From 15aa91bbd13ca17b6f992e40f9baec05c12a75c6 Mon Sep 17 00:00:00 2001
From: Richard Hughes <richard@hughsie.com>
Date: Fri, 25 May 2018 12:09:20 +0100
Subject: [PATCH] dfu: Add dfu_element_get_contents_chunk()

---
 plugins/dfu/dfu-element.c | 59 +++++++++++++++++++++++++++++++++++++++
 plugins/dfu/dfu-element.h |  4 +++
 2 files changed, 63 insertions(+)

diff --git a/plugins/dfu/dfu-element.c b/plugins/dfu/dfu-element.c
index 29aedaf74..ae595f13c 100644
--- a/plugins/dfu/dfu-element.c
+++ b/plugins/dfu/dfu-element.c
@@ -39,6 +39,8 @@
 #include "dfu-common.h"
 #include "dfu-element.h"
 
+#include "fwupd-error.h"
+
 static void dfu_element_finalize			 (GObject *object);
 
 typedef struct {
@@ -252,3 +254,60 @@ dfu_element_set_target_size (DfuElement *element, guint32 target_size)
 	g_bytes_unref (priv->contents);
 	priv->contents = g_bytes_new_take (buf, target_size);
 }
+
+/**
+ * dfu_element_get_contents_chunk:
+ * @element: a #DfuElement
+ * @address: an address greater than dfu_element_get_address()
+ * @chunk_sz_max: the size of the new chunk
+ * @error: a #GError, or %NULL
+ *
+ * Gets a block of data from the @element. If the contents of the element is
+ * smaller than the requested chunk size then the #GBytes will be smaller
+ * than @chunk_sz_max. Use dfu_utils_bytes_pad() if padding is required.
+ *
+ * If the @address is larger than the size of the @element then an error is returned.
+ *
+ * Return value: (transfer full): a #GBytes, or %NULL
+ **/
+GBytes *
+dfu_element_get_contents_chunk (DfuElement *element,
+				guint32 address,
+				guint32 chunk_sz_max,
+				GError **error)
+{
+	GBytes *blob;
+	gsize chunk_left;
+	guint32 offset;
+
+	/* check address requested is larger than base address */
+	if (address < dfu_element_get_address (element)) {
+		g_set_error (error,
+			     FWUPD_ERROR,
+			     FWUPD_ERROR_INTERNAL,
+			     "requested address 0x%x less than base address 0x%x",
+			     (guint) address, (guint) dfu_element_get_address (element));
+		return NULL;
+	}
+
+	/* offset into data */
+	offset = address - dfu_element_get_address (element);
+	blob = dfu_element_get_contents (element);
+	if (offset > g_bytes_get_size (blob)) {
+		g_set_error (error,
+			     FWUPD_ERROR,
+			     FWUPD_ERROR_NOT_FOUND,
+			     "offset 0x%x larger than data size 0x%x",
+			     (guint) offset,
+			     (guint) g_bytes_get_size (blob));
+		return NULL;
+	}
+
+	/* if we have less data than requested */
+	chunk_left = g_bytes_get_size (blob) - offset;
+	if (chunk_sz_max > chunk_left)
+		return g_bytes_new_from_bytes (blob, offset, chunk_left);
+
+	/* check chunk */
+	return g_bytes_new_from_bytes (blob, offset, chunk_sz_max);
+}
diff --git a/plugins/dfu/dfu-element.h b/plugins/dfu/dfu-element.h
index c04d544f2..46e047d5d 100644
--- a/plugins/dfu/dfu-element.h
+++ b/plugins/dfu/dfu-element.h
@@ -39,6 +39,10 @@ DfuElement	*dfu_element_new		(void);
 
 GBytes		*dfu_element_get_contents	(DfuElement	*element);
 guint32		 dfu_element_get_address	(DfuElement	*element);
+GBytes		*dfu_element_get_contents_chunk	(DfuElement	*element,
+						 guint32	 address,
+						 guint32	 chunk_sz_max,
+						 GError		**error);
 
 void		 dfu_element_set_contents	(DfuElement	*element,
 						 GBytes		*contents);