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This implements string serialization for On Demand instances. (#1527) 

* This implementations string serialization for On Demand instances.

* Adding more documentation.

* Another remark.

* Marking the new functions as inline.

* casts apparently do not work.

* Upgrading the API.

* Making the code really free from exceptions.

* At another fix for exceptionless.

* Modify to_chars so that it does not pad integers with '.0'.

* Negative 0 cannot be expressed as an integer.

* Again, accomodating exceptionless usage.

* Using x <= -0 does not allow you to determine the sign since 0 <= -0. I am not sure where
this bug comes from.
This commit is contained in:
Daniel Lemire 2021-04-01 11:25:00 -04:00 committed by GitHub
parent 461bc4c47e
commit d0821adf0e
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GPG Key ID: 4AEE18F83AFDEB23
11 changed files with 570 additions and 10 deletions
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1
doc/basics.md
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@ -202,6 +202,7 @@ support for users who avoid exceptions. See [the simdjson error handling documen
- `field.value()` will get you the value, which you can then use all these other methods on.
* **Array Index:** Because it is forward-only, you cannot look up an array element by index. Instead,
you will need to iterate through the array and keep an index yourself.
* **Output to sstrings:** Given a document or an element (or node) out of a JSON document, you can output a string version: `simdjson::to_string(element)` returns a `simdjson::simdjson_result<std::string>` instance. You can cast it to `std::string` and it will throw when an error was encountered (`std::string(simdjson::to_string(element))`). Or else you can do `std::string s; if(simdjson::to_string(element).get(s) == simdjson::SUCCESS) { ... }`. This consumes fully the element: if you apply it on a document, the JSON pointer is advanced to the end of the document.
### Examples

2
doc/dom.md
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@ -89,7 +89,7 @@ Once you have an element, you can navigate it with idiomatic C++ iterators, oper
with the `size()` method.
* **Checking an Element Type:** You can check an element's type with `element.type()`. It
returns an `element_type` with values such as `simdjson::dom::element_type::ARRAY`, `simdjson::dom::element_type::OBJECT`, `simdjson::dom::element_type::INT64`, `simdjson::dom::element_type::UINT64`,`simdjson::dom::element_type::DOUBLE`, `simdjson::dom::element_type::BOOL` or, `simdjson::dom::element_type::NULL_VALUE`.
* **Output to streams and strings:** Given a document or an element (or node) out of a JSON document, you can output a minified string version using the C++ stream idiom (`out << element`). You can also request the construction of a minified string version (`simdjson::minify(element)`).
* **Output to streams and strings:** Given a document or an element (or node) out of a JSON document, you can output a minified string version using the C++ stream idiom (`out << element`). You can also request the construction of a minified string version (`simdjson::minify(element)`). Numbers are serialized as 64-bit floating-point numbers (`double`).
### Examples

1
include/simdjson/generic/ondemand-inl.h
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@ -12,3 +12,4 @@
#include "simdjson/generic/ondemand/field-inl.h"
#include "simdjson/generic/ondemand/object-inl.h"
#include "simdjson/generic/ondemand/parser-inl.h"
#include "simdjson/generic/ondemand/serialization-inl.h"

1
include/simdjson/generic/ondemand.h
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@ -29,3 +29,4 @@ using depth_t = int32_t;
#include "simdjson/generic/ondemand/field.h"
#include "simdjson/generic/ondemand/object.h"
#include "simdjson/generic/ondemand/parser.h"
#include "simdjson/generic/ondemand/serialization.h"

184
include/simdjson/generic/ondemand/serialization-inl.h Normal file
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@ -0,0 +1,184 @@
namespace simdjson {
namespace SIMDJSON_IMPLEMENTATION {
namespace ondemand {
template <class serializer>
inline simdjson::error_code string_builder<serializer>::append(document& element) noexcept {
json_type t;
auto e = element.type().get(t);
if(e != simdjson::SUCCESS) { return e; }
switch (t) {
case ondemand::json_type::array:
{
array x;
simdjson::error_code error = element.get_array().get(x);
if(error == simdjson::SUCCESS) {
append(x);
}
return error;
}
case ondemand::json_type::object:
{
object x;
simdjson::error_code error = element.get_object().get(x);
if(error == simdjson::SUCCESS) {
append(x);
}
return error;
}
case ondemand::json_type::number:
// Assume it fits in a double. We do not detect integer types. This could be improved.
{
double x;
simdjson::error_code error = element.get_double().get(x);
if(error == simdjson::SUCCESS) {
format.number(x);
}
return error;
}
case ondemand::json_type::string:
{
std::string_view x;
simdjson::error_code error = element.get_string().get(x);
if(error == simdjson::SUCCESS) {
format.string(x);
}
return error;
}
case ondemand::json_type::boolean:
{
bool x;
simdjson::error_code error = element.get_bool().get(x);
if(error == simdjson::SUCCESS) {
x ? format.true_atom() : format.false_atom();
}
return error;
}
case ondemand::json_type::null:
format.null_atom();
return simdjson::SUCCESS;
}
return simdjson::INCORRECT_TYPE;
}
template <class serializer>
inline simdjson::error_code string_builder<serializer>::append(value element) noexcept {
json_type t;
auto e = element.type().get(t);
if(e != simdjson::SUCCESS) { return e; }
switch (t) {
case ondemand::json_type::array:
{
array x;
simdjson::error_code error = element.get_array().get(x);
if(error == simdjson::SUCCESS) {
append(x);
}
return error;
}
case ondemand::json_type::object:
{
object x;
simdjson::error_code error = element.get_object().get(x);
if(error == simdjson::SUCCESS) {
append(x);
}
return error;
}
case ondemand::json_type::number:
// Assume it fits in a double. We do not detect integer types. This could be improved.
{
double x;
simdjson::error_code error = element.get_double().get(x);
if(error == simdjson::SUCCESS) {
format.number(x);
}
return error;
}
case ondemand::json_type::string:
{
std::string_view x;
simdjson::error_code error = element.get_string().get(x);
if(error == simdjson::SUCCESS) {
format.string(x);
}
return error;
}
break;
case ondemand::json_type::boolean:
{
bool x;
simdjson::error_code error = element.get_bool().get(x);
if(error == simdjson::SUCCESS) {
x ? format.true_atom() : format.false_atom();
}
return error;
}
case ondemand::json_type::null:
format.null_atom();
return simdjson::SUCCESS;
}
return simdjson::INCORRECT_TYPE;
}
template <class serializer>
inline simdjson::error_code string_builder<serializer>::append(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::field x) noexcept {
// Performance note: There is a sizeable performance opportunity here to avoid unescaping
// and the re-escaping the key!!!!
std::string_view v;
auto error = x.unescaped_key().get(v);
if (error) { return error; }
format.key(v);
return append(x.value());
}
template <class serializer>
inline simdjson::error_code string_builder<serializer>::append(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::array x) noexcept {
format.start_array();
bool first{true};
for(simdjson::simdjson_result<simdjson::SIMDJSON_IMPLEMENTATION::ondemand::value> v: x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::value element;
simdjson::error_code error = std::move(v).get(element);
if(error != simdjson::SUCCESS) { return error; }
if(first) { first = false; } else { format.comma(); };
error = append(element);
if(error != simdjson::SUCCESS) { return error; }
}
format.end_array();
return simdjson::SUCCESS;
}
template <class serializer>
inline simdjson::error_code string_builder<serializer>::append(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::object x) noexcept {
format.start_object();
bool first{true};
for(simdjson::simdjson_result<simdjson::SIMDJSON_IMPLEMENTATION::ondemand::field> r: x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::field element;
simdjson::error_code error = std::move(r).get(element);
if(error != simdjson::SUCCESS) { return error; }
if(first) { first = false; } else { format.comma(); };
error = append(element);
if(error != simdjson::SUCCESS) { return error; }
}
format.end_object();
return simdjson::SUCCESS;
}
template <class serializer>
simdjson_really_inline void string_builder<serializer>::clear() {
format.clear();
}
template <class serializer>
simdjson_really_inline std::string_view string_builder<serializer>::str() const {
return format.str();
}
} // namespace ondemand
} // namespace SIMDJSON_IMPLEMENTATION
} // namespace simdjson

204
include/simdjson/generic/ondemand/serialization.h Normal file
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@ -0,0 +1,204 @@
#include "simdjson/dom/serialization.h"
#include "simdjson/error.h"
namespace simdjson {
namespace SIMDJSON_IMPLEMENTATION {
namespace ondemand {
template <class formatter = simdjson::internal::mini_formatter>
class string_builder {
public:
/** Append an document to the builder (to be printed), numbers are
* assumed to be 64-bit floating-point numbers.
**/
inline simdjson::error_code append(document& value) noexcept;
/** Append an element to the builder (to be printed) **/
inline simdjson::error_code append(value element) noexcept;
/** Append an array to the builder (to be printed) **/
inline simdjson::error_code append(array value) noexcept;
/** Append an objet to the builder (to be printed) **/
inline simdjson::error_code append(object value) noexcept;
/** Append a field to the builder (to be printed) **/
inline simdjson::error_code append(field value) noexcept;
/** Reset the builder (so that it would print the empty string) **/
simdjson_really_inline void clear();
/**
* Get access to the string. The string_view is owned by the builder
* and it is invalid to use it after the string_builder has been
* destroyed.
* However you can make a copy of the string_view on memory that you
* own.
*/
simdjson_really_inline std::string_view str() const;
private:
formatter format{};
};
/**
* Print JSON to an output stream.
*
* @param out The output stream.
* @param value The element.
* @throw if there is an error with the underlying output stream. simdjson itself will not throw.
*/
#if SIMDJSON_EXCEPTIONS
inline std::ostream& operator<<(std::ostream& out, value x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto err = sb.append(x);
if(err == simdjson::SUCCESS) {
return (out << sb.str());
} else {
throw simdjson::simdjson_error(err);
}
}
inline std::ostream& operator<<(std::ostream& out, simdjson::simdjson_result<value> x) {
if (x.error()) { throw simdjson::simdjson_error(x.error()); }
return (out << x.value());
}
#else
inline std::ostream& operator<<(std::ostream& out, value x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(x);
if(error == simdjson::SUCCESS) {
return (out << sb.str());
} else {
return (out << error);
}
}
#endif
/**
* Print JSON to an output stream.
*
* @param out The output stream.
* @param value The array.
* @throw if there is an error with the underlying output stream. simdjson itself will not throw.
*/
#if SIMDJSON_EXCEPTIONS
inline std::ostream& operator<<(std::ostream& out, array value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto err = sb.append(value);
if(err == simdjson::SUCCESS) {
return (out << sb.str());
} else {
throw simdjson::simdjson_error(err);
}
}
inline std::ostream& operator<<(std::ostream& out, simdjson::simdjson_result<array> x) {
if (x.error()) { throw simdjson::simdjson_error(x.error()); }
return (out << x.value());
}
#else
inline std::ostream& operator<<(std::ostream& out, array value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(value);
if(error == simdjson::SUCCESS) {
return (out << sb.str());
} else {
return (out << error);
}
}
#endif
/**
* Print JSON to an output stream.
*
* @param out The output stream.
* @param value The array.
* @throw if there is an error with the underlying output stream. simdjson itself will not throw.
*/
#if SIMDJSON_EXCEPTIONS
inline std::ostream& operator<<(std::ostream& out, document& value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto err = sb.append(value);
if(err == simdjson::SUCCESS) {
return (out << sb.str());
} else {
throw simdjson::simdjson_error(err);
}
}
inline std::ostream& operator<<(std::ostream& out, simdjson::simdjson_result<document> x) {
if (x.error()) { throw simdjson::simdjson_error(x.error()); }
return (out << x.value());
}
#else
inline std::ostream& operator<<(std::ostream& out, document& value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(value);
if(error == simdjson::SUCCESS) {
return (out << sb.str());
} else {
return (out << error);
}
}
#endif
/**
* Print JSON to an output stream.
*
* @param out The output stream.
* @param value The objet.
* @throw if there is an error with the underlying output stream. simdjson itself will not throw.
*/
#if SIMDJSON_EXCEPTIONS
inline std::ostream& operator<<(std::ostream& out, object value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto err = sb.append(value);
if(err == simdjson::SUCCESS) {
return (out << sb.str());
} else {
throw simdjson::simdjson_error(err);
}
}
inline std::ostream& operator<<(std::ostream& out, simdjson::simdjson_result<object> x) {
if (x.error()) { throw simdjson::simdjson_error(x.error()); }
return (out << x.value());
}
#else
inline std::ostream& operator<<(std::ostream& out, object value) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(value);
if(error == simdjson::SUCCESS) {
return (out << sb.str());
} else {
return (out << error);
}
}
#endif
} // namespace ondemand
} // namespace SIMDJSON_IMPLEMENTATION
} // namespace simdjson
namespace simdjson {
inline simdjson::simdjson_result<std::string> to_string(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::document& x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(x);
if(error != simdjson::SUCCESS) { return error; }
std::string_view answer = sb.str();
return std::string(answer.data(), answer.size());
}
inline simdjson::simdjson_result<std::string> to_string(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::value& x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(x);
if(error != simdjson::SUCCESS) { return error; }
std::string_view answer = sb.str();
return std::string(answer.data(), answer.size());
}
inline simdjson::simdjson_result<std::string> to_string(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::object& x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(x);
if(error != simdjson::SUCCESS) { return error; }
std::string_view answer = sb.str();
return std::string(answer.data(), answer.size());
}
inline simdjson::simdjson_result<std::string> to_string(simdjson::SIMDJSON_IMPLEMENTATION::ondemand::array& x) {
simdjson::SIMDJSON_IMPLEMENTATION::ondemand::string_builder<> sb;
auto error = sb.append(x);
if(error != simdjson::SUCCESS) { return error; }
std::string_view answer = sb.str();
return std::string(answer.data(), answer.size());
}
} // namespace simdjson

17
src/to_chars.cpp
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@ -1,6 +1,8 @@
#include <cstring>
#include <cstdint>
#include <array>
#include <cmath>
namespace simdjson {
namespace internal {
/*!
@ -858,9 +860,9 @@ inline char *format_buffer(char *buf, int len, int decimal_exponent,
std::memset(buf + k, '0', static_cast<size_t>(n) - static_cast<size_t>(k));
// Make it look like a floating-point number (#362, #378)
buf[n + 0] = '.';
buf[n + 1] = '0';
return buf + (static_cast<size_t>(n) + 2);
// buf[n + 0] = '.';
// buf[n + 1] = '0';
return buf + (static_cast<size_t>(n));
}
if (0 < n && n <= max_exp) {
@ -913,7 +915,8 @@ format. Returns an iterator pointing past-the-end of the decimal representation.
*/
char *to_chars(char *first, const char *last, double value) {
static_cast<void>(last); // maybe unused - fix warning
if (value <= -0) {
bool negative = std::signbit(value);
if (negative) {
value = -value;
*first++ = '-';
}
@ -922,8 +925,10 @@ char *to_chars(char *first, const char *last, double value) {
{
*first++ = '0';
// Make it look like a floating-point number (#362, #378)
*first++ = '.';
*first++ = '0';
if(negative) {
*first++ = '.';
*first++ = '0';
}
return first;
}
// Compute v = buffer * 10^decimal_exponent.

4
tests/minify_tests.cpp
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@ -42,6 +42,8 @@ bool load_to_string(const char *filename) {
std::cout << "Parsing to_string and calling to_string again results in the "
"same content."
<< std::endl;
} else {
std::cout << "The content differs!" << std::endl;
}
return match;
}
@ -61,6 +63,8 @@ bool load_minify(const char *filename) {
std::cout << "Parsing minify and calling minify again results in the same "
"content."
<< std::endl;
} else {
std::cout << "The content differs!" << std::endl;
}
return match;
}

2
tests/ondemand/CMakeLists.txt
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@ -2,7 +2,7 @@
link_libraries(simdjson)
include_directories(..)
add_subdirectory(compilation_failure_tests)
add_cpp_test(ondemand_tostring_tests LABELS ondemand acceptance per_implementation)
add_cpp_test(ondemand_active_tests LABELS ondemand acceptance per_implementation)
add_cpp_test(ondemand_array_tests LABELS ondemand acceptance per_implementation)
add_cpp_test(ondemand_array_error_tests LABELS ondemand acceptance per_implementation)

149
tests/ondemand/ondemand_tostring_tests.cpp Normal file
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@ -0,0 +1,149 @@
#include <cinttypes>
#include <ciso646>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <set>
#include <sstream>
#include <string>
#include <unistd.h>
#include <utility>
#include <vector>
#include "simdjson.h"
#include "test_ondemand.h"
namespace tostring_tests {
const char *test_files[] = {
TWITTER_JSON, TWITTER_TIMELINE_JSON, REPEAT_JSON, CANADA_JSON,
MESH_JSON, APACHE_JSON, GSOC_JSON};
#if SIMDJSON_EXCEPTIONS
/**
* The general idea of these tests if that if you take a JSON file,
* load it, then convert it into a string, then parse that, and
* convert it again into a second string, then the two strings should
* be identifical. If not, then something was lost or added in the
* process.
*/
bool load_to_string(const char *filename) {
simdjson::ondemand::parser parser;
std::cout << "Loading " << filename << std::endl;
simdjson::padded_string docdata;
auto error = simdjson::padded_string::load(filename).get(docdata);
if (error) {
std::cerr << "could not load " << filename << " got " << error << std::endl;
return false;
}
std::cout << "file loaded: " << docdata.size() << " bytes." << std::endl;
simdjson::ondemand::document doc;
error = parser.iterate(docdata).get(doc);
if (error) {
std::cerr << error << std::endl;
return false;
}
std::cout << "serializing once." << std::endl;
std::string serial1 = simdjson::to_string(doc);
serial1.reserve(serial1.size() + simdjson::SIMDJSON_PADDING);
error = parser.iterate(serial1).get(doc);
if (error) {
std::cerr << error << std::endl;
return false;
}
std::cout << "serializing twice." << std::endl;
std::string serial2 = simdjson::to_string(doc);
bool match = (serial1 == serial2);
if (match) {
std::cout << "Parsing to_string and calling to_string again results in the "
"same content."
<< "Got " << serial1.size() << " bytes." << std::endl;
}
return match;
}
bool minify_test() {
TEST_START();
for (size_t i = 0; i < sizeof(test_files) / sizeof(test_files[0]); i++) {
bool ok = load_to_string(test_files[i]);
if (!ok) {
return false;
}
}
return true;
}
#endif // SIMDJSON_EXCEPTIONS
bool load_to_string_exceptionless(const char *filename) {
simdjson::ondemand::parser parser;
std::cout << "Loading " << filename << std::endl;
simdjson::padded_string docdata;
auto error = simdjson::padded_string::load(filename).get(docdata);
if (error) {
std::cerr << "could not load " << filename << " got " << error << std::endl;
return false;
}
std::cout << "file loaded: " << docdata.size() << " bytes." << std::endl;
simdjson::ondemand::document doc;
error = parser.iterate(docdata).get(doc);
if (error) {
std::cerr << error << std::endl;
return false;
}
std::cout << "serializing once." << std::endl;
std::string serial1;
error = simdjson::to_string(doc).get(serial1);
if (error) {
std::cerr << error << std::endl;
return false;
}
serial1.reserve(serial1.size() + simdjson::SIMDJSON_PADDING);
error = parser.iterate(serial1).get(doc);
if (error) {
std::cerr << error << std::endl;
return false;
}
std::cout << "serializing twice." << std::endl;
std::string serial2;
error = simdjson::to_string(doc).get(serial2);
if (error) {
std::cerr << error << std::endl;
return false;
}
bool match = (serial1 == serial2);
if (match) {
std::cout << "Parsing to_string and calling to_string again results in the "
"same content."
<< "Got " << serial1.size() << " bytes." << std::endl;
}
return match;
}
bool minify_exceptionless_test() {
TEST_START();
for (size_t i = 0; i < sizeof(test_files) / sizeof(test_files[0]); i++) {
bool ok = load_to_string_exceptionless(test_files[i]);
if (!ok) {
return false;
}
}
return true;
}
bool run() {
return
#if SIMDJSON_EXCEPTIONS
minify_test() &&
#endif // SIMDJSON_EXCEPTIONS
minify_exceptionless_test() &&
true;
}
} // namespace tostring_tests
int main(int argc, char *argv[]) {
return test_main(argc, argv, tostring_tests::run);
}

15
tools/json2json.cpp
View File

@ -31,6 +31,7 @@ int main(int argc, const char *argv[]) {
cxxopts::Options options(progName, progUsage);
options.add_options()
("z,ondemand", "Use On Demand front-end.", cxxopts::value<bool>()->default_value("false"))
("d,rawdump", "Dumps the raw content of the tape.", cxxopts::value<bool>()->default_value("false"))
("f,file", "File name.", cxxopts::value<std::string>())
("h,help", "Print usage.")
@ -44,7 +45,7 @@ int main(int argc, const char *argv[]) {
std::cerr << options.help() << std::endl;
return EXIT_SUCCESS;
}
bool ondemand = result["ondemand"].as<bool>();
bool rawdump = result["rawdump"].as<bool>();
if(!result.count("file")) {
@ -54,7 +55,17 @@ int main(int argc, const char *argv[]) {
}
const char *filename = result["file"].as<std::string>().c_str();
if(ondemand) {
simdjson::ondemand::parser parser;
simdjson::padded_string docdata;
auto error = simdjson::padded_string::load(filename).get(docdata);
if(error != simdjson::SUCCESS) { std::cout << error << std::endl; return EXIT_FAILURE; }
simdjson::ondemand::document doc;
error = parser.iterate(docdata).get(doc);
if(error != simdjson::SUCCESS) { std::cout << error << std::endl; return EXIT_FAILURE; }
std::cout << doc;
return EXIT_SUCCESS;
}
simdjson::dom::parser parser;
simdjson::dom::element doc;
auto error = parser.load(filename).get(doc); // do the parsing, return false on error