libcruft-util/cruft/util/io.hpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2010-2014 Danny Robson <danny@nerdcruft.net>
 */

#pragma once

#include "std.hpp"
#include "platform.hpp"
#include "posix/fd.hpp"

#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <filesystem>
#include <vector>
#include <streambuf>
#include <functional>


#ifdef PLATFORM_WIN32
#include "win32/windows.hpp"
#else
#define O_BINARY 0
#endif

namespace cruft {
    ///////////////////////////////////////////////////////////////////////////
    /// Reads an entire file into memory in one operation.
    template <typename T = std::byte>
    std::vector<T>
    slurp (std::filesystem::path const&);


    ///------------------------------------------------------------------------
    /// Read the entire contents of a FILE object into memory.
    ///
    /// * This may trigger an arbitrary number of read calls.
    /// * This may block indefinitely depending on the contents of the fd.
    template <typename T = std::byte>
    std::vector<T>
    slurp (FILE *);


    ///------------------------------------------------------------------------
    /// Read the entire contents of a file-descriptor into memory in one
    /// operation.
    ///
    /// * This may trigger an arbitrary number of read calls.
    /// * This may block indefinitely depending on the contents of the fd.
    template <typename T = std::byte>
    std::vector<T>
    slurp (cruft::posix::fd&);


    ///////////////////////////////////////////////////////////////////////////
    /// Repeatedly calls FunctionT to transfer data from a supplied view to a
    /// file-like-object.
    ///
    /// FunctionT must return a view of the consumed data.
    ///
    /// The operation will iterate until the entire view has been consumed and
    /// hence may block for an indefinate period.
    ///
    /// An exception may be throw in the event forward progress is impossible
    /// (depending on the supplied FunctionT).
    ///
    /// TODO: enforce constness of view iterators
    template <
        typename DstT,
        typename FunctionT,
        typename ValueT,
        typename ...Args
    >
    [[nodiscard]] decltype(auto)
    drain (
        DstT &&dst,
        FunctionT &&func,
        cruft::view<ValueT*> const &src,
        Args&& ...args
    ) {
        auto cursor = reinterpret_cast<u08 const*> (src.data ());
        auto remain = src.size () * sizeof (ValueT);

        while (remain) {
            auto count = std::invoke (func, dst, cursor, remain, args...);
            cursor += count;
            remain -= count;
        }

        return src;
    }


    ///////////////////////////////////////////////////////////////////////////
    /// Drains all data from the supplied view `src` to the file-like-object
    /// `dst` by way of repeated calls to `write`.
    ///
    /// Returns a view over the consumed data. This SHOULD always be identical
    /// to `src`.
    template <
        typename DstT,
        typename ValueT
    >
    decltype(auto)
    write (DstT &&dst, cruft::view<ValueT*> const &src)
    {
        constexpr auto func = &std::decay_t<DstT>::write;
        return drain (std::forward<DstT> (dst), func, src);
    }


    ///------------------------------------------------------------------------
    /// Drain the supplied data view into the destination object by calling
    /// pwrite repeatedly.
    ///
    /// Returns a view over the consumed data. This SHOULD always be identical
    /// to `src`.
    template <
        typename DstT,
        typename ValueT
    >
    decltype(auto)
    pwrite (DstT &&dst, cruft::view<ValueT*> const &src, size_t offset)
    {
        return drain (std::forward<DstT> (dst), &std::decay_t<DstT>::pwrite, src, offset);
    }


    ///------------------------------------------------------------------------
    /// Read the number of bytes covered by the destination view from the
    /// source descriptor.
    template <typename SrcT>
    decltype (auto)
    read (SrcT &&src, cruft::view<u08*> dst)
    {
        auto remain = dst;

        while (!remain.empty ()) {
            auto const count = src.read (remain.begin (), remain.size () * sizeof (decltype(dst)::value_type));
            remain = remain.consume (count);
        }

        return dst;
    }


    template <typename ValueT>
    requires (std::is_trivial_v<ValueT>)
    ValueT
    read (cruft::posix::fd &src)
    {
        ValueT res;
        read (src, cruft::make_byte_view<u08> (res));
        return res;
    }


    ///////////////////////////////////////////////////////////////////////////
    class indenter : public std::streambuf {
    protected:
        std::streambuf* m_dest;
        bool            m_line_start;
        std::string     m_indent;
        std::ostream*   m_owner;

    protected:
        virtual int overflow (int ch) override;

    public:
        explicit indenter (std::streambuf* _dest, size_t _indent = 4);
        explicit indenter (std::ostream&   _dest, size_t _indent = 4);

        virtual ~indenter ();
    };

    //-------------------------------------------------------------------------
    // a wrapper type that implicitly indents a single value when passed to an
    // ostream operator.
    template <typename ValueT>
    struct indented {
        explicit indented (const ValueT &_data):
            data (_data)
        { ; }

        const ValueT &data;
    };


    //-------------------------------------------------------------------------
    template <typename ValueT>
    std::ostream&
    operator<< (std::ostream &os, const cruft::indented<ValueT> &value)
    {
        cruft::indenter scoped_indent (os);
        return os << value.data;

    }


    //-------------------------------------------------------------------------
    class scoped_cwd {
        public:
            scoped_cwd ();
            ~scoped_cwd ();

        protected:
            std::string m_original;
    };


    //-------------------------------------------------------------------------
    class path_error : public std::runtime_error {
    public:
        explicit path_error (std::filesystem::path const &path);

        std::filesystem::path const& path (void) const noexcept;

    private:
        std::filesystem::path const m_path;
    };


    class expected_directory_error : public path_error {
        using path_error::path_error;
    };


    class stream_error : public std::exception {
    public:
        const char* what (void) const noexcept override
        { return "error on C stream"; }
    };
}

#ifdef PLATFORM_WIN32
#include "io_win32.hpp"
#else
#include "io_posix.hpp"
#endif