dovecot-2.0: istream-crlf optimization.

[dovecot at dovecot.org]

details:   http://hg.dovecot.org/dovecot-2.0/rev/5163d94d4272
changeset: 12054:5163d94d4272
user:      Timo Sirainen <tss at iki.fi>
date:      Wed Sep 01 16:22:20 2010 +0100
description:
istream-crlf optimization.
Based on patch by Len7hir

diffstat:

 src/lib/istream-crlf.c |  76 ++++++++++++++++++++++++++++---------
 1 files changed, 57 insertions(+), 19 deletions(-)

diffs (99 lines):

diff -r e9358064c45e -r 5163d94d4272 src/lib/istream-crlf.c
--- a/src/lib/istream-crlf.c	Wed Sep 01 16:22:00 2010 +0100
+++ b/src/lib/istream-crlf.c	Wed Sep 01 16:22:20 2010 +0100
@@ -38,38 +38,76 @@
 static ssize_t i_stream_crlf_read_crlf(struct istream_private *stream)
 {
 	struct crlf_istream *cstream = (struct crlf_istream *)stream;
-	const unsigned char *data;
-	size_t i, dest, size;
+	const unsigned char *data, *ptr, *src, *src_end;
+	unsigned char *dest, *dest_end;
+	size_t size, copy_len;
 	ssize_t ret;
 
 	ret = i_stream_crlf_read_common(cstream);
 	if (ret <= 0)
 		return ret;
 
+	/* at least one byte was read */
 	data = i_stream_get_data(stream->parent, &size);
 
+	dest = stream->w_buffer + stream->pos;
+	dest_end = stream->w_buffer + stream->buffer_size;
+	src = data;
+	src_end = data + size;
+
 	/* @UNSAFE: add missing CRs */
-	dest = stream->pos;
-	for (i = 0; i < size && dest < stream->buffer_size; i++) {
-		if (data[i] == '\n') {
-			if (i == 0) {
-				if (!cstream->last_cr)
-					stream->w_buffer[dest++] = '\r';
-			} else {
-				if (data[i-1] != '\r')
-					stream->w_buffer[dest++] = '\r';
-			}
-			if (dest == stream->buffer_size)
-				break;
+	if (*src == '\n') {
+		if (!cstream->last_cr && dest < dest_end)
+			*dest++ = '\r';
+
+		if (dest < dest_end) {
+			*dest++ = '\n';
+			src++;
 		}
-		stream->w_buffer[dest++] = data[i];
 	}
-	cstream->last_cr = stream->w_buffer[dest-1] == '\r';
-	i_stream_skip(stream->parent, i);
 
-	ret = dest - stream->pos;
+	while (dest < dest_end) {
+		ptr = memchr(src, '\n', src_end - src);
+		if (ptr == NULL)
+			ptr = src_end;
+
+		/* copy data up to LF */
+		copy_len = ptr - src;
+		if (dest + copy_len > dest_end)
+			copy_len = dest_end - dest;
+
+		if (copy_len > 0) {
+			memcpy(dest, src, copy_len);
+
+			dest += copy_len;
+			src += copy_len;
+		}
+
+		i_assert(dest <= dest_end && src <= src_end);
+		if (dest == dest_end || src == src_end)
+			break;
+
+		/* add the CR if necessary and copy the LF.
+		   (src >= data+1, because data[0]=='\n' was
+		   handled before this loop) */
+		if (src[-1] != '\r')
+			*dest++ = '\r';
+
+		if (dest < dest_end) {
+			*dest++ = '\n';
+			src++;
+		}
+
+		i_assert(src == ptr + 1);
+	}
+
+	i_assert(dest != stream->w_buffer);
+ 	cstream->last_cr = dest[-1] == '\r';
+	i_stream_skip(stream->parent, src - data);
+
+	ret = (dest - stream->w_buffer) - stream->pos;
 	i_assert(ret > 0);
-	stream->pos = dest;
+	stream->pos = dest - stream->w_buffer;
 	return ret;
 }