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Fix | Avoid high mem alloc in TDSWriter#writeReader #1476

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Jan 12, 2021
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Fix | Avoid high mem alloc in TDSWriter#writeReader #1476

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Avoid high mem alloc in TDSWriter#writeReader
vyaslav Dec 6, 2020
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vyaslav Dec 6, 2020
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vyaslav Dec 6, 2020
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21 changes: 11 additions & 10 deletions src/main/java/com/microsoft/sqlserver/jdbc/IOBuffer.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3151,6 +3151,11 @@ boolean isEOMSent() {
private ByteBuffer socketBuffer;
private ByteBuffer logBuffer;

// Intermediate arrays
// It is assumed, startMessage is called before use, to alloc arrays
private char[] streamCharBuffer;
private byte[] streamByteBuffer;

private CryptoMetadata cryptoMeta = null;

TDSWriter(TDSChannel tdsChannel, SQLServerConnection con) {
Expand Down Expand Up @@ -3247,6 +3252,8 @@ void startMessage(TDSCommand command, byte tdsMessageType) throws SQLServerExcep
stagingBuffer = ByteBuffer.allocate(negotiatedPacketSize).order(ByteOrder.LITTLE_ENDIAN);
logBuffer = ByteBuffer.allocate(negotiatedPacketSize).order(ByteOrder.LITTLE_ENDIAN);
currentPacketSize = negotiatedPacketSize;
streamCharBuffer = new char[2 * currentPacketSize];
streamByteBuffer = new byte[4 * currentPacketSize];
}

((Buffer) socketBuffer).position(((Buffer) socketBuffer).limit());
Expand Down Expand Up @@ -4015,21 +4022,17 @@ void writeNonUnicodeReader(Reader reader, long advertisedLength, boolean isDestB
assert DataTypes.UNKNOWN_STREAM_LENGTH == advertisedLength || advertisedLength >= 0;

long actualLength = 0;
char[] streamCharBuffer = new char[currentPacketSize];
// The unicode version, writeReader() allocates a byte buffer that is 4 times the currentPacketSize, not sure
// why.
byte[] streamByteBuffer = new byte[currentPacketSize];
int charsRead = 0;
int charsToWrite;
int bytesToWrite;
String streamString;

do {
// Read in next chunk
for (charsToWrite = 0; -1 != charsRead && charsToWrite < streamCharBuffer.length;
for (charsToWrite = 0; -1 != charsRead && charsToWrite < currentPacketSize;
charsToWrite += charsRead) {
try {
charsRead = reader.read(streamCharBuffer, charsToWrite, streamCharBuffer.length - charsToWrite);
charsRead = reader.read(streamCharBuffer, charsToWrite, currentPacketSize - charsToWrite);
} catch (IOException e) {
MessageFormat form = new MessageFormat(SQLServerException.getErrString("R_errorReadingStream"));
Object[] msgArgs = {e.toString()};
Expand All @@ -4040,7 +4043,7 @@ void writeNonUnicodeReader(Reader reader, long advertisedLength, boolean isDestB
break;

// Check for invalid bytesRead returned from Reader.read
if (charsRead < 0 || charsRead > streamCharBuffer.length - charsToWrite) {
if (charsRead < 0 || charsRead > currentPacketSize - charsToWrite) {
MessageFormat form = new MessageFormat(SQLServerException.getErrString("R_errorReadingStream"));
Object[] msgArgs = {SQLServerException.getErrString("R_streamReadReturnedInvalidValue")};
error(form.format(msgArgs), SQLState.DATA_EXCEPTION_NOT_SPECIFIC, DriverError.NOT_SET);
Expand Down Expand Up @@ -4070,7 +4073,7 @@ void writeNonUnicodeReader(Reader reader, long advertisedLength, boolean isDestB
if (0 != charsToWrite)
bytesToWrite = charsToWrite / 2;

streamString = new String(streamCharBuffer);
streamString = new String(streamCharBuffer, 0, currentPacketSize);
byte[] bytes = ParameterUtils.HexToBin(streamString.trim());
writeInt(bytesToWrite);
writeBytes(bytes, 0, bytesToWrite);
Expand All @@ -4096,8 +4099,6 @@ void writeReader(Reader reader, long advertisedLength, boolean writeChunkSizes)
assert DataTypes.UNKNOWN_STREAM_LENGTH == advertisedLength || advertisedLength >= 0;

long actualLength = 0;
char[] streamCharBuffer = new char[2 * currentPacketSize];
byte[] streamByteBuffer = new byte[4 * currentPacketSize];
int charsRead = 0;
int charsToWrite;
do {
Expand Down