/**
 * Written in the D programming language.
 * This module provides Win32-specific support for sections.
 *
 * Copyright: Copyright Digital Mars 2008 - 2012.
 * License: Distributed under the
 *      $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost Software License 1.0).
 *    (See accompanying file LICENSE)
 * Authors:   Walter Bright, Sean Kelly, Martin Nowak
 * Source: $(DRUNTIMESRC rt/_sections_win64.d)
 */

module rt.sections_win64;

version (CRuntime_Microsoft):

// debug = PRINTF;
debug(PRINTF) import core.stdc.stdio;
import core.stdc.stdlib : malloc, free;
import core.sys.windows.winbase : FreeLibrary, GetProcAddress, LoadLibraryA, LoadLibraryW;
import core.sys.windows.winnt : WCHAR;
import rt.deh, rt.minfo;

version (LDC) { /* implemented in rt.sections_elf_shared, we just need some helpers */ } else
{

struct SectionGroup
{
    static int opApply(scope int delegate(ref SectionGroup) dg)
    {
        return dg(_sections);
    }

    static int opApplyReverse(scope int delegate(ref SectionGroup) dg)
    {
        return dg(_sections);
    }

    @property immutable(ModuleInfo*)[] modules() const nothrow @nogc
    {
        return _moduleGroup.modules;
    }

    @property ref inout(ModuleGroup) moduleGroup() inout return nothrow @nogc
    {
        return _moduleGroup;
    }

    version (DigitalMars)
    version (Win64)
    @property immutable(FuncTable)[] ehTables() const nothrow @nogc
    {
        auto pbeg = cast(immutable(FuncTable)*)&_deh_beg;
        auto pend = cast(immutable(FuncTable)*)&_deh_end;
        return pbeg[0 .. pend - pbeg];
    }

    @property inout(void[])[] gcRanges() inout nothrow @nogc
    {
        return _gcRanges[];
    }

private:
    ModuleGroup _moduleGroup;
    void[][] _gcRanges;
}

shared(bool) conservative;

/****
 * Gets called on program startup just before GC is initialized.
 */
void initSections() nothrow @nogc
{
    auto doshdr = cast(IMAGE_DOS_HEADER*) &__ImageBase;

    _sections._moduleGroup = ModuleGroup(getModuleInfos(doshdr));

    // the ".data" image section includes both object file sections ".data" and ".bss"
    void[] dataSection = findImageSection(doshdr, ".data");
    debug(PRINTF) printf("found .data section: [%p,+%llx]\n", dataSection.ptr,
                         cast(ulong)dataSection.length);

    import rt.sections;
    conservative = !scanDataSegPrecisely();

    version (LDC)
    {
        /* FIXME: Precise DATA/TLS GC scanning requires compiler support
         * (emitting mutable pointers into special sections bracketed
         * by _{D,T}P_{beg,end} symbols).
         */
        _sections._gcRanges = (cast(void[]*) malloc((void[]).sizeof))[0..1];
        _sections._gcRanges[0] = dataSection;
    }
    else if (conservative)
    {
        _sections._gcRanges = (cast(void[]*) malloc((void[]).sizeof))[0..1];
        _sections._gcRanges[0] = dataSection;
    }
    else
    {
        size_t count = &_DP_end - &_DP_beg;
        auto ranges = cast(void[]*) malloc(count * (void[]).sizeof);
        size_t r = 0;
        void* prev = null;
        for (size_t i = 0; i < count; i++)
        {
            auto off = (&_DP_beg)[i];
            if (off == 0) // skip zero entries added by incremental linking
                continue; // assumes there is no D-pointer at the very beginning of .data
            void* addr = dataSection.ptr + off;
            debug(PRINTF) printf("  scan %p\n", addr);
            // combine consecutive pointers into single range
            if (prev + (void*).sizeof == addr)
                ranges[r-1] = ranges[r-1].ptr[0 .. ranges[r-1].length + (void*).sizeof];
            else
                ranges[r++] = (cast(void**)addr)[0..1];
            prev = addr;
        }
        _sections._gcRanges = ranges[0..r];
    }
}

/***
 * Gets called on program shutdown just after GC is terminated.
 */
void finiSections() nothrow @nogc
{
    .free(cast(void*)_sections.modules.ptr);
    .free(_sections._gcRanges.ptr);
}

/***
 * Called once per thread; returns array of thread local storage ranges
 */
void[] initTLSRanges() nothrow @nogc
{
    void* pbeg;
    void* pend;
    // with VS2017 15.3.1, the linker no longer puts TLS segments into a
    //  separate image section. That way _tls_start and _tls_end no
    //  longer generate offsets into .tls, but DATA.
    // Use the TEB entry to find the start of TLS instead and read the
    //  length from the TLS directory
    version (D_InlineAsm_X86)
    {
        asm @nogc nothrow
        {
            mov EAX, _tls_index;
            mov ECX, FS:[0x2C];     // _tls_array
            mov EAX, [ECX+4*EAX];
            mov pbeg, EAX;
            add EAX, [_tls_used+4]; // end
            sub EAX, [_tls_used+0]; // start
            mov pend, EAX;
        }
    }
    else version (D_InlineAsm_X86_64)
    {
        asm @nogc nothrow
        {
            xor RAX, RAX;
            mov EAX, _tls_index;
            mov RCX, 0x58;
            mov RCX, GS:[RCX];      // _tls_array (immediate value causes fixup)
            mov RAX, [RCX+8*RAX];
            mov pbeg, RAX;
            add RAX, [_tls_used+8]; // end
            sub RAX, [_tls_used+0]; // start
            mov pend, RAX;
        }
    }
    else
        static assert(false, "Architecture not supported.");

    return pbeg[0 .. pend - pbeg];
}

void finiTLSRanges(void[] rng) nothrow @nogc
{
}

void scanTLSRanges(void[] rng, scope void delegate(void* pbeg, void* pend) nothrow dg) nothrow
{
    version (LDC)
    {
        // FIXME
        dg(rng.ptr, rng.ptr + rng.length);
    }
    else if (conservative)
    {
        dg(rng.ptr, rng.ptr + rng.length);
    }
    else
    {
        for (auto p = &_TP_beg; p < &_TP_end; )
        {
            uint beg = *p++;
            uint end = beg + cast(uint)((void*).sizeof);
            while (p < &_TP_end && *p == end)
            {
                end += (void*).sizeof;
                p++;
            }
            dg(rng.ptr + beg, rng.ptr + end);
        }
    }
}

} // !LDC

private:

///////////////////////////////////////////////////////////////////////////////
// Compiler to runtime interface.
///////////////////////////////////////////////////////////////////////////////

version (LDC) {} else
{
    __gshared SectionGroup _sections;

    extern(C)
    {
        extern __gshared void* _minfo_beg;
        extern __gshared void* _minfo_end;
    }
}

package immutable(ModuleInfo*)[] getModuleInfos(IMAGE_DOS_HEADER* doshdr) nothrow @nogc
out (result)
{
    foreach (m; result)
        assert(m !is null);
}
do
{
    version (LDC)
    {
        // the ".minfo" section consists of pointers to all ModuleInfos defined in object files linked into the image
        void[] minfoSection = findImageSection(doshdr, ".minfo");
        auto m = (cast(immutable(ModuleInfo*)*)minfoSection.ptr)[0 .. minfoSection.length / size_t.sizeof];
    }
    else
    {
        auto m = (cast(immutable(ModuleInfo*)*)&_minfo_beg)[1 .. &_minfo_end - &_minfo_beg];
    }

    /* Because of alignment inserted by the linker, various null pointers
     * are there. We need to filter them out.
     */

    // count non-null pointers
    size_t count;
    foreach (mi; m)
        if (mi !is null) ++count;

    if (count == m.length)
        return m;

    auto result = (cast(immutable(ModuleInfo)**) malloc(count * size_t.sizeof))[0 .. count];

    count = 0;
    foreach (mi; m)
        if (mi !is null) result[count++] = mi;

    return cast(immutable) result;
}

extern(C)
{
    /* Symbols created by the compiler/linker and inserted into the
     * object file that 'bracket' sections.
     */
    extern __gshared
    {
        void* __ImageBase;

        void* _deh_beg;
        void* _deh_end;

        uint _DP_beg;
        uint _DP_end;
        uint _TP_beg;
        uint _TP_end;

        void*[2] _tls_used; // start, end
        int _tls_index;
    }
}

///////////////////////////////////////////////////////////////////////////////
// dynamic loading
///////////////////////////////////////////////////////////////////////////////

/***********************************
 * These are a temporary means of providing a GC hook for DLL use.  They may be
 * replaced with some other similar functionality later.
 */
extern (C)
{
    void* gc_getProxy();
    void  gc_setProxy(void* p);
    void  gc_clrProxy();

    alias void  function(void*) gcSetFn;
    alias void  function()      gcClrFn;
}

version (LDC) version (Shared) version = LDC_Shared;

version (LDC_Shared) { /* in rt.sections_elf_shared */ } else
{

/*******************************************
 * Loads a DLL written in D with the name 'name'.
 * Returns:
 *      opaque handle to the DLL if successfully loaded
 *      null if failure
 */
extern (C) void* rt_loadLibrary(const char* name)
{
    return initLibrary(.LoadLibraryA(name));
}

extern (C) void* rt_loadLibraryW(const WCHAR* name)
{
    return initLibrary(.LoadLibraryW(name));
}

void* initLibrary(void* mod)
{
    // BUG: LoadLibrary() call calls rt_init(), which fails if proxy is not set!
    // (What? LoadLibrary() is a Windows API call, it shouldn't call rt_init().)
    if (mod is null)
        return mod;
    gcSetFn gcSet = cast(gcSetFn) GetProcAddress(mod, "gc_setProxy");
    if (gcSet !is null)
    {   // BUG: Set proxy, but too late
        gcSet(gc_getProxy());
    }
    return mod;
}

/*************************************
 * Unloads DLL that was previously loaded by rt_loadLibrary().
 * Input:
 *      ptr     the handle returned by rt_loadLibrary()
 * Returns:
 *      1   succeeded
 *      0   some failure happened
 */
extern (C) int rt_unloadLibrary(void* ptr)
{
    gcClrFn gcClr  = cast(gcClrFn) GetProcAddress(ptr, "gc_clrProxy");
    if (gcClr !is null)
        gcClr();
    return FreeLibrary(ptr) != 0;
}

} // !LDC_Shared

///////////////////////////////////////////////////////////////////////////////
// PE/COFF program header iteration
///////////////////////////////////////////////////////////////////////////////

enum IMAGE_DOS_SIGNATURE = 0x5A4D;      // MZ

package struct IMAGE_DOS_HEADER // DOS .EXE header
{
    ushort   e_magic;    // Magic number
    ushort[29] e_res2;   // Reserved ushorts
    int      e_lfanew;   // File address of new exe header
}

struct IMAGE_FILE_HEADER
{
    ushort Machine;
    ushort NumberOfSections;
    uint   TimeDateStamp;
    uint   PointerToSymbolTable;
    uint   NumberOfSymbols;
    ushort SizeOfOptionalHeader;
    ushort Characteristics;
}

struct IMAGE_NT_HEADERS
{
    uint Signature;
    IMAGE_FILE_HEADER FileHeader;
    // optional header follows
}

struct IMAGE_SECTION_HEADER
{
    char[8] Name = 0;
    union {
        uint   PhysicalAddress;
        uint   VirtualSize;
    }
    uint   VirtualAddress;
    uint   SizeOfRawData;
    uint   PointerToRawData;
    uint   PointerToRelocations;
    uint   PointerToLinenumbers;
    ushort NumberOfRelocations;
    ushort NumberOfLinenumbers;
    uint   Characteristics;
}

bool compareSectionName(ref IMAGE_SECTION_HEADER section, string name) nothrow @nogc
{
    if (name[] != section.Name[0 .. name.length])
        return false;
    return name.length == 8 || section.Name[name.length] == 0;
}

package void[] findImageSection(IMAGE_DOS_HEADER* doshdr, string name) nothrow @nogc
{
    if (name.length > 8) // section name from string table not supported
        return null;
    if (doshdr.e_magic != IMAGE_DOS_SIGNATURE)
        return null;

    auto nthdr = cast(IMAGE_NT_HEADERS*) (cast(void*)doshdr + doshdr.e_lfanew);
    auto sections = cast(IMAGE_SECTION_HEADER*) (cast(void*)nthdr + IMAGE_NT_HEADERS.sizeof + nthdr.FileHeader.SizeOfOptionalHeader);
    for (ushort i = 0; i < nthdr.FileHeader.NumberOfSections; i++)
        if (compareSectionName(sections[i], name))
            return (cast(void*)doshdr + sections[i].VirtualAddress)[0 .. sections[i].VirtualSize];

    return null;
}
