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poco/MongoDB/include/Poco/MongoDB/Element.h

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//
// Element.h
//
// Library: MongoDB
// Package: MongoDB
// Module: Element
//
// Definition of the Element class.
//
// Copyright (c) 2012-2025, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef MongoDB_Element_INCLUDED
#define MongoDB_Element_INCLUDED
#include "Poco/BinaryReader.h"
#include "Poco/BinaryWriter.h"
#include "Poco/SharedPtr.h"
#include "Poco/Timestamp.h"
#include "Poco/Nullable.h"
#include "Poco/NumberFormatter.h"
#include "Poco/DateTimeFormatter.h"
#include "Poco/MongoDB/MongoDB.h"
#include "Poco/MongoDB/BSONReader.h"
#include "Poco/MongoDB/BSONWriter.h"
#include <string>
#include <sstream>
#include <iomanip>
#include <list>
namespace Poco {
namespace MongoDB {
class MongoDB_API Element
/// Represents an Element of a Document or an Array.
{
public:
using Ptr = Poco::SharedPtr<Element>;
explicit Element(const std::string& name);
/// Creates the Element with the given name.
explicit Element(std::string&& name);
/// Creates the Element with the given name (move semantics).
virtual ~Element();
/// Destructor
[[nodiscard]] const std::string& name() const noexcept;
/// Returns the name of the element.
[[nodiscard]] virtual std::string toString(int indent = 0) const = 0;
/// Returns a string representation of the element.
[[nodiscard]] virtual int type() const noexcept = 0;
/// Returns the MongoDB type of the element.
private:
virtual void read(BinaryReader& reader) = 0;
virtual void write(BinaryWriter& writer) const = 0;
friend class Document;
std::string _name;
};
//
// inlines
//
inline const std::string& Element::name() const noexcept
{
return _name;
}
template<typename T>
struct ElementTraits
{
};
// BSON Floating point
// spec: double
template<>
struct ElementTraits<double>
{
enum { TypeId = 0x01 };
static std::string toString(const double& value, int indent = 0)
{
return Poco::NumberFormatter::format(value);
}
};
// BSON UTF-8 string
// spec: int32 (byte*) "\x00"
// int32 is the number bytes in byte* + 1 (for trailing "\x00")
template<>
struct ElementTraits<std::string>
{
enum { TypeId = 0x02 };
static std::string toString(const std::string& value, int indent = 0)
{
// Fast path: check if escaping is needed at all
bool needsEscaping = false;
for (char c : value)
{
if (c == '"' || c == '\\' || c == '\b' || c == '\f' ||
c == '\n' || c == '\r' || c == '\t' || (c > 0 && c <= 0x1F))
{
needsEscaping = true;
break;
}
}
// Fast path: no escaping needed - just wrap in quotes
if (!needsEscaping)
{
std::string result;
result.reserve(value.size() + 2);
result += '"';
result += value;
result += '"';
return result;
}
// Slow path: escaping needed
std::string result;
result.reserve(value.size() * 2 + 2); // Pessimistic estimate
result += '"';
for (char c : value)
{
switch (c)
{
case '"':
result += "\\\"";
break;
case '\\':
result += "\\\\";
break;
case '\b':
result += "\\b";
break;
case '\f':
result += "\\f";
break;
case '\n':
result += "\\n";
break;
case '\r':
result += "\\r";
break;
case '\t':
result += "\\t";
break;
default:
if (c > 0 && c <= 0x1F)
{
// Unicode escape sequence
char buf[7]; // "\uXXXX" + null terminator
std::snprintf(buf, sizeof(buf), "\\u%04X", static_cast<unsigned char>(c));
result += buf;
}
else
{
result += c;
}
break;
}
}
result += '"';
return result;
}
};
template<>
inline void BSONReader::read<std::string>(std::string& to)
{
Poco::Int32 size;
_reader >> size;
_reader.readRaw(size, to);
to.erase(to.end() - 1); // remove terminating 0
}
template<>
inline void BSONWriter::write<std::string>(const std::string& from)
{
_writer << static_cast<Poco::Int32>(from.length() + 1);
writeCString(from);
}
// BSON bool
// spec: "\x00" "\x01"
template<>
struct ElementTraits<bool>
{
enum { TypeId = 0x08 };
static std::string toString(const bool& value, int indent = 0)
{
return value ? "true" : "false";
}
};
template<>
inline void BSONReader::read<bool>(bool& to)
{
unsigned char b;
_reader >> b;
to = b != 0;
}
template<>
inline void BSONWriter::write<bool>(const bool& from)
{
unsigned char b = from ? 0x01 : 0x00;
_writer << b;
}
// BSON 32-bit integer
// spec: int32
template<>
struct ElementTraits<Int32>
{
enum { TypeId = 0x10 };
static std::string toString(const Int32& value, int indent = 0)
{
return Poco::NumberFormatter::format(value);
}
};
// BSON UTC datetime
// spec: int64
template<>
struct ElementTraits<Timestamp>
{
enum { TypeId = 0x09 };
static std::string toString(const Timestamp& value, int indent = 0)
{
std::string result;
result.reserve(32); // Pre-allocate for typical timestamp string length
result += '"';
result += DateTimeFormatter::format(value, "%Y-%m-%dT%H:%M:%s%z");
result += '"';
return result;
}
};
template<>
inline void BSONReader::read<Timestamp>(Timestamp& to)
{
Poco::Int64 value;
_reader >> value;
to = Timestamp::fromEpochTime(static_cast<std::time_t>(value / 1000));
to += (value % 1000 * 1000);
}
template<>
inline void BSONWriter::write<Timestamp>(const Timestamp& from)
{
_writer << (from.epochMicroseconds() / 1000);
}
using NullValue = Nullable<unsigned char>;
// BSON Null Value
// spec:
template<>
struct ElementTraits<NullValue>
{
enum { TypeId = 0x0A };
static std::string toString(const NullValue& value, int indent = 0)
{
return "null";
}
};
template<>
inline void BSONReader::read<NullValue>(NullValue& to)
{
}
template<>
inline void BSONWriter::write<NullValue>(const NullValue& from)
{
}
struct BSONTimestamp
{
Poco::Timestamp ts;
Poco::Int32 inc;
};
// BSON Timestamp
// spec: int64
template<>
struct ElementTraits<BSONTimestamp>
{
enum { TypeId = 0x11 };
static std::string toString(const BSONTimestamp& value, int indent = 0)
{
std::string result;
result.reserve(48); // Pre-allocate for timestamp + space + increment + quotes
result += '"';
result += DateTimeFormatter::format(value.ts, "%Y-%m-%dT%H:%M:%s%z");
result += ' ';
result += NumberFormatter::format(value.inc);
result += '"';
return result;
}
};
template<>
inline void BSONReader::read<BSONTimestamp>(BSONTimestamp& to)
{
Poco::Int64 value;
_reader >> value;
to.inc = value & 0xffffffff;
value >>= 32;
to.ts = Timestamp::fromEpochTime(static_cast<std::time_t>(value));
}
template<>
inline void BSONWriter::write<BSONTimestamp>(const BSONTimestamp& from)
{
Poco::Int64 value = from.ts.epochMicroseconds() / 1000;
value <<= 32;
value += from.inc;
_writer << value;
}
// BSON 64-bit integer
// spec: int64
template<>
struct ElementTraits<Int64>
{
enum { TypeId = 0x12 };
static std::string toString(const Int64& value, int indent = 0)
{
return NumberFormatter::format(value);
}
};
template<typename T>
class ConcreteElement: public Element
{
public:
ConcreteElement(const std::string& name, const T& init):
Element(name),
_value(init)
{
}
ConcreteElement(std::string&& name, T&& init):
Element(std::move(name)),
_value(std::move(init))
{
}
~ConcreteElement() override = default;
const T& value() const noexcept
{
return _value;
}
[[nodiscard]] std::string toString(int indent = 0) const override
{
return ElementTraits<T>::toString(_value, indent);
}
[[nodiscard]] int type() const noexcept override
{
return ElementTraits<T>::TypeId;
}
void read(BinaryReader& reader) override
{
BSONReader(reader).read(_value);
}
void write(BinaryWriter& writer) const override
{
BSONWriter(writer).write(_value);
}
private:
T _value;
};
} } // namespace Poco::MongoDB
#endif // MongoDB_Element_INCLUDED