summaryrefslogtreecommitdiffstats
path: root/mozglue/baseprofiler/public/BaseProfileJSONWriter.h
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 19:33:14 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 19:33:14 +0000
commit36d22d82aa202bb199967e9512281e9a53db42c9 (patch)
tree105e8c98ddea1c1e4784a60a5a6410fa416be2de /mozglue/baseprofiler/public/BaseProfileJSONWriter.h
parentInitial commit. (diff)
downloadfirefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.tar.xz
firefox-esr-36d22d82aa202bb199967e9512281e9a53db42c9.zip
Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'mozglue/baseprofiler/public/BaseProfileJSONWriter.h')
-rw-r--r--mozglue/baseprofiler/public/BaseProfileJSONWriter.h600
1 files changed, 600 insertions, 0 deletions
diff --git a/mozglue/baseprofiler/public/BaseProfileJSONWriter.h b/mozglue/baseprofiler/public/BaseProfileJSONWriter.h
new file mode 100644
index 0000000000..00a2926366
--- /dev/null
+++ b/mozglue/baseprofiler/public/BaseProfileJSONWriter.h
@@ -0,0 +1,600 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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 BASEPROFILEJSONWRITER_H
+#define BASEPROFILEJSONWRITER_H
+
+#include "mozilla/FailureLatch.h"
+#include "mozilla/HashFunctions.h"
+#include "mozilla/HashTable.h"
+#include "mozilla/JSONWriter.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/NotNull.h"
+#include "mozilla/ProgressLogger.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/UniquePtrExtensions.h"
+
+#include <functional>
+#include <ostream>
+#include <string_view>
+
+namespace mozilla {
+namespace baseprofiler {
+
+class SpliceableJSONWriter;
+
+// On average, profile JSONs are large enough such that we want to avoid
+// reallocating its buffer when expanding. Additionally, the contents of the
+// profile are not accessed until the profile is entirely written. For these
+// reasons we use a chunked writer that keeps an array of chunks, which is
+// concatenated together after writing is finished.
+class ChunkedJSONWriteFunc final : public JSONWriteFunc, public FailureLatch {
+ public:
+ friend class SpliceableJSONWriter;
+
+ explicit ChunkedJSONWriteFunc(FailureLatch& aFailureLatch)
+ : mFailureLatch(WrapNotNullUnchecked(&aFailureLatch)) {
+ (void)AllocChunk(kChunkSize);
+ }
+
+ [[nodiscard]] bool IsEmpty() const {
+ MOZ_ASSERT_IF(!mChunkPtr, !mChunkEnd && mChunkList.length() == 0 &&
+ mChunkLengths.length() == 0);
+ return !mChunkPtr;
+ }
+
+ // Length of data written so far, excluding null terminator.
+ [[nodiscard]] size_t Length() const {
+ MOZ_ASSERT(mChunkLengths.length() == mChunkList.length());
+ size_t totalLen = 0;
+ for (size_t i = 0; i < mChunkLengths.length(); i++) {
+ MOZ_ASSERT(strlen(mChunkList[i].get()) == mChunkLengths[i]);
+ totalLen += mChunkLengths[i];
+ }
+ return totalLen;
+ }
+
+ void Write(const Span<const char>& aStr) final {
+ if (Failed()) {
+ return;
+ }
+
+ MOZ_ASSERT(mChunkPtr >= mChunkList.back().get() && mChunkPtr <= mChunkEnd);
+ MOZ_ASSERT(mChunkEnd >= mChunkList.back().get() + mChunkLengths.back());
+ MOZ_ASSERT(*mChunkPtr == '\0');
+
+ // Most strings to be written are small, but subprocess profiles (e.g.,
+ // from the content process in e10s) may be huge. If the string is larger
+ // than a chunk, allocate its own chunk.
+ char* newPtr;
+ if (aStr.size() >= kChunkSize) {
+ if (!AllocChunk(aStr.size() + 1)) {
+ return;
+ }
+ newPtr = mChunkPtr + aStr.size();
+ } else {
+ newPtr = mChunkPtr + aStr.size();
+ if (newPtr >= mChunkEnd) {
+ if (!AllocChunk(kChunkSize)) {
+ return;
+ }
+ newPtr = mChunkPtr + aStr.size();
+ }
+ }
+
+ memcpy(mChunkPtr, aStr.data(), aStr.size());
+ *newPtr = '\0';
+ mChunkPtr = newPtr;
+ mChunkLengths.back() += aStr.size();
+ }
+
+ [[nodiscard]] bool CopyDataIntoLazilyAllocatedBuffer(
+ const std::function<char*(size_t)>& aAllocator) const {
+ // Request a buffer for the full content plus a null terminator.
+ if (Failed()) {
+ return false;
+ }
+
+ char* ptr = aAllocator(Length() + 1);
+
+ if (!ptr) {
+ // Failed to allocate memory.
+ return false;
+ }
+
+ for (size_t i = 0; i < mChunkList.length(); i++) {
+ size_t len = mChunkLengths[i];
+ memcpy(ptr, mChunkList[i].get(), len);
+ ptr += len;
+ }
+ *ptr = '\0';
+ return true;
+ }
+
+ [[nodiscard]] UniquePtr<char[]> CopyData() const {
+ UniquePtr<char[]> c;
+ if (!CopyDataIntoLazilyAllocatedBuffer([&](size_t allocationSize) {
+ c = MakeUnique<char[]>(allocationSize);
+ return c.get();
+ })) {
+ // Something went wrong, make sure the returned pointer is null even if
+ // the allocation happened.
+ c = nullptr;
+ }
+ return c;
+ }
+
+ void Take(ChunkedJSONWriteFunc&& aOther) {
+ SetFailureFrom(aOther);
+ if (Failed()) {
+ return;
+ }
+
+ for (size_t i = 0; i < aOther.mChunkList.length(); i++) {
+ MOZ_ALWAYS_TRUE(mChunkLengths.append(aOther.mChunkLengths[i]));
+ MOZ_ALWAYS_TRUE(mChunkList.append(std::move(aOther.mChunkList[i])));
+ }
+ mChunkPtr = mChunkList.back().get() + mChunkLengths.back();
+ mChunkEnd = mChunkPtr;
+ aOther.Clear();
+ }
+
+ FAILURELATCH_IMPL_PROXY(*mFailureLatch)
+
+ // Change the failure latch to be used here, and if the previous latch was
+ // already in failure state, set that failure in the new latch.
+ // This allows using this WriteFunc in isolation, before attempting to bring
+ // it into another operation group with its own FailureLatch.
+ void ChangeFailureLatchAndForwardState(FailureLatch& aFailureLatch) {
+ aFailureLatch.SetFailureFrom(*this);
+ mFailureLatch = WrapNotNullUnchecked(&aFailureLatch);
+ }
+
+ private:
+ void Clear() {
+ mChunkPtr = nullptr;
+ mChunkEnd = nullptr;
+ mChunkList.clear();
+ mChunkLengths.clear();
+ }
+
+ void ClearAndSetFailure(std::string aFailure) {
+ Clear();
+ SetFailure(std::move(aFailure));
+ }
+
+ [[nodiscard]] bool ClearAndSetFailureAndFalse(std::string aFailure) {
+ ClearAndSetFailure(std::move(aFailure));
+ return false;
+ }
+
+ [[nodiscard]] bool AllocChunk(size_t aChunkSize) {
+ if (Failed()) {
+ if (mChunkPtr) {
+ // FailureLatch is in failed state, but chunks have not been cleared yet
+ // (error must have happened elsewhere).
+ Clear();
+ }
+ return false;
+ }
+
+ MOZ_ASSERT(mChunkLengths.length() == mChunkList.length());
+ UniquePtr<char[]> newChunk = MakeUniqueFallible<char[]>(aChunkSize);
+ if (!newChunk) {
+ return ClearAndSetFailureAndFalse(
+ "OOM in ChunkedJSONWriteFunc::AllocChunk allocating new chunk");
+ }
+ mChunkPtr = newChunk.get();
+ mChunkEnd = mChunkPtr + aChunkSize;
+ *mChunkPtr = '\0';
+ if (!mChunkLengths.append(0)) {
+ return ClearAndSetFailureAndFalse(
+ "OOM in ChunkedJSONWriteFunc::AllocChunk appending length");
+ }
+ if (!mChunkList.append(std::move(newChunk))) {
+ return ClearAndSetFailureAndFalse(
+ "OOM in ChunkedJSONWriteFunc::AllocChunk appending new chunk");
+ }
+ return true;
+ }
+
+ static const size_t kChunkSize = 4096 * 512;
+
+ // Pointer for writing inside the current chunk.
+ //
+ // The current chunk is always at the back of mChunkList, i.e.,
+ // mChunkList.back() <= mChunkPtr <= mChunkEnd.
+ char* mChunkPtr = nullptr;
+
+ // Pointer to the end of the current chunk.
+ //
+ // The current chunk is always at the back of mChunkList, i.e.,
+ // mChunkEnd >= mChunkList.back() + mChunkLengths.back().
+ char* mChunkEnd = nullptr;
+
+ // List of chunks and their lengths.
+ //
+ // For all i, the length of the string in mChunkList[i] is
+ // mChunkLengths[i].
+ Vector<UniquePtr<char[]>> mChunkList;
+ Vector<size_t> mChunkLengths;
+
+ NotNull<FailureLatch*> mFailureLatch;
+};
+
+struct OStreamJSONWriteFunc final : public JSONWriteFunc {
+ explicit OStreamJSONWriteFunc(std::ostream& aStream) : mStream(aStream) {}
+
+ void Write(const Span<const char>& aStr) final {
+ std::string_view sv(aStr.data(), aStr.size());
+ mStream << sv;
+ }
+
+ std::ostream& mStream;
+};
+
+class UniqueJSONStrings;
+
+class SpliceableJSONWriter : public JSONWriter, public FailureLatch {
+ public:
+ SpliceableJSONWriter(JSONWriteFunc& aWriter, FailureLatch& aFailureLatch)
+ : JSONWriter(aWriter, JSONWriter::SingleLineStyle),
+ mFailureLatch(WrapNotNullUnchecked(&aFailureLatch)) {}
+
+ SpliceableJSONWriter(UniquePtr<JSONWriteFunc> aWriter,
+ FailureLatch& aFailureLatch)
+ : JSONWriter(std::move(aWriter), JSONWriter::SingleLineStyle),
+ mFailureLatch(WrapNotNullUnchecked(&aFailureLatch)) {}
+
+ void StartBareList() { StartCollection(scEmptyString, scEmptyString); }
+
+ void EndBareList() { EndCollection(scEmptyString); }
+
+ // Output a time (int64_t given in nanoseconds) in milliseconds. trim zeroes.
+ // E.g.: 1'234'567'890 -> "1234.56789"
+ void TimeI64NsProperty(const Span<const char>& aMaybePropertyName,
+ int64_t aTime_ns) {
+ if (aTime_ns == 0) {
+ Scalar(aMaybePropertyName, MakeStringSpan("0"));
+ return;
+ }
+
+ static constexpr int64_t million = 1'000'000;
+ const int64_t absNanos = std::abs(aTime_ns);
+ const int64_t integerMilliseconds = absNanos / million;
+ auto remainderNanoseconds = static_cast<uint32_t>(absNanos % million);
+
+ // Plenty enough to fit INT64_MIN (-9223372036854775808).
+ static constexpr size_t DIGITS_MAX = 23;
+ char buf[DIGITS_MAX + 1];
+ int len =
+ snprintf(buf, DIGITS_MAX, (aTime_ns >= 0) ? "%" PRIu64 : "-%" PRIu64,
+ integerMilliseconds);
+ if (remainderNanoseconds != 0) {
+ buf[len++] = '.';
+ // Output up to 6 fractional digits. Exit early if the rest would
+ // be trailing zeros.
+ uint32_t powerOfTen = static_cast<uint32_t>(million / 10);
+ for (;;) {
+ auto digit = remainderNanoseconds / powerOfTen;
+ buf[len++] = '0' + static_cast<char>(digit);
+ remainderNanoseconds %= powerOfTen;
+ if (remainderNanoseconds == 0) {
+ break;
+ }
+ powerOfTen /= 10;
+ if (powerOfTen == 0) {
+ break;
+ }
+ }
+ }
+
+ Scalar(aMaybePropertyName, Span<const char>(buf, len));
+ }
+
+ // Output a (double) time in milliseconds, with at best nanosecond precision.
+ void TimeDoubleMsProperty(const Span<const char>& aMaybePropertyName,
+ double aTime_ms) {
+ const double dTime_ns = aTime_ms * 1'000'000.0;
+ // Make sure it's well within int64_t range.
+ // 2^63 nanoseconds is almost 300 years; these times are relative to
+ // firefox startup, this should be enough for most uses.
+ if (dTime_ns >= 0.0) {
+ MOZ_RELEASE_ASSERT(dTime_ns < double(INT64_MAX - 1));
+ } else {
+ MOZ_RELEASE_ASSERT(dTime_ns > double(INT64_MIN + 2));
+ }
+ // Round to nearest integer nanosecond. The conversion to integer truncates
+ // the fractional part, so first we need to push it 0.5 away from zero.
+ const int64_t iTime_ns =
+ (dTime_ns >= 0.0) ? int64_t(dTime_ns + 0.5) : int64_t(dTime_ns - 0.5);
+ TimeI64NsProperty(aMaybePropertyName, iTime_ns);
+ }
+
+ // Output a (double) time in milliseconds, with at best nanosecond precision.
+ void TimeDoubleMsElement(double aTime_ms) {
+ TimeDoubleMsProperty(nullptr, aTime_ms);
+ }
+
+ // This function must be used to correctly stream timestamps in profiles.
+ // Null timestamps don't output anything.
+ void TimeProperty(const Span<const char>& aMaybePropertyName,
+ const TimeStamp& aTime) {
+ if (!aTime.IsNull()) {
+ TimeDoubleMsProperty(
+ aMaybePropertyName,
+ (aTime - TimeStamp::ProcessCreation()).ToMilliseconds());
+ }
+ }
+
+ void NullElements(uint32_t aCount) {
+ for (uint32_t i = 0; i < aCount; i++) {
+ NullElement();
+ }
+ }
+
+ void Splice(const Span<const char>& aStr) {
+ Separator();
+ WriteFunc().Write(aStr);
+ mNeedComma[mDepth] = true;
+ }
+
+ void Splice(const char* aStr, size_t aLen) {
+ Separator();
+ WriteFunc().Write(Span<const char>(aStr, aLen));
+ mNeedComma[mDepth] = true;
+ }
+
+ // Splice the given JSON directly in, without quoting.
+ void SplicedJSONProperty(const Span<const char>& aMaybePropertyName,
+ const Span<const char>& aJsonValue) {
+ Scalar(aMaybePropertyName, aJsonValue);
+ }
+
+ void CopyAndSplice(const ChunkedJSONWriteFunc& aFunc) {
+ Separator();
+ for (size_t i = 0; i < aFunc.mChunkList.length(); i++) {
+ WriteFunc().Write(
+ Span<const char>(aFunc.mChunkList[i].get(), aFunc.mChunkLengths[i]));
+ }
+ mNeedComma[mDepth] = true;
+ }
+
+ // Takes the chunks from aFunc and write them. If move is not possible
+ // (e.g., using OStreamJSONWriteFunc), aFunc's chunks are copied and its
+ // storage cleared.
+ virtual void TakeAndSplice(ChunkedJSONWriteFunc&& aFunc) {
+ Separator();
+ for (size_t i = 0; i < aFunc.mChunkList.length(); i++) {
+ WriteFunc().Write(
+ Span<const char>(aFunc.mChunkList[i].get(), aFunc.mChunkLengths[i]));
+ }
+ aFunc.mChunkPtr = nullptr;
+ aFunc.mChunkEnd = nullptr;
+ aFunc.mChunkList.clear();
+ aFunc.mChunkLengths.clear();
+ mNeedComma[mDepth] = true;
+ }
+
+ // Set (or reset) the pointer to a UniqueJSONStrings.
+ void SetUniqueStrings(UniqueJSONStrings& aUniqueStrings) {
+ MOZ_RELEASE_ASSERT(!mUniqueStrings);
+ mUniqueStrings = &aUniqueStrings;
+ }
+
+ // Set (or reset) the pointer to a UniqueJSONStrings.
+ void ResetUniqueStrings() {
+ MOZ_RELEASE_ASSERT(mUniqueStrings);
+ mUniqueStrings = nullptr;
+ }
+
+ // Add `aStr` to the unique-strings list (if not already there), and write its
+ // index as a named object property.
+ inline void UniqueStringProperty(const Span<const char>& aName,
+ const Span<const char>& aStr);
+
+ // Add `aStr` to the unique-strings list (if not already there), and write its
+ // index as an array element.
+ inline void UniqueStringElement(const Span<const char>& aStr);
+
+ // THe following functions override JSONWriter functions non-virtually. The
+ // goal is to try and prevent calls that specify a style, which would be
+ // ignored anyway because the whole thing is single-lined. It's fine if some
+ // calls still make it through a `JSONWriter&`, no big deal.
+ void Start() { JSONWriter::Start(); }
+ void StartArrayProperty(const Span<const char>& aName) {
+ JSONWriter::StartArrayProperty(aName);
+ }
+ template <size_t N>
+ void StartArrayProperty(const char (&aName)[N]) {
+ JSONWriter::StartArrayProperty(Span<const char>(aName, N));
+ }
+ void StartArrayElement() { JSONWriter::StartArrayElement(); }
+ void StartObjectProperty(const Span<const char>& aName) {
+ JSONWriter::StartObjectProperty(aName);
+ }
+ template <size_t N>
+ void StartObjectProperty(const char (&aName)[N]) {
+ JSONWriter::StartObjectProperty(Span<const char>(aName, N));
+ }
+ void StartObjectElement() { JSONWriter::StartObjectElement(); }
+
+ FAILURELATCH_IMPL_PROXY(*mFailureLatch)
+
+ protected:
+ NotNull<FailureLatch*> mFailureLatch;
+
+ private:
+ UniqueJSONStrings* mUniqueStrings = nullptr;
+};
+
+class SpliceableChunkedJSONWriter final : public SpliceableJSONWriter {
+ public:
+ explicit SpliceableChunkedJSONWriter(FailureLatch& aFailureLatch)
+ : SpliceableJSONWriter(MakeUnique<ChunkedJSONWriteFunc>(aFailureLatch),
+ aFailureLatch) {}
+
+ // Access the ChunkedJSONWriteFunc as reference-to-const, usually to copy data
+ // out.
+ const ChunkedJSONWriteFunc& ChunkedWriteFunc() const {
+ return ChunkedWriteFuncRef();
+ }
+
+ // Access the ChunkedJSONWriteFunc as rvalue-reference, usually to take its
+ // data out. This writer shouldn't be used anymore after this.
+ ChunkedJSONWriteFunc&& TakeChunkedWriteFunc() {
+ ChunkedJSONWriteFunc& ref = ChunkedWriteFuncRef();
+#ifdef DEBUG
+ mTaken = true;
+#endif //
+ return std::move(ref);
+ }
+
+ // Adopts the chunks from aFunc without copying.
+ void TakeAndSplice(ChunkedJSONWriteFunc&& aFunc) override {
+ MOZ_ASSERT(!mTaken);
+ Separator();
+ ChunkedWriteFuncRef().Take(std::move(aFunc));
+ mNeedComma[mDepth] = true;
+ }
+
+ void ChangeFailureLatchAndForwardState(FailureLatch& aFailureLatch) {
+ mFailureLatch = WrapNotNullUnchecked(&aFailureLatch);
+ return ChunkedWriteFuncRef().ChangeFailureLatchAndForwardState(
+ aFailureLatch);
+ }
+
+ private:
+ const ChunkedJSONWriteFunc& ChunkedWriteFuncRef() const {
+ MOZ_ASSERT(!mTaken);
+ // The WriteFunc was non-fallibly allocated as a ChunkedJSONWriteFunc in the
+ // only constructor above, so it's safe to cast to ChunkedJSONWriteFunc&.
+ return static_cast<const ChunkedJSONWriteFunc&>(WriteFunc());
+ }
+
+ ChunkedJSONWriteFunc& ChunkedWriteFuncRef() {
+ MOZ_ASSERT(!mTaken);
+ // The WriteFunc was non-fallibly allocated as a ChunkedJSONWriteFunc in the
+ // only constructor above, so it's safe to cast to ChunkedJSONWriteFunc&.
+ return static_cast<ChunkedJSONWriteFunc&>(WriteFunc());
+ }
+
+#ifdef DEBUG
+ bool mTaken = false;
+#endif
+};
+
+class JSONSchemaWriter {
+ JSONWriter& mWriter;
+ uint32_t mIndex;
+
+ public:
+ explicit JSONSchemaWriter(JSONWriter& aWriter) : mWriter(aWriter), mIndex(0) {
+ aWriter.StartObjectProperty("schema",
+ SpliceableJSONWriter::SingleLineStyle);
+ }
+
+ void WriteField(const Span<const char>& aName) {
+ mWriter.IntProperty(aName, mIndex++);
+ }
+
+ template <size_t Np1>
+ void WriteField(const char (&aName)[Np1]) {
+ WriteField(Span<const char>(aName, Np1 - 1));
+ }
+
+ ~JSONSchemaWriter() { mWriter.EndObject(); }
+};
+
+// This class helps create an indexed list of unique strings, and inserts the
+// index as a JSON value. The collected list of unique strings can later be
+// inserted as a JSON array.
+// This can be useful for elements/properties with many repeated strings.
+//
+// With only JSONWriter w,
+// `w.WriteElement("a"); w.WriteElement("b"); w.WriteElement("a");`
+// when done inside a JSON array, will generate:
+// `["a", "b", "c"]`
+//
+// With UniqueStrings u,
+// `u.WriteElement(w, "a"); u.WriteElement(w, "b"); u.WriteElement(w, "a");`
+// when done inside a JSON array, will generate:
+// `[0, 1, 0]`
+// and later, `u.SpliceStringTableElements(w)` (inside a JSON array), will
+// output the corresponding indexed list of unique strings:
+// `["a", "b"]`
+class UniqueJSONStrings final : public FailureLatch {
+ public:
+ // Start an empty list of unique strings.
+ MFBT_API explicit UniqueJSONStrings(FailureLatch& aFailureLatch);
+
+ // Start with a copy of the strings from another list.
+ MFBT_API UniqueJSONStrings(FailureLatch& aFailureLatch,
+ const UniqueJSONStrings& aOther,
+ ProgressLogger aProgressLogger);
+
+ MFBT_API ~UniqueJSONStrings();
+
+ // Add `aStr` to the list (if not already there), and write its index as a
+ // named object property.
+ void WriteProperty(SpliceableJSONWriter& aWriter,
+ const Span<const char>& aName,
+ const Span<const char>& aStr) {
+ if (const Maybe<uint32_t> maybeIndex = GetOrAddIndex(aStr); maybeIndex) {
+ aWriter.IntProperty(aName, *maybeIndex);
+ } else {
+ aWriter.SetFailureFrom(*this);
+ }
+ }
+
+ // Add `aStr` to the list (if not already there), and write its index as an
+ // array element.
+ void WriteElement(SpliceableJSONWriter& aWriter,
+ const Span<const char>& aStr) {
+ if (const Maybe<uint32_t> maybeIndex = GetOrAddIndex(aStr); maybeIndex) {
+ aWriter.IntElement(*maybeIndex);
+ } else if (!aWriter.Failed()) {
+ aWriter.SetFailureFrom(*this);
+ }
+ }
+
+ // Splice all collected unique strings into an array. This should only be done
+ // once, and then this UniqueStrings shouldn't be used anymore.
+ MFBT_API void SpliceStringTableElements(SpliceableJSONWriter& aWriter);
+
+ FAILURELATCH_IMPL_PROXY(mStringTableWriter)
+
+ void ChangeFailureLatchAndForwardState(FailureLatch& aFailureLatch) {
+ mStringTableWriter.ChangeFailureLatchAndForwardState(aFailureLatch);
+ }
+
+ private:
+ MFBT_API void ClearAndSetFailure(std::string aFailure);
+
+ // If `aStr` is already listed, return its index.
+ // Otherwise add it to the list and return the new index.
+ MFBT_API Maybe<uint32_t> GetOrAddIndex(const Span<const char>& aStr);
+
+ SpliceableChunkedJSONWriter mStringTableWriter;
+ HashMap<HashNumber, uint32_t> mStringHashToIndexMap;
+};
+
+void SpliceableJSONWriter::UniqueStringProperty(const Span<const char>& aName,
+ const Span<const char>& aStr) {
+ MOZ_RELEASE_ASSERT(mUniqueStrings);
+ mUniqueStrings->WriteProperty(*this, aName, aStr);
+}
+
+// Add `aStr` to the list (if not already there), and write its index as an
+// array element.
+void SpliceableJSONWriter::UniqueStringElement(const Span<const char>& aStr) {
+ MOZ_RELEASE_ASSERT(mUniqueStrings);
+ mUniqueStrings->WriteElement(*this, aStr);
+}
+
+} // namespace baseprofiler
+} // namespace mozilla
+
+#endif // BASEPROFILEJSONWRITER_H