string_reader.h

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#pragma once
 
#include "di/container/algorithm/copy.h"
#include "di/container/string/encoding.h"
#include "di/container/string/mutable_string.h"
#include "di/container/string/string.h"
#include "di/container/string/utf8_encoding.h"
#include "di/meta/core.h"
#include "di/meta/operations.h"
#include "di/meta/vocab.h"
#include "di/util/bit_cast.h"
#include "di/util/declval.h"
#include "di/vocab/error/prelude.h"
#include "di/vocab/span/as_bytes.h"
 
namespace di::io {
template<concepts::detail::ConstantString String>
class StringReader {
public:
    template<typename U>
    requires(concepts::ConstructibleFrom<String, U>)
    constexpr explicit StringReader(U&& buffer) : m_buffer(util::forward<U>(buffer)) {}
 
    constexpr auto read_some(vocab::Span<byte> data) -> usize {
        auto to_read = container::min(data.size(), m_buffer.size_bytes() - m_byte_offset);
 
        for (auto i : view::range(to_read)) {
            data[i] = read_byte();
        }
 
        return to_read;
    }
    constexpr auto read_some(vocab::Span<byte> data) -> usize {…}
 
private:
    constexpr auto read_byte() -> byte {
        using CodeUnit = meta::EncodingCodeUnit<meta::Encoding<String>>;
        constexpr auto code_unit_size = sizeof(CodeUnit);
 
        auto word_index = m_byte_offset / code_unit_size;
        auto byte_index = m_byte_offset % code_unit_size;
 
        auto code_units = m_buffer.span();
        auto code_unit = code_units[word_index];
        auto as_bytes = util::bit_cast<vocab::Array<byte, code_unit_size>>(code_unit);
 
        m_byte_offset++;
        return as_bytes[byte_index];
    }
 
    String m_buffer;
    usize m_byte_offset { 0 };
};
class StringReader {…};
 
template<typename String>
StringReader(String&&) -> StringReader<String>;
}
 
namespace di {
using io::StringReader;
}