diff options
Diffstat (limited to 'modules/skjson/src/SkJSON.cpp')
| -rw-r--r-- | modules/skjson/src/SkJSON.cpp | 480 |
1 files changed, 349 insertions, 131 deletions
diff --git a/modules/skjson/src/SkJSON.cpp b/modules/skjson/src/SkJSON.cpp index 05bf04d8f0..8af85ba695 100644 --- a/modules/skjson/src/SkJSON.cpp +++ b/modules/skjson/src/SkJSON.cpp @@ -18,130 +18,356 @@ namespace skjson { //#define SK_JSON_REPORT_ERRORS +namespace { + +/* + Value's impl side: + + -- fixed 64-bit size + + -- 8-byte aligned + + -- union of: + + bool + int32 + float + char[8] (short string storage) + external payload pointer + -- highest 3 bits reserved for type storage + + */ static_assert( sizeof(Value) == 8, ""); static_assert(alignof(Value) == 8, ""); static constexpr size_t kRecAlign = alignof(Value); -void Value::init_tagged(Tag t) { - memset(fData8, 0, sizeof(fData8)); - fData8[Value::kTagOffset] = SkTo<uint8_t>(t); - SkASSERT(this->getTag() == t); -} +// The current record layout assumes LE and will take some tweaking for BE. +#if defined(SK_CPU_BENDIAN) +static_assert(false, "Big-endian builds are not supported."); +#endif + +class ValueRec : public Value { +public: + static constexpr uint64_t kTypeBits = 3, + kTypeShift = 64 - kTypeBits, + kTypeMask = ((1ULL << kTypeBits) - 1) << kTypeShift; + + enum RecType : uint64_t { + // We picked kShortString == 0 so that tag 0b000 and stored max_size-size (7-7=0) + // conveniently overlap the '\0' terminator, allowing us to store a 7 character + // C string inline. + kShortString = 0b000ULL << kTypeShift, // inline payload + kNull = 0b001ULL << kTypeShift, // no payload + kBool = 0b010ULL << kTypeShift, // inline payload + kInt = 0b011ULL << kTypeShift, // inline payload + kFloat = 0b100ULL << kTypeShift, // inline payload + kString = 0b101ULL << kTypeShift, // ptr to external storage + kArray = 0b110ULL << kTypeShift, // ptr to external storage + kObject = 0b111ULL << kTypeShift, // ptr to external storage + }; -// Pointer values store a type (in the upper kTagBits bits) and a pointer. -void Value::init_tagged_pointer(Tag t, void* p) { - *this->cast<uintptr_t>() = reinterpret_cast<uintptr_t>(p); + RecType getRecType() const { + return static_cast<RecType>(*this->cast<uint64_t>() & kTypeMask); + } - if (sizeof(Value) == sizeof(uintptr_t)) { - // For 64-bit, we rely on the pointer upper bits being unused/zero. - SkASSERT(!(fData8[kTagOffset] & kTagMask)); - fData8[kTagOffset] |= SkTo<uint8_t>(t); - } else { - // For 32-bit, we need to zero-initialize the upper 32 bits - SkASSERT(sizeof(Value) == sizeof(uintptr_t) * 2); - this->cast<uintptr_t>()[kTagOffset >> 2] = 0; - fData8[kTagOffset] = SkTo<uint8_t>(t); + // Access the record data as T. + // + // This is also used to access the payload for inline records. Since the record type lives in + // the high bits, sizeof(T) must be less than sizeof(Value) when accessing inline payloads. + // + // E.g. + // + // uint8_t + // ----------------------------------------------------------------------- + // | val8 | val8 | val8 | val8 | val8 | val8 | val8 | TYPE| + // ----------------------------------------------------------------------- + // + // uint32_t + // ----------------------------------------------------------------------- + // | val32 | unused | TYPE| + // ----------------------------------------------------------------------- + // + // T* (64b) + // ----------------------------------------------------------------------- + // | T* (kTypeShift bits) |TYPE| + // ----------------------------------------------------------------------- + // + template <typename T> + const T* cast() const { + static_assert(sizeof (T) <= sizeof(ValueRec), ""); + static_assert(alignof(T) <= alignof(ValueRec), ""); + return reinterpret_cast<const T*>(this); } - SkASSERT(this->getTag() == t); - SkASSERT(this->ptr<void>() == p); -} + template <typename T> + T* cast() { return const_cast<T*>(const_cast<const ValueRec*>(this)->cast<T>()); } -NullValue::NullValue() { - this->init_tagged(Tag::kNull); - SkASSERT(this->getTag() == Tag::kNull); -} + // Access the pointer payload. + template <typename T> + const T* ptr() const { + static_assert(sizeof(uintptr_t) == sizeof(Value) || + sizeof(uintptr_t) * 2 == sizeof(Value), ""); + + return (sizeof(uintptr_t) < sizeof(Value)) + // For 32-bit, pointers are stored unmodified. + ? *this->cast<const T*>() + // For 64-bit, we use the high bits of the pointer as type storage. + : reinterpret_cast<T*>(*this->cast<uintptr_t>() & ~kTypeMask); + } + + // Type-bound recs only store their type. + static ValueRec MakeTypeBound(RecType t) { + ValueRec v; + *v.cast<uint64_t>() = t; + SkASSERT(v.getRecType() == t); + return v; + } + + // Primitive recs store a type and inline primitive payload. + template <typename T> + static ValueRec MakePrimitive(RecType t, T src) { + ValueRec v = MakeTypeBound(t); + *v.cast<T>() = src; + SkASSERT(v.getRecType() == t); + return v; + } + + // Pointer recs store a type (in the upper kTypeBits bits) and a pointer. + template <typename T> + static ValueRec MakePtr(RecType t, const T* p) { + SkASSERT((t & kTypeMask) == t); + if (sizeof(uintptr_t) == sizeof(Value)) { + // For 64-bit, we rely on the pointer hi bits being unused. + SkASSERT(!(reinterpret_cast<uintptr_t>(p) & kTypeMask)); + } + + ValueRec v = MakeTypeBound(t); + *v.cast<uintptr_t>() |= reinterpret_cast<uintptr_t>(p); + + SkASSERT(v.getRecType() == t); + SkASSERT(v.ptr<T>() == p); + + return v; + } + + // Vector recs point to externally allocated slabs with the following layout: + // + // [size_t n] [REC_0] ... [REC_n-1] [optional extra trailing storage] + // + // Long strings use extra_alloc_size == 1 to store the \0 terminator. + template <typename T, size_t extra_alloc_size = 0> + static ValueRec MakeVector(RecType t, const T* src, size_t size, SkArenaAlloc& alloc) { + // For zero-size arrays, we just store a nullptr. + size_t* size_ptr = nullptr; + + if (size) { + // The Ts are already in memory, so their size should be safeish. + const auto total_size = sizeof(size_t) + sizeof(T) * size + extra_alloc_size; + size_ptr = reinterpret_cast<size_t*>(alloc.makeBytesAlignedTo(total_size, kRecAlign)); + auto* data_ptr = reinterpret_cast<T*>(size_ptr + 1); + *size_ptr = size; + memcpy(data_ptr, src, sizeof(T) * size); + } + + return MakePtr(t, size_ptr); + } + + size_t vectorSize(RecType t) const { + if (this->is<NullValue>()) return 0; + SkASSERT(this->getRecType() == t); + + const auto* size_ptr = this->ptr<const size_t>(); + return size_ptr ? *size_ptr : 0; + } + + template <typename T> + const T* vectorBegin(RecType t) const { + if (this->is<NullValue>()) return nullptr; + SkASSERT(this->getRecType() == t); + + const auto* size_ptr = this->ptr<const size_t>(); + return size_ptr ? reinterpret_cast<const T*>(size_ptr + 1) : nullptr; + } + + template <typename T> + const T* vectorEnd(RecType t) const { + if (this->is<NullValue>()) return nullptr; + SkASSERT(this->getRecType() == t); + + const auto* size_ptr = this->ptr<const size_t>(); + return size_ptr ? reinterpret_cast<const T*>(size_ptr + 1) + *size_ptr : nullptr; + } + + // Strings have two flavors: + // + // -- short strings (len <= 7) -> these are stored inline, in the record + // (one byte reserved for null terminator/type): + // + // [str] [\0]|[max_len - actual_len] + // + // Storing [max_len - actual_len] allows the 'len' field to double-up as a + // null terminator when size == max_len (this works 'cause kShortString == 0). + // + // -- long strings (len > 7) -> these are externally allocated vectors (VectorRec<char>). + // + // The string data plus a null-char terminator are copied over. + static constexpr size_t kMaxInlineStringSize = sizeof(Value) - 1; + + static ValueRec MakeString(const char* src, size_t size, SkArenaAlloc& alloc) { + ValueRec v; + + if (size > kMaxInlineStringSize) { + v = MakeVector<char, 1>(kString, src, size, alloc); + const_cast<char *>(v.vectorBegin<char>(ValueRec::kString))[size] = '\0'; + } else { + v = MakeTypeBound(kShortString); + auto* payload = v.cast<char>(); + memcpy(payload, src, size); + payload[size] = '\0'; + + const auto len_tag = SkTo<char>(kMaxInlineStringSize - size); + // This technically overwrites the type hi bits, but is safe because + // 1) kShortString == 0 + // 2) 0 <= len_tag <= 7 + static_assert(kShortString == 0, "please don't break this"); + payload[kMaxInlineStringSize] = len_tag; + SkASSERT(v.getRecType() == kShortString); + } + return v; + } -BoolValue::BoolValue(bool b) { - this->init_tagged(Tag::kBool); - *this->cast<bool>() = b; - SkASSERT(this->getTag() == Tag::kBool); + size_t stringSize() const { + if (this->getRecType() == ValueRec::kShortString) { + const auto* payload = this->cast<char>(); + return kMaxInlineStringSize - SkToSizeT(payload[kMaxInlineStringSize]); + } + + return this->vectorSize(ValueRec::kString); + } + + const char* stringBegin() const { + if (this->getRecType() == ValueRec::kShortString) { + return this->cast<char>(); + } + + return this->vectorBegin<char>(ValueRec::kString); + } + + const char* stringEnd() const { + if (this->getRecType() == ValueRec::kShortString) { + const auto* payload = this->cast<char>(); + return payload + kMaxInlineStringSize - SkToSizeT(payload[kMaxInlineStringSize]); + } + + return this->vectorEnd<char>(ValueRec::kString); + } +}; + +} // namespace + + +// Boring public Value glue. + +const Value& Value::Null() { + static const Value g_null = ValueRec::MakeTypeBound(ValueRec::kNull); + return g_null; } -NumberValue::NumberValue(int32_t i) { - this->init_tagged(Tag::kInt); - *this->cast<int32_t>() = i; - SkASSERT(this->getTag() == Tag::kInt); +const Member& Member::Null() { + static const Member g_null = { Value::Null().as<StringValue>(), Value::Null() }; + return g_null; } -NumberValue::NumberValue(float f) { - this->init_tagged(Tag::kFloat); - *this->cast<float>() = f; - SkASSERT(this->getTag() == Tag::kFloat); +Value::Type Value::getType() const { + static constexpr Value::Type kTypeMap[] = { + Value::Type::kString, // kShortString + Value::Type::kNull, // kNull + Value::Type::kBool, // kBool + Value::Type::kNumber, // kInt + Value::Type::kNumber, // kFloat + Value::Type::kString, // kString + Value::Type::kArray, // kArray + Value::Type::kObject, // kObject + }; + + const auto& rec = *reinterpret_cast<const ValueRec*>(this); + const auto type_index = static_cast<size_t>(rec.getRecType() >> ValueRec::kTypeShift); + SkASSERT(type_index < SK_ARRAY_COUNT(kTypeMap)); + + return kTypeMap[type_index]; } -// Vector recs point to externally allocated slabs with the following layout: -// -// [size_t n] [REC_0] ... [REC_n-1] [optional extra trailing storage] -// -// Long strings use extra_alloc_size == 1 to store the \0 terminator. -// -template <typename T, size_t extra_alloc_size = 0> -static void* MakeVector(const void* src, size_t size, SkArenaAlloc& alloc) { - // The Ts are already in memory, so their size should be safe. - const auto total_size = sizeof(size_t) + size * sizeof(T) + extra_alloc_size; - auto* size_ptr = reinterpret_cast<size_t*>(alloc.makeBytesAlignedTo(total_size, kRecAlign)); - auto* data_ptr = reinterpret_cast<void*>(size_ptr + 1); - *size_ptr = size; - memcpy(data_ptr, src, size * sizeof(T)); - - return size_ptr; +template <> +bool PrimitiveValue<bool, Value::Type::kBool>::operator*() const { + const auto& rec = *reinterpret_cast<const ValueRec*>(this); + + if (rec.is<NullValue>()) return false; + + SkASSERT(rec.getRecType() == ValueRec::kBool); + + return *rec.cast<bool>(); } -ArrayValue::ArrayValue(const Value* src, size_t size, SkArenaAlloc& alloc) { - this->init_tagged_pointer(Tag::kArray, MakeVector<Value>(src, size, alloc)); - SkASSERT(this->getTag() == Tag::kArray); +template <> +double PrimitiveValue<double, Value::Type::kNumber>::operator*() const { + const auto& rec = *reinterpret_cast<const ValueRec*>(this); + + if (rec.is<NullValue>()) return 0; + + SkASSERT(rec.getRecType() == ValueRec::kInt || + rec.getRecType() == ValueRec::kFloat); + + return rec.getRecType() == ValueRec::kInt + ? static_cast<double>(*rec.cast<int32_t>()) + : static_cast<double>(*rec.cast<float>()); } -// Strings have two flavors: -// -// -- short strings (len <= 7) -> these are stored inline, in the record -// (one byte reserved for null terminator/type): -// -// [str] [\0]|[max_len - actual_len] -// -// Storing [max_len - actual_len] allows the 'len' field to double-up as a -// null terminator when size == max_len (this works 'cause kShortString == 0). -// -// -- long strings (len > 7) -> these are externally allocated vectors (VectorRec<char>). -// -// The string data plus a null-char terminator are copied over. -// -StringValue::StringValue(const char* src, size_t size, SkArenaAlloc& alloc) { - if (size > kMaxInlineStringSize) { - this->init_tagged_pointer(Tag::kString, MakeVector<char, 1>(src, size, alloc)); +template <> +size_t VectorValue<Value, Value::Type::kArray>::size() const { + return reinterpret_cast<const ValueRec*>(this)->vectorSize(ValueRec::kArray); +} - auto* data = this->cast<VectorValue<char, Value::Type::kString>>()->begin(); - const_cast<char*>(data)[size] = '\0'; - SkASSERT(this->getTag() == Tag::kString); - return; - } +template <> +const Value* VectorValue<Value, Value::Type::kArray>::begin() const { + return reinterpret_cast<const ValueRec*>(this)->vectorBegin<Value>(ValueRec::kArray); +} - this->init_tagged(Tag::kShortString); +template <> +const Value* VectorValue<Value, Value::Type::kArray>::end() const { + return reinterpret_cast<const ValueRec*>(this)->vectorEnd<Value>(ValueRec::kArray); +} - auto* payload = this->cast<char>(); - memcpy(payload, src, size); - payload[size] = '\0'; +template <> +size_t VectorValue<Member, Value::Type::kObject>::size() const { + return reinterpret_cast<const ValueRec*>(this)->vectorSize(ValueRec::kObject); +} - const auto len_tag = SkTo<char>(kMaxInlineStringSize - size); - // This technically overwrites the tag, but is safe because - // 1) kShortString == 0 - // 2) 0 <= len_tag <= 7 - static_assert(static_cast<uint8_t>(Tag::kShortString) == 0, "please don't break this"); - payload[kMaxInlineStringSize] = len_tag; +template <> +const Member* VectorValue<Member, Value::Type::kObject>::begin() const { + return reinterpret_cast<const ValueRec*>(this)->vectorBegin<Member>(ValueRec::kObject); +} - SkASSERT(this->getTag() == Tag::kShortString); +template <> +const Member* VectorValue<Member, Value::Type::kObject>::end() const { + return reinterpret_cast<const ValueRec*>(this)->vectorEnd<Member>(ValueRec::kObject); } -ObjectValue::ObjectValue(const Member* src, size_t size, SkArenaAlloc& alloc) { - this->init_tagged_pointer(Tag::kObject, MakeVector<Member>(src, size, alloc)); - SkASSERT(this->getTag() == Tag::kObject); +template <> +size_t VectorValue<char, Value::Type::kString>::size() const { + return reinterpret_cast<const ValueRec*>(this)->stringSize(); } +template <> +const char* VectorValue<char, Value::Type::kString>::begin() const { + return reinterpret_cast<const ValueRec*>(this)->stringBegin(); +} -// Boring public Value glue. +template <> +const char* VectorValue<char, Value::Type::kString>::end() const { + return reinterpret_cast<const ValueRec*>(this)->stringEnd(); +} const Value& ObjectValue::operator[](const char* key) const { // Reverse search for duplicates resolution (policy: return last). @@ -155,8 +381,7 @@ const Value& ObjectValue::operator[](const char* key) const { } } - static const Value g_null = NullValue(); - return g_null; + return Value::Null(); } namespace { @@ -232,7 +457,7 @@ public: fScopeStack.reserve(kScopeStackReserve); } - const Value parse(const char* p) { + const Value& parse(const char* p) { p = skip_ws(p); switch (*p) { @@ -241,7 +466,7 @@ public: case '[': goto match_array; default: - return this->error(NullValue(), p, "invalid top-level value"); + return this->error(Value::Null(), p, "invalid top-level value"); } match_object: @@ -255,15 +480,15 @@ public: // goto match_object_key; match_object_key: p = skip_ws(p); - if (*p != '"') return this->error(NullValue(), p, "expected object key"); + if (*p != '"') return this->error(Value::Null(), p, "expected object key"); p = this->matchString(p, [this](const char* key, size_t size) { this->pushObjectKey(key, size); }); - if (!p) return NullValue(); + if (!p) return Value::Null(); p = skip_ws(p); - if (*p != ':') return this->error(NullValue(), p, "expected ':' separator"); + if (*p != ':') return this->error(Value::Null(), p, "expected ':' separator"); ++p; @@ -273,7 +498,7 @@ public: switch (*p) { case '\0': - return this->error(NullValue(), p, "unexpected input end"); + return this->error(Value::Null(), p, "unexpected input end"); case '"': p = this->matchString(p, [this](const char* str, size_t size) { this->pushString(str, size); @@ -297,7 +522,7 @@ public: break; } - if (!p) return NullValue(); + if (!p) return Value::Null(); // goto match_post_value; match_post_value: @@ -317,7 +542,7 @@ public: case '}': goto pop_object; default: - return this->error(NullValue(), p - 1, "unexpected value-trailing token"); + return this->error(Value::Null(), p - 1, "unexpected value-trailing token"); } // unreachable @@ -327,7 +552,7 @@ public: SkASSERT(*p == '}'); if (fScopeStack.back() < 0) { - return this->error(NullValue(), p, "unexpected object terminator"); + return this->error(Value::Null(), p, "unexpected object terminator"); } this->popObjectScope(); @@ -340,11 +565,13 @@ public: if (fScopeStack.empty()) { SkASSERT(fValueStack.size() == 1); + auto* root = fAlloc.make<Value>(); + *root = fValueStack.front(); // Stop condition: parsed the top level element and there is no trailing garbage. return *skip_ws(p) == '\0' - ? fValueStack.front() - : this->error(NullValue(), p, "trailing root garbage"); + ? *root + : this->error(Value::Null(), p, "trailing root garbage"); } goto match_post_value; @@ -362,7 +589,7 @@ public: SkASSERT(*p == ']'); if (fScopeStack.back() >= 0) { - return this->error(NullValue(), p, "unexpected array terminator"); + return this->error(Value::Null(), p, "unexpected array terminator"); } this->popArrayScope(); @@ -370,7 +597,7 @@ public: goto pop_common; SkASSERT(false); - return NullValue(); + return Value::Null(); } const SkString& getError() const { @@ -387,12 +614,11 @@ private: SkString fError; - template <typename VectorT> - void popScopeAsVec(size_t scope_start) { + template <typename T> + void popScopeAsVec(ValueRec::RecType type, size_t scope_start) { SkASSERT(scope_start > 0); SkASSERT(scope_start <= fValueStack.size()); - using T = typename VectorT::ValueT; static_assert( sizeof(T) >= sizeof(Value), ""); static_assert( sizeof(T) % sizeof(Value) == 0, ""); static_assert(alignof(T) == alignof(Value), ""); @@ -404,7 +630,7 @@ private: const auto* begin = reinterpret_cast<const T*>(fValueStack.data() + scope_start); // Instantiate the placeholder value added in onPush{Object/Array}. - fValueStack[scope_start - 1] = VectorT(begin, count, fAlloc); + fValueStack[scope_start - 1] = ValueRec::MakeVector<T>(type, begin, count, fAlloc); // Drop the current scope. fScopeStack.pop_back(); @@ -422,7 +648,7 @@ private: void popObjectScope() { const auto scope_start = fScopeStack.back(); SkASSERT(scope_start > 0); - this->popScopeAsVec<ObjectValue>(SkTo<size_t>(scope_start)); + this->popScopeAsVec<Member>(ValueRec::kObject, SkTo<size_t>(scope_start)); SkDEBUGCODE( const auto& obj = fValueStack.back().as<ObjectValue>(); @@ -444,7 +670,7 @@ private: void popArrayScope() { const auto scope_start = -fScopeStack.back(); SkASSERT(scope_start > 0); - this->popScopeAsVec<ArrayValue>(SkTo<size_t>(scope_start)); + this->popScopeAsVec<Value>(ValueRec::kArray, SkTo<size_t>(scope_start)); SkDEBUGCODE( const auto& arr = fValueStack.back().as<ArrayValue>(); @@ -460,31 +686,31 @@ private: } void pushTrue() { - fValueStack.push_back(BoolValue(true)); + fValueStack.push_back(ValueRec::MakePrimitive<bool>(ValueRec::kBool, true)); } void pushFalse() { - fValueStack.push_back(BoolValue(false)); + fValueStack.push_back(ValueRec::MakePrimitive<bool>(ValueRec::kBool, false)); } void pushNull() { - fValueStack.push_back(NullValue()); + fValueStack.push_back(ValueRec::MakeTypeBound(ValueRec::kNull)); } void pushString(const char* s, size_t size) { - fValueStack.push_back(StringValue(s, size, fAlloc)); + fValueStack.push_back(ValueRec::MakeString(s, size, fAlloc)); } void pushInt32(int32_t i) { - fValueStack.push_back(NumberValue(i)); + fValueStack.push_back(ValueRec::MakePrimitive<int32_t>(ValueRec::kInt, i)); } void pushFloat(float f) { - fValueStack.push_back(NumberValue(f)); + fValueStack.push_back(ValueRec::MakePrimitive<float>(ValueRec::kFloat, f)); } template <typename T> - T error(T&& ret_val, const char* p, const char* msg) { + const T& error(const T& ret_val, const char* p, const char* msg) { #if defined(SK_JSON_REPORT_ERRORS) static constexpr size_t kMaxContext = 128; fError = SkStringPrintf("%s: >", msg); @@ -704,25 +930,17 @@ void Write(const Value& v, SkWStream* stream) { } // namespace -SkString Value::toString() const { - SkDynamicMemoryWStream wstream; - Write(*this, &wstream); - const auto data = wstream.detachAsData(); - // TODO: is there a better way to pass data around without copying? - return SkString(static_cast<const char*>(data->data()), data->size()); -} - static constexpr size_t kMinChunkSize = 4096; -DOM::DOM(const char* c_str) +DOM::DOM(const char* cstr) : fAlloc(kMinChunkSize) { DOMParser parser(fAlloc); - fRoot = parser.parse(c_str); + fRoot = &parser.parse(cstr); } void DOM::write(SkWStream* stream) const { - Write(fRoot, stream); + Write(*fRoot, stream); } } // namespace skjson |