Changeset 2179

Timestamp:

6/18/2010 6:53:20 AM (20 months ago)

Author:

lowjoel

Message:

Refactor a function which parses null-delimited string arrays.

Location:

trunk/eraser/Eraser.Util

Files:

• NativeMethods/Kernel.cs (modified) (4 diffs)
• VolumeInfo.cs (modified) (1 diff)

trunk/eraser/Eraser.Util/NativeMethods/Kernel.cs

@@ -599 +599 @@
                 //Do we have enough space for all the text
                 if (written != 0)
-                    break;
+                    return ParseNullDelimitedArray(buffer, (int)written);
                 else if (Marshal.GetLastWin32Error() == Win32ErrorCode.InsufficientBuffer)
                     continue;
@@ -605 +605 @@
                     throw Win32ErrorCode.GetExceptionForWin32Error(Marshal.GetLastWin32Error());
             }
-
-            List<string> result = new List<string>();
-            for (int lastIndex = 0, i = 0; i != buffer.Length; ++i)
-            {
-                if (buffer[i] == '\0')
-                {
-                    //If there are no mount points for this volume, the string will only
-                    //have one NULL
-                    if (i - lastIndex == 0)
-                        break;
-
-                    //Resolve the DOS name to the device name
-                    result.Add(new string(buffer, lastIndex, i - lastIndex));
-
-                    lastIndex = i + 1;
-                    if (buffer[lastIndex] == '\0')
-                        break;
-                }
-            }
-
-            return result.ToArray();
         }
 
@@ -1167 +1146 @@
         [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
         [return: MarshalAs(UnmanagedType.Bool)]
-        public static extern bool GetVolumePathNamesForVolumeName(string lpszVolumeName,
+        private static extern bool GetVolumePathNamesForVolumeName(string lpszVolumeName,
             [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] char[] lpszVolumePathNames,
             uint cchBufferLength, out uint lpcchReturnLength);
+
+        /// <summary>
+        /// Retrieves a list of path names for the specified volume name.
+        /// </summary>
+        /// <param name="lpszVolumeName">The volume name.</param>
+        public static string[] GetVolumePathNamesForVolumeName(string lpszVolumeName)
+        {
+            uint returnLength = 0;
+            char[] pathNamesBuffer = new char[NativeMethods.MaxPath];
+            while (!NativeMethods.GetVolumePathNamesForVolumeName(lpszVolumeName,
+                pathNamesBuffer, (uint)pathNamesBuffer.Length, out returnLength))
+            {
+                int errorCode = Marshal.GetLastWin32Error();
+                switch (errorCode)
+                {
+                    case Win32ErrorCode.NotReady:
+                        //The drive isn't ready yet: just return an empty list.
+                        return new string[0];
+                    case Win32ErrorCode.MoreData:
+                        pathNamesBuffer = new char[pathNamesBuffer.Length * 2];
+                        break;
+                    default:
+                        throw Win32ErrorCode.GetExceptionForWin32Error(errorCode);
+                }
+            }
+
+            return ParseNullDelimitedArray(pathNamesBuffer, (int)returnLength);
+        }
 
         public const int MaxPath = 260;
@@ -1244 +1251 @@
         [DllImport("Kernel32.dll", SetLastError = true)]
         public static extern IntPtr LocalFree(IntPtr hMem);
+
+        /// <summary>
+        /// Parses a null-delimited array into a string array.
+        /// </summary>
+        /// <param name="buffer">The buffer to parse.</param>
+        /// <param name="length">The valid length of the array.</param>
+        /// <returns>The array found in the buffer</returns>
+        private static string[] ParseNullDelimitedArray(char[] buffer, int length)
+        {
+            List<string> result = new List<string>();
+            for (int lastIndex = 0, i = 0; i != length; ++i)
+            {
+                if (buffer[i] == '\0')
+                {
+                    //If the string formed is empty, there are no elements left.
+                    if (i - lastIndex == 0)
+                        break;
+
+                    result.Add(new string(buffer, lastIndex, i - lastIndex));
+
+                    lastIndex = i + 1;
+                    if (buffer[lastIndex] == '\0')
+                        break;
+                }
+            }
+
+            return result.ToArray();
+        }
     }
 }

trunk/eraser/Eraser.Util/VolumeInfo.cs

@@ -92 +92 @@
         private List<string> GetLocalVolumeMountPoints()
         {
-            List<string> result = new List<string>();
-
-            //Get the paths of the said volume
-            string pathNames;
-            {
-                uint returnLength = 0;
-                char[] pathNamesBuffer = new char[NativeMethods.MaxPath];
-                while (!NativeMethods.GetVolumePathNamesForVolumeName(VolumeId,
-                    pathNamesBuffer, (uint)pathNamesBuffer.Length, out returnLength))
-                {
-                    int errorCode = Marshal.GetLastWin32Error();
-                    switch (errorCode)
-                    {
-                        case Win32ErrorCode.NotReady:
-                            //The drive isn't ready yet: just return an empty list.
-                            return result;
-                        case Win32ErrorCode.MoreData:
-                            pathNamesBuffer = new char[pathNamesBuffer.Length * 2];
-                            break;
-                        default:
-                            throw Win32ErrorCode.GetExceptionForWin32Error(errorCode);
-                    }
-                }
-
-                pathNames = new string(pathNamesBuffer, 0, (int)returnLength);
-            }
-
-            //OK, the marshalling is complete. Convert the pathNames string into a list
-            //of strings containing all of the volumes mountpoints; because the
-            //GetVolumePathNamesForVolumeName function returns a convoluted structure
-            //containing the path names.
-            for (int lastIndex = 0, i = 0; i != pathNames.Length; ++i)
-            {
-                if (pathNames[i] == '\0')
-                {
-                    //If there are no mount points for this volume, the string will only
-                    //have one NULL
-                    if (i - lastIndex == 0)
-                        break;
-
-                    result.Add(pathNames.Substring(lastIndex, i - lastIndex));
-
-                    lastIndex = i + 1;
-                    if (pathNames[lastIndex] == '\0')
-                        break;
-                }
-            }
-
-            return result;
+            return new List<string>(NativeMethods.GetVolumePathNamesForVolumeName(VolumeId));
         }