string_types.hpp

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#pragma once
 
/// @file userver/storages/postgres/io/string_types.hpp
/// @brief Strings I/O support
/// @ingroup userver_postgres_parse_and_format
 
#include <cstring>
#include <string>
#include <string_view>
 
#include <algorithm>
 
#include <userver/storages/postgres/exceptions.hpp>
#include <userver/storages/postgres/io/buffer_io_base.hpp>
#include <userver/storages/postgres/io/traits.hpp>
#include <userver/storages/postgres/io/type_mapping.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace storages::postgres::io {
 
//@{
/** @name const char* formatting */
template <>
struct BufferFormatter<const char*> {
    const char* value;
 
    explicit BufferFormatter(const char* val)
        : value{val}
    {}
 
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        auto sz = std::strlen(value);
        WriteN(buf, value, sz);
    }
 
    template <typename Buffer>
    static void WriteN(Buffer& buf, const char* c, std::size_t n) {
        // Don't copy zero-terminator in binary mode
        while (n > 0 && c[n - 1] == '\0') {
            --n;
        }
        buf.reserve(buf.size() + n);
        std::copy(c, c + n, std::back_inserter(buf));
    }
};
//@}
 
//@{
/** @name char[N] formatting */
template <std::size_t N>
struct BufferFormatter<char[N]> {
    using CharFormatter = BufferFormatter<const char*>;
    const char* value;
 
    explicit BufferFormatter(const char* val)
        : value{val}
    {}
 
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        CharFormatter::WriteN(buf, value, N);
    }
};
 
//@}
 
//@{
/** @name std::string I/O */
template <>
struct BufferFormatter<std::string> {
    using CharFormatter = BufferFormatter<const char*>;
    const std::string& value;
 
    explicit BufferFormatter(const std::string& val)
        : value{val}
    {}
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        CharFormatter::WriteN(buf, value.data(), value.size());
    }
};
 
template <>
struct BufferParser<std::string> {
    std::string& value;
 
    explicit BufferParser(std::string& val)
        : value{val}
    {}
 
    void operator()(const FieldBuffer& buffer);
};
//@}
 
//@{
/** @name string_view I/O */
template <>
struct BufferFormatter<std::string_view> : detail::BufferFormatterBase<std::string_view> {
    using BaseType = detail::BufferFormatterBase<std::string_view>;
    using CharFormatter = BufferFormatter<const char*>;
 
    using BaseType::BaseType;
 
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buffer) const {
        CharFormatter::WriteN(buffer, value.data(), value.size());
    }
};
 
template <>
struct BufferParser<std::string_view> : detail::BufferParserBase<std::string_view> {
    using BaseType = detail::BufferParserBase<std::string_view>;
    using BaseType::BaseType;
 
    void operator()(const FieldBuffer& buffer) {
        using std::swap;
        ValueType tmp{reinterpret_cast<const char*>(buffer.buffer), buffer.length};
        swap(tmp, value);
    }
};
//@}
 
//@{
/** @name char I/O */
template <>
struct BufferFormatter<char> {
    char value;
 
    explicit BufferFormatter(char val)
        : value{val}
    {}
    template <typename Buffer>
    void operator()(const UserTypes&, Buffer& buf) const {
        buf.push_back(value);
    }
};
 
template <>
struct BufferParser<char> {
    char& value;
 
    explicit BufferParser(char& val)
        : value{val}
    {}
 
    void operator()(const FieldBuffer& buffer) {
        if (buffer.length != 1) {
            throw InvalidInputBufferSize{fmt::format("Buffer size {} is invalid for type char", buffer.length)};
        }
        value = *buffer.buffer;
    }
};
//@}
 
//@{
/** @name C++ to PostgreSQL mapping for string types */
template <>
struct CppToSystemPg<const char*> : PredefinedOid<PredefinedOids::kText> {};
template <std::size_t N>
struct CppToSystemPg<char[N]> : PredefinedOid<PredefinedOids::kText> {};
template <>
struct CppToSystemPg<std::string> : PredefinedOid<PredefinedOids::kText> {};
template <>
struct CppToSystemPg<std::string_view> : PredefinedOid<PredefinedOids::kText> {};
template <>
struct CppToSystemPg<char> : PredefinedOid<PredefinedOids::kChar> {};
//@}
 
}  // namespace storages::postgres::io
 
USERVER_NAMESPACE_END