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Andrew Scullcdfcccc2018-10-05 20:58:37 +01001//===--- JSON.h - JSON values, parsing and serialization -------*- C++ -*-===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===---------------------------------------------------------------------===//
9///
10/// \file
11/// This file supports working with JSON data.
12///
13/// It comprises:
14///
15/// - classes which hold dynamically-typed parsed JSON structures
16/// These are value types that can be composed, inspected, and modified.
17/// See json::Value, and the related types json::Object and json::Array.
18///
19/// - functions to parse JSON text into Values, and to serialize Values to text.
20/// See parse(), operator<<, and format_provider.
21///
22/// - a convention and helpers for mapping between json::Value and user-defined
23/// types. See fromJSON(), ObjectMapper, and the class comment on Value.
24///
25/// Typically, JSON data would be read from an external source, parsed into
26/// a Value, and then converted into some native data structure before doing
27/// real work on it. (And vice versa when writing).
28///
29/// Other serialization mechanisms you may consider:
30///
31/// - YAML is also text-based, and more human-readable than JSON. It's a more
32/// complex format and data model, and YAML parsers aren't ubiquitous.
33/// YAMLParser.h is a streaming parser suitable for parsing large documents
34/// (including JSON, as YAML is a superset). It can be awkward to use
35/// directly. YAML I/O (YAMLTraits.h) provides data mapping that is more
36/// declarative than the toJSON/fromJSON conventions here.
37///
38/// - LLVM bitstream is a space- and CPU- efficient binary format. Typically it
39/// encodes LLVM IR ("bitcode"), but it can be a container for other data.
40/// Low-level reader/writer libraries are in Bitcode/Bitstream*.h
41///
42//===---------------------------------------------------------------------===//
43
44#ifndef LLVM_SUPPORT_JSON_H
45#define LLVM_SUPPORT_JSON_H
46
47#include "llvm/ADT/DenseMap.h"
48#include "llvm/ADT/SmallVector.h"
49#include "llvm/ADT/StringRef.h"
50#include "llvm/Support/Error.h"
51#include "llvm/Support/FormatVariadic.h"
52#include "llvm/Support/raw_ostream.h"
53#include <map>
54
55namespace llvm {
56namespace json {
57
58// === String encodings ===
59//
60// JSON strings are character sequences (not byte sequences like std::string).
61// We need to know the encoding, and for simplicity only support UTF-8.
62//
63// - When parsing, invalid UTF-8 is a syntax error like any other
64//
65// - When creating Values from strings, callers must ensure they are UTF-8.
66// with asserts on, invalid UTF-8 will crash the program
67// with asserts off, we'll substitute the replacement character (U+FFFD)
68// Callers can use json::isUTF8() and json::fixUTF8() for validation.
69//
70// - When retrieving strings from Values (e.g. asString()), the result will
71// always be valid UTF-8.
72
73/// Returns true if \p S is valid UTF-8, which is required for use as JSON.
74/// If it returns false, \p Offset is set to a byte offset near the first error.
75bool isUTF8(llvm::StringRef S, size_t *ErrOffset = nullptr);
76/// Replaces invalid UTF-8 sequences in \p S with the replacement character
77/// (U+FFFD). The returned string is valid UTF-8.
78/// This is much slower than isUTF8, so test that first.
79std::string fixUTF8(llvm::StringRef S);
80
81class Array;
82class ObjectKey;
83class Value;
84template <typename T> Value toJSON(const llvm::Optional<T> &Opt);
85
86/// An Object is a JSON object, which maps strings to heterogenous JSON values.
87/// It simulates DenseMap<ObjectKey, Value>. ObjectKey is a maybe-owned string.
88class Object {
89 using Storage = DenseMap<ObjectKey, Value, llvm::DenseMapInfo<StringRef>>;
90 Storage M;
91
92public:
93 using key_type = ObjectKey;
94 using mapped_type = Value;
95 using value_type = Storage::value_type;
96 using iterator = Storage::iterator;
97 using const_iterator = Storage::const_iterator;
98
99 explicit Object() = default;
100 // KV is a trivial key-value struct for list-initialization.
101 // (using std::pair forces extra copies).
102 struct KV;
103 explicit Object(std::initializer_list<KV> Properties);
104
105 iterator begin() { return M.begin(); }
106 const_iterator begin() const { return M.begin(); }
107 iterator end() { return M.end(); }
108 const_iterator end() const { return M.end(); }
109
110 bool empty() const { return M.empty(); }
111 size_t size() const { return M.size(); }
112
113 void clear() { M.clear(); }
114 std::pair<iterator, bool> insert(KV E);
115 template <typename... Ts>
116 std::pair<iterator, bool> try_emplace(const ObjectKey &K, Ts &&... Args) {
117 return M.try_emplace(K, std::forward<Ts>(Args)...);
118 }
119 template <typename... Ts>
120 std::pair<iterator, bool> try_emplace(ObjectKey &&K, Ts &&... Args) {
121 return M.try_emplace(std::move(K), std::forward<Ts>(Args)...);
122 }
123
124 iterator find(StringRef K) { return M.find_as(K); }
125 const_iterator find(StringRef K) const { return M.find_as(K); }
126 // operator[] acts as if Value was default-constructible as null.
127 Value &operator[](const ObjectKey &K);
128 Value &operator[](ObjectKey &&K);
129 // Look up a property, returning nullptr if it doesn't exist.
130 Value *get(StringRef K);
131 const Value *get(StringRef K) const;
132 // Typed accessors return None/nullptr if
133 // - the property doesn't exist
134 // - or it has the wrong type
135 llvm::Optional<std::nullptr_t> getNull(StringRef K) const;
136 llvm::Optional<bool> getBoolean(StringRef K) const;
137 llvm::Optional<double> getNumber(StringRef K) const;
138 llvm::Optional<int64_t> getInteger(StringRef K) const;
139 llvm::Optional<llvm::StringRef> getString(StringRef K) const;
140 const json::Object *getObject(StringRef K) const;
141 json::Object *getObject(StringRef K);
142 const json::Array *getArray(StringRef K) const;
143 json::Array *getArray(StringRef K);
144};
145bool operator==(const Object &LHS, const Object &RHS);
146inline bool operator!=(const Object &LHS, const Object &RHS) {
147 return !(LHS == RHS);
148}
149
150/// An Array is a JSON array, which contains heterogeneous JSON values.
151/// It simulates std::vector<Value>.
152class Array {
153 std::vector<Value> V;
154
155public:
156 using value_type = Value;
157 using iterator = std::vector<Value>::iterator;
158 using const_iterator = std::vector<Value>::const_iterator;
159
160 explicit Array() = default;
161 explicit Array(std::initializer_list<Value> Elements);
162 template <typename Collection> explicit Array(const Collection &C) {
163 for (const auto &V : C)
164 emplace_back(V);
165 }
166
167 Value &operator[](size_t I) { return V[I]; }
168 const Value &operator[](size_t I) const { return V[I]; }
169 Value &front() { return V.front(); }
170 const Value &front() const { return V.front(); }
171 Value &back() { return V.back(); }
172 const Value &back() const { return V.back(); }
173 Value *data() { return V.data(); }
174 const Value *data() const { return V.data(); }
175
176 iterator begin() { return V.begin(); }
177 const_iterator begin() const { return V.begin(); }
178 iterator end() { return V.end(); }
179 const_iterator end() const { return V.end(); }
180
181 bool empty() const { return V.empty(); }
182 size_t size() const { return V.size(); }
183
184 void clear() { V.clear(); }
185 void push_back(const Value &E) { V.push_back(E); }
186 void push_back(Value &&E) { V.push_back(std::move(E)); }
187 template <typename... Args> void emplace_back(Args &&... A) {
188 V.emplace_back(std::forward<Args>(A)...);
189 }
190 void pop_back() { V.pop_back(); }
191 // FIXME: insert() takes const_iterator since C++11, old libstdc++ disagrees.
192 iterator insert(iterator P, const Value &E) { return V.insert(P, E); }
193 iterator insert(iterator P, Value &&E) {
194 return V.insert(P, std::move(E));
195 }
196 template <typename It> iterator insert(iterator P, It A, It Z) {
197 return V.insert(P, A, Z);
198 }
199 template <typename... Args> iterator emplace(const_iterator P, Args &&... A) {
200 return V.emplace(P, std::forward<Args>(A)...);
201 }
202
203 friend bool operator==(const Array &L, const Array &R) { return L.V == R.V; }
204};
205inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
206
207/// A Value is an JSON value of unknown type.
208/// They can be copied, but should generally be moved.
209///
210/// === Composing values ===
211///
212/// You can implicitly construct Values from:
213/// - strings: std::string, SmallString, formatv, StringRef, char*
214/// (char*, and StringRef are references, not copies!)
215/// - numbers
216/// - booleans
217/// - null: nullptr
218/// - arrays: {"foo", 42.0, false}
219/// - serializable things: types with toJSON(const T&)->Value, found by ADL
220///
221/// They can also be constructed from object/array helpers:
222/// - json::Object is a type like map<ObjectKey, Value>
223/// - json::Array is a type like vector<Value>
224/// These can be list-initialized, or used to build up collections in a loop.
225/// json::ary(Collection) converts all items in a collection to Values.
226///
227/// === Inspecting values ===
228///
229/// Each Value is one of the JSON kinds:
230/// null (nullptr_t)
231/// boolean (bool)
232/// number (double or int64)
233/// string (StringRef)
234/// array (json::Array)
235/// object (json::Object)
236///
237/// The kind can be queried directly, or implicitly via the typed accessors:
238/// if (Optional<StringRef> S = E.getAsString()
239/// assert(E.kind() == Value::String);
240///
241/// Array and Object also have typed indexing accessors for easy traversal:
242/// Expected<Value> E = parse(R"( {"options": {"font": "sans-serif"}} )");
243/// if (Object* O = E->getAsObject())
244/// if (Object* Opts = O->getObject("options"))
245/// if (Optional<StringRef> Font = Opts->getString("font"))
246/// assert(Opts->at("font").kind() == Value::String);
247///
248/// === Converting JSON values to C++ types ===
249///
250/// The convention is to have a deserializer function findable via ADL:
251/// fromJSON(const json::Value&, T&)->bool
252/// Deserializers are provided for:
253/// - bool
254/// - int and int64_t
255/// - double
256/// - std::string
257/// - vector<T>, where T is deserializable
258/// - map<string, T>, where T is deserializable
259/// - Optional<T>, where T is deserializable
260/// ObjectMapper can help writing fromJSON() functions for object types.
261///
262/// For conversion in the other direction, the serializer function is:
263/// toJSON(const T&) -> json::Value
264/// If this exists, then it also allows constructing Value from T, and can
265/// be used to serialize vector<T>, map<string, T>, and Optional<T>.
266///
267/// === Serialization ===
268///
269/// Values can be serialized to JSON:
270/// 1) raw_ostream << Value // Basic formatting.
271/// 2) raw_ostream << formatv("{0}", Value) // Basic formatting.
272/// 3) raw_ostream << formatv("{0:2}", Value) // Pretty-print with indent 2.
273///
274/// And parsed:
275/// Expected<Value> E = json::parse("[1, 2, null]");
276/// assert(E && E->kind() == Value::Array);
277class Value {
278public:
279 enum Kind {
280 Null,
281 Boolean,
282 /// Number values can store both int64s and doubles at full precision,
283 /// depending on what they were constructed/parsed from.
284 Number,
285 String,
286 Array,
287 Object,
288 };
289
290 // It would be nice to have Value() be null. But that would make {} null too.
291 Value(const Value &M) { copyFrom(M); }
292 Value(Value &&M) { moveFrom(std::move(M)); }
293 Value(std::initializer_list<Value> Elements);
294 Value(json::Array &&Elements) : Type(T_Array) {
295 create<json::Array>(std::move(Elements));
296 }
297 Value(json::Object &&Properties) : Type(T_Object) {
298 create<json::Object>(std::move(Properties));
299 }
300 // Strings: types with value semantics. Must be valid UTF-8.
301 Value(std::string V) : Type(T_String) {
302 if (LLVM_UNLIKELY(!isUTF8(V))) {
303 assert(false && "Invalid UTF-8 in value used as JSON");
304 V = fixUTF8(std::move(V));
305 }
306 create<std::string>(std::move(V));
307 }
308 Value(const llvm::SmallVectorImpl<char> &V)
309 : Value(std::string(V.begin(), V.end())){};
310 Value(const llvm::formatv_object_base &V) : Value(V.str()){};
311 // Strings: types with reference semantics. Must be valid UTF-8.
312 Value(StringRef V) : Type(T_StringRef) {
313 create<llvm::StringRef>(V);
314 if (LLVM_UNLIKELY(!isUTF8(V))) {
315 assert(false && "Invalid UTF-8 in value used as JSON");
316 *this = Value(fixUTF8(V));
317 }
318 }
319 Value(const char *V) : Value(StringRef(V)) {}
320 Value(std::nullptr_t) : Type(T_Null) {}
321 // Boolean (disallow implicit conversions).
322 // (The last template parameter is a dummy to keep templates distinct.)
323 template <
324 typename T,
325 typename = typename std::enable_if<std::is_same<T, bool>::value>::type,
326 bool = false>
327 Value(T B) : Type(T_Boolean) {
328 create<bool>(B);
329 }
330 // Integers (except boolean). Must be non-narrowing convertible to int64_t.
331 template <
332 typename T,
333 typename = typename std::enable_if<std::is_integral<T>::value>::type,
334 typename = typename std::enable_if<!std::is_same<T, bool>::value>::type>
335 Value(T I) : Type(T_Integer) {
336 create<int64_t>(int64_t{I});
337 }
338 // Floating point. Must be non-narrowing convertible to double.
339 template <typename T,
340 typename =
341 typename std::enable_if<std::is_floating_point<T>::value>::type,
342 double * = nullptr>
343 Value(T D) : Type(T_Double) {
344 create<double>(double{D});
345 }
346 // Serializable types: with a toJSON(const T&)->Value function, found by ADL.
347 template <typename T,
348 typename = typename std::enable_if<std::is_same<
349 Value, decltype(toJSON(*(const T *)nullptr))>::value>,
350 Value * = nullptr>
351 Value(const T &V) : Value(toJSON(V)) {}
352
353 Value &operator=(const Value &M) {
354 destroy();
355 copyFrom(M);
356 return *this;
357 }
358 Value &operator=(Value &&M) {
359 destroy();
360 moveFrom(std::move(M));
361 return *this;
362 }
363 ~Value() { destroy(); }
364
365 Kind kind() const {
366 switch (Type) {
367 case T_Null:
368 return Null;
369 case T_Boolean:
370 return Boolean;
371 case T_Double:
372 case T_Integer:
373 return Number;
374 case T_String:
375 case T_StringRef:
376 return String;
377 case T_Object:
378 return Object;
379 case T_Array:
380 return Array;
381 }
382 llvm_unreachable("Unknown kind");
383 }
384
385 // Typed accessors return None/nullptr if the Value is not of this type.
386 llvm::Optional<std::nullptr_t> getAsNull() const {
387 if (LLVM_LIKELY(Type == T_Null))
388 return nullptr;
389 return llvm::None;
390 }
391 llvm::Optional<bool> getAsBoolean() const {
392 if (LLVM_LIKELY(Type == T_Boolean))
393 return as<bool>();
394 return llvm::None;
395 }
396 llvm::Optional<double> getAsNumber() const {
397 if (LLVM_LIKELY(Type == T_Double))
398 return as<double>();
399 if (LLVM_LIKELY(Type == T_Integer))
400 return as<int64_t>();
401 return llvm::None;
402 }
403 // Succeeds if the Value is a Number, and exactly representable as int64_t.
404 llvm::Optional<int64_t> getAsInteger() const {
405 if (LLVM_LIKELY(Type == T_Integer))
406 return as<int64_t>();
407 if (LLVM_LIKELY(Type == T_Double)) {
408 double D = as<double>();
409 if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&
410 D >= double(std::numeric_limits<int64_t>::min()) &&
411 D <= double(std::numeric_limits<int64_t>::max())))
412 return D;
413 }
414 return llvm::None;
415 }
416 llvm::Optional<llvm::StringRef> getAsString() const {
417 if (Type == T_String)
418 return llvm::StringRef(as<std::string>());
419 if (LLVM_LIKELY(Type == T_StringRef))
420 return as<llvm::StringRef>();
421 return llvm::None;
422 }
423 const json::Object *getAsObject() const {
424 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
425 }
426 json::Object *getAsObject() {
427 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
428 }
429 const json::Array *getAsArray() const {
430 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
431 }
432 json::Array *getAsArray() {
433 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
434 }
435
436 /// Serializes this Value to JSON, writing it to the provided stream.
437 /// The formatting is compact (no extra whitespace) and deterministic.
438 /// For pretty-printing, use the formatv() format_provider below.
439 friend llvm::raw_ostream &operator<<(llvm::raw_ostream &, const Value &);
440
441private:
442 void destroy();
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);
448 friend class Array;
449 friend class Object;
450
451 template <typename T, typename... U> void create(U &&... V) {
452 new (reinterpret_cast<T *>(Union.buffer)) T(std::forward<U>(V)...);
453 }
454 template <typename T> T &as() const {
Andrew Scull0372a572018-11-16 15:47:06 +0000455 // 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);
Andrew Scullcdfcccc2018-10-05 20:58:37 +0100459 }
460
461 template <typename Indenter>
462 void print(llvm::raw_ostream &, const Indenter &) const;
463 friend struct llvm::format_provider<llvm::json::Value>;
464
465 enum ValueType : char {
466 T_Null,
467 T_Boolean,
468 T_Double,
469 T_Integer,
470 T_StringRef,
471 T_String,
472 T_Object,
473 T_Array,
474 };
475 // All members mutable, see moveFrom().
476 mutable ValueType Type;
477 mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, llvm::StringRef,
478 std::string, json::Array, json::Object>
479 Union;
480};
481
482bool operator==(const Value &, const Value &);
483inline bool operator!=(const Value &L, const Value &R) { return !(L == R); }
484llvm::raw_ostream &operator<<(llvm::raw_ostream &, const Value &);
485
486/// ObjectKey is a used to capture keys in Object. Like Value but:
487/// - only strings are allowed
488/// - it's optimized for the string literal case (Owned == nullptr)
489/// Like Value, strings must be UTF-8. See isUTF8 documentation for details.
490class ObjectKey {
491public:
492 ObjectKey(const char *S) : ObjectKey(StringRef(S)) {}
493 ObjectKey(std::string S) : Owned(new std::string(std::move(S))) {
494 if (LLVM_UNLIKELY(!isUTF8(*Owned))) {
495 assert(false && "Invalid UTF-8 in value used as JSON");
496 *Owned = fixUTF8(std::move(*Owned));
497 }
498 Data = *Owned;
499 }
500 ObjectKey(llvm::StringRef S) : Data(S) {
501 if (LLVM_UNLIKELY(!isUTF8(Data))) {
502 assert(false && "Invalid UTF-8 in value used as JSON");
503 *this = ObjectKey(fixUTF8(S));
504 }
505 }
506 ObjectKey(const llvm::SmallVectorImpl<char> &V)
507 : ObjectKey(std::string(V.begin(), V.end())) {}
508 ObjectKey(const llvm::formatv_object_base &V) : ObjectKey(V.str()) {}
509
510 ObjectKey(const ObjectKey &C) { *this = C; }
511 ObjectKey(ObjectKey &&C) : ObjectKey(static_cast<const ObjectKey &&>(C)) {}
512 ObjectKey &operator=(const ObjectKey &C) {
513 if (C.Owned) {
514 Owned.reset(new std::string(*C.Owned));
515 Data = *Owned;
516 } else {
517 Data = C.Data;
518 }
519 return *this;
520 }
521 ObjectKey &operator=(ObjectKey &&) = default;
522
523 operator llvm::StringRef() const { return Data; }
524 std::string str() const { return Data.str(); }
525
526private:
527 // FIXME: this is unneccesarily large (3 pointers). Pointer + length + owned
528 // could be 2 pointers at most.
529 std::unique_ptr<std::string> Owned;
530 llvm::StringRef Data;
531};
532
533inline bool operator==(const ObjectKey &L, const ObjectKey &R) {
534 return llvm::StringRef(L) == llvm::StringRef(R);
535}
536inline bool operator!=(const ObjectKey &L, const ObjectKey &R) {
537 return !(L == R);
538}
539inline bool operator<(const ObjectKey &L, const ObjectKey &R) {
540 return StringRef(L) < StringRef(R);
541}
542
543struct Object::KV {
544 ObjectKey K;
545 Value V;
546};
547
548inline Object::Object(std::initializer_list<KV> Properties) {
549 for (const auto &P : Properties) {
550 auto R = try_emplace(P.K, nullptr);
551 if (R.second)
552 R.first->getSecond().moveFrom(std::move(P.V));
553 }
554}
555inline std::pair<Object::iterator, bool> Object::insert(KV E) {
556 return try_emplace(std::move(E.K), std::move(E.V));
557}
558
559// Standard deserializers are provided for primitive types.
560// See comments on Value.
561inline bool fromJSON(const Value &E, std::string &Out) {
562 if (auto S = E.getAsString()) {
563 Out = *S;
564 return true;
565 }
566 return false;
567}
568inline bool fromJSON(const Value &E, int &Out) {
569 if (auto S = E.getAsInteger()) {
570 Out = *S;
571 return true;
572 }
573 return false;
574}
575inline bool fromJSON(const Value &E, int64_t &Out) {
576 if (auto S = E.getAsInteger()) {
577 Out = *S;
578 return true;
579 }
580 return false;
581}
582inline bool fromJSON(const Value &E, double &Out) {
583 if (auto S = E.getAsNumber()) {
584 Out = *S;
585 return true;
586 }
587 return false;
588}
589inline bool fromJSON(const Value &E, bool &Out) {
590 if (auto S = E.getAsBoolean()) {
591 Out = *S;
592 return true;
593 }
594 return false;
595}
596template <typename T> bool fromJSON(const Value &E, llvm::Optional<T> &Out) {
597 if (E.getAsNull()) {
598 Out = llvm::None;
599 return true;
600 }
601 T Result;
602 if (!fromJSON(E, Result))
603 return false;
604 Out = std::move(Result);
605 return true;
606}
607template <typename T> bool fromJSON(const Value &E, std::vector<T> &Out) {
608 if (auto *A = E.getAsArray()) {
609 Out.clear();
610 Out.resize(A->size());
611 for (size_t I = 0; I < A->size(); ++I)
612 if (!fromJSON((*A)[I], Out[I]))
613 return false;
614 return true;
615 }
616 return false;
617}
618template <typename T>
619bool fromJSON(const Value &E, std::map<std::string, T> &Out) {
620 if (auto *O = E.getAsObject()) {
621 Out.clear();
622 for (const auto &KV : *O)
623 if (!fromJSON(KV.second, Out[llvm::StringRef(KV.first)]))
624 return false;
625 return true;
626 }
627 return false;
628}
629
630// Allow serialization of Optional<T> for supported T.
631template <typename T> Value toJSON(const llvm::Optional<T> &Opt) {
632 return Opt ? Value(*Opt) : Value(nullptr);
633}
634
635/// Helper for mapping JSON objects onto protocol structs.
636///
637/// Example:
638/// \code
639/// bool fromJSON(const Value &E, MyStruct &R) {
640/// ObjectMapper O(E);
641/// if (!O || !O.map("mandatory_field", R.MandatoryField))
642/// return false;
643/// O.map("optional_field", R.OptionalField);
644/// return true;
645/// }
646/// \endcode
647class ObjectMapper {
648public:
649 ObjectMapper(const Value &E) : O(E.getAsObject()) {}
650
651 /// True if the expression is an object.
652 /// Must be checked before calling map().
653 operator bool() { return O; }
654
655 /// Maps a property to a field, if it exists.
656 template <typename T> bool map(StringRef Prop, T &Out) {
657 assert(*this && "Must check this is an object before calling map()");
658 if (const Value *E = O->get(Prop))
659 return fromJSON(*E, Out);
660 return false;
661 }
662
663 /// Maps a property to a field, if it exists.
664 /// (Optional requires special handling, because missing keys are OK).
665 template <typename T> bool map(StringRef Prop, llvm::Optional<T> &Out) {
666 assert(*this && "Must check this is an object before calling map()");
667 if (const Value *E = O->get(Prop))
668 return fromJSON(*E, Out);
669 Out = llvm::None;
670 return true;
671 }
672
673private:
674 const Object *O;
675};
676
677/// Parses the provided JSON source, or returns a ParseError.
678/// The returned Value is self-contained and owns its strings (they do not refer
679/// to the original source).
680llvm::Expected<Value> parse(llvm::StringRef JSON);
681
682class ParseError : public llvm::ErrorInfo<ParseError> {
683 const char *Msg;
684 unsigned Line, Column, Offset;
685
686public:
687 static char ID;
688 ParseError(const char *Msg, unsigned Line, unsigned Column, unsigned Offset)
689 : Msg(Msg), Line(Line), Column(Column), Offset(Offset) {}
690 void log(llvm::raw_ostream &OS) const override {
691 OS << llvm::formatv("[{0}:{1}, byte={2}]: {3}", Line, Column, Offset, Msg);
692 }
693 std::error_code convertToErrorCode() const override {
694 return llvm::inconvertibleErrorCode();
695 }
696};
697} // namespace json
698
699/// Allow printing json::Value with formatv().
700/// The default style is basic/compact formatting, like operator<<.
701/// A format string like formatv("{0:2}", Value) pretty-prints with indent 2.
702template <> struct format_provider<llvm::json::Value> {
703 static void format(const llvm::json::Value &, raw_ostream &, StringRef);
704};
705} // namespace llvm
706
707#endif