使用地图将多行语句转换为单行

我想真正的挑战是拥有一个map<>不区分大小写的键比较。

您可以通过使用比较谓词来做到这一点：

struct ci_less {
    bool operator()(std::string_view a, std::string_view b) const {
        return boost::lexicographical_compare(a, b, boost::is_iless{});
    }
};

您声明地图使用该谓词：

std::map<std::string, int, ci_less> const dataTypes {
    { "INT",      1 },
    { "BIGINT",   2 },
    { "uint8_t",  3 },
    { "uint16_t", 4 },
    { "LONG",     5 },
};

请注意，它现在是const，并且我翻转了键/值对。见下文

一些测试：Live on Coliru

// your sqlBufferTypes[i][j] e.g.:
for (std::string const key : { "uint32_t", "long", "lONg" }) {
    if (auto match = dataTypes.find(key); match != dataTypes.end()) {
        std::cout << std::quoted(key) << " maps to " << match->second;

        // more readable repeats lookup:
        std::cout << " or the same: " << dataTypes.at(key) << "\n"; // throws unless found
    } else {
        std::cout << std::quoted(key) << " not found\n";
    }
}

版画

"uint32_t" not found
"long" maps to 5 or the same: 5
"lONg" maps to 5 or the same: 5

翻转键/值

词典有一个关键字段，可用于所有语言/库的查找。因此，要反向查找，您最终会进行线性搜索（只需查看每个元素）。

在Boost中，您可以通过定义多索引容器来吃蛋糕。

多索引

这可以促进通过多个索引（包括组合键）进行查找。（搜索我的答案以获取更多实际示例）

生活在Coliru

#include <boost/algorithm/string.hpp> // for is_iless et al.
#include <string_view>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <iostream> // for std::cout
#include <iomanip> // for std::quoted
#include <boost/locale.hpp>

namespace bmi = boost::multi_index;

struct ci_less {
    bool operator()(std::string_view a, std::string_view b) const {
        return boost::lexicographical_compare(a, b, boost::is_iless{});
    }
};

struct DbType {
    std::string_view name;
    int type_id;

    friend std::ostream& operator<<(std::ostream& os, DbType const& t) {
        return os << "DbType{" << std::quoted(t.name) << ", " << t.type_id << "}";
    }
};

using Map = bmi::multi_index_container<
    DbType,
    bmi::indexed_by<
        bmi::ordered_unique<
            bmi::tag<struct by_id>,
            bmi::member<DbType, int, &DbType::type_id> >,
        bmi::ordered_unique<
            bmi::tag<struct by_name>,
            bmi::member<DbType, std::string_view, &DbType::name>, ci_less>
    >
>;

int main() {

    Map dataTypes {
        { "INT",      1 },
        { "BIGINT",   2 },
        { "uint8_t",  3 },
        { "uint16_t", 4 },
        { "LONG",     5 },
    };

    auto& idx = dataTypes.get<by_name>();

    // your sqlBufferTypes[i][j] e.g.:
    for (std::string_view const key : { "uint32_t", "long", "lONg" }) {
        if (auto match = idx.find(key); match != idx.end()) {
            std::cout << std::quoted(key) << " -> " << *match << std::endl;
        } else {
            std::cout << std::quoted(key) << " not found\n";
        }
    }
}

版画

"uint32_t" not found
"long" -> DbType{"LONG", 5}
"lONg" -> DbType{"LONG", 5}

双图

Boost Bimap是地图专用的一种专业。它具有较少的选项，特别是增加了operator[]样式界面。

using Map = boost::bimap<
    int,
    boost::bimaps::set_of<std::string_view, ci_less>>;

遗憾的是，构造函数不支持初始化列表，但是我们可以使用迭代器接口，然后使用rightbimap的视图按名称进行查找：

生活在Coliru

static const Map::relation s_mappings[] = {
    { 1, "INT" },
    { 2, "BIGINT" },
    { 3, "uint8_t" },
    { 4, "uint16_t" },
    { 5, "LONG" },
};

Map const dataTypes { std::begin(s_mappings), std::end(s_mappings) };

// your sqlBufferTypes[i][j] e.g.:
auto& vw = dataTypes.right;
for (std::string_view const key : { "uint32_t", "long", "lONg" }) {
    if (auto match = vw.find(key); match != vw.end()) {
        std::cout << std::quoted(key) << " -> " << match->second << "\n";
    } else {
        std::cout << std::quoted(key) << " not found\n";
    }
}

版画

"uint32_t" not found
"long" -> 5
"lONg" -> 5