--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lib-fs/ostream-cmp.c	Tue Oct 19 18:16:10 2010 +0100
@@ -0,0 +1,118 @@
+/* Copyright (c) 2010 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream.h"
+#include "ostream-internal.h"
+#include "ostream-cmp.h"
+
+struct cmp_ostream {
+	struct ostream_private ostream;
+
+	struct istream *input;
+	struct ostream *output;
+	bool equals;
+};
+
+static void cstream_copy_error(struct cmp_ostream *cstream)
+{
+	struct ostream *src = cstream->output;
+	struct ostream *dest = &cstream->ostream.ostream;
+
+	dest->stream_errno = src->stream_errno;
+	dest->last_failed_errno = src->last_failed_errno;
+	dest->overflow = src->overflow;
+}
+
+static void o_stream_cmp_close(struct iostream_private *stream)
+{
+	struct cmp_ostream *cstream = (struct cmp_ostream *)stream;
+
+	if (cstream->output == NULL)
+		return;
+
+	i_stream_unref(&cstream->input);
+	o_stream_flush(&cstream->ostream.ostream);
+	o_stream_unref(&cstream->output);
+}
+
+static int o_stream_cmp_flush(struct ostream_private *stream)
+{
+	struct cmp_ostream *cstream = (struct cmp_ostream *)stream;
+	int ret;
+
+	ret = o_stream_flush(cstream->output);
+	if (ret < 0)
+		cstream_copy_error(cstream);
+	return ret;
+}
+
+bool stream_cmp_block(struct istream *input,
+		      const unsigned char *data, size_t size)
+{
+	const unsigned char *indata;
+	size_t insize, max;
+
+	while (size > 0) {
+		(void)i_stream_read_data(input, &indata, &insize, size-1);
+		max = I_MIN(insize, size);
+		if (insize == 0 || memcmp(data, indata, max) != 0)
+			return FALSE;
+		data += max;
+		size -= max;
+		i_stream_skip(input, max);
+	}
+	return TRUE;
+}
+
+static ssize_t
+o_stream_cmp_sendv(struct ostream_private *stream,
+		   const struct const_iovec *iov, unsigned int iov_count)
+{
+	struct cmp_ostream *cstream = (struct cmp_ostream *)stream;
+	unsigned int i;
+	ssize_t ret;
+
+	if (cstream->equals) {
+		for (i = 0; i < iov_count; i++) {
+			if (!stream_cmp_block(cstream->input, iov[i].iov_base,
+					      iov[i].iov_len)) {
+				cstream->equals = FALSE;
+				break;
+			}
+		}
+	}
+
+	if ((ret = o_stream_sendv(cstream->output, iov, iov_count)) < 0) {
+		cstream_copy_error(cstream);
+		return -1;
+	}
+
+	stream->ostream.offset += ret;
+	return ret;
+}
+
+struct ostream *
+o_stream_create_cmp(struct ostream *output, struct istream *input)
+{
+	struct cmp_ostream *cstream;
+
+	cstream = i_new(struct cmp_ostream, 1);
+	cstream->ostream.sendv = o_stream_cmp_sendv;
+	cstream->ostream.flush = o_stream_cmp_flush;
+	cstream->ostream.iostream.close = o_stream_cmp_close;
+	cstream->input = input;
+	cstream->output = output;
+	cstream->equals = TRUE;
+	i_stream_ref(input);
+	o_stream_ref(output);
+
+	return o_stream_create(&cstream->ostream);
+}
+
+bool o_stream_cmp_equals(struct ostream *_output)
+{
+	struct cmp_ostream *cstream =
+		(struct cmp_ostream *)_output->real_stream;
+
+	return cstream->equals;
+}