istream-chain: Fixed handling small streams that get merged into same buffer.

diff --git a/src/lib/istream-chain.c b/src/lib/istream-chain.c
index c89c1255beb22fa818cc7bce0f0e57c2e4376501..3e0fe98af0040c0b7dabd21f7daf989f3ef13f0a 100644 (file)
--- a/src/lib/istream-chain.c
+++ b/src/lib/istream-chain.c
@@ -118,21 +118,24 @@ static void i_stream_chain_read_next(struct chain_istream *cstream)
        if (link != NULL && link->stream != NULL)
                i_stream_seek(link->stream, 0);
 
-       /* we already verified that the data size is less than the
-          maximum buffer size */
-       cstream->istream.pos = 0;
-       if (data_size > 0) {
-               if (!i_stream_try_alloc(&cstream->istream, data_size, &size))
-                       i_unreached();
-               i_assert(size >= data_size);
+       if (cstream->istream.buffer == cstream->istream.w_buffer) {
+               /* we've already buffered the prev_input */
+       } else {
+               /* we already verified that the data size is less than the
+                  maximum buffer size */
+               cstream->istream.pos = 0;
+               if (data_size > 0) {
+                       if (!i_stream_try_alloc(&cstream->istream, data_size, &size))
+                               i_unreached();
+                       i_assert(size >= data_size);
+               }
+               memcpy(cstream->istream.w_buffer, data, data_size);
+               cstream->istream.skip = 0;
+               cstream->istream.pos = data_size;
+               cstream->prev_stream_left = data_size;
        }
-
-       memcpy(cstream->istream.w_buffer, data, data_size);
        i_stream_skip(prev_input, data_size);
        i_stream_unref(&prev_input);
-       cstream->istream.skip = 0;
-       cstream->istream.pos = data_size;
-       cstream->prev_stream_left = data_size;
 }
 
 static ssize_t i_stream_chain_read(struct istream_private *stream)