/* -*- Mode: C++; c-basic-offset:4 ; -*- */
/*
 *  (C) 2001 by Argonne National Laboratory.
 *      See COPYRIGHT in top-level directory.
 */

#include <windows.h>
#include <stdio.h>
#include <time.h>

/* This function returns a pointer to the section header containing the RVA. Return NULL on error */
template < typename NTHeaderType > static inline PIMAGE_SECTION_HEADER GetSecHeader(DWORD rva,
                                                                                    NTHeaderType *
                                                                                    pNTHeader)
{
    PIMAGE_SECTION_HEADER section;
    section = IMAGE_FIRST_SECTION(pNTHeader);
    for (int i = 0; i < pNTHeader->FileHeader.NumberOfSections; i++, section++) {
        DWORD size = section->Misc.VirtualSize;
        DWORD secRVA = section->VirtualAddress;
        if ((secRVA <= rva) && (rva < (secRVA + size))) {
            return section;
        }
    }
    return NULL;
}

/* This function returns the real address from the RVA. Returns NULL on error */
template < typename NTHeaderType > static inline LPVOID GetRealAddrFromRVA(DWORD rva,
                                                                           NTHeaderType * pNTHeader,
                                                                           PBYTE imageBase)
{
    PIMAGE_SECTION_HEADER pSectionHdr = GetSecHeader(rva, pNTHeader);
    if (!pSectionHdr) {
        return NULL;
    }
    /* Since we map the DLL manually we need to calculate mapShift to get the real addr */
    INT mapShift = (INT) (pSectionHdr->VirtualAddress - pSectionHdr->PointerToRawData);

    return (PVOID) (imageBase + rva - mapShift);
}

/* This function reads the exported symbols from a dll/exe and prints a DLL definition file, compatible with gcc,
   with those symbols.
    INPUT:
        pImageBase  : Pointer to the base of the dll image, offset = 0
        pNTHeader   : Pointer to the NT header (32-bit/64-bit) section of image.
*/
template < typename NTHeaderType > void PrintDefFileWithExpSymbols(PBYTE pImageBase,
                                                                   NTHeaderType * pNTHeader)
{
    /* Export Section RVA */
    DWORD expSecRVA =
        pNTHeader->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress;

    /* From RVA get the real addrs for the various components of the exports section */
    PIMAGE_EXPORT_DIRECTORY pExportDir =
        (PIMAGE_EXPORT_DIRECTORY) GetRealAddrFromRVA(expSecRVA, pNTHeader, pImageBase);
    PDWORD pszFuncNames =
        (PDWORD) GetRealAddrFromRVA(pExportDir->AddressOfNames, pNTHeader, pImageBase);

    printf("EXPORTS\n");

    for (unsigned int i = 0; i < pExportDir->NumberOfFunctions; i++) {
        /* FIXME: Assumes that the current DLL does not have ordinal nums */
        if (i < pExportDir->NumberOfNames) {
            /* Ordinal numbers start at 1 - not 0 */
            printf("\t%s @ %d ;\n", GetRealAddrFromRVA(pszFuncNames[i], pNTHeader, pImageBase),
                   i + 1);
        } else {
            break;
        }
    }
}

static void HelpUsage(char *exe_name)
{
    printf("Usage: %s <DLLNAME>\n", exe_name);
    printf
        ("\t\t The tool reads the export section from <DLLNAME> and prints the definition file for gcc to stdout\n");
}

int main(int argc, char *argv[])
{
    HANDLE hFile, hFileMapping;
    LPVOID lpFileBase;
    PIMAGE_DOS_HEADER pImgHeader;
    PIMAGE_NT_HEADERS pImgNTHeader;
    PIMAGE_NT_HEADERS64 pImgNTHeader64;

    if ((argc < 2) || (strcmp(argv[1], "/?") == 0) || (strcmp(argv[1], "--help") == 0)) {
        HelpUsage(argv[0]);
        exit(1);
    }

    /* Open the DLL and map it to memory */
    hFile =
        CreateFile(argv[1], GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING,
                   FILE_ATTRIBUTE_NORMAL, 0);
    if (hFile == INVALID_HANDLE_VALUE) {
        printf("Unable to open dll, %s\n", argv[1]);
        exit(-1);
    }

    hFileMapping = CreateFileMapping(hFile, NULL, PAGE_READONLY, 0, 0, NULL);
    if (hFileMapping == 0) {
        CloseHandle(hFile);
        printf("Cannot open file mapping for dll, %s\n", argv[1]);
        exit(-1);
    }

    lpFileBase = MapViewOfFile(hFileMapping, FILE_MAP_READ, 0, 0, 0);
    if (lpFileBase == 0) {
        CloseHandle(hFileMapping);
        CloseHandle(hFile);
        printf("Cannot map view of dll, %s\n", argv[1]);
        exit(-1);
    }

    /* pImgHeader points to the MS-DOS HEADER section, offset=0, of dll */
    pImgHeader = (PIMAGE_DOS_HEADER) lpFileBase;

    /* pImgNTHeader points to the NT HEADER section of the dll, pImgHeader + <File address of new exe header> */
    pImgNTHeader = (PIMAGE_NT_HEADERS) ((DWORD_PTR) pImgHeader + (DWORD_PTR) pImgHeader->e_lfanew);

    /* In the case of the 64-bit dlls, the Optional header section within NT header has 64-bit fields */
    pImgNTHeader64 = (PIMAGE_NT_HEADERS64) pImgNTHeader;

    /* The Magic number is always a WORD. This number is used to determine if the dll is 32-bit or 64-bit */
    if (pImgNTHeader->OptionalHeader.Magic == IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
        /* 64-bit dll */
        PrintDefFileWithExpSymbols((PBYTE) pImgHeader, pImgNTHeader64);
    } else {
        /* 32-bit dll */
        PrintDefFileWithExpSymbols((PBYTE) pImgHeader, pImgNTHeader);
    }

    UnmapViewOfFile(lpFileBase);
    CloseHandle(hFileMapping);
    CloseHandle(hFile);
}