1 files changed, 87 insertions, 0 deletions
diff --git a/src/lib/istream-hash.c b/src/lib/istream-hash.c
new file mode 100644
index 0000000..09d2ac2
--- /dev/null
+++ b/src/lib/istream-hash.c
@@ -0,0 +1,87 @@
+/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "hash-method.h"
+#include "istream-private.h"
+#include "istream-hash.h"
+
+struct hash_istream {
+	struct istream_private istream;
+
+	const struct hash_method *method;
+	void *hash_context;
+	uoff_t high_offset;
+};
+
+static ssize_t
+i_stream_hash_read(struct istream_private *stream)
+{
+	struct hash_istream *hstream =
+		container_of(stream, struct hash_istream, istream);
+	const unsigned char *data;
+	size_t size;
+	uoff_t skip;
+	ssize_t ret;
+
+	i_stream_seek(stream->parent, stream->parent_start_offset +
+		      stream->istream.v_offset);
+
+	ret = i_stream_read_copy_from_parent(&stream->istream);
+	if (ret > 0 && hstream->hash_context != NULL) {
+		data = i_stream_get_data(&stream->istream, &size);
+		i_assert((size_t)ret <= size);
+
+		i_assert(stream->istream.v_offset <= hstream->high_offset);
+		skip = hstream->high_offset - stream->istream.v_offset;
+		if (skip < (size_t)size) {
+			hstream->high_offset += (size-skip);
+			hstream->method->loop(hstream->hash_context,
+					      data+skip, size-skip);
+		}
+	} else if (ret < 0) {
+		/* we finished hashing it. don't access it anymore, because
+		   the memory pointed by the hash may be freed before the
+		   istream itself */
+		hstream->hash_context = NULL;
+	}
+	return ret;
+}
+
+static void
+i_stream_hash_seek(struct istream_private *stream,
+		   uoff_t v_offset, bool mark ATTR_UNUSED)
+{
+	struct hash_istream *hstream =
+		container_of(stream, struct hash_istream, istream);
+
+	if (hstream->hash_context != NULL) {
+		io_stream_set_error(&stream->iostream,
+			"Seeking not supported before hashing is finished");
+		stream->istream.stream_errno = ESPIPE;
+	}
+	stream->istream.v_offset = v_offset;
+	stream->skip = stream->pos = 0;
+}
+
+struct istream *
+i_stream_create_hash(struct istream *input, const struct hash_method *method,
+		     void *hash_context)
+{
+	struct hash_istream *hstream;
+
+	hstream = i_new(struct hash_istream, 1);
+	hstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
+	hstream->istream.stream_size_passthrough = TRUE;
+
+	hstream->istream.read = i_stream_hash_read;
+	hstream->istream.seek = i_stream_hash_seek;
+
+	hstream->istream.istream.readable_fd = input->readable_fd;
+	hstream->istream.istream.blocking = input->blocking;
+	hstream->istream.istream.seekable = input->seekable;
+
+	hstream->method = method;
+	hstream->hash_context = hash_context;
+	return i_stream_create(&hstream->istream, input,
+			       i_stream_get_fd(input), 0);
+}