Recupero di una stringa che descrive un filtro

Un'applicazione spesso deve visualizzare una stringa che descrive il formato corrente. Questa attività può essere eseguita facilmente con le funzioni acmFilterTagDetails e acmFilterDetails . Queste funzioni devono essere chiamate con il filtro o il tag di filtro appropriato. Nell'esempio seguente viene illustrato come usare queste funzioni.

#include <mmsystem.h>
#include <mmreg.h>
#include <msacm.h>

BOOL GetFilterDescription 
( 
    LPWAVEFILTER  pwfltr, 
    LPTSTR        pszFilterTag, 
    DWORD         cchFilterTag, // Size of pszFilterTag buffer.
    LPTSTR        pszFilter,
    DWORD         cchFilter     // Size of pszFilter buffer.

) 
{ 
    MMRESULT      mmr; 
    errno_t       errno;
 
    // Retrieve the name for the filter tag of the specified filter. 
    if (NULL != pszFilterTag) { 
        ACMFILTERTAGDETAILS aftd; 
 
        // Initialize all unused members of the ACMFILTERTAGDETAILS 
        // structure to zero. 
        memset(&aftd, 0, sizeof(aftd)); 
 
        // Fill in the required members of the ACMFILTERTAGDETAILS 
        // structure for the ACM_FILTERTAGDETAILSF_FILTERTAG query. 
        aftd.cbStruct = sizeof(aftd); 
        aftd.dwFilterTag = pwfltr->dwFilterTag; 
 
        // Ask the ACM to find the first available driver that 
        // supports the specified filter tag. 
        mmr = acmFilterTagDetails(NULL, &aftd, 
            ACM_FILTERTAGDETAILSF_FILTERTAG); 
        if (MMSYSERR_NOERROR != mmr) { 
            // No ACM driver is available that supports the 
            // specified filter tag. 
            return FALSE; 
        } 
 
        // Copy the filter tag name into the calling application's 
        // buffer. 

        errno = wcscpy_s(pszFilterTag, cchFilterTag, aftd.szFilterTag); 
        if (errno != 0)
        {
            return FALSE;
        }
    } 
 
    // Retrieve the description of the attributes for the specified 
    // filter. 
    if (NULL != pszFilter) { 
        ACMFILTERDETAILS afd; 
 
        // Initialize all unused members of the ACMFILTERDETAILS 
        // structure to zero. 
        memset(&afd, 0, sizeof(afd)); 
 
        // Fill in the required members of the ACMFILTERDETAILS 
        // structure for the ACM_FILTERDETAILSF_FILTER query. 
        afd.cbStruct    = sizeof(afd); 
        afd.dwFilterTag = pwfltr->dwFilterTag; 
        afd.pwfltr      = pwfltr; 
        afd.cbwfltr     = pwfltr->cbStruct; 
 
        // Ask the ACM to find the first available driver that 
        // supports the specified filter. 
        mmr = acmFilterDetails(NULL, &afd, ACM_FILTERDETAILSF_FILTER); 
        if (MMSYSERR_NOERROR != mmr) { 
            // No ACM driver is available that supports the 
            // specified filter. 
            return FALSE; 
        } 
 
        // Copy the description string into the caller's buffer. 
        errno = wcscpy_s(pszFilter, cchFilter, afd.szFilter); 
        if (errno != 0)
        {
            return FALSE;
        }
    } 
 
    return TRUE; 
}