fpexif: Add missing unit fpeXmpReadWrite

git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@8203 8e941d3f-bd1b-0410-a28a-d453659cc2b4

components/fpexif/fpexmpreadwrite.pas

@@ -0,0 +1,73 @@
+unit fpeXMPReadWrite;
+
+{$mode objfpc}{$H+}
+
+interface
+
+uses
+  Classes, SysUtils, 
+  fpeGlobal, fpeMetaData;
+
+const
+  XMP_BASE_KEY = 'http://ns.adobe.com/xap/1.0/';
+  XMP_KEY = XMP_BASE_KEY + #0; 
+
+type 
+  TXMPWriter = class(TBasicMetadataWriter)
+  protected
+    procedure WriteXMPHeader(AStream: TStream; ADataSize: Int64);
+  public
+    procedure WriteToStream(AStream: TStream; AImgFormat: TImgFormat); override;
+  end;
+  
+function HasXMPHeader(AStream: TStream): Boolean;
+  
+implementation
+ 
+function HasXMPHeader(AStream: TStream): Boolean;
+var
+  p: Int64;
+  hdr: array of ansichar; 
+begin
+  p := AStream.Position;
+  SetLength(hdr, Length(XMP_KEY));
+  AStream.Read(hdr[0], Length(XMP_KEY)); 
+  Result := CompareMem(@hdr[0], @XMP_KEY[1], Length(XMP_KEY));
+  if not Result then
+    AStream.Position := p;
+end;
+
+{ TXMPWriter }
+
+procedure TXMPWriter.WriteToStream(AStream: TStream; AImgFormat: TImgFormat);
+var
+  ms: TMemoryStream;
+begin
+  ms := TMemoryStream.Create;
+  FImgInfo.XMPData.SaveToStream(ms);
+  
+  // Write header
+  WriteXMPHeader(AStream, ms.Size);
+  
+  // Write data
+  ms.Position := 0;
+  AStream.CopyFrom(ms, ms.Size);
+end;
+
+procedure TXMPWriter.WriteXMPHeader(AStream: TStream; ADataSize: Int64);
+const
+  SEGMENT_MARKER: array[0..1] of byte = ($FF, $E1);
+begin
+  ADataSize := 2 + Length(XMP_KEY) + ADataSize;
+  if ADataSize > Word($FFFF) then
+    Error('[TXMPWriter.WriteXMPHeader] Data size too large.');
+  // Segment marker
+  AStream.WriteBuffer(SEGMENT_MARKER[0], 2);
+  // Size of the segment
+  ADataSize := NToBE(Word(ADataSize));
+  AStream.WriteBuffer(ADataSize, 2);
+  AStream.WriteBuffer(XMP_KEY, Length(XMP_KEY));
+end;
+
+end.
+