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[Support] Make JSON handle doubles and int64s losslessly 

Summary:
This patch adds a new "integer" ValueType, and renames Number -> Double.
This allows us to preserve the full precision of int64_t when parsing integers
from the wire, or constructing from an integer.
The API is unchanged, other than giving asInteger() a clearer contract.

In addition, always output doubles with enough precision that parsing will
reconstruct the same double.

Reviewers: simon_tatham

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D46209

llvm-svn: 336541
This commit is contained in:
Sam McCall 2018-07-09 12:16:40 +00:00
parent 6f33b330ae
commit d93eaeb7c3
3 changed files with 129 additions and 33 deletions
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60
llvm/include/llvm/Support/JSON.h
View File

@ -204,7 +204,7 @@ inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
/// Each Value is one of the JSON kinds:
/// null (nullptr_t)
/// boolean (bool)
/// number (double)
/// number (double or int64)
/// string (StringRef)
/// array (json::Array)
/// object (json::Object)
@ -226,7 +226,7 @@ inline bool operator!=(const Array &L, const Array &R) { return !(L == R); }
/// fromJSON(const json::Value&, T&)->bool
/// Deserializers are provided for:
/// - bool
/// - int
/// - int and int64_t
/// - double
/// - std::string
/// - vector<T>, where T is deserializable
@ -254,6 +254,8 @@ public:
enum Kind {
Null,
Boolean,
/// Number values can store both int64s and doubles at full precision,
/// depending on what they were constructed/parsed from.
Number,
String,
Array,
@ -281,24 +283,36 @@ public:
Value(llvm::StringRef V) : Type(T_StringRef) { create<llvm::StringRef>(V); }
Value(const char *V) : Type(T_StringRef) { create<llvm::StringRef>(V); }
Value(std::nullptr_t) : Type(T_Null) {}
// Prevent implicit conversions to boolean.
template <typename T, typename = typename std::enable_if<
std::is_same<T, bool>::value>::type>
// Boolean (disallow implicit conversions).
// (The last template parameter is a dummy to keep templates distinct.)
template <
typename T,
typename = typename std::enable_if<std::is_same<T, bool>::value>::type,
bool = false>
Value(T B) : Type(T_Boolean) {
create<bool>(B);
}
// Numbers: arithmetic types that are not boolean.
// Integers (except boolean). Must be non-narrowing convertible to int64_t.
template <
typename T,
typename = typename std::enable_if<std::is_arithmetic<T>::value>::type,
typename = typename std::enable_if<std::is_integral<T>::value>::type,
typename = typename std::enable_if<!std::is_same<T, bool>::value>::type>
Value(T D) : Type(T_Number) {
create<double>(D);
Value(T I) : Type(T_Integer) {
create<int64_t>(int64_t{I});
}
// Floating point. Must be non-narrowing convertible to double.
template <typename T,
typename =
typename std::enable_if<std::is_floating_point<T>::value>::type,
double * = nullptr>
Value(T D) : Type(T_Double) {
create<double>(double{D});
}
// Serializable types: with a toJSON(const T&)->Value function, found by ADL.
template <typename T,
typename = typename std::enable_if<std::is_same<
Value, decltype(toJSON(*(const T *)nullptr))>::value>>
Value, decltype(toJSON(*(const T *)nullptr))>::value>,
Value * = nullptr>
Value(const T &V) : Value(toJSON(V)) {}
Value &operator=(const Value &M) {
@ -319,7 +333,8 @@ public:
return Null;
case T_Boolean:
return Boolean;
case T_Number:
case T_Double:
case T_Integer:
return Number;
case T_String:
case T_StringRef:
@ -344,12 +359,17 @@ public:
return llvm::None;
}
llvm::Optional<double> getAsNumber() const {
if (LLVM_LIKELY(Type == T_Number))
if (LLVM_LIKELY(Type == T_Double))
return as<double>();
if (LLVM_LIKELY(Type == T_Integer))
return as<int64_t>();
return llvm::None;
}
// Succeeds if the Value is a Number, and exactly representable as int64_t.
llvm::Optional<int64_t> getAsInteger() const {
if (LLVM_LIKELY(Type == T_Number)) {
if (LLVM_LIKELY(Type == T_Integer))
return as<int64_t>();
if (LLVM_LIKELY(Type == T_Double)) {
double D = as<double>();
if (LLVM_LIKELY(std::modf(D, &D) == 0.0 &&
D >= double(std::numeric_limits<int64_t>::min()) &&
@ -407,9 +427,8 @@ private:
enum ValueType : char {
T_Null,
T_Boolean,
// FIXME: splitting Number into Double and Integer would allow us to
// round-trip 64-bit integers.
T_Number,
T_Double,
T_Integer,
T_StringRef,
T_String,
T_Object,
@ -417,7 +436,7 @@ private:
};
// All members mutable, see moveFrom().
mutable ValueType Type;
mutable llvm::AlignedCharArrayUnion<bool, double, llvm::StringRef,
mutable llvm::AlignedCharArrayUnion<bool, double, int64_t, llvm::StringRef,
std::string, json::Array, json::Object>
Union;
};
@ -505,6 +524,13 @@ inline bool fromJSON(const Value &E, int &Out) {
}
return false;
}
inline bool fromJSON(const Value &E, int64_t &Out) {
if (auto S = E.getAsInteger()) {
Out = *S;
return true;
}
return false;
}
inline bool fromJSON(const Value &E, double &Out) {
if (auto S = E.getAsNumber()) {
Out = *S;

42
llvm/lib/Support/JSON.cpp
View File

@ -104,7 +104,8 @@ void Value::copyFrom(const Value &M) {
switch (Type) {
case T_Null:
case T_Boolean:
case T_Number:
case T_Double:
case T_Integer:
memcpy(Union.buffer, M.Union.buffer, sizeof(Union.buffer));
break;
case T_StringRef:
@ -127,7 +128,8 @@ void Value::moveFrom(const Value &&M) {
switch (Type) {
case T_Null:
case T_Boolean:
case T_Number:
case T_Double:
case T_Integer:
memcpy(Union.buffer, M.Union.buffer, sizeof(Union.buffer));
break;
case T_StringRef:
@ -152,7 +154,8 @@ void Value::destroy() {
switch (Type) {
case T_Null:
case T_Boolean:
case T_Number:
case T_Double:
case T_Integer:
break;
case T_StringRef:
as<StringRef>().~StringRef();
@ -217,7 +220,7 @@ private:
}
// On invalid syntax, parseX() functions return false and set Err.
bool parseNumber(char First, double &Out);
bool parseNumber(char First, Value &Out);
bool parseString(std::string &Out);
bool parseUnicode(std::string &Out);
bool parseError(const char *Msg); // always returns false
@ -317,25 +320,28 @@ bool Parser::parseValue(Value &Out) {
}
}
default:
if (isNumber(C)) {
double Num;
if (parseNumber(C, Num)) {
Out = Num;
return true;
} else {
return false;
}
}
if (isNumber(C))
return parseNumber(C, Out);
return parseError("Invalid JSON value");
}
}
bool Parser::parseNumber(char First, double &Out) {
bool Parser::parseNumber(char First, Value &Out) {
// Read the number into a string. (Must be null-terminated for strto*).
SmallString<24> S;
S.push_back(First);
while (isNumber(peek()))
S.push_back(next());
char *End;
// Try first to parse as integer, and if so preserve full 64 bits.
// strtoll returns long long >= 64 bits, so check it's in range too.
auto I = std::strtoll(S.c_str(), &End, 10);
if (End == S.end() && I >= std::numeric_limits<int64_t>::min() &&
I <= std::numeric_limits<int64_t>::max()) {
Out = int64_t(I);
return true;
}
// If it's not an integer
Out = std::strtod(S.c_str(), &End);
return End == S.end() || parseError("Invalid JSON value (number?)");
}
@ -558,8 +564,12 @@ void llvm::json::Value::print(raw_ostream &OS, const Indenter &I) const {
case T_Boolean:
OS << (as<bool>() ? "true" : "false");
break;
case T_Number:
OS << format("%g", as<double>());
case T_Double:
OS << format("%.*g", std::numeric_limits<double>::max_digits10,
as<double>());
break;
case T_Integer:
OS << as<int64_t>();
break;
case T_StringRef:
quote(OS, as<StringRef>());

60
llvm/unittests/Support/JSONTest.cpp
View File

@ -227,6 +227,66 @@ TEST(JSONTest, Inspection) {
}
}
// Verify special integer handling - we try to preserve exact int64 values.
TEST(JSONTest, Integers) {
struct {
const char *Desc;
Value Val;
const char *Str;
llvm::Optional<int64_t> AsInt;
llvm::Optional<double> AsNumber;
} TestCases[] = {
{
"Non-integer. Stored as double, not convertible.",
double{1.5},
"1.5",
llvm::None,
1.5,
},
{
"Integer, not exact double. Stored as int64, convertible.",
int64_t{0x4000000000000001},
"4611686018427387905",
int64_t{0x4000000000000001},
double{0x4000000000000000},
},
{
"Negative integer, not exact double. Stored as int64, convertible.",
int64_t{-0x4000000000000001},
"-4611686018427387905",
int64_t{-0x4000000000000001},
double{-0x4000000000000000},
},
{
"Dynamically exact integer. Stored as double, convertible.",
double{0x6000000000000000},
"6.9175290276410819e+18",
int64_t{0x6000000000000000},
double{0x6000000000000000},
},
{
"Dynamically integer, >64 bits. Stored as double, not convertible.",
1.5 * double{0x8000000000000000},
"1.3835058055282164e+19",
llvm::None,
1.5 * double{0x8000000000000000},
},
};
for (const auto &T : TestCases) {
EXPECT_EQ(T.Str, s(T.Val)) << T.Desc;
llvm::Expected<Value> Doc = parse(T.Str);
EXPECT_TRUE(!!Doc) << T.Desc;
EXPECT_EQ(Doc->getAsInteger(), T.AsInt) << T.Desc;
EXPECT_EQ(Doc->getAsNumber(), T.AsNumber) << T.Desc;
EXPECT_EQ(T.Val, *Doc) << T.Desc;
EXPECT_EQ(T.Str, s(*Doc)) << T.Desc;
}
}
// Sample struct with typical JSON-mapping rules.
struct CustomStruct {
CustomStruct() : B(false) {}