Static library in C, compiled with MSVC, called from MASM app

[MichaelW]

I did this for another purpose, but I think it could be useful here. The C source is from the Wikipedia MD5 page, with the main function removed and a few other modifications, all commented with a leading "////".

md5.c:

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/*
* Simple MD5 implementation
*
* Compile with: gcc -o md5 md5.c
*/
////#include <stdio.h>  //// Not needed.
////#include <stdlib.h> //// Not needed.
#include <string.h>
////#include <stdint.h> //// Not for MSVC, replaced with typedefs below:

typedef unsigned char uint8_t;
typedef unsigned int uint32_t;

// Constants are the integer part of the sines of integers (in radians) * 2^32.
const uint32_t k[64] = {
0xd76aa478, 0xe8c7b756, 0x242070db, 0xc1bdceee ,
0xf57c0faf, 0x4787c62a, 0xa8304613, 0xfd469501 ,
0x698098d8, 0x8b44f7af, 0xffff5bb1, 0x895cd7be ,
0x6b901122, 0xfd987193, 0xa679438e, 0x49b40821 ,
0xf61e2562, 0xc040b340, 0x265e5a51, 0xe9b6c7aa ,
0xd62f105d, 0x02441453, 0xd8a1e681, 0xe7d3fbc8 ,
0x21e1cde6, 0xc33707d6, 0xf4d50d87, 0x455a14ed ,
0xa9e3e905, 0xfcefa3f8, 0x676f02d9, 0x8d2a4c8a ,
0xfffa3942, 0x8771f681, 0x6d9d6122, 0xfde5380c ,
0xa4beea44, 0x4bdecfa9, 0xf6bb4b60, 0xbebfbc70 ,
0x289b7ec6, 0xeaa127fa, 0xd4ef3085, 0x04881d05 ,
0xd9d4d039, 0xe6db99e5, 0x1fa27cf8, 0xc4ac5665 ,
0xf4292244, 0x432aff97, 0xab9423a7, 0xfc93a039 ,
0x655b59c3, 0x8f0ccc92, 0xffeff47d, 0x85845dd1 ,
0x6fa87e4f, 0xfe2ce6e0, 0xa3014314, 0x4e0811a1 ,
0xf7537e82, 0xbd3af235, 0x2ad7d2bb, 0xeb86d391 };

// r specifies the per-round shift amounts
const uint32_t r[] = {7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22, 7, 12, 17, 22,
                      5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20, 5,  9, 14, 20,
                      4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23, 4, 11, 16, 23,
                      6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21, 6, 10, 15, 21};

// leftrotate function definition
#define LEFTROTATE(x, c) (((x) << (c)) | ((x) >> (32 - (c))))

void to_bytes(uint32_t val, uint8_t *bytes)
{
    bytes[0] = (uint8_t) val;
    bytes[1] = (uint8_t) (val >> 8);
    bytes[2] = (uint8_t) (val >> 16);
    bytes[3] = (uint8_t) (val >> 24);
}

uint32_t to_int32(uint8_t *bytes)
{
    return (uint32_t) bytes[0]
        | ((uint32_t) bytes[1] << 8)
        | ((uint32_t) bytes[2] << 16)
        | ((uint32_t) bytes[3] << 24);
}

void md5(uint8_t *initial_msg, size_t initial_len, uint8_t *digest) {

    // These vars will contain the hash
    uint32_t h0, h1, h2, h3;

    // Message (to prepare)
    uint8_t *msg = NULL;

    size_t new_len, offset;
    uint32_t w[16];
    uint32_t a, b, c, d, i, f, g, temp;

    // Initialize variables - simple count in nibbles:
    h0 = 0x67452301;
    h1 = 0xefcdab89;
    h2 = 0x98badcfe;
    h3 = 0x10325476;

    //Pre-processing:
    //append "1" bit to message
    //append "0" bits until message length in bits = 448 (mod 512)
    //append length mod (2^64) to message

    for (new_len = initial_len + 1; new_len % (512/8) != 448/8; new_len++)

    //// Instead of bothering to initialize the heap so malloc
    //// will work, just allocate a buffer from the stack, that
    //// will be freed automatically when the function returns.

    //// msg = (uint8_t*)malloc(new_len + 8);
    msg = (uint8_t*)_alloca(new_len + 8);

    memcpy(msg, initial_msg, initial_len);
    msg[initial_len] = 0x80; // append the "1" bit; most significant bit is "first"
    for (offset = initial_len + 1; offset < new_len; offset++)
        msg[offset] = 0; // append "0" bits

    // append the len in bits at the end of the buffer.
    to_bytes(initial_len*8, msg + new_len);
    // initial_len>>29 == initial_len*8>>32, but avoids overflow.
    to_bytes(initial_len>>29, msg + new_len + 4);

    // Process the message in successive 512-bit chunks:
    //for each 512-bit chunk of message:
    for(offset=0; offset<new_len; offset += (512/8)) {

        // break chunk into sixteen 32-bit words w[j], 0 = j = 15
        for (i = 0; i < 16; i++)
            w[i] = to_int32(msg + offset + i*4);

        // Initialize hash value for this chunk:
        a = h0;
        b = h1;
        c = h2;
        d = h3;

        // Main loop:
        for(i = 0; i<64; i++) {

            if (i < 16) {
                f = (b & c) | ((~b) & d);
                g = i;
            } else if (i < 32) {
                f = (d & b) | ((~d) & c);
                g = (5*i + 1) % 16;
            } else if (i < 48) {
                f = b ^ c ^ d;
                g = (3*i + 5) % 16;
            } else {
                f = c ^ (b | (~d));
                g = (7*i) % 16;
            }

            temp = d;
            d = c;
            c = b;
            b = b + LEFTROTATE((a + f + k[i] + w[g]), r[i]);
            a = temp;

        }

        // Add this chunk's hash to result so far:
        h0 += a;
        h1 += b;
        h2 += c;
        h3 += d;

    }

    // cleanup
    ////free(msg); //// Not needed with _alloca, must not be called w/o malloc.

    //var char digest[16] := h0 append h1 append h2 append h3 //(Output is in little-endian)
    to_bytes(h0, digest);
    to_bytes(h1, digest + 4);
    to_bytes(h2, digest + 8);
    to_bytes(h3, digest + 12);
}


test.asm:

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;==============================================================================
include \masm32\include\masm32rt.inc
includelib md5.lib
;==============================================================================
md5 PROTO C pmessage:DWORD, msglength:DWORD, pdigest:DWORD
;==============================================================================
.data
    digest  db 18 dup(0)
    msg1    db "a"                          ; 0cc175b9c0f1b6a831c399e269772661
            db 0
    msg2    db "abc"                        ; 900150983cd24fb0d6963f7d28e17f72
            db 0
    msg3    db "message digest"             ; f96b697d7cb7938d525a2f31aaf161d0
            db 0
    msg4    db "abcdefghijklmnopqrstuvwxyz" ; c3fcd3d76192e4007dfb496cca67e13b
            db 0
.code
;==============================================================================
start:
;==============================================================================

    FOR msg,<msg1,msg2,msg3,msg4>
        invoke md5, ADDR msg, SIZEOF msg, ADDR digest
        xor ebx, ebx
        .WHILE ebx < 16
            movzx eax, digest[ebx]
            printf("%2.2x", eax)
            inc ebx
        .ENDW
        printf("\n")
    ENDM

    printf("\n")
    inkey
    exit
;==============================================================================
end start


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set file="md5"

set PATH=C:\Program Files\Microsoft Visual C++ Toolkit 2003\bin;%PATH%
set INCLUDE=C:\Program Files\Microsoft Platform SDK\include;C:\Program Files\Microsoft Visual C++ Toolkit 2003\include;%INCLUDE%
set LIB=C:\Program Files\Microsoft Platform SDK\Lib;C:\Program Files\Microsoft Visual C++ Toolkit 2003\lib;%LIB%

cl /W4 /O2 /FA /c %file%.c
pause

link -lib %file%.obj
pause


\masm32\bin\ml /W3 /c /coff test.asm
pause

\masm32\bin\link /MAP /SUBSYSTEM:CONSOLE /OPT:NOREF test
pause