SQL Server对图像数据存储机制介绍(2)

Public Function AppendBlobFromFile
(blobColumn As ADODB.Field, ByVal FileName) As Boolean
Dim FileNumber     As Integer     '文件号
           Dim DataLen             As Long            '文件长度
Dim Chunks               As Long            '数据块数
Dim ChunkAry()     As Byte     '数据块数组
Dim ChunkSize      As Long            '数据块大小
Dim Fragment       As Long            '零碎数据大小
Dim lngI                   As Long  '计数器
 
On Error GoTo ErrorHandle
AppendBlobFromFile = False
ChunkSize = 2048                          '限制每次读取的块大小为 2K
 
FileNumber = FreeFile                        '产生随机的文件号
Open FileName For Binary Access Read As FileNumber     '打开图像文件
DataLen = LOF(FileNumber)               '获得文件长度
      If IsNull(blobColumn) Then Exit Function
 
If DataLen = 0 Then                      '文件长度为0
Close FileNumber
  AppendBlobFromFile = True
  Exit Function
End If
       
Chunks = DataLen \ ChunkSize           '数据块的个数
Fragment = DataLen Mod ChunkSize
If Fragment > 0 Then                    '先写零碎数据
ReDim ChunkAry(Fragment - 1)
  Get FileNumber, , ChunkAry()          '读出文件
  blobColumn.AppendChunk ChunkAry   '调用AppendChunk函数写数据
End If
    
ReDim ChunkAry(ChunkSize - 1)        '为数据块开辟空间
For lngI = 1 To Chunks                        '循环读出所有数据块
  Get FileNumber, , ChunkAry()          '读出一块数据
  blobColumn.AppendChunk ChunkAry '在数据库中增加数据块
Next lngI
    
Close FileNumber                   '关闭文件
AppendBlobFromFile = True
Exit Function
ErrorHandle:
AppendBlobFromFile = False
MsgBox Err.Description, vbCritical, "写图像数据出错!"
End Function