1 //===--- JSON.h - JSON values, parsing and serialization -------*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===---------------------------------------------------------------------===//
10 /// This file supports working with JSON data.
14 /// - classes which hold dynamically-typed parsed JSON structures
15 /// These are value types that can be composed, inspected, and modified.
16 /// See json::Value, and the related types json::Object and json::Array.
18 /// - functions to parse JSON text into Values, and to serialize Values to text.
19 /// See parse(), operator<<, and format_provider.
21 /// - a convention and helpers for mapping between json::Value and user-defined
22 /// types. See fromJSON(), ObjectMapper, and the class comment on Value.
24 /// - an output API json::OStream which can emit JSON without materializing
25 /// all structures as json::Value.
27 /// Typically, JSON data would be read from an external source, parsed into
28 /// a Value, and then converted into some native data structure before doing
29 /// real work on it. (And vice versa when writing).
31 /// Other serialization mechanisms you may consider:
33 /// - YAML is also text-based, and more human-readable than JSON. It's a more
34 /// complex format and data model, and YAML parsers aren't ubiquitous.
35 /// YAMLParser.h is a streaming parser suitable for parsing large documents
36 /// (including JSON, as YAML is a superset). It can be awkward to use
37 /// directly. YAML I/O (YAMLTraits.h) provides data mapping that is more
38 /// declarative than the toJSON/fromJSON conventions here.
40 /// - LLVM bitstream is a space- and CPU- efficient binary format. Typically it
41 /// encodes LLVM IR ("bitcode"), but it can be a container for other data.
42 /// Low-level reader/writer libraries are in Bitstream/Bitstream*.h
44 //===---------------------------------------------------------------------===//
46 #ifndef LLVM_SUPPORT_JSON_H
47 #define LLVM_SUPPORT_JSON_H
49 #include "llvm/ADT/DenseMap.h"
50 #include "llvm/ADT/SmallVector.h"
51 #include "llvm/ADT/StringRef.h"
52 #include "llvm/Support/Error.h"
53 #include "llvm/Support/FormatVariadic.h"
54 #include "llvm/Support/raw_ostream.h"
60 // === String encodings ===
62 // JSON strings are character sequences (not byte sequences like std::string).
63 // We need to know the encoding, and for simplicity only support UTF-8.
65 // - When parsing, invalid UTF-8 is a syntax error like any other
67 // - When creating Values from strings, callers must ensure they are UTF-8.
68 // with asserts on, invalid UTF-8 will crash the program
69 // with asserts off, we'll substitute the replacement character (U+FFFD)
70 // Callers can use json::isUTF8() and json::fixUTF8() for validation.
72 // - When retrieving strings from Values (e.g. asString()), the result will
73 // always be valid UTF-8.
75 /// Returns true if \p S is valid UTF-8, which is required for use as JSON.
76 /// If it returns false, \p Offset is set to a byte offset near the first error.
77 bool isUTF8(llvm::StringRef S, size_t *ErrOffset = nullptr);
78 /// Replaces invalid UTF-8 sequences in \p S with the replacement character
79 /// (U+FFFD). The returned string is valid UTF-8.
80 /// This is much slower than isUTF8, so test that first.
81 std::string fixUTF8(llvm::StringRef S);
86 template <typename T> Value toJSON(const llvm::Optional<T> &Opt);
88 /// An Object is a JSON object, which maps strings to heterogenous JSON values.
89 /// It simulates DenseMap<ObjectKey, Value>. ObjectKey is a maybe-owned string.
91 using Storage = DenseMap<ObjectKey, Value, llvm::DenseMapInfo<StringRef>>;
95 using key_type = ObjectKey;
96 using mapped_type = Value;
97 using value_type = Storage::value_type;
98 using iterator = Storage::iterator;
99 using const_iterator = Storage::const_iterator;
102 // KV is a trivial key-value struct for list-initialization.
103 // (using std::pair forces extra copies).
105 explicit Object(std::initializer_list<KV> Properties);
107 iterator begin() { return M.begin(); }
108 const_iterator begin() const { return M.begin(); }
109 iterator end() { return M.end(); }
110 const_iterator end() const { return M.end(); }
112 bool empty() const { return M.empty(); }
113 size_t size() const { return M.size(); }
115 void clear() { M.clear(); }
116 std::pair<iterator, bool> insert(KV E);
117 template <typename... Ts>
118 std::pair<iterator, bool> try_emplace(const ObjectKey &K, Ts &&... Args) {
119 return M.try_emplace(K, std::forward<Ts>(Args)...);
121 template <typename... Ts>
122 std::pair<iterator, bool> try_emplace(ObjectKey &&K, Ts &&... Args) {
123 return M.try_emplace(std::move(K), std::forward<Ts>(Args)...);
125 bool erase(StringRef K);
126 void erase(iterator I) { M.erase(I); }
128 iterator find(StringRef K) { return M.find_as(K); }
129 const_iterator find(StringRef K) const { return M.find_as(K); }
130 // operator[] acts as if Value was default-constructible as null.
131 Value &operator[](const ObjectKey &K);
132 Value &operator[](ObjectKey &&K);
133 // Look up a property, returning nullptr if it doesn't exist.
134 Value *get(StringRef K);
135 const Value *get(StringRef K) const;
136 // Typed accessors return None/nullptr if
137 // - the property doesn't exist
138 // - or it has the wrong type
139 llvm::Optional<std::nullptr_t> getNull(StringRef K) const;
140 llvm::Optional<bool> getBoolean(StringRef K) const;
141 llvm::Optional<double> getNumber(StringRef K) const;
142 llvm::Optional<int64_t> getInteger(StringRef K) const;
143 llvm::Optional<llvm::StringRef> getString(StringRef K) const;
144 const json::Object *getObject(StringRef K) const;
145 json::Object *getObject(StringRef K);
146 const json::Array *getArray(StringRef K) const;
147 json::Array *getArray(StringRef K);
149 bool operator==(const Object &LHS, const Object &RHS);
150 inline bool operator!=(const Object &LHS, const Object &RHS) {
151 return !(LHS == RHS);
154 /// An Array is a JSON array, which contains heterogeneous JSON values.
155 /// It simulates std::vector<Value>.
157 std::vector<Value> V;
160 using value_type = Value;
161 using iterator = std::vector<Value>::iterator;
162 using const_iterator = std::vector<Value>::const_iterator;
165 explicit Array(std::initializer_list<Value> Elements);
166 template <typename Collection> explicit Array(const Collection &C) {
167 for (const auto &V : C)
171 Value &operator[](size_t I) { return V[I]; }
172 const Value &operator[](size_t I) const { return V[I]; }
173 Value &front() { return V.front(); }
174 const Value &front() const { return V.front(); }
175 Value &back() { return V.back(); }
176 const Value &back() const { return V.back(); }
177 Value *data() { return V.data(); }
178 const Value *data() const { return V.data(); }
180 iterator begin() { return V.begin(); }
181 const_iterator begin() const { return V.begin(); }
182 iterator end() { return V.end(); }
183 const_iterator end() const { return V.end(); }
185 bool empty() const { return V.empty(); }
186 size_t size() const { return V.size(); }
187 void reserve(size_t S) { V.reserve(S); }
189 void clear() { V.clear(); }
190 void push_back(const Value &E) { V.push_back(E); }
191 void push_back(Value &&E) { V.push_back(std::move(E)); }
192 template <typename... Args> void emplace_back(Args &&... A) {
193 V.emplace_back(std::forward<Args>(A)...);
195 void pop_back() { V.pop_back(); }
196 // FIXME: insert() takes const_iterator since C++11, old libstdc++ disagrees.
197 iterator insert(iterator P, const Value &E) { return V.insert(P, E); }
198 iterator insert(iterator P, Value &&E) {
199 return V.insert(P, std::move(E));
201 template <typename It> iterator insert(iterator P, It A, It Z) {
202 return V.insert(P, A, Z);
204 template <typename... Args> iterator emplace(const_iterator P, Args &&... A) {
205 return V.emplace(P, std::forward<Args>(A)...);
208 friend bool operator==(const Array &L, const Array &R) { return L.V == R.V; }
210 inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
212 /// A Value is an JSON value of unknown type.
213 /// They can be copied, but should generally be moved.
215 /// === Composing values ===
217 /// You can implicitly construct Values from:
218 /// - strings: std::string, SmallString, formatv, StringRef, char*
219 /// (char*, and StringRef are references, not copies!)
223 /// - arrays: {"foo", 42.0, false}
224 /// - serializable things: types with toJSON(const T&)->Value, found by ADL
226 /// They can also be constructed from object/array helpers:
227 /// - json::Object is a type like map<ObjectKey, Value>
228 /// - json::Array is a type like vector<Value>
229 /// These can be list-initialized, or used to build up collections in a loop.
230 /// json::ary(Collection) converts all items in a collection to Values.
232 /// === Inspecting values ===
234 /// Each Value is one of the JSON kinds:
237 /// number (double or int64)
238 /// string (StringRef)
239 /// array (json::Array)
240 /// object (json::Object)
242 /// The kind can be queried directly, or implicitly via the typed accessors:
243 /// if (Optional<StringRef> S = E.getAsString()
244 /// assert(E.kind() == Value::String);
246 /// Array and Object also have typed indexing accessors for easy traversal:
247 /// Expected<Value> E = parse(R"( {"options": {"font": "sans-serif"}} )");
248 /// if (Object* O = E->getAsObject())
249 /// if (Object* Opts = O->getObject("options"))
250 /// if (Optional<StringRef> Font = Opts->getString("font"))
251 /// assert(Opts->at("font").kind() == Value::String);
253 /// === Converting JSON values to C++ types ===
255 /// The convention is to have a deserializer function findable via ADL:
256 /// fromJSON(const json::Value&, T&)->bool
257 /// Deserializers are provided for:
259 /// - int and int64_t
262 /// - vector<T>, where T is deserializable
263 /// - map<string, T>, where T is deserializable
264 /// - Optional<T>, where T is deserializable
265 /// ObjectMapper can help writing fromJSON() functions for object types.
267 /// For conversion in the other direction, the serializer function is:
268 /// toJSON(const T&) -> json::Value
269 /// If this exists, then it also allows constructing Value from T, and can
270 /// be used to serialize vector<T>, map<string, T>, and Optional<T>.
272 /// === Serialization ===
274 /// Values can be serialized to JSON:
275 /// 1) raw_ostream << Value // Basic formatting.
276 /// 2) raw_ostream << formatv("{0}", Value) // Basic formatting.
277 /// 3) raw_ostream << formatv("{0:2}", Value) // Pretty-print with indent 2.
280 /// Expected<Value> E = json::parse("[1, 2, null]");
281 /// assert(E && E->kind() == Value::Array);
287 /// Number values can store both int64s and doubles at full precision,
288 /// depending on what they were constructed/parsed from.
295 // It would be nice to have Value() be null. But that would make {} null too.
296 Value(const Value &M) { copyFrom(M); }
297 Value(Value &&M) { moveFrom(std::move(M)); }
298 Value(std::initializer_list<Value> Elements);
299 Value(json::Array &&Elements) : Type(T_Array) {
300 create<json::Array>(std::move(Elements));
302 template <typename Elt>
303 Value(const std::vector<Elt> &C) : Value(json::Array(C)) {}
304 Value(json::Object &&Properties) : Type(T_Object) {
305 create<json::Object>(std::move(Properties));
307 template <typename Elt>
308 Value(const std::map<std::string, Elt> &C) : Value(json::Object(C)) {}
309 // Strings: types with value semantics. Must be valid UTF-8.
310 Value(std::string V) : Type(T_String) {
311 if (LLVM_UNLIKELY(!isUTF8(V))) {
312 assert(false && "Invalid UTF-8 in value used as JSON");
313 V = fixUTF8(std::move(V));
315 create<std::string>(std::move(V));
317 Value(const llvm::SmallVectorImpl<char> &V)
318 : Value(std::string(V.begin(), V.end())) {}
319 Value(const llvm::formatv_object_base &V) : Value(V.str()) {}
320 // Strings: types with reference semantics. Must be valid UTF-8.
321 Value(StringRef V) : Type(T_StringRef) {
322 create<llvm::StringRef>(V);
323 if (LLVM_UNLIKELY(!isUTF8(V))) {
324 assert(false && "Invalid UTF-8 in value used as JSON");
325 *this = Value(fixUTF8(V));
328 Value(const char *V) : Value(StringRef(V)) {}
329 Value(std::nullptr_t) : Type(T_Null) {}
330 // Boolean (disallow implicit conversions).
331 // (The last template parameter is a dummy to keep templates distinct.)
332 template <typename T,
333 typename = std::enable_if_t<std::is_same<T, bool>::value>,
335 Value(T B) : Type(T_Boolean) {
338 // Integers (except boolean). Must be non-narrowing convertible to int64_t.
339 template <typename T, typename = std::enable_if_t<std::is_integral<T>::value>,
340 typename = std::enable_if_t<!std::is_same<T, bool>::value>>
341 Value(T I) : Type(T_Integer) {
342 create<int64_t>(int64_t{I});
344 // Floating point. Must be non-narrowing convertible to double.
345 template <typename T,
346 typename = std::enable_if_t<std::is_floating_point<T>::value>,
348 Value(T D) : Type(T_Double) {
349 create<double>(double{D});
351 // Serializable types: with a toJSON(const T&)->Value function, found by ADL.
352 template <typename T,
353 typename = std::enable_if_t<std::is_same<
354 Value, decltype(toJSON(*(const T *)nullptr))>::value>,
356 Value(const T &V) : Value(toJSON(V)) {}
358 Value &operator=(const Value &M) {
363 Value &operator=(Value &&M) {
365 moveFrom(std::move(M));
368 ~Value() { destroy(); }
387 llvm_unreachable("Unknown kind");
390 // Typed accessors return None/nullptr if the Value is not of this type.
391 llvm::Optional<std::nullptr_t> getAsNull() const {
392 if (LLVM_LIKELY(Type == T_Null))
396 llvm::Optional<bool> getAsBoolean() const {
397 if (LLVM_LIKELY(Type == T_Boolean))
401 llvm::Optional<double> getAsNumber() const {
402 if (LLVM_LIKELY(Type == T_Double))
404 if (LLVM_LIKELY(Type == T_Integer))
405 return as<int64_t>();
408 // Succeeds if the Value is a Number, and exactly representable as int64_t.
409 llvm::Optional<int64_t> getAsInteger() const {
410 if (LLVM_LIKELY(Type == T_Integer))
411 return as<int64_t>();
412 if (LLVM_LIKELY(Type == T_Double)) {
413 double D = as<double>();
414 if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&
415 D >= double(std::numeric_limits<int64_t>::min()) &&
416 D <= double(std::numeric_limits<int64_t>::max())))
421 llvm::Optional<llvm::StringRef> getAsString() const {
422 if (Type == T_String)
423 return llvm::StringRef(as<std::string>());
424 if (LLVM_LIKELY(Type == T_StringRef))
425 return as<llvm::StringRef>();
428 const json::Object *getAsObject() const {
429 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
431 json::Object *getAsObject() {
432 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
434 const json::Array *getAsArray() const {
435 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
437 json::Array *getAsArray() {
438 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
443 void copyFrom(const Value &M);
444 // We allow moving from *const* Values, by marking all members as mutable!
445 // This hack is needed to support initializer-list syntax efficiently.
446 // (std::initializer_list<T> is a container of const T).
447 void moveFrom(const Value &&M);
451 template <typename T, typename... U> void create(U &&... V) {
452 new (reinterpret_cast<T *>(Union.buffer)) T(std::forward<U>(V)...);
454 template <typename T> T &as() const {
455 // Using this two-step static_cast via void * instead of reinterpret_cast
456 // silences a -Wstrict-aliasing false positive from GCC6 and earlier.
457 void *Storage = static_cast<void *>(Union.buffer);
458 return *static_cast<T *>(Storage);
461 friend class OStream;
463 enum ValueType : char {
473 // All members mutable, see moveFrom().
474 mutable ValueType Type;
475 mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, llvm::StringRef,
476 std::string, json::Array, json::Object>
478 friend bool operator==(const Value &, const Value &);
481 bool operator==(const Value &, const Value &);
482 inline bool operator!=(const Value &L, const Value &R) { return !(L == R); }
484 /// ObjectKey is a used to capture keys in Object. Like Value but:
485 /// - only strings are allowed
486 /// - it's optimized for the string literal case (Owned == nullptr)
487 /// Like Value, strings must be UTF-8. See isUTF8 documentation for details.
490 ObjectKey(const char *S) : ObjectKey(StringRef(S)) {}
491 ObjectKey(std::string S) : Owned(new std::string(std::move(S))) {
492 if (LLVM_UNLIKELY(!isUTF8(*Owned))) {
493 assert(false && "Invalid UTF-8 in value used as JSON");
494 *Owned = fixUTF8(std::move(*Owned));
498 ObjectKey(llvm::StringRef S) : Data(S) {
499 if (LLVM_UNLIKELY(!isUTF8(Data))) {
500 assert(false && "Invalid UTF-8 in value used as JSON");
501 *this = ObjectKey(fixUTF8(S));
504 ObjectKey(const llvm::SmallVectorImpl<char> &V)
505 : ObjectKey(std::string(V.begin(), V.end())) {}
506 ObjectKey(const llvm::formatv_object_base &V) : ObjectKey(V.str()) {}
508 ObjectKey(const ObjectKey &C) { *this = C; }
509 ObjectKey(ObjectKey &&C) : ObjectKey(static_cast<const ObjectKey &&>(C)) {}
510 ObjectKey &operator=(const ObjectKey &C) {
512 Owned.reset(new std::string(*C.Owned));
519 ObjectKey &operator=(ObjectKey &&) = default;
521 operator llvm::StringRef() const { return Data; }
522 std::string str() const { return Data.str(); }
525 // FIXME: this is unneccesarily large (3 pointers). Pointer + length + owned
526 // could be 2 pointers at most.
527 std::unique_ptr<std::string> Owned;
528 llvm::StringRef Data;
531 inline bool operator==(const ObjectKey &L, const ObjectKey &R) {
532 return llvm::StringRef(L) == llvm::StringRef(R);
534 inline bool operator!=(const ObjectKey &L, const ObjectKey &R) {
537 inline bool operator<(const ObjectKey &L, const ObjectKey &R) {
538 return StringRef(L) < StringRef(R);
546 inline Object::Object(std::initializer_list<KV> Properties) {
547 for (const auto &P : Properties) {
548 auto R = try_emplace(P.K, nullptr);
550 R.first->getSecond().moveFrom(std::move(P.V));
553 inline std::pair<Object::iterator, bool> Object::insert(KV E) {
554 return try_emplace(std::move(E.K), std::move(E.V));
556 inline bool Object::erase(StringRef K) {
557 return M.erase(ObjectKey(K));
560 // Standard deserializers are provided for primitive types.
561 // See comments on Value.
562 inline bool fromJSON(const Value &E, std::string &Out) {
563 if (auto S = E.getAsString()) {
564 Out = std::string(*S);
569 inline bool fromJSON(const Value &E, int &Out) {
570 if (auto S = E.getAsInteger()) {
576 inline bool fromJSON(const Value &E, int64_t &Out) {
577 if (auto S = E.getAsInteger()) {
583 inline bool fromJSON(const Value &E, double &Out) {
584 if (auto S = E.getAsNumber()) {
590 inline bool fromJSON(const Value &E, bool &Out) {
591 if (auto S = E.getAsBoolean()) {
597 inline bool fromJSON(const Value &E, std::nullptr_t &Out) {
598 if (auto S = E.getAsNull()) {
604 template <typename T> bool fromJSON(const Value &E, llvm::Optional<T> &Out) {
610 if (!fromJSON(E, Result))
612 Out = std::move(Result);
615 template <typename T> bool fromJSON(const Value &E, std::vector<T> &Out) {
616 if (auto *A = E.getAsArray()) {
618 Out.resize(A->size());
619 for (size_t I = 0; I < A->size(); ++I)
620 if (!fromJSON((*A)[I], Out[I]))
626 template <typename T>
627 bool fromJSON(const Value &E, std::map<std::string, T> &Out) {
628 if (auto *O = E.getAsObject()) {
630 for (const auto &KV : *O)
631 if (!fromJSON(KV.second, Out[std::string(llvm::StringRef(KV.first))]))
638 // Allow serialization of Optional<T> for supported T.
639 template <typename T> Value toJSON(const llvm::Optional<T> &Opt) {
640 return Opt ? Value(*Opt) : Value(nullptr);
643 /// Helper for mapping JSON objects onto protocol structs.
647 /// bool fromJSON(const Value &E, MyStruct &R) {
648 /// ObjectMapper O(E);
649 /// if (!O || !O.map("mandatory_field", R.MandatoryField))
651 /// O.map("optional_field", R.OptionalField);
657 ObjectMapper(const Value &E) : O(E.getAsObject()) {}
659 /// True if the expression is an object.
660 /// Must be checked before calling map().
661 operator bool() { return O; }
663 /// Maps a property to a field, if it exists.
664 template <typename T> bool map(StringRef Prop, T &Out) {
665 assert(*this && "Must check this is an object before calling map()");
666 if (const Value *E = O->get(Prop))
667 return fromJSON(*E, Out);
671 /// Maps a property to a field, if it exists.
672 /// (Optional requires special handling, because missing keys are OK).
673 template <typename T> bool map(StringRef Prop, llvm::Optional<T> &Out) {
674 assert(*this && "Must check this is an object before calling map()");
675 if (const Value *E = O->get(Prop))
676 return fromJSON(*E, Out);
685 /// Parses the provided JSON source, or returns a ParseError.
686 /// The returned Value is self-contained and owns its strings (they do not refer
687 /// to the original source).
688 llvm::Expected<Value> parse(llvm::StringRef JSON);
690 class ParseError : public llvm::ErrorInfo<ParseError> {
692 unsigned Line, Column, Offset;
696 ParseError(const char *Msg, unsigned Line, unsigned Column, unsigned Offset)
697 : Msg(Msg), Line(Line), Column(Column), Offset(Offset) {}
698 void log(llvm::raw_ostream &OS) const override {
699 OS << llvm::formatv("[{0}:{1}, byte={2}]: {3}", Line, Column, Offset, Msg);
701 std::error_code convertToErrorCode() const override {
702 return llvm::inconvertibleErrorCode();
706 /// json::OStream allows writing well-formed JSON without materializing
707 /// all structures as json::Value ahead of time.
708 /// It's faster, lower-level, and less safe than OS << json::Value.
710 /// Only one "top-level" object can be written to a stream.
711 /// Simplest usage involves passing lambdas (Blocks) to fill in containers:
713 /// json::OStream J(OS);
715 /// for (const Event &E : Events)
717 /// J.attribute("timestamp", int64_t(E.Time));
718 /// J.attributeArray("participants", [&] {
719 /// for (const Participant &P : E.Participants)
720 /// J.value(P.toString());
725 /// This would produce JSON like:
729 /// "timestamp": 19287398741,
730 /// "participants": [
739 /// The lower level begin/end methods (arrayBegin()) are more flexible but
740 /// care must be taken to pair them correctly:
742 /// json::OStream J(OS);
744 /// for (const Event &E : Events) {
746 /// J.attribute("timestamp", int64_t(E.Time));
747 /// J.attributeBegin("participants");
748 /// for (const Participant &P : E.Participants)
749 /// J.value(P.toString());
750 /// J.attributeEnd();
755 /// If the call sequence isn't valid JSON, asserts will fire in debug mode.
756 /// This can be mismatched begin()/end() pairs, trying to emit attributes inside
757 /// an array, and so on.
758 /// With asserts disabled, this is undefined behavior.
761 using Block = llvm::function_ref<void()>;
762 // If IndentSize is nonzero, output is pretty-printed.
763 explicit OStream(llvm::raw_ostream &OS, unsigned IndentSize = 0)
764 : OS(OS), IndentSize(IndentSize) {
765 Stack.emplace_back();
768 assert(Stack.size() == 1 && "Unmatched begin()/end()");
769 assert(Stack.back().Ctx == Singleton);
770 assert(Stack.back().HasValue && "Did not write top-level value");
773 /// Flushes the underlying ostream. OStream does not buffer internally.
774 void flush() { OS.flush(); }
776 // High level functions to output a value.
777 // Valid at top-level (exactly once), in an attribute value (exactly once),
778 // or in an array (any number of times).
780 /// Emit a self-contained value (number, string, vector<string> etc).
781 void value(const Value &V);
782 /// Emit an array whose elements are emitted in the provided Block.
783 void array(Block Contents) {
788 /// Emit an object whose elements are emitted in the provided Block.
789 void object(Block Contents) {
795 // High level functions to output object attributes.
796 // Valid only within an object (any number of times).
798 /// Emit an attribute whose value is self-contained (number, vector<int> etc).
799 void attribute(llvm::StringRef Key, const Value& Contents) {
800 attributeImpl(Key, [&] { value(Contents); });
802 /// Emit an attribute whose value is an array with elements from the Block.
803 void attributeArray(llvm::StringRef Key, Block Contents) {
804 attributeImpl(Key, [&] { array(Contents); });
806 /// Emit an attribute whose value is an object with attributes from the Block.
807 void attributeObject(llvm::StringRef Key, Block Contents) {
808 attributeImpl(Key, [&] { object(Contents); });
811 // Low-level begin/end functions to output arrays, objects, and attributes.
812 // Must be correctly paired. Allowed contexts are as above.
818 void attributeBegin(llvm::StringRef Key);
822 void attributeImpl(llvm::StringRef Key, Block Contents) {
832 Singleton, // Top level, or object attribute.
837 Context Ctx = Singleton;
838 bool HasValue = false;
840 llvm::SmallVector<State, 16> Stack; // Never empty.
841 llvm::raw_ostream &OS;
846 /// Serializes this Value to JSON, writing it to the provided stream.
847 /// The formatting is compact (no extra whitespace) and deterministic.
848 /// For pretty-printing, use the formatv() format_provider below.
849 inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Value &V) {
850 OStream(OS).value(V);
855 /// Allow printing json::Value with formatv().
856 /// The default style is basic/compact formatting, like operator<<.
857 /// A format string like formatv("{0:2}", Value) pretty-prints with indent 2.
858 template <> struct format_provider<llvm::json::Value> {
859 static void format(const llvm::json::Value &, raw_ostream &, StringRef);