Objective-C Runtime Object Using MSVC

/***
 * File: StrBuff.c
 * AUTHOR:  FX. J. Adi Lima ( adi7598@gmail.com )
 * DESCRIPTION:
 *      A simple implementation of MSVC DLL which link against GNU libobjc.
 *      This module implements a simple StringBuffer object, creatable from Objective-C.
 *      The resulting Objective-C interface should be:
 *
 *      // typedef for Range (unsigned __int64)
 *      typedef unsigned __int64 Range;
 *      #define MakeRange(vStart, vEnd) (Range)(((Range)(vEnd) << 32) | (vEnd & 0xFFFFFFFF))
 *      @interface StringBuffer {
 *          Class isa;
 *      }
 *      + stringWithString:(id)aString;
 *      + stringWithFormat:(LPCWSTR)pszFormat, ...;
 *      - retain;
 *      - (void) release;
 *      - (LPCWSTR) string;
 *      - (UINT) length;
 *      - (StringBuffer*) description;
 *      - (LPCWSTR) concatW:(LPCWSTR)pszFormat, ...;
 *      - (StringBuffer*) substringFromRange:(Range)range;
 *      @end
 *
 *      // You should also define the following
 *      __inline LPCSTR __objc_class_name_StringBuffer() { return "StringBuffer"; }
 *
 *      // And use the StringBuffer object like normal.
 *      // Ah, yes... please load the DLL first!!! (and free it when done)
*/

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <string.h>

HINSTANCE hDllInstance = NULL;
HINSTANCE hObjc = NULL;

typedef struct objc_class *Class;
typedef struct objc_object *id;
typedef struct objc_selector *SEL;
typedef struct objc_protocol *Protocol;

struct objc_class { Class isa; };
struct objc_object { Class isa; };
typedef id (*IMP)(id _self, SEL _cmd, ...);

id (*objc_getClass)(LPCSTR) = NULL;
id (*objc_allocateClassPair)(Class, LPCSTR, size_t) = NULL;
void (*objc_registerClassPair)(Class) = NULL;
Protocol (*objc_getProtocol)(LPCSTR) = NULL;

LPCSTR (*class_getName)(Class) = NULL;
int (*class_addMethod)(Class, SEL, IMP, LPCSTR) = NULL;
int (*class_addIvar)(Class, LPCSTR, size_t, BYTE, LPCSTR) = NULL;
IMP (*class_getMethodImplementation)(Class, SEL) = NULL;

SEL (*selector)(LPCSTR) = NULL;
LPCSTR (*selectorName)(SEL) = NULL;
BOOL (*selectorEqual)(SEL, SEL) = NULL;

static int LoadFunctions(FARPROC* buffer, LPCSTR pszFirst, ...)
{
    FARPROC* pp = buffer;
    LPCSTR psz = pszFirst;
    int nRes = 0;
    va_list args;
    va_start(args, pszFirst);
    while (psz)
    {
        *pp = GetProcAddress(hObjc, psz);
        if (*pp) ++nRes;
        pp++;
        psz = va_arg(args, LPCSTR);
    }
    return nRes;
}

BYTE log2Of(size_t ilen)
{
    size_t n = ilen;
    BYTE ret = 0;
    while ((n >>= 1) != 0) ++ret;
    return ret;
}

typedef struct CSTR {
    Class isa;
    LPCSTR pszText;
    UINT length;
} CSTR;

static Class __stringBufferClass = NULL;
typedef unsigned __int64 UInt64;

typedef struct __GFSTRING {
    Class isa;
    LPWSTR lpw;
    size_t length;
    DWORD dwRef;
} GFSTRING, *LPGFSTRING;

static Class GFStringInitialize(Class cls);
static LPGFSTRING GFStringCreateWithString(Class cls, SEL _cmd, CSTR* pStr);
static LPGFSTRING GFStringCreateWithFormat(Class cls, SEL _cmd, LPCWSTR pszFormat, ...);
static LPGFSTRING GFStringRetain(LPGFSTRING pThis);
static void GFStringRelease(LPGFSTRING pThis);
static LPCWSTR GFStringGetString(LPGFSTRING pThis);
static UINT GFStringGetLength(LPGFSTRING pThis);
static LPGFSTRING GFStringGetDescription(LPGFSTRING pThis);
static LPCWSTR GFStringConcatW(LPGFSTRING pThis, SEL _cmd, LPCWSTR pszFormat, ...);
static LPGFSTRING GFStringSubstringFromRange(LPGFSTRING pThis, SEL _cmd, UInt64 range);

static BOOL GFStringRegisterClass(void)
{
    Class c = (Class)objc_allocateClassPair(NULL, "StringBuffer", 0);
    if (!c) return FALSE;
    class_addIvar(c, "isa", sizeof(Class), log2Of(sizeof(Class)), "#");
    class_addMethod(c->isa, selector("initialize"), (IMP)GFStringInitialize, "##");
    class_addMethod(c->isa, selector("stringWithString:"), (IMP)GFStringCreateWithString, "@#:@");
    class_addMethod(c, selector("stringWithFormat:"), (IMP)GFStringCreateWithFormat, "@#:*");
    class_addMethod(c, selector("retain"), (IMP)GFStringRetain, "@@:");
    class_addMethod(c, selector("release"), (IMP)GFStringRelease, "v@:");
    class_addMethod(c, selector("string"), (IMP)GFStringGetString, "*@:");
    class_addMethod(c, selector("length"), (IMP)GFStringGetLength, "I@:");
    class_addMethod(c, selector("description"), (IMP)GFStringGetDescription, "@@:");
    class_addMethod(c, selector("concatW:"), (IMP)GFStringConcatW, "*@:*");
    class_addMethod(c, selector("substringFromRange:"), (IMP)GFStringSubstringFromRange, "@@:Q");
    objc_registerClassPair(c);
    __stringBufferClass = c;
    return TRUE;
}

BOOL DllMain(HINSTANCE hInstance, DWORD dwReason, LPVOID lpReserved)
{
    if (dwReason == DLL_PROCESS_ATTACH)
    {
        hDllInstance = hInstance;
        /* the following hardcoded path should be replaced according to what you need */
        if (hObjc = LoadLibrary(L"E:\\mingw64\\bin\\libobjc-4.dll"))
        {
            FARPROC buffer[10];
            int nRes = LoadFunctions(buffer, "objc_getClass", "objc_allocateClassPair",
                "objc_registerClassPair", "objc_getProtocol", NULL);
            if (!nRes) return FALSE;
            objc_getClass = (id (*)(LPCSTR))buffer[0];
            objc_allocateClassPair = (id (*)(Class, LPCSTR, size_t))buffer[1];
            objc_registerClassPair = (void (*)(Class))buffer[2];
            objc_getProtocol = (Protocol (*)(LPCSTR))buffer[3];
            nRes = LoadFunctions(buffer, "class_getName", "class_addMethod", "class_addIvar", "class_getMethodImplementation", NULL);
            if (!nRes) return FALSE;
            class_getName = (LPCSTR(*)(Class))buffer[0];
            class_addMethod = (int(*)(Class, SEL, IMP, LPCSTR))buffer[1];
            class_addIvar = (int(*)(Class, LPCSTR, size_t, BYTE, LPCSTR))buffer[2];
            class_getMethodImplementation = (IMP(*)(Class, SEL))buffer[3];
            nRes = LoadFunctions(buffer, "sel_registerName", "sel_getName", "sel_isEqual", NULL);
            if (!nRes) return FALSE;
            selector = (SEL(*)(LPCSTR))buffer[0];
            selectorName = (LPCSTR(*)(SEL))buffer[1];
            selectorEqual = (BOOL(*)(SEL, SEL))buffer[2];
            return GFStringRegisterClass();
        }
        return FALSE;
    }
    else if (dwReason == DLL_PROCESS_DETACH)
    {
        if (hObjc)
        {
            FreeLibrary(hObjc);
            hObjc = NULL;
        }
    }
    return TRUE;
}

static Class GFStringInitialize(Class cls) {
    return cls;
}

static LPGFSTRING GFStringCreateWithString(Class cls, SEL _cmd, CSTR* pStr) {
    LPGFSTRING pObj = (LPGFSTRING)malloc(sizeof(GFSTRING));
    size_t len = 0;
    memset(pObj, 0, sizeof(GFSTRING));
    pObj->isa = cls;
    len = MultiByteToWideChar(CP_UTF8, 0, pStr->pszText, lstrlenA(pStr->pszText),
        NULL, 0) ;
    pObj->lpw = (LPWSTR)malloc(sizeof(wchar_t) * len);
    pObj->lpw[len-1] = 0;
    MultiByteToWideChar(CP_UTF8, 0, pStr->pszText, lstrlenA(pStr->pszText),
        pObj->lpw, len);
    pObj->dwRef = 1;
    pObj->length = len;
    return pObj;
}

static LPGFSTRING GFStringCreateWithFormat(Class cls, SEL _cmd, LPCWSTR pszFormat, ...) {
    LPWSTR temp = NULL;
    size_t len = 0;
    va_list args;
    LPGFSTRING pObj = (LPGFSTRING)malloc(sizeof(GFSTRING));
    memset(pObj, 0, sizeof(GFSTRING));
    pObj->isa = cls;

    va_start(args, pszFormat);
    len = _vscwprintf(pszFormat, args) + 1;
    temp = (LPWSTR)malloc(sizeof(WCHAR) * len);
    vswprintf_s(temp, len, pszFormat, args);
    va_end(args);

    pObj->lpw = temp;
    pObj->length = len;
    pObj->dwRef = 1;
    return pObj;
}

static LPGFSTRING GFStringRetain(LPGFSTRING pThis) {
    ++pThis->dwRef;
    return pThis;
}

static void GFStringRelease(LPGFSTRING pThis) {
    if (--pThis->dwRef) return;
    if (pThis->lpw) {
        free(pThis->lpw);
        pThis->lpw = NULL;
        pThis->length = 0;
    }
    free((void*)pThis);
}

static LPCWSTR GFStringGetString(LPGFSTRING pThis) {
    return (LPCWSTR)pThis->lpw;
}

static UINT GFStringGetLength(LPGFSTRING pThis) {
    return (UINT)lstrlenW(pThis->lpw);
}

static LPGFSTRING GFStringGetDescription(LPGFSTRING pThis) {
    LPGFSTRING retVal = NULL;
    LPWSTR lpw = NULL;
    size_t len = lstrlenW(pThis->lpw) + 150;
    lpw = (LPWSTR)malloc(sizeof(WCHAR) * len);
    wsprintfW(lpw, L"<GFString 0x%p { string = %s, length = %lu }>",
        pThis, pThis->lpw, pThis->length);
    retVal = (LPGFSTRING)malloc(sizeof(GFSTRING));
    retVal->isa = pThis->isa;
    retVal->lpw = lpw;
    retVal->length = len;
    retVal->dwRef = 1;
    return retVal;
}

static LPCWSTR GFStringConcatW(LPGFSTRING pThis, SEL _cmd, LPCWSTR pszFormat, ...) {
    LPWSTR lpw = NULL;
    LPWSTR temp = NULL;
    size_t len, total;
    va_list args;
    va_start(args, pszFormat);
    len = _vscwprintf(pszFormat, args) + 1;
    temp = (LPWSTR)malloc(sizeof(WCHAR) * len);
    vswprintf_s(temp, len, pszFormat, args);
    va_end(args);
    total = lstrlenW(pThis->lpw) + len;
    lpw = (LPWSTR)malloc(sizeof(WCHAR) * total);
    lstrcpyW(lpw, pThis->lpw);
    lstrcatW(lpw, temp);
    free(temp);
    free(pThis->lpw);
    pThis->lpw = lpw;
    pThis->length = total;
    return lpw;
}

static LPGFSTRING GFStringSubstringFromRange(LPGFSTRING pThis, SEL _cmd, UInt64 range) {
    LPGFSTRING pObj = NULL;
    size_t nStart = (size_t)(range & 0xFFFFFFFF);
    size_t nEnd = (size_t)((range >> 32) & 0xFFFFFFFF);
    size_t total = nEnd - nStart;
    size_t i;
    LPWSTR p1, p2;

    if ((nEnd >= lstrlenW(pThis->lpw)) || (total > lstrlenW(pThis->lpw))) {
        OutputDebugString(L"Invalid range specified!\n");
        return NULL;
    }
    pObj = (LPGFSTRING)malloc(sizeof(GFSTRING));
    memset(pObj, 0, sizeof(GFSTRING));
    pObj->isa = pThis->isa;
    pObj->lpw = (LPWSTR)malloc(sizeof(WCHAR) * (total+1));
    pObj->lpw[total] = 0;

    p1 = &pThis->lpw[nStart];
    p2 = pObj->lpw;
    for (i = 0; i < total; i++)
        *p2++ = *p1++;

    pObj->length = lstrlenW(pObj->lpw);
    pObj->dwRef = 1;
    return pObj;
}