PowerShell/impl/getcomputername.cpp

#include "getcomputername.h"
#include <errno.h>
#include <langinfo.h>
#include <locale.h>
#include <unistd.h>
#include <string>
#include <vector>
#include <scxcorelib/scxstrencodingconv.h>


// https://msdn.microsoft.com/en-us/library/windows/desktop/ms724432(v=vs.85).aspx
// Sets errno to:
//     ERROR_INVALID_PARAMETER - parameter is not valid
//     ERROR_BAD_ENVIRONMENT - locale is not UTF-8
//     ERROR_TOO_MANY_OPEN_FILES - already have the maximum allowed number of open files
//     ERROR_NO_ASSOCIATION - calling process has no controlling terminal
//     ERROR_INSUFFICIENT_BUFFER - buffer not large enough to hold username string
//     ERROR_NO_SUCH_USER - there was no corresponding entry in the utmp-file
//     ERROR_OUTOFMEMORY - insufficient memory to allocate passwd structure
//     ERROR_NO_ASSOCIATION - standard input didn't refer to a terminal
//     ERROR_INVALID_FUNCTION - getlogin_r() returned an unrecognized error code
//
// Returns:
//     1 - succeeded
//     0 - failed
BOOL GetComputerNameW(LPTSTR name, LPDWORD len)
{
    const std::string utf8 = "UTF-8";
    errno = 0;
    
    // Check parameters
    if (!name || !len) {
        errno = ERROR_INVALID_PARAMETER;
        return 0;
    }
    
    // Select locale from environment
    setlocale(LC_ALL, "");
    // Check that locale is UTF-8
    if (nl_langinfo(CODESET) != utf8) {
        errno = ERROR_BAD_ENVIRONMENT;
        return 0;
    }
    
    // Get username from system in a thread-safe manner
    std::string username(LOGIN_NAME_MAX, '\0');
    int err = gethostname(&username[0], username.size());
    // Map errno to Win32 Error Codes
    if (err != 0) {
        switch (errno) {
            case EMFILE:
            case ENFILE:
                errno = ERROR_TOO_MANY_OPEN_FILES;
                break;
            case ENXIO:
                errno = ERROR_NO_ASSOCIATION;
                break;
            case ERANGE:
                errno = ERROR_INSUFFICIENT_BUFFER;
                break;
            case ENOENT:
                errno = ERROR_NO_SUCH_USER;
                break;
            case ENOMEM:
                errno = ERROR_OUTOFMEMORY;
                break;
            case ENOTTY:
                errno = ERROR_NO_ASSOCIATION;
                break;
            default:
                errno = ERROR_INVALID_FUNCTION;
        }
        return 0;
    }
    
    // "Trim" the username to the first trailing null because
    // otherwise the std::string with repeated null characters is
    // valid, and the conversion will still include all the null
    // characters. Creating a std::string from the C string of the
    // original effectively trims it to the first null, without
    // the need to manually trim whitespace (nor using Boost).
    username = std::string(username.c_str());
    
    // Convert to char * to WCHAR_T * (UTF-8 to UTF-16 LE w/o BOM)
    std::vector<unsigned char> output;
    SCXCoreLib::Utf8ToUtf16le(username, output);
    
    // The length is the number of characters in the string, which
    // is half the string size because UTF-16 encodes two bytes
    // per character, plus one for the trailing null.
    const DWORD length = output.size()/2 + 1;
    if (length > *len) {
        errno = ERROR_INSUFFICIENT_BUFFER;
        // Set lpnSize if buffer is too small to inform user
        // of necessary size
        *len= length;
        return 0;
    }
    
    // Add two null bytes (because it's UTF-16)
    output.push_back('\0');
    output.push_back('\0');
    
    memcpy(name, &output[0], output.size());
    *len = output.size()/2;
    
    return 1;
    
  /*  
    size_t len2 = *len; 
    int host =  gethostname(name, len2);
    if(host == 0)
    {
        return TRUE;
    }
    else 
    {
        errno = ERROR_BUFFER_OVERFLOW;
        return FALSE;
    }
    */
}