--- a/NEWS	Tue Jan 19 12:03:49 2021 +0100
+++ b/NEWS	Tue Jan 19 14:31:04 2021 +0100
@@ -27,6 +27,7 @@
 * Fix upload of multiple DICOM files using one single POST call to "multipart/form-data"
   Could be the final resolution of issue #21 (DICOM files missing after uploading with Firefox)
 * Partial fix of issue #48 (Windows service not stopped properly), cf. comments 4 and 5
+* Explicitly use little-endian to encode uncompressed file size with zlib compression
 * Upgraded dependencies for static builds (notably on Windows):
   - jsoncpp 1.9.4
 

--- a/OrthancFramework/Sources/Compression/ZlibCompressor.cpp	Tue Jan 19 12:03:49 2021 +0100
+++ b/OrthancFramework/Sources/Compression/ZlibCompressor.cpp	Tue Jan 19 14:31:04 2021 +0100
@@ -23,6 +23,7 @@
 #include "../PrecompiledHeaders.h"
 #include "ZlibCompressor.h"
 
+#include "../Endianness.h"
 #include "../OrthancException.h"
 #include "../Logging.h"
 
@@ -90,6 +91,10 @@
     if (HasPrefixWithUncompressedSize())
     {
       uint64_t s = static_cast<uint64_t>(uncompressedSize);
+
+      // New in Orthanc 1.9.0: Explicitly use litte-endian encoding in size prefix
+      s = htole64(s);
+
       memcpy(&compressed[0], &s, sizeof(uint64_t));
       compressed.resize(compressedSize + sizeof(uint64_t));
     }
@@ -127,6 +132,9 @@
       throw OrthancException(ErrorCode_NotEnoughMemory);
     }
 
+    // New in Orthanc 1.9.0: Explicitly use litte-endian encoding in size prefix
+    uncompressedSize = le64toh(uncompressedSize);
+
     uLongf tmp = static_cast<uLongf>(uncompressedSize);
     int error = uncompress
       (reinterpret_cast<uint8_t*>(&uncompressed[0]),