Adding external assembler function to C project - c

Question

I'm trying to call assembler procedure which is supposed to calculate CRC32 checksum for file from C app.
C code:
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
extern 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;
}
Assember code:
.686
.387
.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
While bulding, I'm getting those three errors:
1>------ Build started: Project: ConsoleApplication5, Configuration: Debug Win32 ------
1> Assembling C:\Users\sliwkacz\Desktop\New folder\crc32.asm...
1>C:\Users\sliwkacz\Desktop\New folder\crc32.asm(7): error A2206: missing operator in expression
1>C:\Users\sliwkacz\Desktop\New folder\crc32.asm(12): error A2006: undefined symbol : file
1>C:\Users\sliwkacz\Desktop\New folder\crc32.asm(15): error A2081: missing operand after unary operator
1>C:\Program Files (x86)\MSBuild\Microsoft.Cpp\v4.0\V110\BuildCustomizations\masm.targets(49,5): error MSB3721: The command "ml.exe /c /nologo /Zi /Fo"Debug\crc32.obj" /W3 /errorReport:prompt /Ta"C:\Users\sliwkacz\Desktop\New folder\crc32.asm"" exited with code 1.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
I'll be very greatful for any hint that can helps.

Answer 1

size is a reserved word in MASM assembly, so you'll have to come up with a different name for your parameter.
You're also missing a CRC32 ENDP after the ret.
And you might have to change the function declaration in your C file to extern unsigned long __stdcall CRC32(size_t *bufLen, FILE *file);
By the looks of it, your CRC32 function is using its arguments in an incorrect manner. The size argument is a pointer to the size, but you're using it as if it was the size itself. And it seems like you try to read from a FILE* as if was a pointer to the data in the file, but I'm pretty sure a FILE* is just a pointer to a struct containing information about an opened file. To access the data in the file you should use fread to read chunks of data into a buffer.