_cast<Length>(ULEB128Size(len) + sizeof(start) + len + + sizeof(aBuffer.mPushedBlockCount) + + sizeof(aBuffer.mClearedBlockCount)); + }); + } + + static void Write(ProfileBufferEntryWriter& aEW, + const ProfileChunkedBuffer& aBuffer) { + aBuffer.Read([&](ProfileChunkedBuffer::Reader* aReader) { + if (!aReader) { + // Out-of-session, only store a length of 0. + aEW.WriteULEB128<Length>(0); + return; + } + ProfileBufferEntryReader reader = aReader->SingleChunkDataAsEntry(); + const ProfileBufferIndex start = + reader.CurrentBlockIndex().ConvertToProfileBufferIndex(); + const ProfileBufferIndex end = + reader.NextBlockIndex().ConvertToProfileBufferIndex(); + MOZ_ASSERT(end - start <= std::numeric_limits<Length>::max()); + const Length len = static_cast<Length>(end - start); + MOZ_ASSERT(len <= aEW.RemainingBytes()); + if (len == 0) { + // In-session but empty, only store a length of 0. + aEW.WriteULEB128<Length>(0); + return; + } + // In-session. + // Store buffer length, and start index. + aEW.WriteULEB128(len); + aEW.WriteObject(start); + // Write all the bytes. + aEW.WriteFromReader(reader, reader.RemainingBytes()); + // And write stats. + aEW.WriteObject(static_cast<uint64_t>(aBuffer.mPushedBlockCount)); + aEW.WriteObject(static_cast<uint64_t>(aBuffer.mClearedBlockCount)); + // Note: Failed pushes are not important to serialize. + }); + } +}; + +// A serialized ProfileChunkedBuffer can be read into an empty buffer (either +// out-of-session, or in-session with enough room). +template <> +struct ProfileBufferEntryReader::Deserializer<ProfileChunkedBuffer> { + static void ReadInto(ProfileBufferEntryReader& aER, + ProfileChunkedBuffer& aBuffer) { + // Expect an empty buffer, as we're going to overwrite it. + MOZ_ASSERT(aBuffer.GetState().mRangeStart == aBuffer.GetState().mRangeEnd); + // Read the stored buffer length. + const auto len = aER.ReadULEB128<ProfileChunkedBuffer::Length>(); + if (len == 0) { + // 0-length means an "uninteresting" buffer, just return now. + return; + } + // We have a non-empty buffer to read. + + // Read start and end indices. + const auto start = aER.ReadObject<ProfileBufferIndex>(); + aBuffer.mRangeStart = start; + // For now, set the end to be the start (the buffer is still empty). It will + // be updated in `ReserveAndPutRaw()` below. + aBuffer.mRangeEnd = start; + + if (aBuffer.IsInSession()) { + // Output buffer is in-session (i.e., it already has a memory buffer + // attached). Make sure the caller allocated enough space. + MOZ_RELEASE_ASSERT(aBuffer.BufferLength().value() >= len); + } else { + // Output buffer is out-of-session, set a new chunk manager that will + // provide a single chunk of just the right size. + aBuffer.SetChunkManager(MakeUnique<ProfileBufferChunkManagerSingle>(len)); + MOZ_ASSERT(aBuffer.BufferLength().value() >= len); + } + + // Copy bytes into the buffer. + aBuffer.ReserveAndPutRaw( + len, + [&](Maybe<ProfileBufferEntryWriter>& aEW) { + MOZ_RELEASE_ASSERT(aEW.isSome()); + aEW->WriteFromReader(aER, len); + }, + 0); + // Finally copy stats. + aBuffer.mPushedBlockCount = aER.ReadObject<uint64_t>(); + aBuffer.mClearedBlockCount = aER.ReadObject<uint64_t>(); + // Failed puts are not important to keep. + aBuffer.mFailedPutBytes = 0; + } + + // We cannot output a ProfileChunkedBuffer object (not copyable), use + // `ReadInto()` or `aER.ReadObject<UniquePtr<BlocksRinbBuffer>>()` instead. + static ProfileChunkedBuffer Read(ProfileBufferEntryReader& aER) = delete; +}; + +// A ProfileChunkedBuffer is usually refererenced through a UniquePtr, for +// convenience we support (de)serializing that UniquePtr directly. +// This is compatible with the non-UniquePtr serialization above, with a null +// pointer being treated like an out-of-session or empty buffer; and any of +// these would be deserialized into a null pointer. +template <> +struct ProfileBufferEntryWriter::Serializer<UniquePtr<ProfileChunkedBuffer>> { + static Length Bytes(const UniquePtr<ProfileChunkedBuffer>& aBufferUPtr) { + if (!aBufferUPtr) { + // Null pointer, treat it like an empty buffer, i.e., write length of 0. + return ULEB128Size<Length>(0); + } + // Otherwise write the pointed-at ProfileChunkedBuffer (which could be + // out-of-session or empty.) + return SumBytes(*aBufferUPtr); + } + + static void Write(ProfileBufferEntryWriter& aEW, + const UniquePtr<ProfileChunkedBuffer>& aBufferUPtr) { + if (!aBufferUPtr) { + // Null pointer, treat it like an empty buffer, i.e., write length of 0. + aEW.WriteULEB128<Length>(0); + return; + } + // Otherwise write the pointed-at ProfileChunkedBuffer (which could be + // out-of-session or empty.) + aEW.WriteObject(*aBufferUPtr); + } +}; + +// Serialization of a raw pointer to ProfileChunkedBuffer. +// Use Deserializer<UniquePtr<ProfileChunkedBuffer>> to read it back. +template <> +struct ProfileBufferEntryWriter::Serializer<ProfileChunkedBuffer*> { + static Length Bytes(ProfileChunkedBuffer* aBufferUPtr) { + if (!aBufferUPtr) { + // Null pointer, treat it like an empty buffer, i.e., write length of 0. + return ULEB128Size<Length>(0); + } + // Otherwise write the pointed-at ProfileChunkedBuffer (which could be + // out-of-session or empty.) + return SumBytes(*aBufferUPtr); + } + + static void Write(ProfileBufferEntryWriter& aEW, + ProfileChunkedBuffer* aBufferUPtr) { + if (!aBufferUPtr) { + // Null pointer, treat it like an empty buffer, i.e., write length of 0. + aEW.WriteULEB128<Length>(0); + return; + } + // Otherwise write the pointed-at ProfileChunkedBuffer (which could be + // out-of-session or empty.) + aEW.WriteObject(*aBufferUPtr); + } +}; + +template <> +struct ProfileBufferEntryReader::Deserializer<UniquePtr<ProfileChunkedBuffer>> { + static void ReadInto(ProfileBufferEntryReader& aER, + UniquePtr<ProfileChunkedBuffer>& aBuffer) { + aBuffer = Read(aER); + } + + static UniquePtr<ProfileChunkedBuffer> Read(ProfileBufferEntryReader& aER) { + UniquePtr<ProfileChunkedBuffer> bufferUPtr; + // Keep a copy of the reader before reading the length, so we can restart + // from here below. + ProfileBufferEntryReader readerBeforeLen = aER; + // Read the stored buffer length. + const auto len = aER.ReadULEB128<ProfileChunkedBuffer::Length>(); + if (len == 0) { + // 0-length means an "uninteresting" buffer, just return nullptr. + return bufferUPtr; + } + // We have a non-empty buffer. + // allocate an empty ProfileChunkedBuffer without mutex. + bufferUPtr = MakeUnique<ProfileChunkedBuffer>( + ProfileChunkedBuffer::ThreadSafety::WithoutMutex); + // Rewind the reader before the length and deserialize the contents, using + // the non-UniquePtr Deserializer. + aER = readerBeforeLen; + aER.ReadIntoObject(*bufferUPtr); + return bufferUPtr; + } +}; + +} // namespace mozilla + +#endif // ProfileChunkedBuffer_h |