?? readfile.htm
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<title>ReadFile</title>
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<td width="100%" height="16"><a name="ReadFile">ReadFile</a></td>
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<td width="100%" colspan="2">VB聲明</td>
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<td width="100%" colspan="2">Declare Function ReadFile Lib "kernel32" Alias
"ReadFile" (ByVal hFile As Long, lpBuffer As Any, ByVal nNumberOfBytesToRead As
Long, lpNumberOfBytesRead As Long, lpOverlapped As OVERLAPPED) As Long</td>
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<td width="100%" colspan="2">說明</td>
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<td width="100%" colspan="2">從文件中讀出數據。與<a href="lread.htm">lread</a>函數相比，這個函數要明顯靈活的多。該函數能夠操作通信設備、管道、套接字以及郵槽</td>
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<td width="100%" colspan="2">返回值</td>
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<td width="100%" colspan="2">Long，非零表示成功，零表示失敗。會設置<a
href="GetLastError.htm">GetLastError</a>。如啟動的是一次異步讀操作，則函數會返回零值，并將ERROR_IO_PENDING設置成<a
href="GetLastError.htm">GetLastError</a>的結果。如結果不是零值，但讀入的字節數小于nNumberOfBytesToRead參數指定的值，表明早已抵達了文件的結尾</td>
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<td width="100%" colspan="2">參數表</td>
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<td width="25%">參數</td>
<td width="75%">類型及說明</td>
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<td width="25%">hFile</td>
<td width="75%">Long，文件的句柄</td>
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<td width="25%">lpBuffer</td>
<td width="75%">Any，用于保存讀入數據的一個緩沖區</td>
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<td width="25%">nNumberOfBytesToRead</td>
<td width="75%">Long，要讀入的字符數</td>
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<td width="25%">lpNumberOfBytesRead</td>
<td width="75%">Long，從文件中實際讀入的字符數</td>
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<td width="25%">lpOverlapped</td>
<td width="75%">OVERLAPPED，如文件打開時指定了FILE_FLAG_OVERLAPPED，那么必須用這個參數引用一個特殊的結構。那個結構定義了一次異步讀取操作。否則，應將這個參數設為NULL（將函數聲明成ByVal
As Long，并傳遞零值）</td>
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<td width="100%" colspan="2">注解</td>
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<td width="100%" colspan="2"><p align="left">并非每種操作系統都支持對每種設備進行異步操作。Windows
95不支持對一個磁盤文件進行異步讀操作（重復讀）</td>
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<td width="100%"><p align="right"><a href="#ReadFile">Top</a></td>
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