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//
// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.
//
// This file contain implementations details that are subject to change without notice.
// Use at your own risk.
//
using System;
using System.IO;
using System.Threading;
using Microsoft.VisualStudio.Text.Utilities;
namespace Microsoft.VisualStudio.Text.Implementation
{
internal static class TextImageLoader
{
public const int BlockSize = 16384;
internal static StringRebuilder Load(TextReader reader, long fileSize,
out bool hasConsistentLineEndings, out int longestLineLength,
int blockSize = 0,
int minCompressedBlockSize = TextImageLoader.BlockSize) // Exposed for unit tests
{
LineEndingState lineEnding = LineEndingState.Unknown;
int currentLineLength = 0;
longestLineLength = 0;
bool useCompressedStringRebuilders = (fileSize >= TextModelOptions.CompressedStorageFileSizeThreshold);
if (blockSize == 0)
blockSize = useCompressedStringRebuilders ? TextModelOptions.CompressedStoragePageSize : TextImageLoader.BlockSize;
PageManager pageManager = null;
char[] buffer;
if (useCompressedStringRebuilders)
{
pageManager = new PageManager();
buffer = new char[blockSize];
}
else
{
buffer = TextImageLoader.AcquireBuffer(blockSize);
}
StringRebuilder content = StringRebuilderForChars.Empty;
try
{
while (true)
{
int read = TextImageLoader.LoadNextBlock(reader, buffer);
if (read == 0)
break;
var lineBreaks = TextImageLoader.ParseBlock(buffer, read, ref lineEnding, ref currentLineLength, ref longestLineLength);
char[] bufferForStringBuilder = buffer;
if (read < (buffer.Length / 2))
{
// We read far less characters than buffer so copy the contents to a new buffer and reuse the original buffer.
bufferForStringBuilder = new char[read];
Array.Copy(buffer, bufferForStringBuilder, read);
}
else
{
// We're using most of buffer so allocate a new block for the next chunk.
buffer = new char[blockSize];
}
var newContent = (useCompressedStringRebuilders && (read > minCompressedBlockSize))
? StringRebuilderForCompressedChars.Create(new Page(pageManager, bufferForStringBuilder, read), lineBreaks)
: StringRebuilderForChars.Create(bufferForStringBuilder, read, lineBreaks);
content = content.Insert(content.Length, newContent);
}
longestLineLength = Math.Max(longestLineLength, currentLineLength);
}
finally
{
if (!useCompressedStringRebuilders)
{
TextImageLoader.ReleaseBuffer(buffer);
}
}
hasConsistentLineEndings = lineEnding != LineEndingState.Inconsistent;
return content;
}
public static int LoadNextBlock(TextReader reader, char[] buffer)
{
// Reserve 1 spot for a potential CR at the end of the buffer (in which we want to add the next LF, if it exists)
int read = reader.ReadBlock(buffer, 0, buffer.Length - 1);
if ((read == buffer.Length - 1) && (buffer[read - 1] == '\r'))
{
// Last character read was a CR and there is, probably since we read the entire block, more to go.
var next = reader.Peek();
if (next == '\n')
{
// We had a crlf that spanned the end of the buffer. Add it to the buffer and carry on.
// In theory we could append anything other than another CR but having the block end at
// the end of a line is a good thing.
reader.Read();
buffer[read++] = '\n';
}
}
return read;
}
private static ILineBreaks ParseBlock(char[] buffer, int length,
ref LineEndingState lineEnding, ref int currentLineLength, ref int longestLineLength)
{
// Note that the lineBreaks created here will (internally) use the pooled list of line breaks.
IPooledLineBreaksEditor lineBreaks = LineBreakManager.CreatePooledLineBreakEditor(length);
int index = 0;
while (index < length)
{
int breakLength = TextUtilities.LengthOfLineBreak(buffer, index, length);
if (breakLength == 0)
{
++currentLineLength;
++index;
}
else
{
lineBreaks.Add(index, breakLength);
longestLineLength = Math.Max(longestLineLength, currentLineLength);
currentLineLength = 0;
if (lineEnding != LineEndingState.Inconsistent)
{
if (breakLength == 2)
{
if (lineEnding == LineEndingState.Unknown)
lineEnding = LineEndingState.CRLF;
else if (lineEnding != LineEndingState.CRLF)
lineEnding = LineEndingState.Inconsistent;
}
else
{
LineEndingState newLineEndingState;
switch (buffer[index])
{
// This code needs to be kep consistent with TextUtilities.LengthOfLineBreak()
case '\r': newLineEndingState = LineEndingState.CR; break;
case '\n': newLineEndingState = LineEndingState.LF; break;
case '\u0085': newLineEndingState = LineEndingState.NEL; break;
case '\u2028': newLineEndingState = LineEndingState.LS; break;
case '\u2029': newLineEndingState = LineEndingState.PS; break;
default: throw new InvalidOperationException("Unexpected line ending");
}
if (lineEnding == LineEndingState.Unknown)
lineEnding = newLineEndingState;
else if (lineEnding != newLineEndingState)
lineEnding = LineEndingState.Inconsistent;
}
}
index += breakLength;
}
}
lineBreaks.ReleasePooledLineBreaks();
return lineBreaks;
}
internal enum LineEndingState
{
Unknown = 0,
CRLF = 1,
CR = 2,
LF = 3,
NEL = 4, // unicode Next Line 0085
LS = 5, // unicode Line Separator 2028
PS = 6, // unicode Paragraph Separator 2029
Inconsistent = 7,
}
private static char[] pooledBuffer;
private static char[] AcquireBuffer(int size)
{
char[] buffer = Volatile.Read(ref pooledBuffer);
if (buffer != null && buffer.Length >= size)
{
if (buffer == Interlocked.CompareExchange(ref pooledBuffer, null, buffer))
{
return buffer;
}
}
return new char[size];
}
private static void ReleaseBuffer(char[] buffer)
{
Interlocked.CompareExchange(ref pooledBuffer, buffer, null);
}
}
}
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