[m-rev.] for review: implement io__read_file_as_string on il backend

[Peter Ross]

On Wed, Dec 04, 2002 at 11:35:09AM +1100, Fergus Henderson wrote:
> With the current implementation, which for .NET does not optimize no-tag
> types, it would be more efficient to avoid constructing buffer/1 values at
> each iteration of the loop.
> 
Done.

> Also, you could use array__unsafe_set here
> (which on .NET is in fact range-checked anyway).
> 
unsafe_set is local to the array modle.

> 
> Also, it would be more efficient to use a char_array type, which could be
> defined in C# as char[], rather than array(char).  For Java or .NET-style
> implementations of array, this would be faster, since indexing into
> an array whose element type is known statically avoids some overhead
> that is required when the element type isn't determined statically.
> (For C-style implementations of array, char_array could use a lot less
> memory than array(char).)  The current implementation is OK for now,
> but it would be good to have an XXX comment about this.
> 

diff -u io.m io.m
--- io.m
+++ io.m
@@ -2087,6 +2087,11 @@
 
 :- type buffer.
 :- pragma foreign_type(c, buffer, "MR_Char *").
+
+	% XXX It would be better to use a char_array (e.g. defined as char[] in
+	% C#) type rather than array(char).  This is because on the Java and IL
+	% backends indexing into an array whose element type is known
+	% statically requires less overhead.
 :- type buffer ---> buffer(array(char)).
 
 	% XXX Extend the workaround for no `ui' modes in array.m.
@@ -2200,6 +2205,13 @@
 }").
 
 io__read_into_buffer(Stream, buffer(Array0), Pos0, Size, buffer(Array), Pos) -->
+	io__read_into_array(Stream, Array0, Pos0, Size, Array, Pos).
+
+:- pred io__read_into_array(stream::in, array(char)::array_di, int::in, int::in,
+		    array(char)::array_uo, int::out,
+		    io__state::di, io__state::uo) is det.
+
+io__read_into_array(Stream, Array0, Pos0, Size, Array, Pos) -->
 	( { Pos0 >= Size } ->
 		{ Array = Array0 },
 		{ Pos = Pos0 }
@@ -2207,8 +2219,8 @@
 		io__read_char(Stream, CharResult),
 		( { CharResult = ok(Char) } ->
 			{ array__set(Array0, Pos0, Char, Array1) },
-			io__read_into_buffer(Stream, buffer(Array1), Pos0 + 1,
-					Size, buffer(Array), Pos)
+			io__read_into_array(Stream, Array1, Pos0 + 1,
+					Size, Array, Pos)
 		;
 			{ Array = Array0 },
 			{ Pos = Pos0}
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