/**
 * Extract symbols from a Mach-O object file.
 *
 * Copyright:   Copyright (C) 1999-2020 by The D Language Foundation, All Rights Reserved
 * Authors:     $(LINK2 http://www.digitalmars.com, Walter Bright)
 * License:     $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/dmd/scanmach.d, _scanmach.d)
 * Documentation:  https://dlang.org/phobos/dmd_scanmach.html
 * Coverage:    https://codecov.io/gh/dlang/dmd/src/master/src/dmd/scanmach.d
 */

module dmd.scanmach;

version(OSX):

import core.stdc.string;
import core.stdc.stdint;
import core.sys.darwin.mach.loader;
import dmd.globals;
import dmd.errors;

private enum LOG = false;

/*****************************************
 * Reads an object module from base[] and passes the names
 * of any exported symbols to (*pAddSymbol)().
 * Params:
 *      pAddSymbol =  function to pass the names to
 *      base =        array of contents of object module
 *      module_name = name of the object module (used for error messages)
 *      loc =         location to use for error printing
 */
void scanMachObjModule(void delegate(const(char)[] name, int pickAny) pAddSymbol,
        const(ubyte)[] base, const(char)* module_name, Loc loc)
{
    static if (LOG)
    {
        printf("scanMachObjModule(%s)\n", module_name);
    }

    void corrupt(int reason)
    {
        error(loc, "corrupt Mach-O object module `%s` %d", module_name, reason);
    }

    const buf = base.ptr;
    const buflen = base.length;
    uint32_t ncmds;
    mach_header* header = cast(mach_header*)buf;
    mach_header_64* header64 = null;
    /* First do sanity checks on object file
     */
    if (buflen < mach_header.sizeof)
        return corrupt(__LINE__);

    if (header.magic == MH_MAGIC)
    {
        if (header.cputype != CPU_TYPE_I386)
        {
            error(loc, "Mach-O object module `%s` has cputype = %d, should be %d", module_name, header.cputype, CPU_TYPE_I386);
            return;
        }
        if (header.filetype != MH_OBJECT)
        {
            error(loc, "Mach-O object module `%s` has file type = %d, should be %d", module_name, header.filetype, MH_OBJECT);
            return;
        }
        if (buflen < mach_header.sizeof + header.sizeofcmds)
            return corrupt(__LINE__);
        ncmds = header.ncmds;
    }
    else if (header.magic == MH_MAGIC_64)
    {
        header64 = cast(mach_header_64*)buf;
        if (buflen < mach_header_64.sizeof)
            return corrupt(__LINE__);
        if (header64.cputype != CPU_TYPE_X86_64)
        {
            error(loc, "Mach-O object module `%s` has cputype = %d, should be %d", module_name, header64.cputype, CPU_TYPE_X86_64);
            return;
        }
        if (header64.filetype != MH_OBJECT)
        {
            error(loc, "Mach-O object module `%s` has file type = %d, should be %d", module_name, header64.filetype, MH_OBJECT);
            return;
        }
        if (buflen < mach_header_64.sizeof + header64.sizeofcmds)
            return corrupt(__LINE__);
        ncmds = header64.ncmds;
    }
    else
        return corrupt(__LINE__);

    symtab_command* symtab_commands;
    // Commands immediately follow mach_header
    char* commands = cast(char*)buf + (header.magic == MH_MAGIC_64 ? mach_header_64.sizeof : mach_header.sizeof);
    for (uint32_t i = 0; i < ncmds; i++)
    {
        load_command* command = cast(load_command*)commands;
        //printf("cmd = 0x%02x, cmdsize = %u\n", command.cmd, command.cmdsize);
        if (command.cmd == LC_SYMTAB)
            symtab_commands = cast(symtab_command*)command;
        commands += command.cmdsize;
    }

    if (!symtab_commands)
        return;

    // Get pointer to string table
    char* strtab = cast(char*)buf + symtab_commands.stroff;
    if (buflen < symtab_commands.stroff + symtab_commands.strsize)
        return corrupt(__LINE__);

    if (header.magic == MH_MAGIC_64)
    {
        // Get pointer to symbol table
        nlist_64* symtab = cast(nlist_64*)(cast(char*)buf + symtab_commands.symoff);
        if (buflen < symtab_commands.symoff + symtab_commands.nsyms * nlist_64.sizeof)
            return corrupt(__LINE__);

        // For each symbol
        for (int i = 0; i < symtab_commands.nsyms; i++)
        {
            nlist_64* s = symtab + i;
            const(char)* name = strtab + s.n_strx;
            const namelen = strlen(name);
            if (s.n_type & N_STAB)
            {
                // values in /usr/include/mach-o/stab.h
                //printf(" N_STAB");
                continue;
            }

            version (none)
            {
                if (s.n_type & N_PEXT)
                {
                }
                if (s.n_type & N_EXT)
                {
                }
            }
            switch (s.n_type & N_TYPE)
            {
            case N_UNDF:
                if (s.n_type & N_EXT && s.n_value != 0) // comdef
                    pAddSymbol(name[0 .. namelen], 1);
                break;
            case N_ABS:
                break;
            case N_SECT:
                if (s.n_type & N_EXT) /*&& !(s.n_desc & N_REF_TO_WEAK)*/
                    pAddSymbol(name[0 .. namelen], 1);
                break;
            case N_PBUD:
                break;
            case N_INDR:
                break;
            default:
                break;
            }

        }
    }
    else
    {
        // Get pointer to symbol table
        nlist* symtab = cast(nlist*)(cast(char*)buf + symtab_commands.symoff);
        if (buflen < symtab_commands.symoff + symtab_commands.nsyms * nlist.sizeof)
            return corrupt(__LINE__);

        // For each symbol
        for (int i = 0; i < symtab_commands.nsyms; i++)
        {
            nlist* s = symtab + i;
            const(char)* name = strtab + s.n_strx;
            const namelen = strlen(name);
            if (s.n_type & N_STAB)
            {
                // values in /usr/include/mach-o/stab.h
                //printf(" N_STAB");
                continue;
            }

            version (none)
            {
                if (s.n_type & N_PEXT)
                {
                }
                if (s.n_type & N_EXT)
                {
                }
            }
            switch (s.n_type & N_TYPE)
            {
            case N_UNDF:
                if (s.n_type & N_EXT && s.n_value != 0) // comdef
                    pAddSymbol(name[0 .. namelen], 1);
                break;
            case N_ABS:
                break;
            case N_SECT:
                if (s.n_type & N_EXT) /*&& !(s.n_desc & N_REF_TO_WEAK)*/
                    pAddSymbol(name[0 .. namelen], 1);
                break;
            case N_PBUD:
                break;
            case N_INDR:
                break;
            default:
                break;
            }
        }
    }
}

private: // for the remainder of this module

enum CPU_TYPE_I386 = 7;
enum CPU_TYPE_X86_64 = CPU_TYPE_I386 | 0x1000000;

enum MH_OBJECT = 0x1;

struct segment_command
{
    uint32_t cmd;
    uint32_t cmdsize;
    char[16] segname;
    uint32_t vmaddr;
    uint32_t vmsize;
    uint32_t fileoff;
    uint32_t filesize;
    int32_t  maxprot;
    int32_t  initprot;
    uint32_t nsects;
    uint32_t flags;
}

struct segment_command_64
{
    uint32_t cmd;
    uint32_t cmdsize;
    char[16] segname;
    uint64_t vmaddr;
    uint64_t vmsize;
    uint64_t fileoff;
    uint64_t filesize;
    int32_t  maxprot;
    int32_t  initprot;
    uint32_t nsects;
    uint32_t flags;
}

struct symtab_command
{
    uint32_t cmd;
    uint32_t cmdsize;
    uint32_t symoff;
    uint32_t nsyms;
    uint32_t stroff;
    uint32_t strsize;
}

struct dysymtab_command
{
    uint32_t cmd;
    uint32_t cmdsize;
    uint32_t ilocalsym;
    uint32_t nlocalsym;
    uint32_t iextdefsym;
    uint32_t nextdefsym;
    uint32_t iundefsym;
    uint32_t nundefsym;
    uint32_t tocoff;
    uint32_t ntoc;
    uint32_t modtaboff;
    uint32_t nmodtab;
    uint32_t extrefsymoff;
    uint32_t nextrefsyms;
    uint32_t indirectsymoff;
    uint32_t nindirectsyms;
    uint32_t extreloff;
    uint32_t nextrel;
    uint32_t locreloff;
    uint32_t nlocrel;
}

enum LC_SEGMENT    = 1;
enum LC_SYMTAB     = 2;
enum LC_DYSYMTAB   = 11;
enum LC_SEGMENT_64 = 0x19;

struct load_command
{
    uint32_t cmd;
    uint32_t cmdsize;
}

enum N_EXT  = 1;
enum N_STAB = 0xE0;
enum N_PEXT = 0x10;
enum N_TYPE = 0x0E;
enum N_UNDF = 0;
enum N_ABS  = 2;
enum N_INDR = 10;
enum N_PBUD = 12;
enum N_SECT = 14;

struct nlist
{
    int32_t n_strx;
    uint8_t n_type;
    uint8_t n_sect;
    int16_t n_desc;
    uint32_t n_value;
}

struct nlist_64
{
    uint32_t n_strx;
    uint8_t n_type;
    uint8_t n_sect;
    uint16_t n_desc;
    uint64_t n_value;
}
