1 files changed, 258 insertions, 0 deletions
diff --git a/src/lib-compression/istream-decompress.c b/src/lib-compression/istream-decompress.c
new file mode 100644
index 0000000..2021a01
--- /dev/null
+++ b/src/lib-compression/istream-decompress.c
@@ -0,0 +1,258 @@
+/* Copyright (c) 2020 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream-private.h"
+#include "compression.h"
+
+struct decompress_istream {
+	struct istream_private istream;
+	struct istream *compressed_input;
+	struct istream *decompressed_input;
+	enum istream_decompress_flags flags;
+};
+
+static void copy_compressed_input_error(struct decompress_istream *zstream)
+{
+	struct istream_private *stream = &zstream->istream;
+
+	stream->istream.stream_errno = zstream->compressed_input->stream_errno;
+	stream->istream.eof = zstream->compressed_input->eof;
+	if (zstream->compressed_input->stream_errno != 0) {
+		io_stream_set_error(&stream->iostream, "%s",
+			i_stream_get_error(&zstream->compressed_input->real_stream->istream));
+	}
+}
+
+static void copy_decompressed_input_error(struct decompress_istream *zstream)
+{
+	struct istream_private *stream = &zstream->istream;
+
+	stream->istream.stream_errno = zstream->decompressed_input->stream_errno;
+	stream->istream.eof = zstream->decompressed_input->eof;
+	if (zstream->decompressed_input->stream_errno != 0) {
+		io_stream_set_error(&stream->iostream, "%s",
+			i_stream_get_error(&zstream->decompressed_input->real_stream->istream));
+	}
+}
+
+static void
+i_stream_decompress_close(struct iostream_private *_stream, bool close_parent)
+{
+	struct istream_private *stream =
+		container_of(_stream, struct istream_private, iostream);
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+
+	if (zstream->decompressed_input != NULL)
+		i_stream_close(zstream->decompressed_input);
+	if (close_parent)
+		i_stream_close(zstream->compressed_input);
+}
+
+static void
+i_stream_decompress_destroy(struct iostream_private *_stream)
+{
+	struct istream_private *stream =
+		container_of(_stream, struct istream_private, iostream);
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+
+	i_stream_unref(&zstream->decompressed_input);
+	i_stream_unref(&zstream->compressed_input);
+}
+
+static int
+i_stream_decompress_not_compressed(struct decompress_istream *zstream)
+{
+	if ((zstream->flags & ISTREAM_DECOMPRESS_FLAG_TRY) == 0) {
+		zstream->istream.istream.stream_errno = EINVAL;
+		io_stream_set_error(&zstream->istream.iostream,
+				    "Stream isn't compressed");
+		return -1;
+	} else {
+		zstream->decompressed_input = zstream->compressed_input;
+		i_stream_ref(zstream->decompressed_input);
+		return 1;
+	}
+}
+
+static int i_stream_decompress_detect(struct decompress_istream *zstream)
+{
+	const struct compression_handler *handler;
+	ssize_t ret;
+
+	ret = i_stream_read(zstream->compressed_input);
+	handler = compression_detect_handler(zstream->compressed_input);
+	if (handler == NULL) {
+		switch (ret) {
+		case -1:
+			if (zstream->compressed_input->stream_errno != 0) {
+				copy_compressed_input_error(zstream);
+				return -1;
+			}
+			/* fall through */
+		case -2:
+			/* we've read a full buffer or we reached EOF -
+			   the stream isn't compressed */
+			return i_stream_decompress_not_compressed(zstream);
+		case 0:
+			return 0;
+		default:
+			if (!zstream->istream.istream.blocking)
+				return 0;
+			return i_stream_decompress_detect(zstream);
+		}
+	}
+	if (handler->create_istream == NULL) {
+		zstream->istream.istream.stream_errno = EINVAL;
+		io_stream_set_error(&zstream->istream.iostream,
+			"Compression handler %s not supported", handler->name);
+		return -1;
+	}
+
+	zstream->decompressed_input =
+		handler->create_istream(zstream->compressed_input);
+	return 1;
+}
+
+static ssize_t i_stream_decompress_read(struct istream_private *stream)
+{
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+	ssize_t ret;
+	size_t pos;
+
+	if (zstream->decompressed_input == NULL) {
+		if ((ret = i_stream_decompress_detect(zstream)) <= 0)
+			return ret;
+	}
+
+	i_stream_seek(zstream->decompressed_input, stream->istream.v_offset);
+	stream->pos -= stream->skip;
+	stream->skip = 0;
+
+	stream->buffer = i_stream_get_data(zstream->decompressed_input, &pos);
+	if (pos > stream->pos)
+		ret = 0;
+	else do {
+		ret = i_stream_read_memarea(zstream->decompressed_input);
+		copy_decompressed_input_error(zstream);
+		stream->buffer = i_stream_get_data(zstream->decompressed_input,
+						   &pos);
+	} while (pos <= stream->pos && ret > 0);
+	if (ret == -2)
+		return -2;
+
+	if (pos <= stream->pos)
+		ret = ret == 0 ? 0 : -1;
+	else
+		ret = (ssize_t)(pos - stream->pos);
+	stream->pos = pos;
+	i_assert(ret != -1 || stream->istream.eof ||
+		 stream->istream.stream_errno != 0);
+	return ret;
+}
+
+static void i_stream_decompress_reset(struct istream_private *stream)
+{
+	stream->skip = stream->pos = 0;
+	stream->istream.v_offset = 0;
+	stream->istream.eof = FALSE;
+}
+
+static void
+i_stream_decompress_seek(struct istream_private *stream,
+			 uoff_t v_offset, bool mark)
+{
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+
+	if (zstream->decompressed_input == NULL) {
+		if (!i_stream_nonseekable_try_seek(stream, v_offset))
+			i_panic("seeking backwards before detecting compression format");
+	} else {
+		i_stream_decompress_reset(stream);
+		stream->istream.v_offset = v_offset;
+		if (mark)
+			i_stream_seek_mark(zstream->decompressed_input, v_offset);
+		else
+			i_stream_seek(zstream->decompressed_input, v_offset);
+		copy_decompressed_input_error(zstream);
+	}
+}
+
+static void i_stream_decompress_sync(struct istream_private *stream)
+{
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+
+	i_stream_decompress_reset(stream);
+	if (zstream->decompressed_input != NULL)
+		i_stream_sync(zstream->decompressed_input);
+}
+
+static int i_stream_decompress_stat(struct istream_private *stream, bool exact)
+{
+	struct decompress_istream *zstream =
+		container_of(stream, struct decompress_istream, istream);
+	const struct stat *st;
+
+	if (!exact) {
+		if (i_stream_stat(zstream->compressed_input, exact, &st) < 0) {
+			copy_compressed_input_error(zstream);
+			return -1;
+		}
+		stream->statbuf = *st;
+		return 0;
+	}
+	if (zstream->decompressed_input == NULL) {
+		(void)i_stream_read(&stream->istream);
+		if (zstream->decompressed_input == NULL) {
+			if (stream->istream.stream_errno == 0) {
+				zstream->istream.istream.stream_errno = EINVAL;
+				io_stream_set_error(&zstream->istream.iostream,
+					"Stream compression couldn't be detected during stat");
+			}
+			return -1;
+		}
+	}
+
+	if (i_stream_stat(zstream->decompressed_input, exact, &st) < 0) {
+		copy_decompressed_input_error(zstream);
+		return -1;
+	}
+	i_stream_decompress_reset(stream);
+	stream->statbuf = *st;
+	return 0;
+}
+
+struct istream *
+i_stream_create_decompress(struct istream *input,
+			   enum istream_decompress_flags flags)
+{
+	struct decompress_istream *zstream;
+
+	zstream = i_new(struct decompress_istream, 1);
+	zstream->compressed_input = input;
+	zstream->flags = flags;
+	i_stream_ref(input);
+
+	zstream->istream.iostream.close = i_stream_decompress_close;
+	zstream->istream.iostream.destroy = i_stream_decompress_destroy;
+	zstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
+	zstream->istream.read = i_stream_decompress_read;
+	zstream->istream.seek = i_stream_decompress_seek;
+	zstream->istream.sync = i_stream_decompress_sync;
+	zstream->istream.stat = i_stream_decompress_stat;
+
+	zstream->istream.istream.readable_fd = FALSE;
+	zstream->istream.istream.blocking = input->blocking;
+	zstream->istream.istream.seekable = input->seekable;
+
+	struct istream *ret = i_stream_create(&zstream->istream, NULL,
+					      i_stream_get_fd(input), 0);
+	/* input isn't used as our parent istream, so need to copy the stream
+	   name to preserve it. */
+	i_stream_set_name(ret, i_stream_get_name(input));
+	return ret;
+}