// Copyright 2014-2015 Renato Tegon Forti, Antony Polukhin.
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)

#ifndef BOOST_DLL_DETAIL_POSIX_PATH_FROM_HANDLE_HPP
#define BOOST_DLL_DETAIL_POSIX_PATH_FROM_HANDLE_HPP

#include <boost/config.hpp>
#include <boost/dll/detail/system_error.hpp>
#include <boost/dll/detail/posix/program_location_impl.hpp>
#include <boost/filesystem/path.hpp>
#include <boost/predef/os.h>

#ifdef BOOST_HAS_PRAGMA_ONCE
# pragma once
#endif

// for dlinfo
#include <dlfcn.h>

#if BOOST_OS_MACOS || BOOST_OS_IOS
#   include <mach-o/dyld.h>
#   include <mach-o/nlist.h>
#   include <cstddef> // for std::ptrdiff_t

namespace boost { namespace dll { namespace detail {
    inline void* strip_handle(void* handle) BOOST_NOEXCEPT {
        return reinterpret_cast<void*>(
            (reinterpret_cast<std::ptrdiff_t>(handle) >> 2) << 2
        );
    }

    inline boost::filesystem::path path_from_handle(void* handle, boost::system::error_code &ec) {
        handle = strip_handle(handle);

        // Iterate through all images currently in memory
        // https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/dyld.3.html
        const std::size_t count = _dyld_image_count(); // not thread safe: other thread my [un]load images
        for (std::size_t i = 0; i <= count; ++i) {
            // on last iteration `i` is equal to `count` which is out of range, so `_dyld_get_image_name`
            // will return NULL. `dlopen(NULL, RTLD_LAZY)` call will open the current executable.
            const char* image_name = _dyld_get_image_name(i);
            void* probe_handle = dlopen(image_name, RTLD_LAZY);
            dlclose(probe_handle);

            // If the handle is the same as what was passed in (modulo mode bits), return this image name
            if (handle == strip_handle(probe_handle)) {
                return image_name;
            }
        }

        ec = boost::system::error_code(
            boost::system::errc::bad_file_descriptor,
            boost::system::generic_category()
        );

        return boost::filesystem::path();
    }

}}} // namespace boost::dll::detail

#else // #if BOOST_OS_MACOS || BOOST_OS_IOS

#if BOOST_OS_QNX
// QNX's copy of <elf.h> and <link.h> reside in sys folder
#   include <sys/link.h>
#else
#   include <link.h>    // struct link_map
#endif

namespace boost { namespace dll { namespace detail {

#if BOOST_OS_ANDROID || BOOST_OS_QNX
    // Android and QNX miss struct link_map. QNX misses ElfW macro, so avoiding it.
    struct link_map {
        void *l_addr;   // Base address shared object is loaded at
        char *l_name;   // Absolute file name object was found in
        // ...          // Ignoring remaning parts of the structure
    };
#endif // #if BOOST_OS_ANDROID

    inline boost::filesystem::path path_from_handle(void* handle, boost::system::error_code &ec) {
        // RTLD_DI_LINKMAP (RTLD_DI_ORIGIN returns only folder and is not suitable for this case)
        // Obtain the Link_map for the handle  that  is  specified.
        // The  p  argument  points to a Link_map pointer (Link_map
        // **p). The actual storage for the Link_map  structure  is
        // maintained by ld.so.1.
        //
        // Unfortunately we can not use `dlinfo(handle, RTLD_DI_LINKMAP, &link_map) < 0`
        // because it is not supported on MacOS X 10.3, NetBSD 3.0, OpenBSD 3.8, AIX 5.1,
        // HP-UX 11, IRIX 6.5, OSF/1 5.1, Cygwin, mingw, Interix 3.5, BeOS.
        // Fortunately investigating the sources of open source projects brought the understanding, that
        // `handle` is just a `struct link_map*` that contains full library name.

        const struct link_map* link_map = 0;
#if BOOST_OS_BSD_FREE
        // FreeBSD has it's own logic http://code.metager.de/source/xref/freebsd/libexec/rtld-elf/rtld.c
        // Fortunately it has the dlinfo call.
        if (dlinfo(handle, RTLD_DI_LINKMAP, &link_map) < 0) {
            link_map = 0;
        }
#else
        link_map = static_cast<const struct link_map*>(handle);
#endif
        if (!link_map) {
            ec = boost::system::error_code(
                boost::system::errc::bad_file_descriptor,
                boost::system::generic_category()
            );

            return boost::filesystem::path();
        }

        if (!link_map->l_name || *link_map->l_name == '\0') {
            return program_location_impl(ec);
        }

        return boost::filesystem::path(link_map->l_name);
    }

}}} // namespace boost::dll::detail

#endif // #if BOOST_OS_MACOS || BOOST_OS_IOS

#endif // BOOST_DLL_DETAIL_POSIX_PATH_FROM_HANDLE_HPP