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Fix loss of precision with BigDateTime #219

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Fix loss of precision with BigDateTime #219

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10 changes: 5 additions & 5 deletions src/AdoNetCore.AseClient/Internal/StreamReadExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -184,10 +184,10 @@ public static DateTime ReadBigDateTime(this Stream stream)
{
var usSinceYearZero = stream.ReadLong();
var usSinceEpoch = usSinceYearZero - Constants.Sql.BigDateTime.EpochMicroSeconds;
var msSinceEpoch = usSinceEpoch / 1000;
var timeSinceEpoch = TimeSpan.FromMilliseconds(msSinceEpoch);
const long ticksPerMicrosecond = TimeSpan.TicksPerMillisecond / 1000;
var ticksSinceEpoch = usSinceEpoch * ticksPerMicrosecond;

return Constants.Sql.BigDateTime.Epoch + timeSinceEpoch;
return Constants.Sql.BigDateTime.Epoch.AddTicks(ticksSinceEpoch);
}

public static DateTime ReadShortPartDateTime(this Stream stream)
Expand Down Expand Up @@ -222,9 +222,9 @@ public static DateTime ReadTime(this Stream stream)
var buf = new byte[length];

stream.Read(buf, 1, remainingLength);

Array.Reverse(buf);

return new AseDecimal(precision, scale, isPositive, buf);
}

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4 changes: 2 additions & 2 deletions src/AdoNetCore.AseClient/Internal/StreamWriteExtensions.cs
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Expand Up @@ -184,8 +184,8 @@ public static void WriteIntPartDateTime(this Stream stream, DateTime value)
public static void WriteBigDateTime(this Stream stream, DateTime value)
{
var timeSinceEpoch = value - Constants.Sql.BigDateTime.Epoch;
var msSinceEpoch = timeSinceEpoch.Ticks / TimeSpan.TicksPerMillisecond;
var usSinceEpoch = msSinceEpoch * 1000;
const long ticksPerMicrosecond = TimeSpan.TicksPerMillisecond / 1000;
var usSinceEpoch = timeSinceEpoch.Ticks / ticksPerMicrosecond;
var usSinceYearZero = usSinceEpoch + Constants.Sql.BigDateTime.EpochMicroSeconds;

stream.WriteByte(8); // length
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14 changes: 9 additions & 5 deletions ....AseClient.Tests/Unit/StreamWriteTests.cs → ...Client.Tests/Unit/StreamWriteReadTests.cs
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Expand Up @@ -6,20 +6,23 @@

namespace AdoNetCore.AseClient.Tests.Unit
{
public class StreamWriteTests
public class StreamWriteReadTests
{
[TestCaseSource(nameof(WriteBigDateTime_Succeeds_Cases))]
public void WriteBigDateTime_Succeeds(string _, DateTime value, byte[] expected)
[TestCaseSource(nameof(WriteReadBigDateTime_Succeeds_Cases))]
public void WriteReadBigDateTime_Succeeds(string _, DateTime value, byte[] expected)
{
using (var ms = new MemoryStream())
{
ms.WriteBigDateTime(value);
ms.Seek(0, SeekOrigin.Begin);
Assert.AreEqual(BitConverter.ToInt64(expected, 0), BitConverter.ToInt64(ms.ToArray(), 1));
ms.Seek(1, SeekOrigin.Begin);
var readBack = ms.ReadBigDateTime();
Assert.AreEqual(value, readBack);
}
}

public static IEnumerable<TestCaseData> WriteBigDateTime_Succeeds_Cases()
public static IEnumerable<TestCaseData> WriteReadBigDateTime_Succeeds_Cases()
{
yield return new TestCaseData("0001_1", new DateTime(0001, 01, 01, 0, 0, 0, 0), new byte[] { 0x00, 0x40, 0xEB, 0xA9, 0xC2, 0x1C, 0x00, 0x00 });
yield return new TestCaseData("0001_2", new DateTime(0001, 01, 01, 0, 0, 0, 1), new byte[] { 0xE8, 0x43, 0xEB, 0xA9, 0xC2, 0x1C, 0x00, 0x00 });
Expand All @@ -30,7 +33,8 @@ public static IEnumerable<TestCaseData> WriteBigDateTime_Succeeds_Cases()
yield return new TestCaseData("1753_1", new DateTime(1753, 1, 1, 0, 0, 0, 0, 0), new byte[] { 0x00, 0xA0, 0x7E, 0xDC, 0xB6, 0x88, 0xC4, 0x00 });
yield return new TestCaseData("1900_1", new DateTime(1900, 1, 1, 0, 0, 0, 0, 0), new byte[] { 0x00, 0x60, 0x5A, 0x60, 0xB1, 0x03, 0xD5, 0x00 });
yield return new TestCaseData("1900_2", new DateTime(1900, 1, 1, 23, 59, 59, 999), new byte[] { 0x18, 0xBC, 0x31, 0x7E, 0xC5, 0x03, 0xD5, 0x00 });
yield return new TestCaseData("1900_3", new DateTime(1900, 01, 01).Add(TimeSpan.FromHours(24).Add(TimeSpan.FromTicks(-1))), new byte[] { 0x18, 0xBC, 0x31, 0x7E, 0xC5, 0x03, 0xD5, 0x00 });
// .Net ticks are 1/10 us, so we must lose the last digit of number of ticks
yield return new TestCaseData("1900_3", new DateTime(1900, 01, 01).Add(TimeSpan.FromHours(24).Add(TimeSpan.FromTicks(-10))), new byte[] { 0xFF, 0xBF, 0x31, 0x7E, 0xC5, 0x03, 0xD5, 0x00 });
yield return new TestCaseData("9999_1", new DateTime(9999, 1, 1, 0, 0, 0, 0, 0), new byte[] { 0x00, 0x80, 0x76, 0xE9, 0x1F, 0x04, 0x61, 0x04 });
}
}
Expand Down