使用 C++ 类进行封装的 SQLite3

sqlite3pp

该库对SQLite3 API使用C++类进行包装，支持几乎所有SQLite3功能（打开数据库、查询、执行命令、事物等）。

示例代码如下：

database 数据库

sqlite3pp::database db("test.db");
db.execute("INSERT INTO contacts (name, phone) VALUES ('Mike', '555-1234')");

command 命令

sqlite3pp::command cmd(
  db, "INSERT INTO contacts (name, phone) VALUES (?, ?)");
cmd.binder() << "Mike" << "555-1234";
cmd.execute();
sqlite3pp::command cmd(db, "INSERT INTO contacts (name, phone) VALUES (?, ?)");
cmd.bind(1, "Mike", sqlite3pp::nocopy);
cmd.bind(2, "555-1234", sqlite3pp::nocopy);
cmd.execute();
sqlite3pp::command cmd(
  db, "INSERT INTO contacts (name, phone) VALUES (?100, ?101)");
cmd.bind(100, "Mike", sqlite3pp::nocopy);
cmd.bind(101, "555-1234", sqlite3pp::nocopy);
cmd.execute();
sqlite3pp::command cmd(
  db, "INSERT INTO contacts (name, phone) VALUES (:user, :phone)");
cmd.bind(":user", "Mike", sqlite3pp::nocopy);
cmd.bind(":phone", "555-1234", sqlite3pp::nocopy);
cmd.execute();
sqlite3pp::command cmd(
  db,  "INSERT INTO contacts (name, phone) VALUES (:user, '555-0000');"
  "INSERT INTO contacts (name, phone) VALUES (:user, '555-1111');"
  "INSERT INTO contacts (name, phone) VALUES (:user, '555-2222')");
cmd.bind(":user", "Mike", sqlite3pp::nocopy);
cmd.execute_all();

transaction 事务

sqlite3pp::transaction xct(db);
{
  sqlite3pp::command cmd(
    db, "INSERT INTO contacts (name, phone) VALUES (:user, :phone)");
  cmd.bind(":user", "Mike", sqlite3pp::nocopy);
  cmd.bind(":phone", "555-1234", sqlite3pp::nocopy);
  cmd.execute();
}
xct.rollback();

query 查询

sqlite3pp::query qry(db, "SELECT id, name, phone FROM contacts");for (int i = 0; i < qry.column_count(); ++i) {
  cout << qry.column_name(i) << "\t";
}
for (sqlite3pp::query::iterator i = qry.begin(); i != qry.end(); ++i) {  for (int j = 0; j < qry.column_count(); ++j) {
    cout << (*i).get(j) << "\t";
  }
  cout << endl;
}
for (sqlite3pp::query::iterator i = qry.begin(); i != qry.end(); ++i) {  int id;  char const* name, *phone;  std::tie(id, name, phone) =
    (*i).get_columns(0, 1, 2);
  cout << id << "\t" << name << "\t" << phone << endl;
}
for (sqlite3pp::query::iterator i = qry.begin(); i != qry.end(); ++i) {
  string name, phone;
  (*i).getter() >> sqlite3pp::ignore >> name >> phone;
  cout << "\t" << name << "\t" << phone << endl;
}
for (auto v : qry) {
  string name, phone;
  v.getter() >> sqlite3pp::ignore >> name >> phone;
  cout << "\t" << name << "\t" << phone << endl;
}

attach

sqlite3pp::database db("foods.db");
db.attach("test.db", "test");

sqlite3pp::query qry(
  db,  "SELECT epi.* FROM episodes epi, test.contacts con WHERE epi.id = con.id");

backup 备份

sqlite3pp::database db("test.db");
sqlite3pp::database backupdb("backup.db");

db.backup(backupdb);
db.backup(
  backupdb,
  [](int pagecount, int remaining, int rc) {
    cout << pagecount << "/" << remaining << endl;if (rc == SQLITE_OK || rc == SQLITE_BUSY || rc == SQLITE_LOCKED) {      // sleep or do nothing.}
  });

callback 回调

struct rollback_handler{  void operator()() {
    cout << "handle_rollback" << endl;
  }
};

sqlite3pp::database db("test.db");

db.set_commit_handler([]{ cout << "handle_commit\n"; return 0; });
db.set_rollback_handler(rollback_handler());
int handle_authorize(int evcode, char const* p1, char const* p2,                     char const* dbname, char const* tvname) {
  cout << "handle_authorize(" << evcode << ")" << endl;  return 0;
}

db.set_authorize_handler(&handle_authorize);
struct handler{  handler() : cnt_(0) {}  void handle_update(int opcode, char const* dbname,                     char const* tablename, int64_t rowid) {
    cout << "handle_update(" << opcode << ", " << dbname << ", " << tablename << ", " << rowid << ") - " << cnt_++ << endl;
  }  int cnt_;
};using namespace std::placeholders;db.set_update_handler(std::bind(&handler::handle_update, &h, _1, _2, _3, _4));

function

int test0()
{  return 100;
}

sqlite3pp::database db("test.db");
sqlite3pp::ext::function func(db);

func.create("test0", &test0);
void test1(sqlite3pp::ext::context& ctx)
{
  ctx.result(200);
}void test2(sqlite3pp::ext::context& ctx)
{
  string args = ctx.get(0);
  ctx.result(args);
}void test3(sqlite3pp::ext::context& ctx)
{
  ctx.result_copy(0);
}

func.create("test1", &test1);
func.create("test2", &test2, 1);
func.create("test3", &test3, 1);
func.create("test4", []{ return 500; });
string test5(string const& value)
{  return value;
}

string test6(string const& s1, string const& s2, string const& s3)
{  return s1 + s2 + s3;
}

func.create("test5", [](int i){ return i + 10000; });
func.create("test6", &test6);
sqlite3pp::query qry(
  db,  "SELECT test0(), test1(), test2('x'), test3('y'), test4(), test5(10), "
  "test6('a', 'b', 'c')");

aggregate

void step(sqlite3pp::ext::context& c)
{  int* sum = (int*) c.aggregate_data(sizeof(int));

  *sum += c.get(0);
}void finalize(sqlite3pp::ext::context& c)
{  int* sum = (int*) c.aggregate_data(sizeof(int));
  c.result(*sum);
}

sqlite3pp::database db("foods.db");
sqlite3pp::ext::aggregate aggr(db);

aggr.create("aggr0", &step, &finalize);
struct mycnt{  void step() {
    ++n_;
  }  int finish() {return n_;
  }  int n_;
};

aggr.create("aggr1");
struct strcnt{  void step(string const& s) {
    s_ += s;
  }  int finish() {return s_.size();
  }
  string s_;
};struct plussum{  void step(int n1, int n2) {
    n_ += n1 + n2;
  }  int finish() {return n_;
  }  int n_;
};

aggr.create("aggr2");
aggr.create("aggr3");
sqlite3pp::query qry(
  db,  "SELECT aggr0(id), aggr1(type_id), aggr2(name), aggr3(id, type_id) "
  "FROM foods");

loadable extension 加载扩展

#define SQLITE3PP_LOADABLE_EXTENSION#include int sqlite3_extension_init(
  sqlite3 *pdb,  char **pzErrMsg,  const sqlite3_api_routines *pApi) {  SQLITE_EXTENSION_INIT2(pApi);
  sqlite3pp:database db(sqlite3pp::ext::borrow(pdb));  // pdb is not closed since db just borrows it.}

本文来自云栖社区合作伙伴“开源中国”

本文作者：王练

原文链接