1//===--- JSON.h - JSON values, parsing and serialization -------*- C++ -*-===//
2//
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
6//
7//===---------------------------------------------------------------------===//
8///
9/// \file
10/// This file supports working with JSON data.
11///
12/// It comprises:
13///
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.
17///
18/// - functions to parse JSON text into Values, and to serialize Values to text.
19/// See parse(), operator<<, and format_provider.
20///
21/// - a convention and helpers for mapping between json::Value and user-defined
22/// types. See fromJSON(), ObjectMapper, and the class comment on Value.
23///
24/// - an output API json::OStream which can emit JSON without materializing
25/// all structures as json::Value.
26///
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).
30///
31/// Other serialization mechanisms you may consider:
32///
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.
39///
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
43///
44//===---------------------------------------------------------------------===//
45
46#ifndef LLVM_SUPPORT_JSON_H
47#define LLVM_SUPPORT_JSON_H
48
49#include "llvm/ADT/DenseMap.h"
50#include "llvm/ADT/STLFunctionalExtras.h"
51#include "llvm/ADT/SmallVector.h"
52#include "llvm/ADT/StringRef.h"
53#include "llvm/Support/Compiler.h"
54#include "llvm/Support/Error.h"
55#include "llvm/Support/FormatVariadic.h"
56#include "llvm/Support/raw_ostream.h"
57#include <cmath>
58#include <map>
59
60namespace llvm {
61namespace json {
62
63// === String encodings ===
64//
65// JSON strings are character sequences (not byte sequences like std::string).
66// We need to know the encoding, and for simplicity only support UTF-8.
67//
68// - When parsing, invalid UTF-8 is a syntax error like any other
69//
70// - When creating Values from strings, callers must ensure they are UTF-8.
71// with asserts on, invalid UTF-8 will crash the program
72// with asserts off, we'll substitute the replacement character (U+FFFD)
73// Callers can use json::isUTF8() and json::fixUTF8() for validation.
74//
75// - When retrieving strings from Values (e.g. asString()), the result will
76// always be valid UTF-8.
77
78template <typename T>
79constexpr bool is_uint_64_bit_v =
80 std::is_integral_v<T> && std::is_unsigned_v<T> &&
81 sizeof(T) == sizeof(uint64_t);
82
83/// Returns true if \p S is valid UTF-8, which is required for use as JSON.
84/// If it returns false, \p Offset is set to a byte offset near the first error.
85bool isUTF8(llvm::StringRef S, size_t *ErrOffset = nullptr);
86/// Replaces invalid UTF-8 sequences in \p S with the replacement character
87/// (U+FFFD). The returned string is valid UTF-8.
88/// This is much slower than isUTF8, so test that first.
89std::string fixUTF8(llvm::StringRef S);
90
91class Array;
92class ObjectKey;
93class Value;
94template <typename T> Value toJSON(const std::optional<T> &Opt);
95
96/// An Object is a JSON object, which maps strings to heterogenous JSON values.
97/// It simulates DenseMap<ObjectKey, Value>. ObjectKey is a maybe-owned string.
98class Object {
99 using Storage = DenseMap<ObjectKey, Value, llvm::DenseMapInfo<StringRef>>;
100 Storage M;
101
102public:
103 using key_type = ObjectKey;
104 using mapped_type = Value;
105 using value_type = Storage::value_type;
106 using iterator = Storage::iterator;
107 using const_iterator = Storage::const_iterator;
108
109 Object() = default;
110 // KV is a trivial key-value struct for list-initialization.
111 // (using std::pair forces extra copies).
112 struct KV;
113 explicit Object(std::initializer_list<KV> Properties);
114
115 iterator begin() { return M.begin(); }
116 const_iterator begin() const { return M.begin(); }
117 iterator end() { return M.end(); }
118 const_iterator end() const { return M.end(); }
119
120 bool empty() const { return M.empty(); }
121 size_t size() const { return M.size(); }
122
123 void clear() { M.clear(); }
124 std::pair<iterator, bool> insert(KV E);
125 template <typename... Ts>
126 std::pair<iterator, bool> try_emplace(const ObjectKey &K, Ts &&... Args) {
127 return M.try_emplace(K, std::forward<Ts>(Args)...);
128 }
129 template <typename... Ts>
130 std::pair<iterator, bool> try_emplace(ObjectKey &&K, Ts &&... Args) {
131 return M.try_emplace(std::move(K), std::forward<Ts>(Args)...);
132 }
133 bool erase(StringRef K);
134 void erase(iterator I) { M.erase(I); }
135
136 iterator find(StringRef K) { return M.find_as(Val: K); }
137 const_iterator find(StringRef K) const { return M.find_as(Val: K); }
138 // operator[] acts as if Value was default-constructible as null.
139 Value &operator[](const ObjectKey &K);
140 Value &operator[](ObjectKey &&K);
141 // Look up a property, returning nullptr if it doesn't exist.
142 Value *get(StringRef K);
143 const Value *get(StringRef K) const;
144 // Typed accessors return std::nullopt/nullptr if
145 // - the property doesn't exist
146 // - or it has the wrong type
147 std::optional<std::nullptr_t> getNull(StringRef K) const;
148 std::optional<bool> getBoolean(StringRef K) const;
149 std::optional<double> getNumber(StringRef K) const;
150 std::optional<int64_t> getInteger(StringRef K) const;
151 std::optional<llvm::StringRef> getString(StringRef K) const;
152 const json::Object *getObject(StringRef K) const;
153 json::Object *getObject(StringRef K);
154 const json::Array *getArray(StringRef K) const;
155 json::Array *getArray(StringRef K);
156};
157bool operator==(const Object &LHS, const Object &RHS);
158inline bool operator!=(const Object &LHS, const Object &RHS) {
159 return !(LHS == RHS);
160}
161
162/// An Array is a JSON array, which contains heterogeneous JSON values.
163/// It simulates std::vector<Value>.
164class Array {
165 std::vector<Value> V;
166
167public:
168 using value_type = Value;
169 using iterator = std::vector<Value>::iterator;
170 using const_iterator = std::vector<Value>::const_iterator;
171
172 Array() = default;
173 explicit Array(std::initializer_list<Value> Elements);
174 template <typename Collection> explicit Array(const Collection &C) {
175 for (const auto &V : C)
176 emplace_back(V);
177 }
178
179 Value &operator[](size_t I);
180 const Value &operator[](size_t I) const;
181 Value &front();
182 const Value &front() const;
183 Value &back();
184 const Value &back() const;
185 Value *data();
186 const Value *data() const;
187
188 iterator begin();
189 const_iterator begin() const;
190 iterator end();
191 const_iterator end() const;
192
193 bool empty() const;
194 size_t size() const;
195 void reserve(size_t S);
196
197 void clear();
198 void push_back(const Value &E);
199 void push_back(Value &&E);
200 template <typename... Args> void emplace_back(Args &&...A);
201 void pop_back();
202 iterator insert(const_iterator P, const Value &E);
203 iterator insert(const_iterator P, Value &&E);
204 template <typename It> iterator insert(const_iterator P, It A, It Z);
205 template <typename... Args> iterator emplace(const_iterator P, Args &&...A);
206
207 friend bool operator==(const Array &L, const Array &R);
208};
209inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
210
211/// A Value is an JSON value of unknown type.
212/// They can be copied, but should generally be moved.
213///
214/// === Composing values ===
215///
216/// You can implicitly construct Values from:
217/// - strings: std::string, SmallString, formatv, StringRef, char*
218/// (char*, and StringRef are references, not copies!)
219/// - numbers
220/// - booleans
221/// - null: nullptr
222/// - arrays: {"foo", 42.0, false}
223/// - serializable things: types with toJSON(const T&)->Value, found by ADL
224///
225/// They can also be constructed from object/array helpers:
226/// - json::Object is a type like map<ObjectKey, Value>
227/// - json::Array is a type like vector<Value>
228/// These can be list-initialized, or used to build up collections in a loop.
229/// json::ary(Collection) converts all items in a collection to Values.
230///
231/// === Inspecting values ===
232///
233/// Each Value is one of the JSON kinds:
234/// null (nullptr_t)
235/// boolean (bool)
236/// number (double, int64 or uint64)
237/// string (StringRef)
238/// array (json::Array)
239/// object (json::Object)
240///
241/// The kind can be queried directly, or implicitly via the typed accessors:
242/// if (std::optional<StringRef> S = E.getAsString()
243/// assert(E.kind() == Value::String);
244///
245/// Array and Object also have typed indexing accessors for easy traversal:
246/// Expected<Value> E = parse(R"( {"options": {"font": "sans-serif"}} )");
247/// if (Object* O = E->getAsObject())
248/// if (Object* Opts = O->getObject("options"))
249/// if (std::optional<StringRef> Font = Opts->getString("font"))
250/// assert(Opts->at("font").kind() == Value::String);
251///
252/// === Converting JSON values to C++ types ===
253///
254/// The convention is to have a deserializer function findable via ADL:
255/// fromJSON(const json::Value&, T&, Path) -> bool
256///
257/// The return value indicates overall success, and Path is used for precise
258/// error reporting. (The Path::Root passed in at the top level fromJSON call
259/// captures any nested error and can render it in context).
260/// If conversion fails, fromJSON calls Path::report() and immediately returns.
261/// This ensures that the first fatal error survives.
262///
263/// Deserializers are provided for:
264/// - bool
265/// - int and int64_t
266/// - double
267/// - std::string
268/// - vector<T>, where T is deserializable
269/// - map<string, T>, where T is deserializable
270/// - std::optional<T>, where T is deserializable
271/// ObjectMapper can help writing fromJSON() functions for object types.
272///
273/// For conversion in the other direction, the serializer function is:
274/// toJSON(const T&) -> json::Value
275/// If this exists, then it also allows constructing Value from T, and can
276/// be used to serialize vector<T>, map<string, T>, and std::optional<T>.
277///
278/// === Serialization ===
279///
280/// Values can be serialized to JSON:
281/// 1) raw_ostream << Value // Basic formatting.
282/// 2) raw_ostream << formatv("{0}", Value) // Basic formatting.
283/// 3) raw_ostream << formatv("{0:2}", Value) // Pretty-print with indent 2.
284///
285/// And parsed:
286/// Expected<Value> E = json::parse("[1, 2, null]");
287/// assert(E && E->kind() == Value::Array);
288class Value {
289public:
290 enum Kind {
291 Null,
292 Boolean,
293 /// Number values can store both int64s and doubles at full precision,
294 /// depending on what they were constructed/parsed from.
295 Number,
296 String,
297 Array,
298 Object,
299 };
300
301 // It would be nice to have Value() be null. But that would make {} null too.
302 Value(const Value &M) { copyFrom(M); }
303 Value(Value &&M) { moveFrom(M: std::move(M)); }
304 Value(std::initializer_list<Value> Elements);
305 Value(json::Array &&Elements) : Type(T_Array) {
306 create<json::Array>(V: std::move(Elements));
307 }
308 template <typename Elt>
309 Value(const std::vector<Elt> &C) : Value(json::Array(C)) {}
310 Value(json::Object &&Properties) : Type(T_Object) {
311 create<json::Object>(V: std::move(Properties));
312 }
313 template <typename Elt>
314 Value(const std::map<std::string, Elt> &C) : Value(json::Object(C)) {}
315 // Strings: types with value semantics. Must be valid UTF-8.
316 Value(std::string V) : Type(T_String) {
317 if (LLVM_UNLIKELY(!isUTF8(V))) {
318 assert(false && "Invalid UTF-8 in value used as JSON");
319 V = fixUTF8(S: std::move(V));
320 }
321 create<std::string>(V: std::move(V));
322 }
323 Value(const llvm::SmallVectorImpl<char> &V)
324 : Value(std::string(V.begin(), V.end())) {}
325 Value(const llvm::formatv_object_base &V) : Value(V.str()) {}
326 // Strings: types with reference semantics. Must be valid UTF-8.
327 Value(StringRef V) : Type(T_StringRef) {
328 create<llvm::StringRef>(V);
329 if (LLVM_UNLIKELY(!isUTF8(V))) {
330 assert(false && "Invalid UTF-8 in value used as JSON");
331 *this = Value(fixUTF8(S: V));
332 }
333 }
334 Value(const char *V) : Value(StringRef(V)) {}
335 Value(std::nullptr_t) : Type(T_Null) {}
336 // Boolean (disallow implicit conversions).
337 // (The last template parameter is a dummy to keep templates distinct.)
338 template <typename T, typename = std::enable_if_t<std::is_same_v<T, bool>>,
339 bool = false>
340 Value(T B) : Type(T_Boolean) {
341 create<bool>(B);
342 }
343
344 // Unsigned 64-bit integers.
345 template <typename T, typename = std::enable_if_t<is_uint_64_bit_v<T>>>
346 Value(T V) : Type(T_UINT64) {
347 create<uint64_t>(V: uint64_t{V});
348 }
349
350 // Integers (except boolean and uint64_t).
351 // Must be non-narrowing convertible to int64_t.
352 template <typename T, typename = std::enable_if_t<std::is_integral_v<T>>,
353 typename = std::enable_if_t<!std::is_same_v<T, bool>>,
354 typename = std::enable_if_t<!is_uint_64_bit_v<T>>>
355 Value(T I) : Type(T_Integer) {
356 create<int64_t>(V: int64_t{I});
357 }
358 // Floating point. Must be non-narrowing convertible to double.
359 template <typename T,
360 typename = std::enable_if_t<std::is_floating_point_v<T>>,
361 double * = nullptr>
362 Value(T D) : Type(T_Double) {
363 create<double>(V: double{D});
364 }
365 // Serializable types: with a toJSON(const T&)->Value function, found by ADL.
366 template <typename T,
367 typename = std::enable_if_t<
368 std::is_same_v<Value, decltype(toJSON(*(const T *)nullptr))>>,
369 Value * = nullptr>
370 Value(const T &V) : Value(toJSON(V)) {}
371
372 Value &operator=(const Value &M) {
373 destroy();
374 copyFrom(M);
375 return *this;
376 }
377 Value &operator=(Value &&M) {
378 destroy();
379 moveFrom(M: std::move(M));
380 return *this;
381 }
382 ~Value() { destroy(); }
383
384 Kind kind() const {
385 switch (Type) {
386 case T_Null:
387 return Null;
388 case T_Boolean:
389 return Boolean;
390 case T_Double:
391 case T_Integer:
392 case T_UINT64:
393 return Number;
394 case T_String:
395 case T_StringRef:
396 return String;
397 case T_Object:
398 return Object;
399 case T_Array:
400 return Array;
401 }
402 llvm_unreachable("Unknown kind");
403 }
404
405 // Typed accessors return std::nullopt/nullptr if the Value is not of this
406 // type.
407 std::optional<std::nullptr_t> getAsNull() const {
408 if (LLVM_LIKELY(Type == T_Null))
409 return nullptr;
410 return std::nullopt;
411 }
412 std::optional<bool> getAsBoolean() const {
413 if (LLVM_LIKELY(Type == T_Boolean))
414 return as<bool>();
415 return std::nullopt;
416 }
417 std::optional<double> getAsNumber() const {
418 if (LLVM_LIKELY(Type == T_Double))
419 return as<double>();
420 if (LLVM_LIKELY(Type == T_Integer))
421 return as<int64_t>();
422 if (LLVM_LIKELY(Type == T_UINT64))
423 return as<uint64_t>();
424 return std::nullopt;
425 }
426 // Succeeds if the Value is a Number, and exactly representable as int64_t.
427 std::optional<int64_t> getAsInteger() const {
428 if (LLVM_LIKELY(Type == T_Integer))
429 return as<int64_t>();
430 if (LLVM_LIKELY(Type == T_UINT64)) {
431 uint64_t U = as<uint64_t>();
432 if (LLVM_LIKELY(U <= uint64_t(std::numeric_limits<int64_t>::max()))) {
433 return U;
434 }
435 }
436 if (LLVM_LIKELY(Type == T_Double)) {
437 double D = as<double>();
438 if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&
439 D >= double(std::numeric_limits<int64_t>::min()) &&
440 D <= double(std::numeric_limits<int64_t>::max())))
441 return D;
442 }
443 return std::nullopt;
444 }
445 std::optional<uint64_t> getAsUINT64() const {
446 if (Type == T_UINT64)
447 return as<uint64_t>();
448 else if (Type == T_Integer) {
449 int64_t N = as<int64_t>();
450 if (N >= 0)
451 return as<uint64_t>();
452 }
453 return std::nullopt;
454 }
455 std::optional<llvm::StringRef> getAsString() const {
456 if (Type == T_String)
457 return llvm::StringRef(as<std::string>());
458 if (LLVM_LIKELY(Type == T_StringRef))
459 return as<llvm::StringRef>();
460 return std::nullopt;
461 }
462 const json::Object *getAsObject() const {
463 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
464 }
465 json::Object *getAsObject() {
466 return LLVM_LIKELY(Type == T_Object) ? &as<json::Object>() : nullptr;
467 }
468 const json::Array *getAsArray() const {
469 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
470 }
471 json::Array *getAsArray() {
472 return LLVM_LIKELY(Type == T_Array) ? &as<json::Array>() : nullptr;
473 }
474
475private:
476 void destroy();
477 void copyFrom(const Value &M);
478 // We allow moving from *const* Values, by marking all members as mutable!
479 // This hack is needed to support initializer-list syntax efficiently.
480 // (std::initializer_list<T> is a container of const T).
481 void moveFrom(const Value &&M);
482 friend class Array;
483 friend class Object;
484
485 template <typename T, typename... U> void create(U &&... V) {
486#if LLVM_ADDRESS_SANITIZER_BUILD
487 // Unpoisoning to prevent overwriting poisoned object (e.g., annotated short
488 // string). Objects that have had their memory poisoned may cause an ASan
489 // error if their memory is reused without calling their destructor.
490 // Unpoisoning the memory prevents this error from occurring.
491 // FIXME: This is a temporary solution to prevent buildbots from failing.
492 // The more appropriate approach would be to call the object's destructor
493 // to unpoison memory. This would prevent any potential memory leaks (long
494 // strings). Read for details:
495 // https://github.com/llvm/llvm-project/pull/79065#discussion_r1462621761
496 __asan_unpoison_memory_region(&Union, sizeof(T));
497#endif
498 new (reinterpret_cast<T *>(&Union)) T(std::forward<U>(V)...);
499 }
500 template <typename T> T &as() const {
501 // Using this two-step static_cast via void * instead of reinterpret_cast
502 // silences a -Wstrict-aliasing false positive from GCC6 and earlier.
503 void *Storage = static_cast<void *>(&Union);
504 return *static_cast<T *>(Storage);
505 }
506
507 friend class OStream;
508
509 enum ValueType : char16_t {
510 T_Null,
511 T_Boolean,
512 T_Double,
513 T_Integer,
514 T_UINT64,
515 T_StringRef,
516 T_String,
517 T_Object,
518 T_Array,
519 };
520 // All members mutable, see moveFrom().
521 mutable ValueType Type;
522 mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, uint64_t,
523 llvm::StringRef, std::string, json::Array,
524 json::Object>
525 Union;
526 friend bool operator==(const Value &, const Value &);
527};
528
529bool operator==(const Value &, const Value &);
530inline bool operator!=(const Value &L, const Value &R) { return !(L == R); }
531
532// Array Methods
533inline Value &Array::operator[](size_t I) { return V[I]; }
534inline const Value &Array::operator[](size_t I) const { return V[I]; }
535inline Value &Array::front() { return V.front(); }
536inline const Value &Array::front() const { return V.front(); }
537inline Value &Array::back() { return V.back(); }
538inline const Value &Array::back() const { return V.back(); }
539inline Value *Array::data() { return V.data(); }
540inline const Value *Array::data() const { return V.data(); }
541
542inline typename Array::iterator Array::begin() { return V.begin(); }
543inline typename Array::const_iterator Array::begin() const { return V.begin(); }
544inline typename Array::iterator Array::end() { return V.end(); }
545inline typename Array::const_iterator Array::end() const { return V.end(); }
546
547inline bool Array::empty() const { return V.empty(); }
548inline size_t Array::size() const { return V.size(); }
549inline void Array::reserve(size_t S) { V.reserve(n: S); }
550
551inline void Array::clear() { V.clear(); }
552inline void Array::push_back(const Value &E) { V.push_back(x: E); }
553inline void Array::push_back(Value &&E) { V.push_back(x: std::move(E)); }
554template <typename... Args> inline void Array::emplace_back(Args &&...A) {
555 V.emplace_back(std::forward<Args>(A)...);
556}
557inline void Array::pop_back() { V.pop_back(); }
558inline typename Array::iterator Array::insert(const_iterator P, const Value &E) {
559 return V.insert(position: P, x: E);
560}
561inline typename Array::iterator Array::insert(const_iterator P, Value &&E) {
562 return V.insert(position: P, x: std::move(E));
563}
564template <typename It>
565inline typename Array::iterator Array::insert(const_iterator P, It A, It Z) {
566 return V.insert(P, A, Z);
567}
568template <typename... Args>
569inline typename Array::iterator Array::emplace(const_iterator P, Args &&...A) {
570 return V.emplace(P, std::forward<Args>(A)...);
571}
572inline bool operator==(const Array &L, const Array &R) { return L.V == R.V; }
573
574/// ObjectKey is a used to capture keys in Object. Like Value but:
575/// - only strings are allowed
576/// - it's optimized for the string literal case (Owned == nullptr)
577/// Like Value, strings must be UTF-8. See isUTF8 documentation for details.
578class ObjectKey {
579public:
580 ObjectKey(const char *S) : ObjectKey(StringRef(S)) {}
581 ObjectKey(std::string S) : Owned(new std::string(std::move(S))) {
582 if (LLVM_UNLIKELY(!isUTF8(*Owned))) {
583 assert(false && "Invalid UTF-8 in value used as JSON");
584 *Owned = fixUTF8(S: std::move(*Owned));
585 }
586 Data = *Owned;
587 }
588 ObjectKey(llvm::StringRef S) : Data(S) {
589 if (LLVM_UNLIKELY(!isUTF8(Data))) {
590 assert(false && "Invalid UTF-8 in value used as JSON");
591 *this = ObjectKey(fixUTF8(S));
592 }
593 }
594 ObjectKey(const llvm::SmallVectorImpl<char> &V)
595 : ObjectKey(std::string(V.begin(), V.end())) {}
596 ObjectKey(const llvm::formatv_object_base &V) : ObjectKey(V.str()) {}
597
598 ObjectKey(const ObjectKey &C) { *this = C; }
599 ObjectKey(ObjectKey &&C) : ObjectKey(static_cast<const ObjectKey &&>(C)) {}
600 ObjectKey &operator=(const ObjectKey &C) {
601 if (C.Owned) {
602 Owned.reset(p: new std::string(*C.Owned));
603 Data = *Owned;
604 } else {
605 Data = C.Data;
606 }
607 return *this;
608 }
609 ObjectKey &operator=(ObjectKey &&) = default;
610
611 operator llvm::StringRef() const { return Data; }
612 std::string str() const { return Data.str(); }
613
614private:
615 // FIXME: this is unneccesarily large (3 pointers). Pointer + length + owned
616 // could be 2 pointers at most.
617 std::unique_ptr<std::string> Owned;
618 llvm::StringRef Data;
619};
620
621inline bool operator==(const ObjectKey &L, const ObjectKey &R) {
622 return llvm::StringRef(L) == llvm::StringRef(R);
623}
624inline bool operator!=(const ObjectKey &L, const ObjectKey &R) {
625 return !(L == R);
626}
627inline bool operator<(const ObjectKey &L, const ObjectKey &R) {
628 return StringRef(L) < StringRef(R);
629}
630
631struct Object::KV {
632 ObjectKey K;
633 Value V;
634};
635
636inline Object::Object(std::initializer_list<KV> Properties) {
637 for (const auto &P : Properties) {
638 auto R = try_emplace(K: P.K, Args: nullptr);
639 if (R.second)
640 R.first->getSecond().moveFrom(M: std::move(P.V));
641 }
642}
643inline std::pair<Object::iterator, bool> Object::insert(KV E) {
644 return try_emplace(K: std::move(E.K), Args: std::move(E.V));
645}
646inline bool Object::erase(StringRef K) {
647 return M.erase(Val: ObjectKey(K));
648}
649
650/// A "cursor" marking a position within a Value.
651/// The Value is a tree, and this is the path from the root to the current node.
652/// This is used to associate errors with particular subobjects.
653class Path {
654public:
655 class Root;
656
657 /// Records that the value at the current path is invalid.
658 /// Message is e.g. "expected number" and becomes part of the final error.
659 /// This overwrites any previously written error message in the root.
660 void report(llvm::StringLiteral Message);
661
662 /// The root may be treated as a Path.
663 Path(Root &R) : Parent(nullptr), Seg(&R) {}
664 /// Derives a path for an array element: this[Index]
665 Path index(unsigned Index) const { return Path(this, Segment(Index)); }
666 /// Derives a path for an object field: this.Field
667 Path field(StringRef Field) const { return Path(this, Segment(Field)); }
668
669private:
670 /// One element in a JSON path: an object field (.foo) or array index [27].
671 /// Exception: the root Path encodes a pointer to the Path::Root.
672 class Segment {
673 uintptr_t Pointer;
674 unsigned Offset;
675
676 public:
677 Segment() = default;
678 Segment(Root *R) : Pointer(reinterpret_cast<uintptr_t>(R)) {}
679 Segment(llvm::StringRef Field)
680 : Pointer(reinterpret_cast<uintptr_t>(Field.data())),
681 Offset(static_cast<unsigned>(Field.size())) {}
682 Segment(unsigned Index) : Pointer(0), Offset(Index) {}
683
684 bool isField() const { return Pointer != 0; }
685 StringRef field() const {
686 return StringRef(reinterpret_cast<const char *>(Pointer), Offset);
687 }
688 unsigned index() const { return Offset; }
689 Root *root() const { return reinterpret_cast<Root *>(Pointer); }
690 };
691
692 const Path *Parent;
693 Segment Seg;
694
695 Path(const Path *Parent, Segment S) : Parent(Parent), Seg(S) {}
696};
697
698/// The root is the trivial Path to the root value.
699/// It also stores the latest reported error and the path where it occurred.
700class Path::Root {
701 llvm::StringRef Name;
702 llvm::StringLiteral ErrorMessage;
703 std::vector<Path::Segment> ErrorPath; // Only valid in error state. Reversed.
704
705 friend void Path::report(llvm::StringLiteral Message);
706
707public:
708 Root(llvm::StringRef Name = "") : Name(Name), ErrorMessage("") {}
709 // No copy/move allowed as there are incoming pointers.
710 Root(Root &&) = delete;
711 Root &operator=(Root &&) = delete;
712 Root(const Root &) = delete;
713 Root &operator=(const Root &) = delete;
714
715 /// Returns the last error reported, or else a generic error.
716 Error getError() const;
717 /// Print the root value with the error shown inline as a comment.
718 /// Unrelated parts of the value are elided for brevity, e.g.
719 /// {
720 /// "id": 42,
721 /// "name": /* expected string */ null,
722 /// "properties": { ... }
723 /// }
724 void printErrorContext(const Value &, llvm::raw_ostream &) const;
725};
726
727// Standard deserializers are provided for primitive types.
728// See comments on Value.
729inline bool fromJSON(const Value &E, std::string &Out, Path P) {
730 if (auto S = E.getAsString()) {
731 Out = std::string(*S);
732 return true;
733 }
734 P.report(Message: "expected string");
735 return false;
736}
737inline bool fromJSON(const Value &E, int &Out, Path P) {
738 if (auto S = E.getAsInteger()) {
739 Out = *S;
740 return true;
741 }
742 P.report(Message: "expected integer");
743 return false;
744}
745inline bool fromJSON(const Value &E, int64_t &Out, Path P) {
746 if (auto S = E.getAsInteger()) {
747 Out = *S;
748 return true;
749 }
750 P.report(Message: "expected integer");
751 return false;
752}
753inline bool fromJSON(const Value &E, double &Out, Path P) {
754 if (auto S = E.getAsNumber()) {
755 Out = *S;
756 return true;
757 }
758 P.report(Message: "expected number");
759 return false;
760}
761inline bool fromJSON(const Value &E, bool &Out, Path P) {
762 if (auto S = E.getAsBoolean()) {
763 Out = *S;
764 return true;
765 }
766 P.report(Message: "expected boolean");
767 return false;
768}
769inline bool fromJSON(const Value &E, uint64_t &Out, Path P) {
770 if (auto S = E.getAsUINT64()) {
771 Out = *S;
772 return true;
773 }
774 P.report(Message: "expected uint64_t");
775 return false;
776}
777inline bool fromJSON(const Value &E, std::nullptr_t &Out, Path P) {
778 if (auto S = E.getAsNull()) {
779 Out = *S;
780 return true;
781 }
782 P.report(Message: "expected null");
783 return false;
784}
785template <typename T>
786bool fromJSON(const Value &E, std::optional<T> &Out, Path P) {
787 if (E.getAsNull()) {
788 Out = std::nullopt;
789 return true;
790 }
791 T Result = {};
792 if (!fromJSON(E, Result, P))
793 return false;
794 Out = std::move(Result);
795 return true;
796}
797template <typename T>
798bool fromJSON(const Value &E, std::vector<T> &Out, Path P) {
799 if (auto *A = E.getAsArray()) {
800 Out.clear();
801 Out.resize(A->size());
802 for (size_t I = 0; I < A->size(); ++I)
803 if (!fromJSON((*A)[I], Out[I], P.index(Index: I)))
804 return false;
805 return true;
806 }
807 P.report(Message: "expected array");
808 return false;
809}
810template <typename T>
811bool fromJSON(const Value &E, std::map<std::string, T> &Out, Path P) {
812 if (auto *O = E.getAsObject()) {
813 Out.clear();
814 for (const auto &KV : *O)
815 if (!fromJSON(KV.second, Out[std::string(llvm::StringRef(KV.first))],
816 P.field(Field: KV.first)))
817 return false;
818 return true;
819 }
820 P.report(Message: "expected object");
821 return false;
822}
823
824// Allow serialization of std::optional<T> for supported T.
825template <typename T> Value toJSON(const std::optional<T> &Opt) {
826 return Opt ? Value(*Opt) : Value(nullptr);
827}
828
829/// Helper for mapping JSON objects onto protocol structs.
830///
831/// Example:
832/// \code
833/// bool fromJSON(const Value &E, MyStruct &R, Path P) {
834/// ObjectMapper O(E, P);
835/// // When returning false, error details were already reported.
836/// return O && O.map("mandatory_field", R.MandatoryField) &&
837/// O.mapOptional("optional_field", R.OptionalField);
838/// }
839/// \endcode
840class ObjectMapper {
841public:
842 /// If O is not an object, this mapper is invalid and an error is reported.
843 ObjectMapper(const Value &E, Path P) : O(E.getAsObject()), P(P) {
844 if (!O)
845 P.report(Message: "expected object");
846 }
847
848 /// True if the expression is an object.
849 /// Must be checked before calling map().
850 operator bool() const { return O; }
851
852 /// Maps a property to a field.
853 /// If the property is missing or invalid, reports an error.
854 template <typename T> bool map(StringLiteral Prop, T &Out) {
855 assert(*this && "Must check this is an object before calling map()");
856 if (const Value *E = O->get(K: Prop))
857 return fromJSON(*E, Out, P.field(Field: Prop));
858 P.field(Field: Prop).report(Message: "missing value");
859 return false;
860 }
861
862 /// Maps a property to a field, if it exists.
863 /// If the property exists and is invalid, reports an error.
864 /// (Optional requires special handling, because missing keys are OK).
865 template <typename T> bool map(StringLiteral Prop, std::optional<T> &Out) {
866 assert(*this && "Must check this is an object before calling map()");
867 if (const Value *E = O->get(K: Prop))
868 return fromJSON(*E, Out, P.field(Field: Prop));
869 Out = std::nullopt;
870 return true;
871 }
872
873 /// Maps a property to a field, if it exists.
874 /// If the property exists and is invalid, reports an error.
875 /// If the property does not exist, Out is unchanged.
876 template <typename T> bool mapOptional(StringLiteral Prop, T &Out) {
877 assert(*this && "Must check this is an object before calling map()");
878 if (const Value *E = O->get(K: Prop))
879 return fromJSON(*E, Out, P.field(Field: Prop));
880 return true;
881 }
882
883private:
884 const Object *O;
885 Path P;
886};
887
888/// Parses the provided JSON source, or returns a ParseError.
889/// The returned Value is self-contained and owns its strings (they do not refer
890/// to the original source).
891llvm::Expected<Value> parse(llvm::StringRef JSON);
892
893class ParseError : public llvm::ErrorInfo<ParseError> {
894 const char *Msg;
895 unsigned Line, Column, Offset;
896
897public:
898 static char ID;
899 ParseError(const char *Msg, unsigned Line, unsigned Column, unsigned Offset)
900 : Msg(Msg), Line(Line), Column(Column), Offset(Offset) {}
901 void log(llvm::raw_ostream &OS) const override {
902 OS << llvm::formatv(Fmt: "[{0}:{1}, byte={2}]: {3}", Vals: Line, Vals: Column, Vals: Offset, Vals: Msg);
903 }
904 std::error_code convertToErrorCode() const override {
905 return llvm::inconvertibleErrorCode();
906 }
907};
908
909/// Version of parse() that converts the parsed value to the type T.
910/// RootName describes the root object and is used in error messages.
911template <typename T>
912Expected<T> parse(const llvm::StringRef &JSON, const char *RootName = "") {
913 auto V = parse(JSON);
914 if (!V)
915 return V.takeError();
916 Path::Root R(RootName);
917 T Result;
918 if (fromJSON(*V, Result, R))
919 return std::move(Result);
920 return R.getError();
921}
922
923/// json::OStream allows writing well-formed JSON without materializing
924/// all structures as json::Value ahead of time.
925/// It's faster, lower-level, and less safe than OS << json::Value.
926/// It also allows emitting more constructs, such as comments.
927///
928/// Only one "top-level" object can be written to a stream.
929/// Simplest usage involves passing lambdas (Blocks) to fill in containers:
930///
931/// json::OStream J(OS);
932/// J.array([&]{
933/// for (const Event &E : Events)
934/// J.object([&] {
935/// J.attribute("timestamp", int64_t(E.Time));
936/// J.attributeArray("participants", [&] {
937/// for (const Participant &P : E.Participants)
938/// J.value(P.toString());
939/// });
940/// });
941/// });
942///
943/// This would produce JSON like:
944///
945/// [
946/// {
947/// "timestamp": 19287398741,
948/// "participants": [
949/// "King Kong",
950/// "Miley Cyrus",
951/// "Cleopatra"
952/// ]
953/// },
954/// ...
955/// ]
956///
957/// The lower level begin/end methods (arrayBegin()) are more flexible but
958/// care must be taken to pair them correctly:
959///
960/// json::OStream J(OS);
961// J.arrayBegin();
962/// for (const Event &E : Events) {
963/// J.objectBegin();
964/// J.attribute("timestamp", int64_t(E.Time));
965/// J.attributeBegin("participants");
966/// for (const Participant &P : E.Participants)
967/// J.value(P.toString());
968/// J.attributeEnd();
969/// J.objectEnd();
970/// }
971/// J.arrayEnd();
972///
973/// If the call sequence isn't valid JSON, asserts will fire in debug mode.
974/// This can be mismatched begin()/end() pairs, trying to emit attributes inside
975/// an array, and so on.
976/// With asserts disabled, this is undefined behavior.
977class OStream {
978 public:
979 using Block = llvm::function_ref<void()>;
980 // If IndentSize is nonzero, output is pretty-printed.
981 explicit OStream(llvm::raw_ostream &OS, unsigned IndentSize = 0)
982 : OS(OS), IndentSize(IndentSize) {
983 Stack.emplace_back();
984 }
985 ~OStream() {
986 assert(Stack.size() == 1 && "Unmatched begin()/end()");
987 assert(Stack.back().Ctx == Singleton);
988 assert(Stack.back().HasValue && "Did not write top-level value");
989 }
990
991 /// Flushes the underlying ostream. OStream does not buffer internally.
992 void flush() { OS.flush(); }
993
994 // High level functions to output a value.
995 // Valid at top-level (exactly once), in an attribute value (exactly once),
996 // or in an array (any number of times).
997
998 /// Emit a self-contained value (number, string, vector<string> etc).
999 void value(const Value &V);
1000 /// Emit an array whose elements are emitted in the provided Block.
1001 void array(Block Contents) {
1002 arrayBegin();
1003 Contents();
1004 arrayEnd();
1005 }
1006 /// Emit an object whose elements are emitted in the provided Block.
1007 void object(Block Contents) {
1008 objectBegin();
1009 Contents();
1010 objectEnd();
1011 }
1012 /// Emit an externally-serialized value.
1013 /// The caller must write exactly one valid JSON value to the provided stream.
1014 /// No validation or formatting of this value occurs.
1015 void rawValue(llvm::function_ref<void(raw_ostream &)> Contents) {
1016 rawValueBegin();
1017 Contents(OS);
1018 rawValueEnd();
1019 }
1020 void rawValue(llvm::StringRef Contents) {
1021 rawValue(Contents: [&](raw_ostream &OS) { OS << Contents; });
1022 }
1023 /// Emit a JavaScript comment associated with the next printed value.
1024 /// The string must be valid until the next attribute or value is emitted.
1025 /// Comments are not part of standard JSON, and many parsers reject them!
1026 void comment(llvm::StringRef);
1027
1028 // High level functions to output object attributes.
1029 // Valid only within an object (any number of times).
1030
1031 /// Emit an attribute whose value is self-contained (number, vector<int> etc).
1032 void attribute(llvm::StringRef Key, const Value& Contents) {
1033 attributeImpl(Key, Contents: [&] { value(V: Contents); });
1034 }
1035 /// Emit an attribute whose value is an array with elements from the Block.
1036 void attributeArray(llvm::StringRef Key, Block Contents) {
1037 attributeImpl(Key, Contents: [&] { array(Contents); });
1038 }
1039 /// Emit an attribute whose value is an object with attributes from the Block.
1040 void attributeObject(llvm::StringRef Key, Block Contents) {
1041 attributeImpl(Key, Contents: [&] { object(Contents); });
1042 }
1043
1044 // Low-level begin/end functions to output arrays, objects, and attributes.
1045 // Must be correctly paired. Allowed contexts are as above.
1046
1047 void arrayBegin();
1048 void arrayEnd();
1049 void objectBegin();
1050 void objectEnd();
1051 void attributeBegin(llvm::StringRef Key);
1052 void attributeEnd();
1053 raw_ostream &rawValueBegin();
1054 void rawValueEnd();
1055
1056private:
1057 void attributeImpl(llvm::StringRef Key, Block Contents) {
1058 attributeBegin(Key);
1059 Contents();
1060 attributeEnd();
1061 }
1062
1063 void valueBegin();
1064 void flushComment();
1065 void newline();
1066
1067 enum Context {
1068 Singleton, // Top level, or object attribute.
1069 Array,
1070 Object,
1071 RawValue, // External code writing a value to OS directly.
1072 };
1073 struct State {
1074 Context Ctx = Singleton;
1075 bool HasValue = false;
1076 };
1077 llvm::SmallVector<State, 16> Stack; // Never empty.
1078 llvm::StringRef PendingComment;
1079 llvm::raw_ostream &OS;
1080 unsigned IndentSize;
1081 unsigned Indent = 0;
1082};
1083
1084/// Serializes this Value to JSON, writing it to the provided stream.
1085/// The formatting is compact (no extra whitespace) and deterministic.
1086/// For pretty-printing, use the formatv() format_provider below.
1087inline llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, const Value &V) {
1088 OStream(OS).value(V);
1089 return OS;
1090}
1091} // namespace json
1092
1093/// Allow printing json::Value with formatv().
1094/// The default style is basic/compact formatting, like operator<<.
1095/// A format string like formatv("{0:2}", Value) pretty-prints with indent 2.
1096template <> struct format_provider<llvm::json::Value> {
1097 static void format(const llvm::json::Value &, raw_ostream &, StringRef);
1098};
1099} // namespace llvm
1100
1101#endif
1102

source code of llvm/include/llvm/Support/JSON.h