1 files changed, 232 insertions, 0 deletions
diff --git a/src/lib/istream-sized.c b/src/lib/istream-sized.c
new file mode 100644
index 0000000..afe95b7
--- /dev/null
+++ b/src/lib/istream-sized.c
@@ -0,0 +1,232 @@
+/* Copyright (c) 2003-2018 Dovecot authors, see the included COPYING file */
+
+#include "lib.h"
+#include "istream-private.h"
+#include "istream-sized.h"
+
+struct sized_istream {
+	struct istream_private istream;
+
+	istream_sized_callback_t *error_callback;
+	void *error_context;
+
+	uoff_t size;
+	bool min_size_only;
+};
+
+static void i_stream_sized_destroy(struct iostream_private *stream)
+{
+	struct sized_istream *sstream =
+		container_of(stream, struct sized_istream, istream.iostream);
+	uoff_t v_offset;
+
+	v_offset = sstream->istream.parent_start_offset +
+		sstream->istream.istream.v_offset;
+	if (sstream->istream.parent->seekable ||
+	    v_offset > sstream->istream.parent->v_offset) {
+		/* get to same position in parent stream */
+		i_stream_seek(sstream->istream.parent, v_offset);
+	}
+}
+
+static const char *
+i_stream_create_sized_default_error_callback(
+	const struct istream_sized_error_data *data, void *context ATTR_UNUSED)
+{
+	if (data->v_offset + data->new_bytes < data->wanted_size) {
+		return t_strdup_printf("Stream is smaller than expected "
+			"(%"PRIuUOFF_T" < %"PRIuUOFF_T")",
+			data->v_offset + data->new_bytes, data->wanted_size);
+	} else {
+		return t_strdup_printf("Stream is larger than expected "
+			"(%"PRIuUOFF_T" > %"PRIuUOFF_T", eof=%d)",
+			data->v_offset + data->new_bytes, data->wanted_size,
+			data->eof ? 1 : 0);
+	}
+}
+
+static ssize_t
+i_stream_sized_parent_read(struct istream_private *stream, size_t *pos_r)
+{
+	ssize_t ret;
+
+	do {
+		ret = i_stream_read_memarea(stream->parent);
+		stream->istream.stream_errno = stream->parent->stream_errno;
+		stream->istream.eof = stream->parent->eof;
+		stream->buffer = i_stream_get_data(stream->parent, pos_r);
+	} while (*pos_r <= stream->pos && ret > 0);
+	return ret;
+}
+
+static ssize_t i_stream_sized_read(struct istream_private *stream)
+{
+	struct sized_istream *sstream =
+		container_of(stream, struct sized_istream, istream);
+	struct istream_sized_error_data data;
+	const char *error;
+	uoff_t left;
+	ssize_t ret;
+	size_t pos;
+
+	i_stream_seek(stream->parent, sstream->istream.parent_start_offset +
+		      stream->istream.v_offset);
+
+	stream->pos -= stream->skip;
+	stream->skip = 0;
+
+	stream->buffer = i_stream_get_data(stream->parent, &pos);
+	if (pos > stream->pos)
+		ret = 0;
+	else {
+		if ((ret = i_stream_sized_parent_read(stream, &pos)) == -2)
+			return -2;
+	}
+
+	left = sstream->size - stream->istream.v_offset;
+	if (pos == left && ret != -1) {
+		/* we have exactly the wanted amount of data left, but we
+		   don't know yet if there is more data in parent. */
+		ret = i_stream_sized_parent_read(stream, &pos);
+	}
+
+	i_zero(&data);
+	data.v_offset = stream->istream.v_offset;
+	data.new_bytes = pos;
+	data.wanted_size = sstream->size;
+	data.eof = stream->istream.eof;
+
+	if (pos == left) {
+		/* we may or may not be finished, depending on whether
+		   parent is at EOF. */
+	} else if (pos > left) {
+		/* parent has more data available than expected */
+		if (!sstream->min_size_only) {
+			error = sstream->error_callback(&data, sstream->error_context);
+			io_stream_set_error(&stream->iostream, "%s", error);
+			stream->istream.stream_errno = EINVAL;
+			return -1;
+		}
+		pos = left;
+		if (pos <= stream->pos) {
+			stream->istream.eof = TRUE;
+			ret = -1;
+		}
+	} else if (!stream->istream.eof) {
+		/* still more to read */
+	} else if (stream->istream.stream_errno == ENOENT) {
+		/* lost the file */
+	} else {
+		/* EOF before we reached the wanted size */
+		error = sstream->error_callback(&data, sstream->error_context);
+		io_stream_set_error(&stream->iostream, "%s", error);
+		stream->istream.stream_errno = EPIPE;
+	}
+
+	ret = pos > stream->pos ? (ssize_t)(pos - stream->pos) :
+		(ret == 0 ? 0 : -1);
+	stream->pos = pos;
+	i_assert(ret != -1 || stream->istream.eof ||
+		 stream->istream.stream_errno != 0);
+	return ret;
+}
+
+static int
+i_stream_sized_stat(struct istream_private *stream, bool exact ATTR_UNUSED)
+{
+	struct sized_istream *sstream =
+		container_of(stream, struct sized_istream, istream);
+	const struct stat *st;
+
+	/* parent stream may be base64-decoder. don't waste time decoding the
+	   entire stream, since we already know what the size is supposed
+	   to be. */
+	if (i_stream_stat(stream->parent, FALSE, &st) < 0) {
+		stream->istream.stream_errno = stream->parent->stream_errno;
+		return -1;
+	}
+
+	stream->statbuf = *st;
+	stream->statbuf.st_size = sstream->size;
+	return 0;
+}
+
+static struct sized_istream *
+i_stream_create_sized_common(struct istream *input, uoff_t size)
+{
+	struct sized_istream *sstream;
+
+	sstream = i_new(struct sized_istream, 1);
+	sstream->size = size;
+	sstream->istream.max_buffer_size = input->real_stream->max_buffer_size;
+
+	sstream->istream.iostream.destroy = i_stream_sized_destroy;
+	sstream->istream.read = i_stream_sized_read;
+	sstream->istream.stat = i_stream_sized_stat;
+
+	sstream->istream.istream.readable_fd = input->readable_fd;
+	sstream->istream.istream.blocking = input->blocking;
+	sstream->istream.istream.seekable = input->seekable;
+	(void)i_stream_create(&sstream->istream, input,
+			      i_stream_get_fd(input), 0);
+	return sstream;
+}
+
+struct istream *i_stream_create_sized(struct istream *input, uoff_t size)
+{
+	struct sized_istream *sstream;
+
+	sstream = i_stream_create_sized_common(input, size);
+	sstream->error_callback = i_stream_create_sized_default_error_callback;
+	sstream->error_context = sstream;
+	return &sstream->istream.istream;
+}
+
+struct istream *i_stream_create_sized_range(struct istream *input,
+					    uoff_t offset, uoff_t size)
+{
+	uoff_t orig_offset = input->v_offset;
+	struct istream *ret;
+
+	input->v_offset = offset;
+	ret = i_stream_create_sized(input, size);
+	input->v_offset = orig_offset;
+	return ret;
+}
+
+struct istream *i_stream_create_min_sized(struct istream *input, uoff_t min_size)
+{
+	struct istream *ret;
+
+	ret= i_stream_create_sized(input, min_size);
+	struct sized_istream *ret_sstream =
+		container_of(ret->real_stream, struct sized_istream, istream);
+	ret_sstream->min_size_only = TRUE;
+	return ret;
+}
+
+struct istream *i_stream_create_min_sized_range(struct istream *input,
+						uoff_t offset, uoff_t min_size)
+{
+	struct istream *ret;
+
+	ret = i_stream_create_sized_range(input, offset, min_size);
+	struct sized_istream *ret_sstream =
+		container_of(ret->real_stream, struct sized_istream, istream);
+	ret_sstream->min_size_only = TRUE;
+	return ret;
+}
+
+#undef i_stream_create_sized_with_callback
+struct istream *
+i_stream_create_sized_with_callback(struct istream *input, uoff_t size,
+				    istream_sized_callback_t *error_callback,
+				    void *context)
+{
+	struct sized_istream *sstream;
+
+	sstream = i_stream_create_sized_common(input, size);
+	sstream->error_callback = error_callback;
+	sstream->error_context = context;
+	return &sstream->istream.istream;
+}