Add support for comments in ERS files

autotest/gdrivers/data/ers/srtm.ers

@@ -1,10 +1,14 @@
+# This is an ERS file with a comment at the start
 DatasetHeader Begin
   Version = "5.2"
   DataSetType = ERStorage
   DataType = Raster
   ByteOrder = MSBFirst
   Foo = { "x\\\"
 y" }
+  Bar = "# not a comment"
+  Baz = { "x\\\"
+#also not a comment" }
 
   CoordinateSpace Begin
     Datum = "WGS84"
@@ -13,8 +17,9 @@ y" }
     Rotation = 0:0:0.0
   CoordinateSpace End
 
+# Comment in the middle
   RasterInfo Begin
-    CellType = Signed16BitInteger
+    CellType = Signed16BitInteger   # Comment at the end of a line
     NullCellValue = +9999
     CellInfo Begin
       Xdimension = 0.00833333
@@ -37,7 +42,8 @@ y" }
     RegionInfo Begin
       RegionName = "All"
       Stats Begin
-        MinimumValue = { -4315 }
+        MinimumValue = { -4315 # comment in brackets
+        }
         MaximumValue = { -3744 }
         MeanValue = { -4020.25 }
         MedianValue = { -4000 }

frmts/ers/ersdataset.cpp

@@ -816,23 +816,20 @@ int ERSDataset::Identify( GDALOpenInfo * poOpenInfo )
 /* -------------------------------------------------------------------- */
 /*      We assume the user selects the .ers file.                       */
 /* -------------------------------------------------------------------- */
-    if( poOpenInfo->nHeaderBytes > 15
-        && STARTS_WITH_CI((const char *) poOpenInfo->pabyHeader, "Algorithm Begin") )
+    CPLString osHeader((const char *)poOpenInfo->pabyHeader, poOpenInfo->nHeaderBytes);
+
+    if( osHeader.ifind( "Algorithm Begin" ) != std::string::npos )
     {
         CPLError( CE_Failure, CPLE_OpenFailed,
                   "%s appears to be an algorithm ERS file, which is not currently supported.",
                   poOpenInfo->pszFilename );
         return FALSE;
     }
 
-/* -------------------------------------------------------------------- */
-/*      We assume the user selects the .ers file.                       */
-/* -------------------------------------------------------------------- */
-    if( poOpenInfo->nHeaderBytes < 15
-        || !STARTS_WITH_CI((const char *) poOpenInfo->pabyHeader, "DatasetHeader ") )
-        return FALSE;
+    if( osHeader.ifind( "DatasetHeader " ) != std::string::npos )
+        return TRUE;
 
-    return TRUE;
+    return FALSE;
 }
 
 /************************************************************************/
@@ -896,17 +893,11 @@ GDALDataset *ERSDataset::Open( GDALOpenInfo * poOpenInfo )
         return nullptr;
 
 /* -------------------------------------------------------------------- */
-/*      Read the first line.                                            */
-/* -------------------------------------------------------------------- */
-
-    CPLReadLineL( poOpenInfo->fpL );
-
-/* -------------------------------------------------------------------- */
-/*      Now ingest the rest of the file as a tree of header nodes.      */
+/*      Ingest the file as a tree of header nodes.                      */
 /* -------------------------------------------------------------------- */
     ERSHdrNode *poHeader = new ERSHdrNode();
 
-    if( !poHeader->ParseChildren( poOpenInfo->fpL ) )
+    if( !poHeader->ParseHeader( poOpenInfo->fpL ) )
     {
         delete poHeader;
         VSIFCloseL( poOpenInfo->fpL );

frmts/ers/ershdrnode.cpp

@@ -130,12 +130,55 @@ int ERSHdrNode::ReadLine( VSILFILE * fp, CPLString &osLine )
             {
                 bLastCharWasSlashInQuote = true;
             }
+            // A comment is a '#' up to the end of the line.
+            else if( ch == '#' && !bInQuote )
+            {
+                osLine = osLine.substr(0, i) + "\n";
+            }
         }
     } while( nBracketLevel > 0 );
 
     return TRUE;
 }
 
+/************************************************************************/
+/*                            ParseHeader()                             */
+/*                                                                      */
+/*      We receive the FILE * positioned at the start of the file       */
+/*      and read all children.  This allows reading comment lines       */
+/*      at the start of the file.                                       */
+/************************************************************************/
+
+int ERSHdrNode::ParseHeader( VSILFILE * fp )
+
+{
+    while( true )
+    {
+/* -------------------------------------------------------------------- */
+/*      Read the next line                                              */
+/* -------------------------------------------------------------------- */
+        CPLString osLine;
+        size_t iOff;
+
+        if( !ReadLine( fp, osLine ) )
+            return FALSE;
+
+/* -------------------------------------------------------------------- */
+/*      Got a DatasetHeader Begin                                       */
+/* -------------------------------------------------------------------- */
+        else if( (iOff = osLine.ifind( " Begin" )) != std::string::npos )
+        {
+            CPLString osName = osLine.substr(0,iOff);
+            osName.Trim();
+
+            if ( osName.tolower() == CPLString("DatasetHeader").tolower() )
+            {
+                return ParseChildren( fp );
+            }
+        }
+    }
+}
+
 /************************************************************************/
 /*                           ParseChildren()                            */
 /*                                                                      */
@@ -155,7 +198,7 @@ int ERSHdrNode::ParseChildren( VSILFILE * fp, int nRecLevel )
     {
         CPLError(CE_Failure, CPLE_AppDefined,
                  "Too many recursion level while parsing .ers header");
-        return false;
+        return FALSE;
     }
 
     while( true )

frmts/ers/ershdrnode.h

@@ -17,6 +17,7 @@ class ERSHdrNode
     ERSHdrNode();
     ~ERSHdrNode();
 
+    int    ParseHeader( VSILFILE *fp );
     int    ParseChildren( VSILFILE *fp, int nRecLevel = 0 );
     int    WriteSelf( VSILFILE *fp, int nIndent );