koobas.hobune.stream
How to get const char * from external dll
I am integrating CMU's PocketSphinx with Unity by compiling my own C++ project in Visual Studio 2010 as a DLL, which I am calling from a C# script from within Unity Pro. I know that the dll works because I have made another project as an exe with the very same code, compiled it, and it works perfectly as a standalone program. I'm using the pocketsphinx_continuous project example, which gets microphone inputs and outputs text to the console. I have customized this code to be called from inside Unity and it is supposed to output back to my C# code as a string rather than to the console. I feel that I almost have this working, but the const char * is just not making it back as a string. I will end up getting access violation errors if I use this declaration:
private static extern string recognize_from_microphone();
so, I have tried to use this one:
private static extern IntPtr recognize_from_microphone();
and then, I use this line of code to try to print the output of that function:
print("you just said " + Marshal.PtrToStringAnsi(recognize_from_microphone()));
but, then I get only "you just said" in return. I can manage to get a memory address back if I do this: print("you just said " + recognize_from_microphone()); So, I know that something is getting returned.
Here is my C++ code (much of this was written originally in C as the example code from pocketsphinx):
char* MakeStringCopy (const char* str)
{
if (str == NULL) return NULL;
char* res = (char*)malloc(strlen(str) + 1);
strcpy(res, str);
return res;
}
extern __declspec(dllexport) const char * recognize_from_microphone()
{
//this is a near complete duplication of the code from main()
char const *cfg;
config = cmd_ln_init(NULL, ps_args(), TRUE,
"-hmm", MODELDIR "\\hmm\\en_US\\hub4wsj_sc_8k",
"-lm", MODELDIR "\\lm\\en\\turtle.DMP",
"-dict", MODELDIR "\\lm\\en\\turtle.dic",
NULL);
if (config == NULL)
{
return "config is null";
}
ps = ps_init(config);
if (ps == NULL)
{
return "ps is null";
}
ad_rec_t *ad;
int16 adbuf[4096];
int32 k, ts, rem;
char const *hyp;
char const *uttid;
cont_ad_t *cont;
char word[256];
char words[1024] = "";
//char temp[] = "hypothesis";
//hyp = temp;
if ((ad = ad_open_dev(cmd_ln_str_r(config, "-adcdev"),
(int)cmd_ln_float32_r(config, "-samprate"))) == NULL)
E_FATAL("Failed to open audio device\n");
/* Initialize continuous listening module */
if ((cont = cont_ad_init(ad, ad_read)) == NULL)
E_FATAL("Failed to initialize voice activity detection\n");
if (ad_start_rec(ad) < 0)
E_FATAL("Failed to start recording\n");
if (cont_ad_calib(cont) < 0)
E_FATAL("Failed to calibrate voice activity detection\n");
for (;;) {
/* Indicate listening for next utterance */
//printf("READY....\n");
fflush(stdout);
fflush(stderr);
/* Wait data for next utterance */
while ((k = cont_ad_read(cont, adbuf, 4096)) == 0)
sleep_msec(100);
if (k < 0)
E_FATAL("Failed to read audio\n");
/*
* Non-zero amount of data received; start recognition of new utterance.
* NULL argument to uttproc_begin_utt => automatic generation of utterance-id.
*/
if (ps_start_utt(ps, NULL) < 0)
E_FATAL("Failed to start utterance\n");
ps_process_raw(ps, adbuf, k, FALSE, FALSE);
//printf("Listening...\n");
fflush(stdout);
/* Note timestamp for this first block of data */
ts = cont->read_ts;
/* Decode utterance until end (marked by a "long" silence, >1sec) */
for (;;) {
/* Read non-silence audio data, if any, from continuous listening module */
if ((k = cont_ad_read(cont, adbuf, 4096)) < 0)
E_FATAL("Failed to read audio\n");
if (k == 0) {
/*
* No speech data available; check current timestamp with most recent
* speech to see if more than 1 sec elapsed. If so, end of utterance.
*/
if ((cont->read_ts - ts) > DEFAULT_SAMPLES_PER_SEC)
break;
}
else {
/* New speech data received; note current timestamp */
ts = cont->read_ts;
}
/*
* Decode whatever data was read above.
*/
rem = ps_process_raw(ps, adbuf, k, FALSE, FALSE);
/* If no work to be done, sleep a bit */
if ((rem == 0) && (k == 0))
sleep_msec(20);
}
/*
* Utterance ended; flush any accumulated, unprocessed A/D data and stop
* listening until current utterance completely decoded
*/
ad_stop_rec(ad);
while (ad_read(ad, adbuf, 4096) >= 0);
cont_ad_reset(cont);
fflush(stdout);
/* Finish decoding, obtain and print result */
ps_end_utt(ps);
hyp = ps_get_hyp(ps, NULL, &uttid);
fflush(stdout);
/* Exit if the first word spoken was GOODBYE */
//actually, for unity, exit if any word was spoken at all! this will avoid an infinite loop of doom!
if (hyp) {
/*sscanf(hyp, "%s", words);
if (strcmp(word, "goodbye") == 0)*/
break;
}
else
return "nothing returned";
/* Resume A/D recording for next utterance */
if (ad_start_rec(ad) < 0)
E_FATAL("Failed to start recording\n");
}
cont_ad_close(cont);
ad_close(ad);
ps_free(ps);
const char *temp = new char[1024];
temp = MakeStringCopy(hyp);
return temp;
}
If change return temp; to return "some string here"; Then I see the text appear inside Unity. That's not helpful, though, because I don't need hardcoded text, I need the output of the speech recognition code, which ends up getting stored inside the hyp variable.
I've spent all day reading web postings on this, including the following: http://www.rbcafe.com/Softwares/Unity/Documentation/Manual/Plugins.html http://limbioliong.wordpress.com/2011/06/16/returning-strings-from-a-c-api/ http://www.mono-project.com/Interop_with_Native_Libraries http://answers.unity3d.com/questions/22553/marshaling-a-string-from-c.html?sort=oldest
Can anyone help me figure out what I'm doing wrong? Thanks!
