从C控制台应用程序调用的CRC32汇编器函数 [英] CRC32 assembler function called from C console app

问题描述

我正在尝试使用C代码从外部文件调用asm函数.它构建良好，但结果却不是预期的那样.我看到的是一些奇怪的字符，而不是文件校验和.

I'm trying to call asm function from external file in C code. It builds fine but the result is not as it's supposed to be. Instead of file checksum, I see some strange characters.

    #include <stdio.h>
    #include <stdlib.h>
    #include <sys/stat.h>

    extern "C" unsigned long __stdcall CRC32(size_t sizeOfFile, char buffer[]);


    int fsize(char* file) {
        int size;
        FILE* fh;

        fopen_s(&fh, file, "rb" );
        if(fh != NULL){
            if( fseek(fh, 0, SEEK_END) ){
                fclose(fh);
                return -1;
            }

            size = ftell(fh);
            fclose(fh);
            return size;
        }

        return -1; //error
    }

    void calculateChecksum(char * filename, char * checksum){
        FILE *file = NULL;

        unsigned long crc32;


        char hex[10];
        fopen_s(&file, filename, "rb" );
        size_t size = fsize(filename);
        char *buffer=(char*)malloc(size);
        fread_s(buffer,size,size,1,file);
        crc32=CRC32(size,buffer);
        int n = sprintf_s(hex,"%x",crc32);

        for (int i=0;i<8;i++){
            checksum[i]=hex[i];
        }
        fclose(file);
        file = NULL;
    }




    int main(){
        char checksum[8];
        calculateChecksum("B:\\secretMessageC#.txt",checksum);

        char hex[10];

        for (int i=0;i<8;i++){
            checksum[i]=hex[i];
            printf("%c",checksum[i]);
        }

        getchar();
        return 0;
    }

我的外部Assember代码:

My external Assember code:

    .586
    .model flat, stdcall 
    .xmm
    .data
    .code
    CRC32 proc sizeOfFile:DWORD, file:DWORD
        push    esi
        push    ecx
        push    edx

        mov esi, file
        xor edx, edx
        or  eax, -1
        mov ecx, sizeOfFile

    CRC32_loop:
        mov dl, byte ptr [esi]
        xor dl, al
        shr eax, 8
        xor eax, dword ptr [crc32_table + 4*edx]
        inc esi
        dec ecx
        jnz CRC32_loop

        not eax

        pop edx
        pop ecx
        pop esi
        ret
            CRC32 endp
    crc32_table dd 000000000h, 077073096h, 0EE0E612Ch, 0990951BAh, 0076DC419h, 0706AF48Fh, 0E963A535h, 09E6495A3h, 00EDB8832h, 079DCB8A4h
                dd 0E0D5E91Eh, 097D2D988h, 009B64C2Bh, 07EB17CBDh, 0E7B82D07h, 090BF1D91h, 01DB71064h, 06AB020F2h, 0F3B97148h, 084BE41DEh
                dd 01ADAD47Dh, 06DDDE4EBh, 0F4D4B551h, 083D385C7h, 0136C9856h, 0646BA8C0h, 0FD62F97Ah, 08A65C9ECh, 014015C4Fh, 063066CD9h
                dd 0FA0F3D63h, 08D080DF5h, 03B6E20C8h, 04C69105Eh, 0D56041E4h, 0A2677172h, 03C03E4D1h, 04B04D447h, 0D20D85FDh, 0A50AB56Bh
                dd 035B5A8FAh, 042B2986Ch, 0DBBBC9D6h, 0ACBCF940h, 032D86CE3h, 045DF5C75h, 0DCD60DCFh, 0ABD13D59h, 026D930ACh, 051DE003Ah
                dd 0C8D75180h, 0BFD06116h, 021B4F4B5h, 056B3C423h, 0CFBA9599h, 0B8BDA50Fh, 02802B89Eh, 05F058808h, 0C60CD9B2h, 0B10BE924h
                dd 02F6F7C87h, 058684C11h, 0C1611DABh, 0B6662D3Dh, 076DC4190h, 001DB7106h, 098D220BCh, 0EFD5102Ah, 071B18589h, 006B6B51Fh
                dd 09FBFE4A5h, 0E8B8D433h, 07807C9A2h, 00F00F934h, 09609A88Eh, 0E10E9818h, 07F6A0DBBh, 0086D3D2Dh, 091646C97h, 0E6635C01h
                dd 06B6B51F4h, 01C6C6162h, 0856530D8h, 0F262004Eh, 06C0695EDh, 01B01A57Bh, 08208F4C1h, 0F50FC457h, 065B0D9C6h, 012B7E950h
                dd 08BBEB8EAh, 0FCB9887Ch, 062DD1DDFh, 015DA2D49h, 08CD37CF3h, 0FBD44C65h, 04DB26158h, 03AB551CEh, 0A3BC0074h, 0D4BB30E2h
                dd 04ADFA541h, 03DD895D7h, 0A4D1C46Dh, 0D3D6F4FBh, 04369E96Ah, 0346ED9FCh, 0AD678846h, 0DA60B8D0h, 044042D73h, 033031DE5h 
                dd 0AA0A4C5Fh, 0DD0D7CC9h, 05005713Ch, 0270241AAh, 0BE0B1010h, 0C90C2086h, 05768B525h, 0206F85B3h, 0B966D409h, 0CE61E49Fh
                dd 05EDEF90Eh, 029D9C998h, 0B0D09822h, 0C7D7A8B4h, 059B33D17h, 02EB40D81h, 0B7BD5C3Bh, 0C0BA6CADh, 0EDB88320h, 09ABFB3B6h
                dd 003B6E20Ch, 074B1D29Ah, 0EAD54739h, 09DD277AFh, 004DB2615h, 073DC1683h, 0E3630B12h, 094643B84h, 00D6D6A3Eh, 07A6A5AA8h 
                dd 0E40ECF0Bh, 09309FF9Dh, 00A00AE27h, 07D079EB1h, 0F00F9344h, 08708A3D2h, 01E01F268h, 06906C2FEh, 0F762575Dh, 0806567CBh
                dd 0196C3671h, 06E6B06E7h, 0FED41B76h, 089D32BE0h, 010DA7A5Ah, 067DD4ACCh, 0F9B9DF6Fh, 08EBEEFF9h, 017B7BE43h, 060B08ED5h
                dd 0D6D6A3E8h, 0A1D1937Eh, 038D8C2C4h, 04FDFF252h, 0D1BB67F1h, 0A6BC5767h, 03FB506DDh, 048B2364Bh, 0D80D2BDAh, 0AF0A1B4Ch
                dd 036034AF6h, 041047A60h, 0DF60EFC3h, 0A867DF55h, 0316E8EEFh, 04669BE79h, 0CB61B38Ch, 0BC66831Ah, 0256FD2A0h, 05268E236h
                dd 0CC0C7795h, 0BB0B4703h, 0220216B9h, 05505262Fh, 0C5BA3BBEh, 0B2BD0B28h, 02BB45A92h, 05CB36A04h, 0C2D7FFA7h, 0B5D0CF31h
                dd 02CD99E8Bh, 05BDEAE1Dh, 09B64C2B0h, 0EC63F226h, 0756AA39Ch, 0026D930Ah, 09C0906A9h, 0EB0E363Fh, 072076785h, 005005713h
                dd 095BF4A82h, 0E2B87A14h, 07BB12BAEh, 00CB61B38h, 092D28E9Bh, 0E5D5BE0Dh, 07CDCEFB7h, 00BDBDF21h, 086D3D2D4h, 0F1D4E242h 
                dd 068DDB3F8h, 01FDA836Eh, 081BE16CDh, 0F6B9265Bh, 06FB077E1h, 018B74777h, 088085AE6h, 0FF0F6A70h, 066063BCAh, 011010B5Ch
                dd 08F659EFFh, 0F862AE69h, 0616BFFD3h, 0166CCF45h, 0A00AE278h, 0D70DD2EEh, 04E048354h, 03903B3C2h, 0A7672661h, 0D06016F7h
                dd 04969474Dh, 03E6E77DBh, 0AED16A4Ah, 0D9D65ADCh, 040DF0B66h, 037D83BF0h, 0A9BCAE53h, 0DEBB9EC5h, 047B2CF7Fh, 030B5FFE9h
                dd 0BDBDF21Ch, 0CABAC28Ah, 053B39330h, 024B4A3A6h, 0BAD03605h, 0CDD70693h, 054DE5729h, 023D967BFh, 0B3667A2Eh, 0C4614AB8h
                dd 05D681B02h, 02A6F2B94h, 0B40BBE37h, 0C30C8EA1h, 05A05DF1Bh, 02D02EF8Dh   
    end

推荐答案

您的calculateChecksum命名错误，并且操作方式错误.

Your calculateChecksum is kind of mis-named, and also works the wrong way.

• 您没有正确检查fread_s()是否真的读取了所有请求的字节. (也许我在这里错了...)
• 您缺少字符串后的终止NUL字节.
• 您没有free(buffer)，所以您发生了内存泄漏.

• You do not correctly check if fread_s() has really read all of the requested bytes. (Maybe I'm wrong here...)
• You are missing the terminating NUL byte after the string.
• You do not free(buffer), so you have a memory leak.

如果满足这些条件，则可以

If these conditions are fulfilled, you can do

printf("%s", hex);

在main()函数中.

但是，您做的事情太复杂了.

However, you do things much too complicated.

我会

void calculateChecksum(char * filename, unsigned long * crc32){
    FILE *file;
    fopen_s(&file, filename, "rb");
    size_t size = fsize(filename);
    char *buffer = malloc(size);
    // TODO: If (!buffer) -> bail out.
    size_t td, crsr=0;
    do {
        rd = fread_s(buffer+crsr,size-crsr,size-crsr,1,file);
        if (rd > 0) crsr += rd;
    } while (rd > 0 && crsr < size)
    fclose(file);

    *crc32=CRC32(size,buffer);
    free(buffer);
}

这将为调用者提供CRC32直接作为unsigned long，可直接使用printf("%08lx", crc32)打印.

This gives the caller the CRC32 directly as an unsigned long which directly can be printed using printf("%08lx", crc32).

(顺便说一句，增强您的CRC32()以将CRC的初始值作为第三个参数可能会更好.在这种情况下，可以对CRC进行逐块计算.)

(BTW, it might be nicer to enhance your CRC32() to take the init value for the CRC as 3rd parameter. In this case, a blockwise calculation of the CRC would be possible.)

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