JPEG2000 writer: remove NUL terminated byte at end of payload of 'lbl ' and 'xml ' boxes

For label boxes, the spec is pretty explicit about that: "Label strings are not null-terminated"
Cf
https://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-T.801-200208-S!!PDF-E&type=items
"M.11.13 Label box", page 197

For XML boxes, nothing explicit, but in the absence of a statement,
null-terminating byte doesn't seem necessary. Furthermore jpylyzer
documentation at https://jpylyzer.openpreservation.org/doc/latest/userManual.html
has a 'nullxml' option because 'Apparently some old versions of the Kakadu demo
applications would erroneously add a null-byte to embedded XML'.

Fixes https://lists.osgeo.org/pipermail/gdal-dev/2025-November/061180.html

Reported-by: Brad Hards <[email protected]>

Author: rouault

autotest/gdrivers/data/jpeg2000/byte_lossless_openjp2_golden.jp2

@@ -488,7 +488,7 @@ GDALJP2Box *GDALJP2Box::CreateLblBox(const char *pszLabel)
 {
     GDALJP2Box *const poBox = new GDALJP2Box();
     poBox->SetType("lbl ");
-    poBox->SetWritableData(static_cast<int>(strlen(pszLabel) + 1),
+    poBox->SetWritableData(static_cast<int>(strlen(pszLabel)),
                            reinterpret_cast<const GByte *>(pszLabel));
 
     return poBox;
@@ -504,12 +504,12 @@ GDALJP2Box *GDALJP2Box::CreateLabelledXMLAssoc(const char *pszLabel,
 {
     GDALJP2Box oLabel;
     oLabel.SetType("lbl ");
-    oLabel.SetWritableData(static_cast<int>(strlen(pszLabel) + 1),
+    oLabel.SetWritableData(static_cast<int>(strlen(pszLabel)),
                            reinterpret_cast<const GByte *>(pszLabel));
 
     GDALJP2Box oXML;
     oXML.SetType("xml ");
-    oXML.SetWritableData(static_cast<int>(strlen(pszXML) + 1),
+    oXML.SetWritableData(static_cast<int>(strlen(pszXML)),
                          reinterpret_cast<const GByte *>(pszXML));
 
     GDALJP2Box *aoList[2] = {&oLabel, &oXML};
@@ -530,6 +530,8 @@ GDALJP2Box *GDALJP2Box::CreateJUMBFDescriptionBox(const GByte *pabyUUIDType,
 
     poBox->AppendWritableData(16, pabyUUIDType);
     poBox->AppendUInt8(3);  // requestable field
+    // +1 since NUL terminated byte requested in the spec
+    // cf other implementation at https://gitlab.com/wg1/jpeg-systems/reference-software/jumbf-reference-implementation-2/-/blame/main/dbench_jumbf/src/db_jumbf_desc_box.cpp?ref_type=heads#L169
     const size_t nLabelLen = strlen(pszLabel) + 1;
     poBox->AppendWritableData(static_cast<int>(nLabelLen), pszLabel);
 

gcore/gdaljp2box.cpp

@@ -3333,7 +3333,7 @@ GDALJP2Metadata::CreateGDALMultiDomainMetadataXMLBox(GDALDataset *poSrcDS,
 
     GDALJP2Box *poBox = new GDALJP2Box();
     poBox->SetType("xml ");
-    poBox->SetWritableData(static_cast<int>(strlen(pszXML) + 1),
+    poBox->SetWritableData(static_cast<int>(strlen(pszXML)),
                            reinterpret_cast<const GByte *>(pszXML));
     CPLFree(pszXML);
 
@@ -3362,7 +3362,7 @@ GDALJP2Box **GDALJP2Metadata::CreateXMLBoxes(GDALDataset *poSrcDS, int *pnBoxes)
                 GDALJP2Box *poBox = new GDALJP2Box();
                 poBox->SetType("xml ");
                 poBox->SetWritableData(
-                    static_cast<int>(strlen(*papszSrcMD) + 1),
+                    static_cast<int>(strlen(*papszSrcMD)),
                     reinterpret_cast<const GByte *>(*papszSrcMD));
                 papoBoxes = static_cast<GDALJP2Box **>(CPLRealloc(
                     papoBoxes, sizeof(GDALJP2Box *) * (*pnBoxes + 1)));
@@ -3385,7 +3385,7 @@ GDALJP2Box *GDALJP2Metadata::CreateXMPBox(GDALDataset *poSrcDS)
     if (papszSrcMD && *papszSrcMD)
     {
         poBox = GDALJP2Box::CreateUUIDBox(
-            xmp_uuid, static_cast<int>(strlen(*papszSrcMD) + 1),
+            xmp_uuid, static_cast<int>(strlen(*papszSrcMD)),
             reinterpret_cast<const GByte *>(*papszSrcMD));
     }
     return poBox;
@@ -3403,7 +3403,7 @@ GDALJP2Box *GDALJP2Metadata::CreateIPRBox(GDALDataset *poSrcDS)
     {
         poBox = new GDALJP2Box();
         poBox->SetType("jp2i");
-        poBox->SetWritableData(static_cast<int>(strlen(*papszSrcMD) + 1),
+        poBox->SetWritableData(static_cast<int>(strlen(*papszSrcMD)),
                                reinterpret_cast<const GByte *>(*papszSrcMD));
     }
     return poBox;