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Updated ImapStream, ImapEngine, and ImapCommand to reuse ByteArrayBui…
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…lders

This drastically reduces the number of allocations made when tokenizing
IMAP responses.

ImapCommand's usage was not really a major issue, but since ImapEngine.ReadLine/Async()
needed a reusable ByteArrayBuilder anyway, might as well share that with ImapCommand.
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@jstedfast
jstedfast committed Aug 27, 2023
1 parent 7632855 commit 9e8e83a
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Showing 4 changed files with 196 additions and 178 deletions.
6 changes: 6 additions & 0 deletions MailKit.sln
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "MailKit", "MailKit\MailKit.
EndProject
Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "UnitTests", "UnitTests\UnitTests.csproj", "{1B670279-AEA7-4D9B-A854-CB4CC177B277}"
EndProject
Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ConsoleApp1", "ConsoleApp1\ConsoleApp1.csproj", "{051C136B-8354-4893-B9F8-11E1B35ABBDF}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Expand All @@ -32,6 +34,10 @@ Global
{1B670279-AEA7-4D9B-A854-CB4CC177B277}.Debug|Any CPU.Build.0 = Debug|Any CPU
{1B670279-AEA7-4D9B-A854-CB4CC177B277}.Release|Any CPU.ActiveCfg = Release|Any CPU
{1B670279-AEA7-4D9B-A854-CB4CC177B277}.Release|Any CPU.Build.0 = Release|Any CPU
{051C136B-8354-4893-B9F8-11E1B35ABBDF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{051C136B-8354-4893-B9F8-11E1B35ABBDF}.Debug|Any CPU.Build.0 = Debug|Any CPU
{051C136B-8354-4893-B9F8-11E1B35ABBDF}.Release|Any CPU.ActiveCfg = Release|Any CPU
{051C136B-8354-4893-B9F8-11E1B35ABBDF}.Release|Any CPU.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
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163 changes: 81 additions & 82 deletions MailKit/Net/Imap/ImapCommand.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -472,92 +472,91 @@ public ImapCommand (ImapEngine engine, CancellationToken cancellationToken, Imap
Engine = engine;
Folder = folder;

using (var builder = new ByteArrayBuilder (1024)) {
byte[] buf, utf8 = new byte[8];
int argc = 0;
string str;

for (int i = 0; i < format.Length; i++) {
if (format[i] == '%') {
switch (format[++i]) {
case '%': // a literal %
builder.Append ((byte) '%');
break;
case 'd': // an integer
str = ((int) args[argc++]).ToString (CultureInfo.InvariantCulture);
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 'u': // an unsigned integer
str = ((uint) args[argc++]).ToString (CultureInfo.InvariantCulture);
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 's':
str = (string) args[argc++];
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 'F': // an ImapFolder
var utf7 = ((ImapFolder) args[argc++]).EncodedName;
AppendString (options, true, builder, utf7);
break;
case 'L': // a MimeMessage or a byte[]
var arg = args[argc++];
ImapLiteral literal;
byte[] prefix;

if (arg is MimeMessage message) {
prefix = options.International ? UTF8LiteralTokenPrefix : LiteralTokenPrefix;
literal = new ImapLiteral (options, message, UpdateProgress);
} else {
literal = new ImapLiteral (options, (byte[]) arg);
prefix = LiteralTokenPrefix;
}

var length = literal.Length;
bool wait = true;

builder.Append (prefix, 0, prefix.Length);
buf = Encoding.ASCII.GetBytes (length.ToString (CultureInfo.InvariantCulture));
builder.Append (buf, 0, buf.Length);

if (CanUseNonSynchronizedLiteral (Engine, length)) {
builder.Append ((byte) '+');
wait = false;
}

builder.Append (LiteralTokenSuffix, 0, LiteralTokenSuffix.Length);

totalSize += length;

parts.Add (new ImapCommandPart (builder.ToArray (), literal, wait));
builder.Clear ();

if (prefix == UTF8LiteralTokenPrefix)
builder.Append ((byte) ')');
break;
case 'S': // a string which may need to be quoted or made into a literal
AppendString (options, true, builder, (string) args[argc++]);
break;
case 'Q': // similar to %S but string must be quoted at a minimum
AppendString (options, false, builder, (string) args[argc++]);
break;
default:
throw new FormatException ($"The %{format[i]} format specifier is not supported.");
var builder = engine.GetCommandBuilder ();
byte[] buf, utf8 = new byte[8];
int argc = 0;
string str;

for (int i = 0; i < format.Length; i++) {
if (format[i] == '%') {
switch (format[++i]) {
case '%': // a literal %
builder.Append ((byte) '%');
break;
case 'd': // an integer
str = ((int) args[argc++]).ToString (CultureInfo.InvariantCulture);
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 'u': // an unsigned integer
str = ((uint) args[argc++]).ToString (CultureInfo.InvariantCulture);
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 's':
str = (string) args[argc++];
buf = Encoding.ASCII.GetBytes (str);
builder.Append (buf, 0, buf.Length);
break;
case 'F': // an ImapFolder
var utf7 = ((ImapFolder) args[argc++]).EncodedName;
AppendString (options, true, builder, utf7);
break;
case 'L': // a MimeMessage or a byte[]
var arg = args[argc++];
ImapLiteral literal;
byte[] prefix;

if (arg is MimeMessage message) {
prefix = options.International ? UTF8LiteralTokenPrefix : LiteralTokenPrefix;
literal = new ImapLiteral (options, message, UpdateProgress);
} else {
literal = new ImapLiteral (options, (byte[]) arg);
prefix = LiteralTokenPrefix;
}
} else if (format[i] < 128) {
builder.Append ((byte) format[i]);
} else {
int nchars = char.IsSurrogate (format[i]) ? 2 : 1;
int nbytes = Encoding.UTF8.GetBytes (format, i, nchars, utf8, 0);
builder.Append (utf8, 0, nbytes);
i += nchars - 1;

var length = literal.Length;
bool wait = true;

builder.Append (prefix, 0, prefix.Length);
buf = Encoding.ASCII.GetBytes (length.ToString (CultureInfo.InvariantCulture));
builder.Append (buf, 0, buf.Length);

if (CanUseNonSynchronizedLiteral (Engine, length)) {
builder.Append ((byte) '+');
wait = false;
}

builder.Append (LiteralTokenSuffix, 0, LiteralTokenSuffix.Length);

totalSize += length;

parts.Add (new ImapCommandPart (builder.ToArray (), literal, wait));
builder.Clear ();

if (prefix == UTF8LiteralTokenPrefix)
builder.Append ((byte) ')');
break;
case 'S': // a string which may need to be quoted or made into a literal
AppendString (options, true, builder, (string) args[argc++]);
break;
case 'Q': // similar to %S but string must be quoted at a minimum
AppendString (options, false, builder, (string) args[argc++]);
break;
default:
throw new FormatException ($"The %{format[i]} format specifier is not supported.");
}
} else if (format[i] < 128) {
builder.Append ((byte) format[i]);
} else {
int nchars = char.IsSurrogate (format[i]) ? 2 : 1;
int nbytes = Encoding.UTF8.GetBytes (format, i, nchars, utf8, 0);
builder.Append (utf8, 0, nbytes);
i += nchars - 1;
}

parts.Add (new ImapCommandPart (builder.ToArray (), null));
}

parts.Add (new ImapCommandPart (builder.ToArray (), null));
}

/// <summary>
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46 changes: 28 additions & 18 deletions MailKit/Net/Imap/ImapEngine.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -148,6 +148,7 @@ class ImapEngine : IDisposable
readonly CreateImapFolderDelegate createImapFolder;
readonly ImapFolderNameComparer cacheComparer;
internal ImapQuirksMode QuirksMode;
readonly ByteArrayBuilder builder;
readonly List<ImapCommand> queue;
internal char TagPrefix;
ImapCommand current;
Expand All @@ -157,6 +158,8 @@ class ImapEngine : IDisposable

public ImapEngine (CreateImapFolderDelegate createImapFolderDelegate)
{
// The builder is used as a buffer for line-reading as well as ImapCommand building, so 1K is probably realistic.
builder = new ByteArrayBuilder (1024);
cacheComparer = new ImapFolderNameComparer ('.');

FolderCache = new Dictionary<string, ImapFolder> (cacheComparer);
Expand Down Expand Up @@ -525,6 +528,13 @@ public ImapFolder Trash {

#endregion

internal ByteArrayBuilder GetCommandBuilder ()
{
builder.Clear ();

return builder;
}

internal ImapFolder CreateImapFolder (string encodedName, FolderAttributes attributes, char delim)
{
var args = new ImapFolderConstructorArgs (this, encodedName, attributes, delim);
Expand Down Expand Up @@ -842,18 +852,18 @@ public void Disconnect ()
/// </exception>
public string ReadLine (CancellationToken cancellationToken)
{
using (var builder = new ByteArrayBuilder (64)) {
bool complete;
builder.Clear ();

do {
complete = Stream.ReadLine (builder, cancellationToken);
} while (!complete);
bool complete;

do {
complete = Stream.ReadLine (builder, cancellationToken);
} while (!complete);

// FIXME: All callers expect CRLF to be trimmed, but many also want all trailing whitespace trimmed.
builder.TrimNewLine ();
// FIXME: All callers expect CRLF to be trimmed, but many also want all trailing whitespace trimmed.
builder.TrimNewLine ();

return builder.ToString ();
}
return builder.ToString ();
}

/// <summary>
Expand All @@ -875,18 +885,18 @@ public string ReadLine (CancellationToken cancellationToken)
/// </exception>
public async Task<string> ReadLineAsync (CancellationToken cancellationToken)
{
using (var builder = new ByteArrayBuilder (64)) {
bool complete;
builder.Clear ();

do {
complete = await Stream.ReadLineAsync (builder, cancellationToken).ConfigureAwait (false);
} while (!complete);
bool complete;

// FIXME: All callers expect CRLF to be trimmed, but many also want all trailing whitespace trimmed.
builder.TrimNewLine ();
do {
complete = await Stream.ReadLineAsync (builder, cancellationToken).ConfigureAwait (false);
} while (!complete);

return builder.ToString ();
}
// FIXME: All callers expect CRLF to be trimmed, but many also want all trailing whitespace trimmed.
builder.TrimNewLine ();

return builder.ToString ();
}

internal Task<string> ReadLineAsync (bool doAsync, CancellationToken cancellationToken)
Expand Down
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