. 前几天无意中看到我之前写的Ｊｓｏｎ库，按今天的眼光去看简直稀烂２３３３，接口烂，实现烂，手一哆嗦就整个删掉了．
. 写C＋＋程序的时候，有时候需要操作一些Ｊｓｏｎ文件，这些Ｊｓｏｎ仅作为配置使用，极少在业务逻辑里频繁操作，所以易用性是首要，性能是次要，我之前用ｃＪＳＯＮ库，无奈它是一个C风格的库，在C＋＋代码里格格不入，即使将其封装后，看起来也十分蹩脚，我尝试写了一个比较符合C＋＋风格的Ｊｓｏｎ库，目前感觉还可以．
. 子节点由ｓｔｄ：：ｓｈａｒｅ＿ｐｔｒ管理，对Ｊｓｏｎ的所有操作都被实现在Ｓｅｔ／Ｇｅｔ／Ｄｅｌ函数里，从Ｊｓｏｎ字符串序列化到对象则通过静态函数ＦｒｏｍＳｔｒｉｎｇ实现，接口相当简洁．
接口清单：
Type() // 返回节点类型
ToInt() // 取int值
ToBool() // 取bool值
ToFloat() // 取float值
ToDouble() // 取double值
ToString() // 取string值
Set(val, key1, key2, ...) // 设key...位置的节点
Get(key1, key2, ...) // 取key...位置的节点
Del(key1, key2, ...) // 删key...位置的节点
JValue::FromString(str) // 从字符串解析json
JValue::FromFile(file) // 从文件解析json
ToPrint() // 将节点序列化为可打印字符串
使用例子：
// 从文件解析
auto jfile = JValue::FromFile("a.json");
// 从字符串解析
auto jstring = JValue::FromString("{}");
// 单独设值
JValue json;
json.Set(0);
json.Set(true);
json.Set("123");
json.Set(JValue::Hash());
json.Set(JValue::List());
json.Set(JValue::FromString("{}"));
// 读函数原型 JValue::Get(key1, key2, key3...)
// 读 json["hash"]["k1"]
json.Get("hash", "k1")->ToInt();
// 读 json["list"][0]
json.Get("list", 0)->ToInt();
// 写函数原型 JValue::Set(val, key1, key2, key3...);
// 写 json["list"] = []
json.Set(JValue::List(), "list");
// 写 json["list"][0] = 0
json.Set(0, "list", 0);
// 写 json["hash"] = {}
json.Set(JValue::Hash(), "hash");
// 写 json["hash"]["k"] = 0
json.Set(0, "hash", "k");
// 删函数原型 JValue::Del(key1, key2, key3...)
// 删 json["hash"]["k"] = undefine
json.Del("hash", "k");
// 左值深拷贝
{
JValue json1, json2;
json1 = json2;
}
// 右值拷贝
{
JValue json1, json2;
json1 = std::move(json2);
}
// 序列化到字符串
std::string str = json.ToPrint();
// 范围遍历
for (auto & jptr : json)
{ }
// 索引遍历
for (auto i = 0; i != json.GetCount(); ++i)
{
json.Get(i);
}
// 可结合C++标准算法
auto it = std::find(std::begin(json), std::end(json), "key");
源码：
#pragma once
#include
#include
#include
#include
#include
#include
#include
#include
#include "sformat.h"
// 条件判断, 抛出异常
#define DEBUG_CHECK(exp, type, ...) if (!exp) { throw type(__VA_ARGS__); }
// 异常说明, 显示Json错误位置往后20个字符
#define DEBUG_EXPINFO(exp, string) SFormat("{0}: {1}", exp, std::string(string).substr(0, 20))
class JValue {
public:
using JValuePtr = std::shared_ptr;
struct Parser {
// 解析异常
class Exception : public std::exception {
public:
Exception(const std::string & what): _what(what), std::exception(what.c_str())
{}
private:
std::string _what;
};
static const char * SkipSpace(const char * string)
{
for (; *string != '\0' && *string <= 32; ++string)
;
return string;
}
static const char * ParseList(const char * string, std::vector * output)
{
output->clear();
while (*string != ']')
{
auto element = std::make_shared();
string = Parser::Parse(string, element.get());
string = SkipSpace(string);
*string == ',' && ++string;
string = SkipSpace(string);
output->push_back(element);
}
return ++string;
}
static const char * ParseHash(const char * string, std::vector * output)
{
output->clear();
while (*string != '}')
{
auto element = std::make_shared();
DEBUG_CHECK((*string == '\"'), Parser::Exception, DEBUG_EXPINFO("Parse Hash Error: ", string));
string = Parser::ParseString(string + 1, &element->_key);
string = SkipSpace(string);
DEBUG_CHECK((*string == ':'), Parser::Exception, DEBUG_EXPINFO("Parse Hash Error: ", string));
string = Parser::Parse(string + 1, element.get());
string = SkipSpace(string);
*string == ',' && ++string;
string = SkipSpace(string);
output->push_back(element);
}
return ++string;
}
static const char * ParseString(const char * string, std::string * output)
{
output->clear();
for (; *string != '\"'; ++string)
{
DEBUG_CHECK(*string != '\0', Parser::Exception, DEBUG_EXPINFO("Parse String Error", string));
output->append(1, *string);
}
return string + 1;
}
static const char * ParseNumber(const char * string, double * output)
{
char value[64] = { 0 };
for (auto i = 0; *string >= '0' &&
*string <= '9' ||
*string == '.'; ++i, ++string)
{
value[i] = *string;
}
*output = std::strtod(value, nullptr);
return string;
}
static const char * ParseFalse(const char * string, double * output)
{
*output = 0;
return string + 5;
}
static const char * ParseTrue(const char * string, double * output)
{
*output = 1;
return string + 4;
}
static const char * Parse(const char * string, JValue * output)
{
string = Parser::SkipSpace(string);
if (*string == '[')
{
string = ParseList(SkipSpace(string + 1), &output->_elements);
output->_type = kLIST;
}
else if (*string == '{')
{
string = ParseHash(SkipSpace(string + 1), &output->_elements);
output->_type = kHASH;
}
else if (*string == '\"')
{
string = ParseString(string + 1, &output->_string);
output->_type = kSTRING;
}
else if (*string >= '0' && *string <= '9')
{
string = ParseNumber(string, &output->_number);
output->_type = kNUMBER;
}
else if (string[0] == 't' &&
string[1] == 'r' &&
string[2] == 'u' &&
string[3] == 'e')
{
string = ParseTrue(string, &output->_number);
output->_type = kBOOL;
}
else if (string[0] == 'f' &&
string[1] == 'a' &&
string[2] == 'l' &&
string[3] == 's' &&
string[4] == 'e')
{
string = ParseFalse(string, &output->_number);
output->_type = kBOOL;
}
else
{
DEBUG_CHECK(false, Parser::Exception, DEBUG_EXPINFO("Parse Json Error", string));
}
return string;
}
};
public:
enum JType {
kNUMBER,
kSTRING,
kHASH,
kLIST,
kBOOL,
kNULL,
};
struct Hash {};
struct List {};
// 如果是C++20, 可去掉这个模板
template
struct remove_cvref {
using type = std::remove_cv_t>;
};
template
using IsHash = std::is_same;
template
using IsList = std::is_same;
template
using IsBool = std::is_same;
template
using IsJValue = std::is_same;
template
using IsNull = std::is_same;
template
struct IsString: public std::false_type {};
template <>
struct IsString: public std::true_type {};
template
struct IsString: public std::true_type {};
template <>
struct IsString: public std::true_type {};
template
struct IsNumber: public std::false_type {};
template <>
struct IsNumber: public std::true_type {};
template <>
struct IsNumber: public std::true_type {};
template
struct IsInteger: public std::false_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
template <>
struct IsInteger: public std::true_type {};
static JValue FromFile(const std::string & fname)
{
std::ifstream ifile(fname);
std::string buffer;
std::copy(std::istream_iterator(ifile),
std::istream_iterator(),
std::back_inserter(buffer));
return std::move(FromString(buffer));
}
static JValue FromString(const std::string & string)
{
JValue jvalue;
try
{
Parser::Parse(string.c_str(), &jvalue);
}
catch (const Parser::Exception &)
{
jvalue.Set(nullptr);
}
return std::move(jvalue);
}
JValue(): _type(JType::kNULL)
{ }
template
JValue(T && value)
{
Set(std::forward(value));
}
JValue(JValue && json)
{
*this = std::move(json);
}
JValue & operator =(const JValue & json)
{
return (*this = std::move(Clone(json)));
}
JValue & operator =(JValue && json)
{
_elements = std::move(json._elements);
_number = std::move(json._number);
_string = std::move(json._string);
_type = std::move(json._type);
_key = std::move(json._key);
json._type = kNULL;
return *this;
}
JType Type() const
{
return _type;
}
const std::string & Key() const
{
return _key;
}
int ToInt() const
{
return static_cast(_number);
}
float ToFloat() const
{
return static_cast(_number);
}
double ToDouble() const
{
return static_cast(_number);
}
bool ToBool() const
{
return _number != 0;
}
const std::string & ToString() const
{
return _string;
}
std::string ToPrint() const
{
std::string space;
return std::move(Print(space));
}
size_t GetCount() const
{
return _elements.size();
}
std::vector::const_iterator begin() const
{
return _elements.begin();
}
std::vector::iterator begin()
{
return _elements.begin();
}
std::vector::const_iterator end() const
{
return _elements.end();
}
std::vector::iterator end()
{
return _elements.end();
}
template
JValuePtr Get(const Keys & ...keys)
{
return GetImpl(keys...);
}
template
bool Set(const char * val, const Keys & ...keys)
{
return SetImpl(val, keys...);
}
template
bool Set(Val && val, const Keys & ...keys)
{
return SetImpl(std::forward(val), keys...);
}
template
void Del(const Keys & ...keys)
{
DelImpl(keys...);
}
private:
JValue Clone(JValue && jvalue) const
{
return std::move(jvalue);
}
JValue Clone(const JValue & jvalue) const
{
JValue newval;
switch (jvalue.Type())
{
case kNUMBER:
{
newval.Set(jvalue.ToDouble());
}
break;
case kSTRING:
{
newval.Set(jvalue.ToString());
}
break;
case kBOOL:
{
newval.Set(jvalue.ToBool());
}
break;
case kHASH:
case kLIST:
{
std::transform(std::cbegin(_elements),
std::cend(_elements),
std::back_inserter(newval._elements),
std::bind(&JValue::ClonePtr, this, std::placeholders::_1));
}
break;
}
newval._key = jvalue.Key();
newval._type = jvalue.Type();
return std::move(newval);
}
JValuePtr ClonePtr(const JValuePtr & ptr) const
{
return std::make_shared(std::move(Clone(*ptr)));
}
template
JValuePtr GetImpl(const Key & key, const Keys & ...keys)
{
auto jptr = GetImpl(key);
if (jptr != nullptr)
{
return jptr->GetImpl(keys...);
}
return nullptr;
}
template
JValuePtr GetImpl(const Key & key)
{
if constexpr (IsInteger::value)
{
return (size_t)key < _elements.size()
? _elements.at(key)
: nullptr;
}
if constexpr (IsString::value)
{
auto it = std::find(std::begin(_elements), std::end(_elements), key);
return it != std::end(_elements)
? *it : nullptr;
}
return nullptr;
}
template
bool SetImpl(Val && val, const Key & key, const Keys & ...keys)
{
auto jptr = GetImpl(key);
if (jptr != nullptr)
{
return jptr->SetImpl(std::forward(val), keys...);
}
return true;
}
template
bool SetImpl(Val && val, const Key & key)
{
if constexpr (IsString::value) { assert(Type() == kHASH); }
if constexpr (IsInteger::value) { assert(Type() == kLIST); }
auto jptr = GetImpl(key);
if (jptr == nullptr)
{
auto newval = std::make_shared(std::forward(val));
if constexpr (IsString::value)
{
newval->_key = key;
}
_elements.push_back(newval);
}
else
{
jptr->SetImpl(std::forward(val));
}
return true;
}
template
bool SetImpl(Val && val)
{
using Naked = remove_cvref::type;
if constexpr (IsNumber::value || IsInteger::value)
{
_number = val;
_elements.clear();
_type = kNUMBER;
}
if constexpr (IsJValue::value)
{
*this = std::move(Clone(std::forward(val)));
}
if constexpr (IsString::value)
{
_string = std::forward(val);
_elements.clear();
_type = kSTRING;
}
if constexpr (IsBool::value)
{
_number = val ? 1 : 0;
_elements.clear();
_type = kBOOL;
}
if constexpr (IsHash::value)
{
_elements.clear();
_type = kHASH;
}
if constexpr (IsList::value)
{
_elements.clear();
_type = kLIST;
}
if constexpr (IsNull::value)
{
_elements.clear();
_type = kNULL;
}
return true;
}
template
void DelImpl(const Key & key, const Keys & ...keys)
{
auto jptr = GetImpl(key);
if (jptr != nullptr)
{
jptr->Del(keys...);
}
}
template
void DelImpl(const Key & key)
{
if constexpr (IsInteger::value)
{
if (key < _elements.size())
{
_elements.erase(std::advance(std::begin(_elements), key));
}
}
if constexpr (IsString::value)
{
auto it = std::find(std::begin(_elements), std::end(_elements), key);
if (it != std::end(_elements))
{
_elements.erase(it);
}
}
}
std::string Print(std::string & space) const
{
switch (Type())
{
case kNUMBER:
{
return std::to_string(_number);
}
break;
case kSTRING:
{
return "\"" + _string + "\"";
}
break;
case kHASH:
{
std::vector strings;
std::string resule("{\n");
space.append("\t");
resule.append(space);
for (const auto & element : _elements)
{
strings.push_back(SFormat("\"{0}\": {1}",
element->Key(), element->Print(space)));
}
resule.append(PrintJoin(strings, ",\n" + space));
space.pop_back();
resule.append("\n");
resule.append(space);
resule.append("}");
return std::move(resule);
}
break;
case kLIST:
{
std::vector strings;
for (const auto & element : _elements)
{
strings.push_back(element->Print(space));
}
return "[" + PrintJoin(strings, ", ") + "]";
}
break;
case kBOOL:
{
return ToBool() ? "\"true\"" : "\"false\"";
}
break;
}
return "null";
}
static std::string PrintJoin(const std::vector & strings, const std::string & join)
{
size_t count = 0;
for (const auto & string : strings)
{
count += string.size();
}
std::string resule;
resule.reserve(count);
if (!strings.empty())
{
resule.append(strings.at(0));
for (auto i = 1; i != strings.size(); ++i)
{
resule.append(join);
resule.append(strings.at(i));
}
}
return resule;
}
private:
std::vector _elements;
std::string _string;
std::string _key;
double _number;
JType _type;
friend struct Parser;
};
inline bool operator==(const JValue::JValuePtr & ptr, const std::string & key)
{
return ptr->Key() == key;
}
inline bool operator!=(const JValue::JValuePtr & ptr, const std::string & key)
{
return ptr->Key() != key;
}
从文件读取Json并打印：
auto json = std::move(JValue::FromFile("a.json"));
std::cout << json.ToPrint() << std::endl;
打印结果
a.json文件