Today I was writing some range-based image-generation code, which produces a range of ubytes representing the resulting image file.  To my astonishment, there was no function in std.stdio that could spool this range to a File.

Initially, I tried lockingTextWriter, but quickly discovered that the resulting file was corrupt, because it's attempting to interpret binary data as text.

Eventually, I came upon the naive solution:

	auto f = File(...);
	ubyteRange
		.chunks(bufSize)
		.map!array
		.each!(b => f.rawWrite(b));

This is rather allocation-heavy, so here's attempt #2, that allocates a single buffer that's reused:

	void bufferedWrite(R)(R range, ref File dest, size_t bufSize = 64*1024)
		if (isInputRange!R && is(ElementType!R : ubyte))
	{
	    import std.algorithm.iteration : each, map;
	    import std.algorithm.mutation : copy;
	    import std.range : chunks;

	    ubyte[] buf;
	    buf.length = bufSize;
	    range.chunks(bufSize)
		 .each!((chunk) {
		    auto sizeLeft = copy(chunk, buf).length;
		    dest.rawWrite(buf[0 .. $-sizeLeft]);
		 });
	}

	auto f = File(...);
	ubyteRange.bufferedWrite(f);

What do y'all think? Is bufferedWrite (potentially under a different name) worth submitting to Phobos?


T

-- 
If creativity is stifled by rigid discipline, then it is not true creativity.

On Friday, 8 January 2016 at 06:27:05 UTC, H. S. Teoh wrote:
> Today I was writing some range-based image-generation code, which produces a range of ubytes representing the resulting image file.  To my astonishment, there was no function in std.stdio that could spool this range to a File.

There's toFile... I need to wrap it up though.

https://github.com/D-Programming-Language/phobos/pull/2011