Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Globalization / EncodingTable.cs / 1 / EncodingTable.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== namespace System.Globalization { using System.Text; using System.Runtime.InteropServices; using System; using System.Collections; using System.Runtime.CompilerServices; using System.Threading; // // Data table for encoding classes. Used by System.Text.Encoding. // This class contains two hashtables to allow System.Text.Encoding // to retrieve the data item either by codepage value or by webName. // // Only statics, does not need to be marked with the serializable attribute internal static class EncodingTable { //This number is the size of the table in native. The value is retrieved by //calling the native GetNumEncodingItems(). private static int lastEncodingItem = GetNumEncodingItems() - 1; //This number is the size of the code page table. Its generated when we walk the table the first time. private static int lastCodePageItem; // // This points to a native data table which maps an encoding name to the correct code page. // unsafe internal static InternalEncodingDataItem *encodingDataPtr = GetEncodingData(); // // This points to a native data table which stores the properties for the code page, and // the table is indexed by code page. // unsafe internal static InternalCodePageDataItem *codePageDataPtr = GetCodePageData(); // // This caches the mapping of an encoding name to a code page. // internal static Hashtable hashByName = new Hashtable(StringComparer.OrdinalIgnoreCase); // // THe caches the data item which is indexed by the code page value. // internal static Hashtable hashByCodePage = new Hashtable(); // Find the data item by binary searching the table that we have in native. // nativeCompareOrdinalWC is an internal-only function. unsafe private static int internalGetCodePageFromName(String name) { int left = 0; int right = lastEncodingItem; int index; int result; //Binary search the array until we have only a couple of elements left and then //just walk those elements. while ((right - left)>3) { index = ((right - left)/2) + left; bool success; result = String.nativeCompareOrdinalWC(name, encodingDataPtr[index].webName, true, out success); if (result == 0) { //We found the item, return the associated codepage. return (encodingDataPtr[index].codePage); } else if (result<0) { //The name that we're looking for is less than our current index. right = index; } else { //The name that we're looking for is greater than our current index left = index; } } //Walk the remaining elements (it'll be 3 or fewer). for (; left<=right; left++) { bool success; if (String.nativeCompareOrdinalWC(name, encodingDataPtr[left].webName, true,out success)==0) { return (encodingDataPtr[left].codePage); } } // The encoding name is not valid. throw new ArgumentException( String.Format( CultureInfo.CurrentCulture, Environment.GetResourceString("Argument_EncodingNotSupported"), name), "name"); } // Return a list of all EncodingInfo objects describing all of our encodings internal static unsafe EncodingInfo[] GetEncodings() { if (lastCodePageItem == 0) { int count; for (count = 0; codePageDataPtr[count].codePage != 0; count++) { // Count them } lastCodePageItem = count; } EncodingInfo[] arrayEncodingInfo = new EncodingInfo[lastCodePageItem]; int i; for (i = 0; i < lastCodePageItem; i++) arrayEncodingInfo[i] = new EncodingInfo(codePageDataPtr[i].codePage, new String(codePageDataPtr[i].webName), Environment.GetResourceString("Globalization.cp_"+codePageDataPtr[i].codePage)); return arrayEncodingInfo; } /*=================================GetCodePageFromName========================== **Action: Given a encoding name, return the correct code page number for this encoding. **Returns: The code page for the encoding. **Arguments: ** name the name of the encoding **Exceptions: ** ArgumentNullException if name is null. ** internalGetCodePageFromName will throw ArgumentException if name is not a valid encoding name. ============================================================================*/ internal static int GetCodePageFromName(String name) { if (name==null) { throw new ArgumentNullException("name"); } Object codePageObj; // // The name is case-insensitive, but ToLower isn't free. Check for // the code page in the given capitalization first. // codePageObj = hashByName[name]; if (codePageObj!=null) { return ((int)codePageObj); } //Okay, we didn't find it in the hash table, try looking it up in the //unmanaged data. int codePage = internalGetCodePageFromName(name); hashByName[name]=codePage; return (codePage); } unsafe internal static CodePageDataItem GetCodePageDataItem(int codepage) { CodePageDataItem dataItem; //Look up the item in the hashtable. dataItem = (CodePageDataItem)hashByCodePage[codepage]; //If we found it, return it. if (dataItem!=null) { return (dataItem); } //If we didn't find it, try looking it up now. //If we find it, add it to the hashtable. //This is a linear search, but we probably won't be doing it very often. // int i = 0; int data; while ((data = codePageDataPtr[i].codePage) != 0) { if (data==codepage) { dataItem = new CodePageDataItem(i); hashByCodePage[codepage]=dataItem; return (dataItem); } i++; } //Nope, we didn't find it. return (null); } [MethodImplAttribute(MethodImplOptions.InternalCall)] private unsafe static extern InternalEncodingDataItem *GetEncodingData(); // // Return the number of encoding data items. // [MethodImplAttribute(MethodImplOptions.InternalCall)] private static extern int GetNumEncodingItems(); [MethodImplAttribute(MethodImplOptions.InternalCall)] private unsafe static extern InternalCodePageDataItem* GetCodePageData(); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal unsafe static extern byte* nativeCreateOpenFileMapping( String inSectionName, int inBytesToAllocate, out IntPtr mappedFileHandle); } /*=================================InternalEncodingDataItem========================== **Action: This is used to map a encoding name to a correct code page number. By doing this, ** we can get the properties of this encoding via the InternalCodePageDataItem. ** ** We use this structure to access native data exposed by the native side. ============================================================================*/ [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)] internal unsafe struct InternalEncodingDataItem { internal char *webName; internal int codePage; } /*=================================InternalCodePageDataItem========================== **Action: This is used to access the properties related to a code page. ** We use this structure to access native data exposed by the native side. ============================================================================*/ [System.Runtime.InteropServices.StructLayout(LayoutKind.Sequential)] internal unsafe struct InternalCodePageDataItem { internal int codePage; internal int uiFamilyCodePage; internal char *webName; internal char *headerName; internal char *bodyName; internal uint flags; } }
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