Added changes to code based on additional documention and using a 16 bit string

impl/getcomputername.cpp

@@ -1,33 +1,74 @@
-#include "getcomputername.h"
+//! @file getcomputername.cpp
+//! @author Aaron Katz <v-aakatz@microsoft.com>
+//! @brief Implements GetComputerName Win32 API
+
 #include <errno.h>
 #include <langinfo.h>
+#include <locale.h>
 #include <unistd.h>
 #include <string>
-#include <iostream>
+#include <unicode/utypes.h>
+#include <unicode/ucnv.h>
+#include <unicode/ustring.h>
+#include <unicode/uchar.h>
+#include "getcomputername.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 nameOfComputer, LPDWORD len)
+//! @brief GetComputerName retrieves the name of the host associated with
+//! the current thread.
+//!
+//! GetComputerNameW is the Unicode variation. See [MSDN documentation].
+//!
+//! @param[out] lpBuffer
+//! @parblock
+//! A pointer to the buffer to receive the hosts's
+//! name. If this buffer is not large enough to contain the
+//! entire user hosts name, the function fails.
+//!
+//! WCHAR_T* is a Unicode [LPTSTR].
+//! @endparblock
+//!
+//! @param[in, out] lpnSize
+//! @parblock
+//! On input, this variable specifies the size of the lpBuffer buffer,
+//! in TCHARs. On output, the variable receives the number of TCHARs
+//! copied to the buffer, including the terminating null character.
+//!
+//! TCHAR is a Unicode 16-bit [WCHAR].
+//!
+//! If lpBuffer is too small, the function fails and GetLastError
+//! returns ERROR_INSUFFICIENT_BUFFER. This parameter receives the
+//! required buffer size, including the terminating null character.
+//! @endparblock
+//!
+//! @exception errno Passes these errors via errno to GetLastError:
+//! - 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
+//!
+//! @retval 1 If the function succeeds, the return value is a nonzero
+//! value, and the variable pointed to by lpnSize contains the number
+//! of TCHARs copied to the buffer specified by lpBuffer, including
+//! the terminating null character.
+//!
+//! @retval 0 If the function fails, the return value is zero. To get
+//! extended error information, call GetLastError.
+//!
+//! [MSDN documentation]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms724295%28v=vs.85%29.aspx
+//! [WCHAR]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx#WCHAR
+//! [LPTSTR]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx#LPTSTR
+BOOL GetComputerNameW(WCHAR_T* lpBuffer, LPDWORD lpnSize)
 {
     const std::string utf8 = "UTF-8";
     errno = 0;
     
     // Check parameters
-    if (!nameOfComputer || !len) {
+    if (!lpBuffer || !lpnSize) {
         errno = ERROR_INVALID_PARAMETER;
         return 0;
     }
@@ -41,8 +82,8 @@ BOOL GetComputerNameW(LPTSTR nameOfComputer, LPDWORD len)
     }
     
     // Get computername from system in a thread-safe manner
-    std::string computerName(HOST_MAX_NAME, '\0');
-    int err = gethostname(&computerName[0], computerName.size());
+    std::string computername(HOST_NAME_MAX, '\0');
+    int err = gethostname(&computername[0], computername.size());
     // Map errno to Win32 Error Codes
     if (err != 0) {
         switch (errno) {
@@ -72,21 +113,31 @@ BOOL GetComputerNameW(LPTSTR nameOfComputer, LPDWORD len)
         return 0;
     }
     
-    //Resize the string to not inlcude extra buffer space
-    const DWORD length = computerName.find_first_of('\0') + 1;
-    computerName.resize(length);
+    // Convert to char* to WCHAR_T* (UTF-8 to UTF-16 LE w/o BOM)
+    std::basic_string<char16_t> computername16(HOST_NAME_MAX + 1, 0);
+    icu::UnicodeString computername8(computername.c_str(), "UTF-8");
+    int32_t targetSize = computername8.extract(0, computername8.length(),
+                                           reinterpret_cast<char*>(&computername16[0]),
+                                           (computername16.size()-1)*sizeof(char16_t),
+                                           "UTF-16LE");
+    // Number of characters including null
+    computername16.resize(targetSize/sizeof(char16_t)+1);
+    
+    // Size in WCHARs including null
+    const DWORD size = computername16.length();
     
     //Check if parameters passed enough buffer space
-    if (length > *len) {
+    if (size > *lpnSize) {
         errno = ERROR_INSUFFICIENT_BUFFER;
         // Set lpnSize if buffer is too small to inform user
         // of necessary size
-        *len= length;
+        *lpnSize= size;
         return 0;
     }
     
-    memcpy(nameOfComputer, &computerName[0], length);
-    *len = length;
+    // Copy bytes from string to buffer
+    memcpy(lpBuffer, &computername16[0],  size*sizeof(char16_t));
+    *lpnSize = size;
     return 1;
     
 }