C++ RPC ORM 高速解析

支持所有常用编程语

https://capnproto.org/
GitHub - capnproto/capnproto: Cap'n Proto serialization/RPC system - core tools and C++ library
https://capnproto.org/capnproto-c++-win32-1.0.2.zip

常用命令：
   capnp help
   capnp compile -oc++ myschema.capnp
   capnp decode myschema.capnp MyType < message.bin > message.txt
   capnp encode myschema.capnp MyType < message.txt > message.bin
   capnp eval myschema.capnp myConstant

myschema.capnp:

@0xa8712255ec118b18;
struct Person {
id @0 :UInt32;
name @1 :Text;
email @2 :Text;
phones @3 :List(PhoneNumber);

struct PhoneNumber {
number @0 :Text;
type @1 :Type;

enum Type {
mobile @0;
home @1;
work @2;
}
}

employment :union {
unemployed @4 :Void;
employer @5 :Text;
school @6 :Text;
selfEmployed @7 :Void;
# We assume that a person is only one of these.
}
}

struct AddressBook {
people @0 :List(Person);
}

示例代码：
   #include "myschema.capnp.h"
   #include <capnp/message.h>
   #include <capnp/serialize-packed.h>
   #include <iostream>

void writeAddressBook(int fd) {
::capnp::MallocMessageBuilder message;

AddressBook::Builder addressBook = message.initRoot<AddressBook>();
::capnp::List<Person>::Builder people = addressBook.initPeople(2);

       Person::Builder alice = people[0];
       alice.setId(123);
       alice.setName("Alice");
       alice.setEmail("alice@example.com");
       // Type shown for explanation purposes; normally you'd use auto.
       ::capnp::List<Person::PhoneNumber>::Builder alicePhones =
           alice.initPhones(1);
       alicePhones[0].setNumber("555-1212");
       alicePhones[0].setType(Person::PhoneNumber::Type::MOBILE);
       alice.getEmployment().setSchool("MIT");

       Person::Builder bob = people[1];
       bob.setId(456);
       bob.setName("Bob");
       bob.setEmail("bob@example.com");
       auto bobPhones = bob.initPhones(2);
       bobPhones[0].setNumber("555-4567");
       bobPhones[0].setType(Person::PhoneNumber::Type::HOME);
       bobPhones[1].setNumber("555-7654");
       bobPhones[1].setType(Person::PhoneNumber::Type::WORK);
       bob.getEmployment().setUnemployed();

writePackedMessageToFd(fd, message);
}

void printAddressBook(int fd) {
::capnp::PackedFdMessageReader message(fd);

AddressBook::Reader addressBook = message.getRoot<AddressBook>();

       for (Person::Reader person : addressBook.getPeople()) {
           std::cout << person.getName().cStr() << ": "
               << person.getEmail().cStr() << std::endl;
           for (Person::PhoneNumber::Reader phone : person.getPhones()) {
               const char* typeName = "UNKNOWN";
               switch (phone.getType()) {
               case Person::PhoneNumber::Type::MOBILE: typeName = "mobile"; break;
               case Person::PhoneNumber::Type::HOME: typeName = "home"; break;
               case Person::PhoneNumber::Type::WORK: typeName = "work"; break;
               }
               std::cout << " " << typeName << " phone: "
                   << phone.getNumber().cStr() << std::endl;
           }
           Person::Employment::Reader employment = person.getEmployment();
           switch (employment.which()) {
           case Person::Employment::UNEMPLOYED:
               std::cout << " unemployed" << std::endl;
               break;
           case Person::Employment::EMPLOYER:
               std::cout << " employer: "
                   << employment.getEmployer().cStr() << std::endl;
               break;
           case Person::Employment::SCHOOL:
               std::cout << " student at: "
                   << employment.getSchool().cStr() << std::endl;
               break;
           case Person::Employment::SELF_EMPLOYED:
               std::cout << " self-employed" << std::endl;
               break;
           }
       }
   }

   void test() {
       auto file = fopen("example.bin", "wt+");
       if (!file)
           return;
       int fd = fileno(file); //如果是W+ 这里文件被清空的影响
       writeAddressBook(fd);
       fclose(file);
       fflush(file);
       file = fopen("example.bin", "rb+");
       fd = fileno(file);
       printAddressBook(fd);
       fclose(file);
   }

运行输出：
   Alice: alice@example.com
   mobile phone: 555-1212
   student at: MIT
   Bob: bob@example.com
   home phone: 555-4567
   work phone: 555-7654
   unemployed

其它类似参考：
GitHub - protocolbuffers/protobuf: Protocol Buffers - Google's data interchange format
evanw (Evan Wallace) · GitHub