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Fixes local copy optimization

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The previous optimization #32 has problem that restoration requires
assignment operator.
Change the backup/restore process using a template wrapper class to
select code path.
This commit is contained in:
Milo Yip 2014-07-02 23:49:47 +08:00
parent 5852c42bb9
commit 9aec8d6ad4
3 changed files with 92 additions and 63 deletions
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42
include/rapidjson/rapidjson.h
View File

@ -203,12 +203,42 @@ template<typename Stream>
struct StreamTraits {
//! Whether to make local copy of stream for optimization during parsing.
/*!
If it is defined as Stream&, it will not make a local copy.
If it is defined as Stream, it will make a local copy for optimization.
By default, for safety, streams do not use local copy optimization, i.e. it is defined as Stream&.
By default, for safety, streams do not use local copy optimization.
Stream that can be copied fast should specialize this, like StreamTraits<StringStream>.
*/
typedef Stream& StreamCopyType;
enum { copyOptimization = 0 };
};
template<typename Stream, bool>
class StreamLocalCopy;
template<typename Stream>
class StreamLocalCopy<Stream, 1> {
public:
StreamLocalCopy(Stream& original) : original_(original), s_(original) {}
~StreamLocalCopy() { original_ = s_; }
Stream* operator->() { return &s_; }
Stream& operator*() { return s_; }
private:
StreamLocalCopy& operator=(const StreamLocalCopy&);
Stream& original_;
Stream s_;
};
template<typename Stream>
class StreamLocalCopy<Stream, 0> {
public:
StreamLocalCopy(Stream& original) : s_(original) {}
~StreamLocalCopy() {}
Stream* operator->() { return &s_; }
Stream& operator*() { return s_; }
private:
StreamLocalCopy& operator=(const StreamLocalCopy&);
Stream& s_;
};
//! Put N copies of a character to a stream.
@ -245,7 +275,7 @@ struct GenericStringStream {
template <typename Encoding>
struct StreamTraits<GenericStringStream<Encoding> > {
typedef GenericStringStream<Encoding> StreamCopyType; // Enable stream copy optimization.
enum { copyOptimization = 1 };
};
typedef GenericStringStream<UTF8<> > StringStream;
@ -281,7 +311,7 @@ struct GenericInsituStringStream {
template <typename Encoding>
struct StreamTraits<GenericInsituStringStream<Encoding> > {
typedef GenericInsituStringStream<Encoding> StreamCopyType; // Enable stream copy optimization.
enum { copyOptimization = 1 };
};
typedef GenericInsituStringStream<UTF8<> > InsituStringStream;

108
include/rapidjson/reader.h
View File

@ -135,10 +135,9 @@ struct BaseReaderHandler {
*/
template<typename InputStream>
void SkipWhitespace(InputStream& is) {
typename StreamTraits<InputStream>::StreamCopyType s = is; // Use a local copy for optimization
while (s.Peek() == ' ' || s.Peek() == '\n' || s.Peek() == '\r' || s.Peek() == '\t')
s.Take();
is = s;
StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
while (s->Peek() == ' ' || s->Peek() == '\n' || s->Peek() == '\r' || s->Peek() == '\t')
s->Take();
}
#ifdef RAPIDJSON_SSE42
@ -295,6 +294,10 @@ public:
size_t GetErrorOffset() const { return errorOffset_; }
private:
// Prohibit copy constructor & assignment operator.
GenericReader(const GenericReader&);
GenericReader& operator=(const GenericReader&);
// Parse object: { string : value, ... }
template<unsigned parseFlags, typename InputStream, typename Handler>
void ParseObject(InputStream& is, Handler& handler) {
@ -406,10 +409,9 @@ private:
// Helper function to parse four hexidecimal digits in \uXXXX in ParseString().
template<typename InputStream>
unsigned ParseHex4(InputStream& is) {
typename StreamTraits<InputStream>::StreamCopyType s = is; // Use a local copy for optimization
unsigned codepoint = 0;
for (int i = 0; i < 4; i++) {
Ch c = s.Take();
Ch c = is.Take();
codepoint <<= 4;
codepoint += static_cast<unsigned>(c);
if (c >= '0' && c <= '9')
@ -419,11 +421,10 @@ private:
else if (c >= 'a' && c <= 'f')
codepoint -= 'a' - 10;
else {
RAPIDJSON_PARSE_ERROR_NORETURN(kParseErrorStringUnicodeEscapeInvalidHex, s.Tell() - 1);
RAPIDJSON_PARSE_ERROR_NORETURN(kParseErrorStringUnicodeEscapeInvalidHex, is.Tell() - 1);
return 0;
}
}
is = s; // Restore is
return codepoint;
}
@ -447,24 +448,23 @@ private:
// Parse string and generate String event. Different code paths for kParseInsituFlag.
template<unsigned parseFlags, typename InputStream, typename Handler>
void ParseString(InputStream& is, Handler& handler) {
typename StreamTraits<InputStream>::StreamCopyType s = is; // Local copy for optimization
StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
if (parseFlags & kParseInsituFlag) {
Ch *head = s.PutBegin();
ParseStringToStream<parseFlags, SourceEncoding, SourceEncoding>(s, s);
Ch *head = s->PutBegin();
ParseStringToStream<parseFlags, SourceEncoding, SourceEncoding>(*s, *s);
if (HasParseError())
return;
size_t length = s.PutEnd(head) - 1;
size_t length = s->PutEnd(head) - 1;
RAPIDJSON_ASSERT(length <= 0xFFFFFFFF);
handler.String((typename TargetEncoding::Ch*)head, SizeType(length), false);
}
else {
StackStream stackStream(stack_);
ParseStringToStream<parseFlags, SourceEncoding, TargetEncoding>(s, stackStream);
ParseStringToStream<parseFlags, SourceEncoding, TargetEncoding>(*s, stackStream);
if (HasParseError())
return;
handler.String(stack_.template Pop<typename TargetEncoding::Ch>(stackStream.length_), stackStream.length_ - 1, true);
}
is = s; // Restore is
}
// Parse string to an output is
@ -527,43 +527,43 @@ private:
template<unsigned parseFlags, typename InputStream, typename Handler>
void ParseNumber(InputStream& is, Handler& handler) {
typename StreamTraits<InputStream>::StreamCopyType s = is; // Local copy for optimization
StreamLocalCopy<InputStream, StreamTraits<InputStream>::copyOptimization> s(is);
// Parse minus
bool minus = false;
if (s.Peek() == '-') {
if (s->Peek() == '-') {
minus = true;
s.Take();
s->Take();
}
// Parse int: zero / ( digit1-9 *DIGIT )
unsigned i;
bool try64bit = false;
if (s.Peek() == '0') {
if (s->Peek() == '0') {
i = 0;
s.Take();
s->Take();
}
else if (s.Peek() >= '1' && s.Peek() <= '9') {
i = static_cast<unsigned>(s.Take() - '0');
else if (s->Peek() >= '1' && s->Peek() <= '9') {
i = static_cast<unsigned>(s->Take() - '0');
if (minus)
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (i >= 214748364) { // 2^31 = 2147483648
if (i != 214748364 || s.Peek() > '8') {
if (i != 214748364 || s->Peek() > '8') {
try64bit = true;
break;
}
}
i = i * 10 + static_cast<unsigned>(s.Take() - '0');
i = i * 10 + static_cast<unsigned>(s->Take() - '0');
}
else
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (i >= 429496729) { // 2^32 - 1 = 4294967295
if (i != 429496729 || s.Peek() > '5') {
if (i != 429496729 || s->Peek() > '5') {
try64bit = true;
break;
}
}
i = i * 10 + static_cast<unsigned>(s.Take() - '0');
i = i * 10 + static_cast<unsigned>(s->Take() - '0');
}
}
else
@ -575,22 +575,22 @@ private:
if (try64bit) {
i64 = i;
if (minus)
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (i64 >= UINT64_C(922337203685477580)) // 2^63 = 9223372036854775808
if (i64 != UINT64_C(922337203685477580) || s.Peek() > '8') {
if (i64 != UINT64_C(922337203685477580) || s->Peek() > '8') {
useDouble = true;
break;
}
i64 = i64 * 10 + static_cast<unsigned>(s.Take() - '0');
i64 = i64 * 10 + static_cast<unsigned>(s->Take() - '0');
}
else
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (i64 >= UINT64_C(1844674407370955161)) // 2^64 - 1 = 18446744073709551615
if (i64 != UINT64_C(1844674407370955161) || s.Peek() > '5') {
if (i64 != UINT64_C(1844674407370955161) || s->Peek() > '5') {
useDouble = true;
break;
}
i64 = i64 * 10 + static_cast<unsigned>(s.Take() - '0');
i64 = i64 * 10 + static_cast<unsigned>(s->Take() - '0');
}
}
@ -598,65 +598,65 @@ private:
double d = 0.0;
if (useDouble) {
d = (double)i64;
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (d >= 1E307)
RAPIDJSON_PARSE_ERROR(kParesErrorNumberTooBig, is.Tell());
d = d * 10 + (s.Take() - '0');
d = d * 10 + (s->Take() - '0');
}
}
// Parse frac = decimal-point 1*DIGIT
int expFrac = 0;
if (s.Peek() == '.') {
if (s->Peek() == '.') {
if (!useDouble) {
d = try64bit ? (double)i64 : (double)i;
useDouble = true;
}
s.Take();
s->Take();
if (s.Peek() >= '0' && s.Peek() <= '9') {
d = d * 10 + (s.Take() - '0');
if (s->Peek() >= '0' && s->Peek() <= '9') {
d = d * 10 + (s->Take() - '0');
--expFrac;
}
else
RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissFraction, is.Tell());
while (s.Peek() >= '0' && s.Peek() <= '9') {
while (s->Peek() >= '0' && s->Peek() <= '9') {
if (expFrac > -16) {
d = d * 10 + (s.Peek() - '0');
d = d * 10 + (s->Peek() - '0');
--expFrac;
}
s.Take();
s->Take();
}
}
// Parse exp = e [ minus / plus ] 1*DIGIT
int exp = 0;
if (s.Peek() == 'e' || s.Peek() == 'E') {
if (s->Peek() == 'e' || s->Peek() == 'E') {
if (!useDouble) {
d = try64bit ? (double)i64 : (double)i;
useDouble = true;
}
s.Take();
s->Take();
bool expMinus = false;
if (s.Peek() == '+')
s.Take();
else if (s.Peek() == '-') {
s.Take();
if (s->Peek() == '+')
s->Take();
else if (s->Peek() == '-') {
s->Take();
expMinus = true;
}
if (s.Peek() >= '0' && s.Peek() <= '9') {
exp = s.Take() - '0';
while (s.Peek() >= '0' && s.Peek() <= '9') {
exp = exp * 10 + (s.Take() - '0');
if (s->Peek() >= '0' && s->Peek() <= '9') {
exp = s->Take() - '0';
while (s->Peek() >= '0' && s->Peek() <= '9') {
exp = exp * 10 + (s->Take() - '0');
if (exp > 308)
RAPIDJSON_PARSE_ERROR(kParesErrorNumberTooBig, is.Tell());
}
}
else
RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissExponent, s.Tell());
RAPIDJSON_PARSE_ERROR(kParseErrorNumberMissExponent, is.Tell());
if (expMinus)
exp = -exp;
@ -689,8 +689,6 @@ private:
handler.Uint(i);
}
}
is = s; // restore is
}
// Parse any JSON value

5
test/unittest/readertest.cpp
View File

@ -623,8 +623,9 @@ public:
size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
private:
// Not support copy constructor.
// Prohibit copy constructor & assignment operator.
CustomStringStream(const CustomStringStream&);
CustomStringStream& operator=(const CustomStringStream&);
const Ch* src_; //!< Current read position.
const Ch* head_; //!< Original head of the string.
@ -637,7 +638,7 @@ namespace rapidjson {
template <typename Encoding>
struct StreamTraits<CustomStringStream<Encoding> > {
typedef CustomStringStream<Encoding> StreamCopyType;
enum { copyOptimization = 1 };
};
} // namespace rapdijson