/// <summary>
/// Recursively pin the retrieve buffers in the JET_RETRIEVECOLUMN
/// structures and then retrieve the columns. This is done to avoid
/// creating GCHandles which is very expensive. This function pins
/// the current retrievecolumn structure (indicated by i) and then
/// recursively calls itself until all structures are pinned. This
/// is done because it isn't possible to create an arbitrary number
/// of pinned variables in a method.
/// </summary>
/// <param name="sesid">
/// The session to use.
/// </param>
/// <param name="tableid">
/// The table to retrieve from.
/// </param>
/// <param name="nativeretrievecolumns">
/// The nativeretrievecolumns structure.</param>
/// <param name="retrievecolumns">
/// The managed retrieve columns structure.
/// </param>
/// <param name="numColumns">The number of columns.</param>
/// <param name="i">The column currently being processed.</param>
/// <returns>An error code from JetRetrieveColumns.</returns>
private static unsafe int PinColumnsAndRetrieve(
JET_SESID sesid,
JET_TABLEID tableid,
NATIVE_RETRIEVECOLUMN *nativeretrievecolumns,
JET_RETRIEVECOLUMN[] retrievecolumns,
int numColumns,
int i)
{
retrievecolumns[i].CheckDataSize();
nativeretrievecolumns[i] = retrievecolumns[i].GetNativeRetrievecolumn();
fixed(byte *pinnedBuffer = retrievecolumns[i].pvData)
{
nativeretrievecolumns[i].pvData = new IntPtr(pinnedBuffer);
if (numColumns - 1 == i)
{
return(Impl.JetRetrieveColumns(sesid, tableid, nativeretrievecolumns, numColumns));
}
return(PinColumnsAndRetrieve(sesid, tableid, nativeretrievecolumns, retrievecolumns, numColumns, i + 1));
}
}
/// <summary>
/// Recursively pin the retrieve buffers in the JET_RETRIEVECOLUMN
/// structures and then retrieve the columns. This is done to avoid
/// creating GCHandles, which are expensive. This function pins
/// the current retrievecolumn structure (indicated by i) and then
/// recursively calls itself until all structures are pinned. This
/// is done because it isn't possible to create an arbitrary number
/// of pinned variables in a method.
/// </summary>
/// <param name="sesid">
/// The session to use.
/// </param>
/// <param name="tableid">
/// The table to retrieve from.
/// </param>
/// <param name="nativeretrievecolumns">
/// The nativeretrievecolumns structure.</param>
/// <param name="retrievecolumns">
/// The managed retrieve columns structure.
/// </param>
/// <param name="numColumns">The number of columns.</param>
/// <param name="i">The column currently being processed.</param>
/// <returns>An error code from JetRetrieveColumns.</returns>
private static unsafe int PinColumnsAndRetrieve(
JET_SESID sesid,
JET_TABLEID tableid,
NATIVE_RETRIEVECOLUMN *nativeretrievecolumns,
IList <JET_RETRIEVECOLUMN> retrievecolumns,
int numColumns,
int i)
{
// If consecutive JET_RETRIEVECOLUMN structures are using the same buffer then only pin it once.
fixed(byte *pinnedBuffer = retrievecolumns[i].pvData)
{
do
{
retrievecolumns[i].CheckDataSize();
retrievecolumns[i].GetNativeRetrievecolumn(ref nativeretrievecolumns[i]);
nativeretrievecolumns[i].pvData = new IntPtr(pinnedBuffer + retrievecolumns[i].ibData);
i++;
}while (i < numColumns && retrievecolumns[i].pvData == retrievecolumns[i - 1].pvData);
return(i == numColumns?
Impl.JetRetrieveColumns(sesid, tableid, nativeretrievecolumns, numColumns)
: PinColumnsAndRetrieve(sesid, tableid, nativeretrievecolumns, retrievecolumns, numColumns, i));
}
}
public static unsafe extern int JetRetrieveColumns(
IntPtr sesid, IntPtr tableid, [In][Out] NATIVE_RETRIEVECOLUMN *psetcolumn, uint csetcolumn);
/// <summary>
/// Recursive RetrieveColumns method for data pinning. This should pin a buffer and
/// call the inherited RetrieveColumns method.
/// </summary>
/// <param name="sesid">The session to use.</param>
/// <param name="tableid">
/// The table to retrieve the columns from.
/// </param>
/// <param name="columnValues">
/// Column values to retrieve.
/// </param>
/// <returns>An error code.</returns>
internal static int RetrieveColumns(JET_SESID sesid, JET_TABLEID tableid, ColumnValue[] columnValues)
{
if (columnValues.Length > 1024)
{
throw new ArgumentOutOfRangeException("columnValues", columnValues.Length, "Too many column values");
}
int err;
unsafe
{
NATIVE_RETRIEVECOLUMN *nativeRetrievecolumns = stackalloc NATIVE_RETRIEVECOLUMN[columnValues.Length];
byte[] buffer = memoryCache.Allocate();
fixed(byte *pinnedBuffer = buffer)
{
byte *currentBuffer = pinnedBuffer;
int numVariableLengthColumns = columnValues.Length;
// First the fixed-size columns
for (int i = 0; i < columnValues.Length; ++i)
{
if (0 != columnValues[i].Size)
{
columnValues[i].MakeNativeRetrieveColumn(ref nativeRetrievecolumns[i]);
nativeRetrievecolumns[i].pvData = new IntPtr(currentBuffer);
nativeRetrievecolumns[i].cbData = checked ((uint)columnValues[i].Size);
currentBuffer += nativeRetrievecolumns[i].cbData;
Debug.Assert(currentBuffer <= pinnedBuffer + buffer.Length, "Moved past end of pinned buffer");
numVariableLengthColumns--;
}
}
// Now the variable-length columns
if (numVariableLengthColumns > 0)
{
int bufferUsed = checked ((int)(currentBuffer - pinnedBuffer));
int bufferRemaining = checked (buffer.Length - bufferUsed);
int bufferPerColumn = bufferRemaining / numVariableLengthColumns;
Debug.Assert(bufferPerColumn > 0, "Not enough buffer left to retrieve variable length columns");
// Now the variable-size columns
for (int i = 0; i < columnValues.Length; ++i)
{
if (0 == columnValues[i].Size)
{
columnValues[i].MakeNativeRetrieveColumn(ref nativeRetrievecolumns[i]);
nativeRetrievecolumns[i].pvData = new IntPtr(currentBuffer);
nativeRetrievecolumns[i].cbData = checked ((uint)bufferPerColumn);
currentBuffer += nativeRetrievecolumns[i].cbData;
Debug.Assert(currentBuffer <= pinnedBuffer + buffer.Length, "Moved past end of pinned buffer");
}
}
}
// Retrieve the columns
err = Api.Impl.JetRetrieveColumns(sesid, tableid, nativeRetrievecolumns, columnValues.Length);
// Propagate the errors.
for (int i = 0; i < columnValues.Length; ++i)
{
columnValues[i].Error = (JET_err)nativeRetrievecolumns[i].err;
}
// Now parse out the columns that were retrieved successfully
for (int i = 0; i < columnValues.Length; ++i)
{
if (nativeRetrievecolumns[i].err >= (int)JET_err.Success &&
nativeRetrievecolumns[i].err != (int)JET_wrn.BufferTruncated)
{
byte *columnBuffer = (byte *)nativeRetrievecolumns[i].pvData;
int startIndex = checked ((int)(columnBuffer - pinnedBuffer));
columnValues[i].GetValueFromBytes(
buffer,
startIndex,
checked ((int)nativeRetrievecolumns[i].cbActual),
nativeRetrievecolumns[i].err);
}
}
}
memoryCache.Free(buffer);
// Finally retrieve the buffers where the columns weren't large enough.
RetrieveTruncatedBuffers(sesid, tableid, columnValues, nativeRetrievecolumns);
}
return(err);
}
/// <summary>
/// Retrieve the value for columns whose buffers were truncated.
/// </summary>
/// <param name="sesid">The session to use.</param>
/// <param name="tableid">The table to use.</param>
/// <param name="columnValues">The column values.</param>
/// <param name="nativeRetrievecolumns">
/// The native retrieve columns that match the column values.
/// </param>
private static unsafe void RetrieveTruncatedBuffers(JET_SESID sesid, JET_TABLEID tableid, ColumnValue[] columnValues, NATIVE_RETRIEVECOLUMN *nativeRetrievecolumns)
{
for (int i = 0; i < columnValues.Length; ++i)
{
if (nativeRetrievecolumns[i].err == (int)JET_wrn.BufferTruncated)
{
var buffer = new byte[nativeRetrievecolumns[i].cbActual];
int actualSize;
int err;
var retinfo = new JET_RETINFO {
itagSequence = columnValues[i].ItagSequence
};
// Pin the buffer and retrieve the data
fixed(byte *pinnedBuffer = buffer)
{
err = Api.Impl.JetRetrieveColumn(
sesid,
tableid,
columnValues[i].Columnid,
new IntPtr(pinnedBuffer),
buffer.Length,
out actualSize,
columnValues[i].RetrieveGrbit,
retinfo);
}
// Set the error in the ColumnValue before checkin it
columnValues[i].Error = (JET_err)err;
Api.Check(err);
// For BytesColumnValue this will copy the data to a new array.
// If this situation becomes common we should simply use the array.
columnValues[i].GetValueFromBytes(buffer, 0, actualSize, err);
}
}
}
/// <summary>
/// Retrieve the value for columns whose buffers were truncated.
/// </summary>
/// <param name="sesid">The session to use.</param>
/// <param name="tableid">The table to use.</param>
/// <param name="columnValues">The column values.</param>
/// <param name="nativeRetrievecolumns">
/// The native retrieve columns that match the column values.
/// </param>
private static unsafe void RetrieveTruncatedBuffers(JET_SESID sesid, JET_TABLEID tableid, IList <ColumnValue> columnValues, NATIVE_RETRIEVECOLUMN *nativeRetrievecolumns)
{
for (int i = 0; i < columnValues.Count; ++i)
{
if (nativeRetrievecolumns[i].err == (int)JET_wrn.BufferTruncated)
{
var buffer = new byte[nativeRetrievecolumns[i].cbActual];
int actualSize;
int err;
var retinfo = new JET_RETINFO {
itagSequence = columnValues[i].ItagSequence
};
// Pin the buffer and retrieve the data
fixed(byte *pinnedBuffer = buffer)
{
err = Api.Impl.JetRetrieveColumn(
sesid,
tableid,
columnValues[i].Columnid,
new IntPtr(pinnedBuffer),
buffer.Length,
out actualSize,
columnValues[i].RetrieveGrbit,
retinfo);
}
if (JET_wrn.BufferTruncated == (JET_wrn)err)
{
string error = string.Format(
CultureInfo.CurrentCulture,
"Column size changed from {0} to {1}. The record was probably updated by another thread.",
buffer.Length,
actualSize);
Trace.TraceError(error);
throw new InvalidOperationException(error);
}
// Throw errors, but put warnings in the structure
Api.Check(err);
columnValues[i].Error = (JET_wrn)err;
// For BytesColumnValue this will copy the data to a new array.
// If this situation becomes common we should simply use the array.
columnValues[i].GetValueFromBytes(buffer, 0, actualSize, err);
}
}
}
/// <summary>
/// Recursive RetrieveColumns method for data pinning. This should pin a buffer and
/// call the inherited RetrieveColumns method.
/// </summary>
/// <param name="sesid">The session to use.</param>
/// <param name="tableid">
/// The table to retrieve the columns from.
/// </param>
/// <param name="columnValues">
/// Column values to retrieve.
/// </param>
internal static void RetrieveColumns(JET_SESID sesid, JET_TABLEID tableid, ColumnValue[] columnValues)
{
const int MaxColumnValues = 1024;
if (columnValues.Length > MaxColumnValues)
{
throw new ArgumentOutOfRangeException("columnValues", columnValues.Length, "Too many column values");
}
unsafe
{
byte[] buffer = null;
NATIVE_RETRIEVECOLUMN *nativeRetrievecolumns = stackalloc NATIVE_RETRIEVECOLUMN[columnValues.Length];
try
{
buffer = Caches.ColumnCache.Allocate();
Debug.Assert(MaxColumnValues * 16 < buffer.Length, "Maximum size of fixed columns could exceed buffer size");
fixed(byte *pinnedBuffer = buffer)
{
byte *currentBuffer = pinnedBuffer;
int numVariableLengthColumns = columnValues.Length;
// First the fixed-size columns
for (int i = 0; i < columnValues.Length; ++i)
{
if (0 != columnValues[i].Size)
{
columnValues[i].MakeNativeRetrieveColumn(ref nativeRetrievecolumns[i]);
nativeRetrievecolumns[i].pvData = new IntPtr(currentBuffer);
nativeRetrievecolumns[i].cbData = checked ((uint)columnValues[i].Size);
currentBuffer += nativeRetrievecolumns[i].cbData;
Debug.Assert(currentBuffer <= pinnedBuffer + buffer.Length, "Moved past end of pinned buffer");
numVariableLengthColumns--;
}
}
// Now the variable-length columns
if (numVariableLengthColumns > 0)
{
int bufferUsed = checked ((int)(currentBuffer - pinnedBuffer));
int bufferRemaining = checked (buffer.Length - bufferUsed);
int bufferPerColumn = bufferRemaining / numVariableLengthColumns;
Debug.Assert(bufferPerColumn > 0, "Not enough buffer left to retrieve variable length columns");
// Now the variable-size columns
for (int i = 0; i < columnValues.Length; ++i)
{
if (0 == columnValues[i].Size)
{
columnValues[i].MakeNativeRetrieveColumn(ref nativeRetrievecolumns[i]);
nativeRetrievecolumns[i].pvData = new IntPtr(currentBuffer);
nativeRetrievecolumns[i].cbData = checked ((uint)bufferPerColumn);
currentBuffer += nativeRetrievecolumns[i].cbData;
Debug.Assert(currentBuffer <= pinnedBuffer + buffer.Length, "Moved past end of pinned buffer");
}
}
}
// Retrieve the columns
Api.Check(Api.Impl.JetRetrieveColumns(sesid, tableid, nativeRetrievecolumns, columnValues.Length));
// Propagate the warnings and output.
for (int i = 0; i < columnValues.Length; ++i)
{
columnValues[i].Error = (JET_wrn)nativeRetrievecolumns[i].err;
columnValues[i].ItagSequence = (int)nativeRetrievecolumns[i].itagSequence;
}
// Now parse out the columns that were retrieved successfully
for (int i = 0; i < columnValues.Length; ++i)
{
if (nativeRetrievecolumns[i].err != (int)JET_wrn.BufferTruncated)
{
byte *columnBuffer = (byte *)nativeRetrievecolumns[i].pvData;
int startIndex = checked ((int)(columnBuffer - pinnedBuffer));
columnValues[i].GetValueFromBytes(
buffer,
startIndex,
checked ((int)nativeRetrievecolumns[i].cbActual),
nativeRetrievecolumns[i].err);
}
}
}
// Finally retrieve the buffers where the columns weren't large enough.
RetrieveTruncatedBuffers(sesid, tableid, columnValues, nativeRetrievecolumns);
}
finally
{
if (buffer != null)
{
Caches.ColumnCache.Free(ref buffer);
}
}
}
}
