openssl evp加解密统一接口

int do_crypt(FILE *in, FILE *out, int do_encrypt)
{
    /* Allow enough space in output buffer for additional block */
    inbuf[1024], outbuf[1024 + EVP_MAX_BLOCK_LENGTH];
    int inlen, outlen;
    
    /* Bogus key and IV: we'd normally set these from
    * another source.
    */
    unsigned char key[] = "0123456789";
    unsigned char iv[] = "12345678";
    /* Don't set key or IV because we will modify the parameters */
    EVP_CIPHER_CTX_init(&ctx);
    EVP_CipherInit_ex(&ctx, EVP_rc2(), NULL, NULL, NULL, do_encrypt);
    EVP_CIPHER_CTX_set_key_length(&ctx, 10);
    /* We finished modifying parameters so now we can set key and IV */
    EVP_CipherInit_ex(&ctx, NULL, NULL, key, iv, do_encrypt);

    for(;;)
    {
        inlen = fread(inbuf, 1, 1024, in);
        if(inlen <= 0) break;
        if(!EVP_CipherUpdate(&ctx, outbuf, &outlen, inbuf, inlen))
        {
            /* Error */
            EVP_CIPHER_CTX_cleanup(&ctx);
            return 0;
        }

        fwrite(outbuf, 1, outlen, out);
    }
       
    if(!EVP_CipherFinal_ex(&ctx, outbuf, &outlen))
    {
        /* Error */
        EVP_CIPHER_CTX_cleanup(&ctx);
        return 0;
    }
    
    fwrite(outbuf, 1, outlen, out);

    EVP_CIPHER_CTX_cleanup(&ctx);
    return 1;
}