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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
namespace System.Globalization
{
using System;
using System.Text;
using System.Collections;
using System.Collections.Generic;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
using System.Security;
using System.Threading;
using System.Diagnostics.Contracts;
//
// 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 volatile 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.
//
private static Hashtable hashByName = Hashtable.Synchronized(new Hashtable(StringComparer.OrdinalIgnoreCase));
//
// THe caches the data item which is indexed by the code page value.
//
private static Hashtable hashByCodePage = Hashtable.Synchronized(new Hashtable());
static EncodingTable()
{
}
// 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;
result = String.nativeCompareOrdinalIgnoreCaseWC(name, encodingDataPtr[index].webName);
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++) {
if (String.nativeCompareOrdinalIgnoreCaseWC(name, encodingDataPtr[left].webName) == 0) {
return (encodingDataPtr[left].codePage);
}
}
// The encoding name is not valid.
throw new ArgumentException(
String.Format(
CultureInfo.CurrentCulture,
Environment.GetResourceString("Argument_EncodingNotSupported"), name), nameof(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, CodePageDataItem.CreateString(codePageDataPtr[i].Names, 0),
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(nameof(name));
}
Contract.EndContractBlock();
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;
// We synchronize around dictionary gets/sets. There's still a possibility that two threads
// will create a CodePageDataItem and the second will clobber the first in the dictionary.
// However, that's acceptable because the contents are correct and we make no guarantees
// other than that.
//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();
}
/*=================================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 sbyte * webName;
internal UInt16 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 UInt16 codePage;
internal UInt16 uiFamilyCodePage;
internal uint flags;
internal sbyte * Names;
}
}
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