Try to capture cause of BTG load failures

Avoid downloading data corresponding to files shipped in FGData.

simgear/io/HTTPRepository.cxx

@@ -221,42 +221,48 @@ public:
 		char* buf = nullptr;
 		size_t bufSize = 0;
 
-		for (const auto& child : children) {
-            if (child.type != HTTPRepository::FileType)
-                continue;
+                for (auto &child : children) {
+                  if (child.type != HTTPRepository::FileType)
+                    continue;
 
-            if (child.path.exists())
-                continue;
+                  if (child.path.exists())
+                    continue;
 
-            SGPath cp = _repository->installedCopyPath;
-            cp.append(relativePath());
-            cp.append(child.name);
-            if (!cp.exists()) {
-                continue;
-            }
+                  SGPath cp = _repository->installedCopyPath;
+                  cp.append(relativePath());
+                  cp.append(child.name);
+                  if (!cp.exists()) {
+                    continue;
+                  }
 
-            SGBinaryFile src(cp);
-			SGBinaryFile dst(child.path);
-			src.open(SG_IO_IN);
-			dst.open(SG_IO_OUT);
+                  SGBinaryFile src(cp);
+                  SGBinaryFile dst(child.path);
+                  src.open(SG_IO_IN);
+                  dst.open(SG_IO_OUT);
 
-			if (bufSize < cp.sizeInBytes()) {
-				bufSize = cp.sizeInBytes();
-				free(buf);
-				buf = (char*) malloc(bufSize);
-				if (!buf) {
-					continue;
-				}
-			}
+                  if (bufSize < cp.sizeInBytes()) {
+                    bufSize = cp.sizeInBytes();
+                    free(buf);
+                    buf = (char *)malloc(bufSize);
+                    if (!buf) {
+                      continue;
+                    }
+                  }
 
-			src.read(buf, cp.sizeInBytes());
-			dst.write(buf, cp.sizeInBytes());
-			src.close();
-			dst.close();
+                  src.read(buf, cp.sizeInBytes());
+                  dst.write(buf, cp.sizeInBytes());
+                  src.close();
+                  dst.close();
 
-		}
+                  // reset caching
+                  child.path.set_cached(false);
+                  child.path.set_cached(true);
 
-		free(buf);
+                  std::string hash = computeHashForPath(child.path);
+                  updatedFileContents(child.path, hash);
+                }
+
+                free(buf);
     }
 
     void updateChildrenBasedOnHash()

simgear/io/sg_binobj.cxx

@@ -42,6 +42,7 @@
 
 #include <simgear/bucket/newbucket.hxx>
 #include <simgear/misc/sg_path.hxx>
+#include <simgear/misc/strutils.hxx>
 #include <simgear/math/SGGeometry.hxx>
 #include <simgear/structure/exception.hxx>
 
@@ -563,6 +564,12 @@ bool SGBinObject::read_bin( const SGPath& file ) {
     // read headers
     unsigned int header;
     sgReadUInt( fp, &header );
+
+    if (sgReadError()) {
+        gzclose(fp);
+        throw sg_io_exception("Unable to read BTG header: " + simgear::strutils::error_string(errno), sg_location(file));
+    }
+
     if ( ((header & 0xFF000000) >> 24) == 'S' &&
          ((header & 0x00FF0000) >> 16) == 'G' ) {
 

simgear/io/untar.cxx

@@ -31,6 +31,8 @@
 #include <simgear/sg_inlines.h>
 #include <simgear/io/sg_file.hxx>
 #include <simgear/misc/sg_dir.hxx>
+#include <simgear/misc/strutils.hxx>
+
 #include <simgear/io/iostreams/sgstream.hxx>
 #include <simgear/debug/logstream.hxx>
 #include <simgear/package/unzip.h>
@@ -592,7 +594,7 @@ public:
 
 		outFile.open(path, std::ios::binary | std::ios::trunc | std::ios::out);
 		if (outFile.fail()) {
-			throw sg_io_exception("failed to open output file for writing", path);
+			throw sg_io_exception("failed to open output file for writing:" + strutils::error_string(errno), path);
 		}
 
 		while (!eof) {

simgear/scene/tsync/terrasync.cxx

@@ -603,12 +603,6 @@ void SGTerraSync::WorkerThread::updateSyncSlot(SyncSlot &slot)
             beginNormalSync(slot);
         }
 
-        if (_installRoot.exists()) {
-            SGPath p = _installRoot;
-            p.append(slot.currentItem._dir);
-            slot.repository->setInstalledCopyPath(p);
-        }
-
         try {
             slot.repository->update();
         } catch (sg_exception& e) {
@@ -676,6 +670,11 @@ void SGTerraSync::WorkerThread::beginSyncTile(SyncSlot& slot)
     slot.repository.reset(new HTTPRepository(path, &_http));
     slot.repository->setBaseUrl(_httpServer + "/" + tileCategory);
 
+    if (_installRoot.exists()) {
+      SGPath p = _installRoot / tileCategory;
+      slot.repository->setInstalledCopyPath(p);
+    }
+
     const auto dirPrefix = tenByTenDir + "/" + oneByOneDir;
 
     // filter callback to *only* sync the 1x1 dir we want, if it exists
@@ -706,6 +705,12 @@ void SGTerraSync::WorkerThread::beginNormalSync(SyncSlot& slot)
     path.append(slot.currentItem._dir);
     slot.repository.reset(new HTTPRepository(path, &_http));
     slot.repository->setBaseUrl(_httpServer + "/" + slot.currentItem._dir);
+
+    if (_installRoot.exists()) {
+      SGPath p = _installRoot;
+      p.append(slot.currentItem._dir);
+      slot.repository->setInstalledCopyPath(p);
+    }
 }
 
 void SGTerraSync::WorkerThread::runInternal()