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<H1> A.12.1 The Package Streams.Stream_IO</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6166"></A>[The subprograms in the child
package Streams.Stream_IO provide control over stream files. Access to
a stream file is either sequential, via a call on Read or Write to transfer
an array of stream elements, or positional (if supported by the implementation
for the given file), by specifying a relative index for an element. Since
a stream file can be converted to a Stream_Access value, calling stream-oriented
attribute subprograms of different element types with the same Stream_Access
value provides heterogeneous input-output.] See <A HREF="AA-13-13.html">13.13</A>
for a general discussion of streams. </DIV>
<H4 ALIGN=CENTER>Static Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>1.1/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>The elements of a stream file are stream elements. If positioning
is supported for the specified external file, a current index and current
size are maintained for the file as described in <A HREF="AA-A-8.html">A.8</A>.
If positioning is not supported, a current index is not maintained, and
the current size is implementation defined.<A NAME="I6167"></A><A NAME="I6168"></A>
</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>1.a.1/1</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Implementation defined: </B><U>Current
size for a stream file for which positioning is not supported.</U></FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> The library package
Streams.Stream_IO has the following declaration: </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Examples"><TT><B>with</B> Ada.IO_Exceptions;<A NAME="I6169"></A><A NAME="I6170"></A><A NAME="I6171"></A><BR>
<B>package</B> Ada.Streams.Stream_IO <B>is</B></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Examples"><TT> <B>type</B> <A NAME="I6172"></A><A NAME="I6173"></A>Stream_Access <B>is</B> <B>access</B> <B>all</B> Root_Stream_Type'Class;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Examples"><TT> <B>type</B> <A NAME="I6174"></A><A NAME="I6175"></A>File_Type <B>is</B> <B>limited</B> <B>private;</B></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Examples"><TT> <B>type</B> <A NAME="I6176"></A><A NAME="I6177"></A>File_Mode <B>is</B> (In_File, Out_File, Append_File);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Examples"><TT> <B>type</B> <A NAME="I6178"></A><A NAME="I6179"></A>Count <B>is</B> <B>range</B> 0 .. <I>implementation-defined</I>;<BR>
<B>subtype</B> <A NAME="I6180"></A>Positive_Count <B>is</B> Count <B>range</B> 1 .. Count'Last;<BR>
-- <I>Index into file, in stream elements.</I></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6181"></A><A NAME="I6182"></A>Create (File : <B>in</B> <B>out</B> File_Type;<BR>
Mode : <B>in</B> File_Mode := Out_File;<BR>
Name : <B>in</B> String := "";<BR>
Form : <B>in</B> String := "");</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6183"></A><A NAME="I6184"></A>Open (File : <B>in</B> <B>out</B> File_Type;<BR>
Mode : <B>in</B> File_Mode;<BR>
Name : <B>in</B> String;<BR>
Form : <B>in</B> String := "");</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6185"></A><A NAME="I6186"></A>Close (File : <B>in</B> <B>out</B> File_Type);<BR>
<B>procedure</B> <A NAME="I6187"></A><A NAME="I6188"></A>Delete (File : <B>in</B> <B>out</B> File_Type);<BR>
<B>procedure</B> <A NAME="I6189"></A><A NAME="I6190"></A>Reset (File : <B>in</B> <B>out</B> File_Type; Mode : <B>in</B> File_Mode);<BR>
<B>procedure</B> <A NAME="I6191"></A><A NAME="I6192"></A>Reset (File : <B>in</B> <B>out</B> File_Type);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6193"></A><A NAME="I6194"></A>Mode (File : <B>in</B> File_Type) <B>return</B> File_Mode;<BR>
<B>function</B> <A NAME="I6195"></A><A NAME="I6196"></A>Name (File : <B>in</B> File_Type) <B>return</B> String;<BR>
<B>function</B> <A NAME="I6197"></A><A NAME="I6198"></A>Form (File : <B>in</B> File_Type) <B>return</B> String;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6199"></A><A NAME="I6200"></A>Is_Open (File : <B>in</B> File_Type) <B>return</B> Boolean;<BR>
<B>function</B> <A NAME="I6201"></A><A NAME="I6202"></A>End_Of_File (File : <B>in</B> File_Type) <B>return</B> Boolean;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6203"></A><A NAME="I6204"></A>Stream (File : <B>in</B> File_Type) <B>return</B> Stream_Access;<BR>
-- <I>Return stream access for use with T'Input and T'Output</I></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14/1</FONT></DIV>
<DIV Class="Examples"><TT><FONT SIZE=-1><I>This paragraph was deleted.</I></FONT><S> </S></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="Examples"><TT> -- <I>Read array of stream elements from file</I><BR>
<B>procedure</B> <A NAME="I6205"></A><A NAME="I6206"></A>Read (File : <B>in</B> File_Type;<BR>
Item : <B>out</B> Stream_Element_Array;<BR>
Last : <B>out</B> Stream_Element_Offset;<BR>
From : <B>in</B> Positive_Count);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6207"></A><A NAME="I6208"></A>Read (File : <B>in</B> File_Type;<BR>
Item : <B>out</B> Stream_Element_Array;<BR>
Last : <B>out</B> Stream_Element_Offset);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>17/1</FONT></DIV>
<DIV Class="Examples"><TT><FONT SIZE=-1><I>This paragraph was deleted.</I></FONT><S> </S></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>18</FONT></DIV>
<DIV Class="Examples"><TT> -- <I>Write array of stream elements into file</I><BR>
<B>procedure</B> <A NAME="I6209"></A><A NAME="I6210"></A>Write (File : <B>in</B> File_Type;<BR>
Item : <B>in</B> Stream_Element_Array;<BR>
To : <B>in</B> Positive_Count);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>19</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6211"></A><A NAME="I6212"></A>Write (File : <B>in</B> File_Type;<BR>
Item : <B>in</B> Stream_Element_Array);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>20/1</FONT></DIV>
<DIV Class="Examples"><TT><FONT SIZE=-1><I>This paragraph was deleted.</I></FONT><S> </S></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>21</FONT></DIV>
<DIV Class="Examples"><TT> -- <I>Operations on position within file</I></TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>22</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6213"></A><A NAME="I6214"></A>Set_Index(File : <B>in</B> File_Type; To : <B>in</B> Positive_Count);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>23</FONT></DIV>
<DIV Class="Examples"><TT> <B>function</B> <A NAME="I6215"></A><A NAME="I6216"></A>Index(File : <B>in</B> File_Type) <B>return</B> Positive_Count;<BR>
<B>function</B> <A NAME="I6217"></A><A NAME="I6218"></A>Size (File : <B>in</B> File_Type) <B>return</B> Count;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>24</FONT></DIV>
<DIV Class="Examples"><TT> <B>procedure</B> <A NAME="I6219"></A><A NAME="I6220"></A>Set_Mode(File : <B>in</B> <B>out</B> File_Type; Mode : <B>in</B> File_Mode);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>25/1</FONT></DIV>
<DIV Class="Examples"><TT>{<I><A HREF="defect1.html#8652/0051">8652/0051</A></I>}
<BR>
<B>procedure</B> <A NAME="I6221"></A><A NAME="I6222"></A>Flush(File : <B>in</B> <S><B>out</B> </S>File_Type);</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>26</FONT></DIV>
<DIV Class="Examples"><TT> -- <I>exceptions</I><BR>
<A NAME="I6223"></A>Status_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Status_Error;<BR>
<A NAME="I6224"></A>Mode_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Mode_Error;<BR>
<A NAME="I6225"></A>Name_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Name_Error;<BR>
<A NAME="I6226"></A>Use_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Use_Error;<BR>
<A NAME="I6227"></A>Device_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Device_Error;<BR>
<A NAME="I6228"></A>End_Error : <B>exception</B> <B>renames</B> IO_Exceptions.End_Error;<BR>
<A NAME="I6229"></A>Data_Error : <B>exception</B> <B>renames</B> IO_Exceptions.Data_Error;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>27</FONT></DIV>
<DIV Class="Examples"><TT><B>private</B><BR>
... -- <I>not specified by the language</I><BR>
<B>end</B> Ada.Streams.Stream_IO;</TT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>28</FONT></DIV>
<DIV Class="Normal"> The subprograms Create, Open, Close, Delete,
Reset, Mode, Name, Form, Is_Open, and End_of_File have the same effect
as the corresponding subprograms in Sequential_IO (see <A HREF="AA-A-8-2.html">A.8.2</A>).</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>28.1/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>The Set_Mode procedure changes the mode of the file. If the new mode
is Append_File, the file is positioned to its end; otherwise, the position
in the file is unchanged.</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>28.2/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>The Flush procedure synchronizes the external file with the internal
file (by flushing any internal buffers) without closing the file or changing
the position. Mode_Error is propagated if the mode of the file is In_File.</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>29/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0056">8652/0056</A></I>}
The Stream function returns a Stream_Access result from a File_Type object,
thus allowing the stream-oriented attributes Read, Write, Input, and
Output to be used on the same file for multiple types. <U>Stream propagates
Status_Error if File is not open.</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>30</FONT></DIV>
<DIV Class="Normal"> The procedures Read and Write are equivalent
to the corresponding operations in the package Streams. Read propagates
Mode_Error if the mode of File is not In_File. Write propagates Mode_Error
if the mode of File is not Out_File or Append_File. The Read procedure
with a Positive_Count parameter starts reading at the specified index.
The Write procedure with a Positive_Count parameter starts writing at
the specified index.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>30.1/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>The Size function returns the current size of the file.</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>31/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
The Index function returns the current <S>file </S>index<S>, as a count
(in stream elements) from the beginning of the file. The position of
the first element in the file is 1</S>. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>31.a/1</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><FONT SIZE=-1><I>This paragraph
was deleted.</I></FONT><B>Ramification: </B><S>The notion of Index for
Stream_IO is analogous to that of Index in Direct_IO, except that the
former is measured in Stream_Element units, whereas the latter is in
terms of Element_Type values.</S> </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>32</FONT></DIV>
<DIV Class="Normal"> The Set_Index procedure sets the current index
to the specified value.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>32.1/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>If positioning is supported for the external file, the current index
is maintained as follows:</U></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>32.2/1</FONT></DIV>
<UL Class="Bulleted" Style="margin-bottom: 0.3em"><LI TYPE=DISC>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>For Open and Create, if the Mode parameter is Append_File, the current
index is set to the current size of the file plus one; otherwise, the
current index is set to one.</U></LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>32.3/1</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>For Reset, if the Mode parameter is Append_File, or no Mode parameter
is given and the current mode is Append_File, the current index is set
to the current size of the file plus one; otherwise, the current index
is set to one.</U></LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>32.4/1</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>For Set_Mode, if the new mode is Append_File, the current index is
set to current size plus one; otherwise, the current index is unchanged.</U></LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>32.5/1</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>For Read and Write without a Positive_Count parameter, the current
index is incremented by the number of stream elements read or written.</U></LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>32.6/1</FONT></DIV>
<UL Class="Bulleted"><LI TYPE=DISC>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<U>For Read and Write with a Positive_Count parameter, the value of the
current index is set to the value of the Positive_Count parameter plus
the number of stream elements read or written.</U> </LI></UL>
<DIV Class="Paranum"><FONT SIZE=-2>33</FONT></DIV>
<DIV Class="Normal"> If positioning is not supported for the given
file, then a call of Index or Set_Index propagates Use_Error. Similarly,
a call of Read or Write with a Positive_Count parameter propagates Use_Error.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>34/1</FONT></DIV>
<DIV Class="Normal"> <FONT SIZE=-1><I>This paragraph was deleted.</I></FONT>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<S>The Size function returns the current size of the file, in stream
elements.</S></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>35/1</FONT></DIV>
<DIV Class="Normal"> <FONT SIZE=-1><I>This paragraph was deleted.</I></FONT>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<S>The Set_Mode procedure changes the mode of the file. If the new mode
is Append_File, the file is positioned to its end; otherwise, the position
in the file is unchanged.</S></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>36/1</FONT></DIV>
<DIV Class="Normal"> <FONT SIZE=-1><I>This paragraph was deleted.</I></FONT>{<I><A HREF="defect1.html#8652/0055">8652/0055</A></I>}
<S>The Flush procedure synchronizes the external file with the internal
file (by flushing any internal buffers) without closing the file or changing
the position. Mode_Error is propagated if the mode of the file is In_File.</S>
</DIV>
<H4 ALIGN=CENTER>Erroneous Execution</H4>
<DIV Class="Paranum"><FONT SIZE=-2>36.1/1</FONT></DIV>
<DIV Class="Normal"> {<I><A HREF="defect1.html#8652/0056">8652/0056</A></I>}
<U><A NAME="I6230"></A>If the File_Type object passed to the Stream function
is later closed or finalized, and the stream-oriented attributes are
subsequently called (explicitly or implicitly) on the Stream_Access value
returned by Stream, execution is erroneous. This rule applies even if
the File_Type object was opened again after it had been closed.</U> </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>36.a.1/1</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Reason: </B><U>These rules
are analogous to the rule for the result of the Current_Input, Current_Output,
and Current_Error functions. These rules make it possible to represent
a value of (some decendant of) Root_Stream_Type which represents a file
as an access value, with a null value corresponding to a closed file.</U>
</FONT></DIV>
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