利用ADO吧,很简单的!
GETCHUNK()
vb exam:
Public Sub AppendChunkX()
Dim cnn1 As ADODB.Connection
Dim rstPubInfo As ADODB.Recordset
Dim strCnn As String
Dim strPubID As String
Dim strPRInfo As String
Dim lngOffset As Long
Dim lngLogoSize As Long
Dim varLogo As Variant
Dim varChunk As Variant
Const conChunkSize = 100
' Open a connection.
Set cnn1 = New ADODB.Connection
strCnn = "Provider=sqloledb;" & _
"Data Source=srv;Initial Catalog=Pubs;User Id=sa;Password=; "
cnn1.Open strCnn
' Open the pub_info table.
Set rstPubInfo = New ADODB.Recordset
rstPubInfo.CursorType = adOpenKeyset
rstPubInfo.LockType = adLockOptimistic
rstPubInf
pen "pub_info", cnn1, , , adCmdTable
' Prompt for a logo to copy.
strMsg = "Available logos are : " & vbCr & vbCr
Do While Not rstPubInfo.EOF
strMsg = strMsg & rstPubInfo!pub_id & vbCr & _
Left(rstPubInfo!pr_info, InStr(rstPubInfo!pr_info, ",") - 1) & _
vbCr & vbCr
rstPubInfo.MoveNext
Loop
strMsg = strMsg & "Enter the ID of a logo to copy:"
strPubID = InputBox(strMsg)
' Copy the logo to a variable in chunks.
rstPubInfo.Filter = "pub_id = '" & strPubID & "'"
lngLogoSize = rstPubInfo!logo.ActualSize
Do While lngOffset < lngLogoSize
varChunk = rstPubInfo!logo.GetChunk(conChunkSize)
varLogo = varLogo & varChunk
lngOffset = lngOffset + conChunkSize
Loop
' Get data from the user.
strPubID = Trim(InputBox("Enter a new pub ID" & _
" [must be > 9899 & < 9999]:"))
strPRInfo = Trim(InputBox("Enter descriptive text:"))
' Add the new publisher to the publishers table to avoid
' getting an error due to foreign key constraint.
cnn1.Execute "INSERT publishers(pub_id, pub_name) VALUES('" & _
strPubID & "','Your Test Publisher')"
' Add a new record, copying the logo in chunks.
rstPubInfo.AddNew
rstPubInfo!pub_id = strPubID
rstPubInfo!pr_info = strPRInfo
lngOffset = 0 ' Reset offset.
Do While lngOffset < lngLogoSize
varChunk = LeftB(RightB(varLogo, lngLogoSize - lngOffset), _
conChunkSize)
rstPubInfo!logo.AppendChunk varChunk
lngOffset = lngOffset + conChunkSize
Loop
rstPubInfo.Update
' Show the newly added data.
MsgBox "New record: " & rstPubInfo!pub_id & vbCr & _
"Description: " & rstPubInfo!pr_info & vbCr & _
"Logo size: " & rstPubInfo!logo.ActualSize
' Delete new records because this is a demonstration.
rstPubInfo.Requery
cnn1.Execute "DELETE FROM pub_info " & _
"WHERE pub_id = '" & strPubID & "'"
cnn1.Execute "DELETE FROM publishers " & _
"WHERE pub_id = '" & strPubID & "'"
rstPubInfo.Close
cnn1.Close
End Sub
VC exam:
#import "C:/Program Files/Common Files/System/ADO/msado15.dll" /
no_namespace rename("EOF", "EndOfFile")
#define ChunkSize 100
#include <ole2.h>
#include <stdio.h>
#include "conio.h"
#include "malloc.h"
#include "AppendChunkX.h"
//Function declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void AppendChunkX(void);
void PrintProviderError(_ConnectionPtr pConnection);
///////////////////////////////////////////////////////////
// //
// Main Function //
// //
///////////////////////////////////////////////////////////
void main()
{
if(FAILED
:CoInitialize(NULL)))
return;
AppendChunkX();
::CoUninitialize();
}
///////////////////////////////////////////////////////////
// //
// AppendChunkX Function //
// //
///////////////////////////////////////////////////////////
void AppendChunkX(void)
{
// Define ADO object pointers.
// Initialize pointers on define.
// These are in the ADODB:: namespace.
_RecordsetPtr pRstPubInfo = NULL;
_ConnectionPtr pConnection = NULL;
//Define other variables
//Interface Pointer declared.(VC++ Extensions)
IADORecordBinding *picRs = NULL;
CPubInfoRs pubrs; //C++ class object
HRESULT hr = S_OK;
_bstr_t strCnn("Provider=sqloledb;Data Source=srv;"
"Initial Catalog=Pubs;User Id=sa;Password=;");
_bstr_t strMessage,strPubID,strPRInfo;
_variant_t varChunk;
long lngOffSet,lngLogoSize;
char pubId[50];
lngOffSet = 0;
UCHAR chData;
CHAR ch;
SAFEARRAY FAR *psa;
SAFEARRAYBOUND rgsabound[1];
rgsabound[0].lLbound = 0;
rgsabound[0].cElements = ChunkSize;
try
{
//Open a Connection.
TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
TESTHR(pConnection->Open(strCnn,"","",NULL));
TESTHR(hr= pRstPubInfo.CreateInstance(__uuidof(Recordset)));
pRstPubInfo->CursorType = adOpenKeyset;
pRstPubInfo->LockType = adLockOptimistic;
TESTHR(pRstPubInfo->Open("pub_info",
_variant_t((IDispatch*)pConnection,true),
adOpenKeyset,adLockOptimistic,adCmdTable));
//Open an IADORecordBinding interface pointer which we'll use
//for Binding Recordset to a class
TESTHR(pRstPubInfo->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
//Bind the Recordset to a C++ Class here
TESTHR(picRs->BindToRecordset(&pubrs));
//Display the available logos here
strMessage = "Available logos are: " + (_bstr_t)"/n/n";
printf(strMessage);
int Counter = 0;
while(!(pRstPubInfo->EndOfFile))
{
printf("/n%s",pubrs.m_sz_pubid);
printf("/n%s",strtok(pubrs.m_sz_prinfo,","));
//Display 5 records at a time and wait for user to continue.
if (++Counter >= 5)
{
Counter = 0;
printf("/nPress any key to continue...");
getch();
}
pRstPubInfo->MoveNext();
}
//Prompt For a Logo to Copy
printf("/nEnter the ID of a logo to copy: ");
scanf("%s",pubId);
strPubID = pubId;
//Copy the logo to a variable in chunks
pRstPubInfo->Filter = "pub_id = '" + strPubID + "'";
lngLogoSize = pRstPubInfo->Fields->Item["logo"]->ActualSize;
//Create a safe array to store the array of BYTES
rgsabound[0].cElements = lngLogoSize;
psa = SafeArrayCreate(VT_UI1,1,rgsabound);
long index1 = 0;
while(lngOffSet < lngLogoSize)
{
varChunk = pRstPubInfo->Fields->
Item["logo"]->GetChunk(ChunkSize);
//Copy the data only up to the Actual Size of Field.
for(long index=0;index<=(ChunkSize-1);index++)
{
hr= SafeArrayGetElement(varChunk.parray,&index,&chData);
if(SUCCEEDED(hr))
{
//Take BYTE by BYTE and advance Memory Location
TESTHR(SafeArrayPutElement(psa,&index1,&chData));
index1++;
}
else
break;
}
lngOffSet = lngOffSet + ChunkSize;
}
lngOffSet = 0;
printf("Enter a new Pub Id: ");
scanf("%s",pubrs.m_sz_pubid);
strPubID = pubrs.m_sz_pubid;
printf("Enter descriptive text: " );
scanf("%c",&ch);
gets(pubrs.m_sz_prinfo);
// Temporarily add new publisher to table to avoid error due
// to foreign key constraint.
pConnection->Execute("INSERT publishers(pub_id) VALUES('" +
strPubID + "')",NULL,adCmdText);
pRstPubInfo->AddNew();
pRstPubInfo->Fields->GetItem("pub_id")->PutValue(strPubID);
pRstPubInfo->Fields->GetItem("pr_info")->
PutValue(pubrs.m_sz_prinfo);
//Assign the Safe array to a variant.
varChunk.vt = VT_ARRAY|VT_UI1;
varChunk.parray = psa;
hr = pRstPubInfo->Fields->GetItem("logo")->
AppendChunk(varChunk);
//Update the table
pRstPubInfo->Update();
lngLogoSize = pRstPubInfo->Fields->Item["logo"]->ActualSize;
//Show the newly added record.
printf("New Record : %s/nDescription : %s/nLogo Size : %s/n",
pubrs.m_sz_pubid,
pubrs.m_sz_prinfo,(LPCSTR)(_bstr_t)pRstPubInfo->Fields->
Item["logo"]->ActualSize);
//Delete new records because this is demonstration.
pConnection->Execute("DELETE FROM PUB_INFO WHERE pub_id = '"
+ strPubID +"'",NULL,adCmdText);
pConnection->Execute("DELETE FROM publishers WHERE pub_id = '"
+ strPubID +"'",NULL,adCmdText);
pRstPubInfo->Close();
pConnection->Close();
}
catch(_com_error &e)
{
// Notify the user of errors if any.
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
PrintProviderError(pConnection);
printf("Source : %s /n Description : %s/n",
(LPCSTR)bstrSource,(LPCSTR)bstrDescription);
}
}
///////////////////////////////////////////////////////////
// //
// PrintProviderError Function //
// //
///////////////////////////////////////////////////////////
void PrintProviderError(_ConnectionPtr pConnection)
{
// Print Provider Errors from Connection object.
// pErr is a record object in the Connection's Error collection.
ErrorPtr pErr = NULL;
long nCount = 0;
long i = 0;
if( (pConnection->Errors->Count) > 0)
{
nCount = pConnection->Errors->Count;
// Collection ranges from 0 to nCount -1.
for(i = 0; i < nCount; i++)
{
pErr = pConnection->Errors->GetItem(i);
printf("/t Error number: %x/t%s", pErr->Number,
(LPCSTR) pErr->Description);
}
}
}
AppendChunkX.h:
#include "icrsint.h"
//This Class extracts pubid,prinfo.
class CPubInfoRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CPubInfoRs)
ADO_VARIABLE_LENGTH_ENTRY2(1, adVarChar, m_sz_pubid,
sizeof(m_sz_pubid), l_pubid, TRUE)
ADO_VARIABLE_LENGTH_ENTRY2(3, adVarChar, m_sz_prinfo,
sizeof(m_sz_prinfo), l_prinfo, TRUE)
END_ADO_BINDING()
public:
CHAR m_sz_pubid[10];
ULONG l_pubid;
CHAR m_sz_prinfo[200];
ULONG l_prinfo;
};
