1 files changed, 39 insertions, 0 deletions
diff --git a/src/lib/istream-callback.h b/src/lib/istream-callback.h
new file mode 100644
index 0000000..1d91ced
--- /dev/null
+++ b/src/lib/istream-callback.h
@@ -0,0 +1,39 @@
+#ifndef ISTREAM_CALLBACK_H
+#define ISTREAM_CALLBACK_H
+
+/* istream-callback can be used to implement an istream that returns data
+   by calling the specified callback. The callback needs to do:
+
+   a) Add data to buffer unless the buffer size is already too large
+   (the callback can decide by itself what is too large). Return TRUE
+   regardless of whether any data was added.
+
+   b) Return FALSE when it's finished adding data or when it reaches an error.
+   On error i_stream_callback_set_error() must be called before returning.
+
+   i_stream_add_destroy_callback() can be also added to do any cleanups that
+   the callback may need to do.
+*/
+typedef bool istream_callback_read_t(buffer_t *buf, void *context);
+
+struct istream *
+i_stream_create_callback(istream_callback_read_t *callback, void *context);
+#define i_stream_create_callback(callback, context) \
+	i_stream_create_callback(1 ? (istream_callback_read_t *)callback : \
+		CALLBACK_TYPECHECK(callback, bool (*)(buffer_t *buf, typeof(context))), \
+		context)
+
+/* Append data to the istream externally. Typically this is used to add a
+   header to the stream before the callbacks are called. */
+void i_stream_callback_append(struct istream *input,
+			      const void *data, size_t size);
+void i_stream_callback_append_str(struct istream *input, const char *str);
+
+/* Returns the istream-callback's internal buffer. This buffer can be used to
+   append data to the stream. */
+buffer_t *i_stream_callback_get_buffer(struct istream *input);
+
+void i_stream_callback_set_error(struct istream *input, int stream_errno,
+				 const char *error);
+
+#endif