erlang nif小结

一、nif获取string参数的两种方式

1、eif_get_string

实例如下：

 1 static ERL_NIF_TERM erl_sm4_encrypt(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 2 {
 3     
 4     unsigned int input_len = 0;
 5     unsigned int key_len   = 1024;
 6     char key_string[1024]   = {0};
 7 
 8     int output_len = sizeof(buff);
 9     enif_get_list_length(env, argv[0],&input_len);
10  
11     char *input_string = NULL;
12     if (input_len <= 1)
13         input_len = 2018;
14     else
15         input_len = input_len +1;
16 
17     input_string = (char*)malloc(input_len);
18     memset(input_string,0x00,input_len);
19     
20     enif_get_string(env,argv[0],input_string,input_len, ERL_NIF_LATIN1);
21     enif_get_string(env,argv[1],key_string,key_len, ERL_NIF_LATIN1);
22     printf("input_string=%s,input_len=%d,key_string=%s,key_len=%d
", input_string,input_len,key_string,key_len);
23     SM4_KEY iKey;
24     sm4_SetKey(&iKey, (unsigned char *)key_string, 1);
25     printf("ERK=%s,DRK=%s,MK=%s
", iKey.ERK,iKey.DRK,iKey.MK);
26     enin_sm4((unsigned char*)input_string,input_len,buff,&output_len, &iKey, 1);
27     memset(buff+output_len,0x00,sizeof(buff)-output_len);
28 
29     free(input_string);
30     input_string = NULL;
31     return enif_make_string_len(env, (const char *)buff, output_len,ERL_NIF_LATIN1);
32 }

2、enif_inspect_iolist_as_binary

 1 static ERL_NIF_TERM erl_sm4_encrypt(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
 2 {
 3     ErlNifBinary ebinary_input,ebinary_key;
 4     
 5     if (!enif_inspect_iolist_as_binary(env, argv[0], &ebinary_input) ||
 6         !enif_inspect_iolist_as_binary(env, argv[1], &ebinary_key)){
 7         
 8         return enif_make_badarg(env); 
 9     }
10 
11     int key_len   = ebinary_key.size;
12     int input_len = ebinary_input.size;
13     int output_len = sizeof(buff);
14 
15     unsigned char *input_string = (unsigned char*)malloc(input_len+1);
16     unsigned char *key_string   = (unsigned char*)malloc(key_len+1);
17     
18     memcpy(input_string, ebinary_input.data, input_len); 
19     memcpy(key_string, ebinary_input.data, key_len);
20     //printf("input_string=%s,input_len=%d,key_string=%s,key_len=%d
", input_string,input_len,key_string,key_len);
21 
22     SM4_KEY iKey;
23     sm4_SetKey(&iKey, key_string, 1);
24 
25     memset(buff,0x00,sizeof(buff));
26     enin_sm4(input_string,input_len,buff,&output_len, &iKey, 1);
27     memset(buff+output_len,'',sizeof(buff)-output_len);
28 
34     free(input_string);
35     free(key_string);

36     return enif_make_string_len(env, (const char *)buff, output_len,ERL_NIF_LATIN1);
37 }

二、nif返回string的两种方式

1、enif_make_string

ERL_NIF_TERM enif_make_string(ErlNifEnv* env, const char* string, ErlNifCharEncoding encoding)

返回一个以空字符结尾的string

2、enif_make_string_len

ERL_NIF_TERM enif_make_string_len(ErlNifEnv* env, const char* string, size_t len, ErlNifCharEncoding encoding)

返回一个长度为len的字符串string，空字符当做普通字符处理