[gcab/wip/hughsie/meson] Fix the calculation of the checksum on big endian machines

[Richard Hughes <rhughes src gnome org>]

commit fc541df3aa05f254b8d3297f85f97e42126d0081
Author: Richard Hughes <richard hughsie com>
Date:   Fri Nov 17 12:31:29 2017 +0000

    Fix the calculation of the checksum on big endian machines

 libgcab/cabinet.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/libgcab/cabinet.c b/libgcab/cabinet.c
index 9361372..bd6753f 100644
--- a/libgcab/cabinet.c
+++ b/libgcab/cabinet.c
@@ -423,7 +423,8 @@ cdata_write (cdata_t *cd, GDataOutputStream *out, int type,
         return FALSE;
 
     CHECKSUM datacsum = compute_checksum(cd->in, cd->ncbytes, 0);
-    cd->checksum = compute_checksum ((guint8*)&cd->ncbytes, 4, datacsum);
+    CHECKSUM sizecsum = GUINT32_TO_LE(cd->ncbytes << 16 | cd->nubytes);
+    cd->checksum = compute_checksum ((guint8*)&sizecsum, 4, datacsum);
     GOutputStream *stream = g_filter_output_stream_get_base_stream (G_FILTER_OUTPUT_STREAM (out));
 
     *bytes_written = 0;
@@ -466,6 +467,7 @@ cdata_read (cdata_t *cd, u1 res_data, gint comptype,
     gint compression = comptype & GCAB_COMPRESSION_MASK;
     guint8 *buf = compression == GCAB_COMPRESSION_NONE ? cd->out : cd->in;
     CHECKSUM datacsum;
+    CHECKSUM sizecsum;
 
     if (compression > GCAB_COMPRESSION_MSZIP &&
         compression != GCAB_COMPRESSION_LZX) {
@@ -482,7 +484,8 @@ cdata_read (cdata_t *cd, u1 res_data, gint comptype,
     RN (buf, cd->ncbytes);
 
     datacsum = compute_checksum(buf, cd->ncbytes, 0);
-    if (cd->checksum != compute_checksum ((guint8*)&cd->ncbytes, 4, datacsum)) {
+    sizecsum = GUINT32_TO_LE(cd->ncbytes << 16 | cd->nubytes);
+    if (cd->checksum != compute_checksum ((guint8*)&sizecsum, 4, datacsum)) {
         g_set_error_literal (error, GCAB_ERROR, GCAB_ERROR_FAILED,
                              _("incorrect checksum detected"));
         return FALSE;