specctra_export: fix an issue with custom pads.

From Master, commit 686254.
In some cases a created pad stack name had the same name as an other pad stack
having a slightly different shape, thus creating pads with a incorrect shape on board.

Fixes #6495 for the 5.1.10 branch.

common/md5_hash.cpp

@@ -92,6 +92,34 @@ bool MD5_HASH::operator!=( const MD5_HASH& aOther ) const
 }
 
 
+std::string MD5_HASH::Format( bool aCompactForm )
+{
+    std::string data;
+
+    // Build a hexadecimal string from the 16 bytes of MD5_HASH:
+    for( int ii = 0; ii < 16; ++ii )
+    {
+        char lsb = ( m_hash[ii] & 0x0F ) + '0';
+
+        if( lsb > '9' )
+            lsb += 'A'-'9';
+
+        char msb = ( ( m_hash[ii] >> 4 ) & 0x0F ) + '0';
+
+        if( msb > '9' )
+            msb += 'A'-'9';
+
+         data += msb;
+         data += lsb;
+
+        if( !aCompactForm )
+            data += ' ';
+    }
+
+    return data;
+}
+
+
 void MD5_HASH::md5_transform(MD5_CTX *ctx, uint8_t data[])
 {
    uint32_t a,b,c,d,m[16],i,j;

include/md5_hash.h

@@ -6,6 +6,7 @@
 #define __MD5_HASH_H
 
 #include <cstdint>
+#include <string>
 
 class MD5_HASH
 {
@@ -29,6 +30,13 @@ public:
     bool operator==( const MD5_HASH& aOther ) const;
     bool operator!=( const MD5_HASH& aOther ) const;
 
+    /** @return a hexadecimal string from the 16 bytes of MD5_HASH
+     *  Mainly for debug purposes.
+     * @param aCompactForm = false to generate a string with spaces between each byte (2 chars)
+     * = true to generate a string filled with 32 hexadecimal chars
+     */
+    std::string Format( bool aCompactForm = false );
+
 private:
     struct MD5_CTX {
        uint8_t data[64];

pcbnew/specctra_import_export/specctra_export.cpp

@@ -594,11 +594,12 @@ PADSTACK* SPECCTRA_DB::makePADSTACK( BOARD* aBoard, D_PAD* aPad )
             }
 
             // this string _must_ be unique for a given physical shape, so try to make it unique
+            MD5_HASH hash  = pad_shape.GetHash();
             EDA_RECT rect = aPad->GetBoundingBox();
-            snprintf( name, sizeof(name), "Cust%sPad_%.6gx%.6g_%.6gx_%.6g_%d_um",
+            snprintf( name, sizeof(name), "Cust%sPad_%.6gx%.6g_%.6gx_%.6g_%d_um_%s",
                      uniqifier.c_str(), IU2um( aPad->GetSize().x ), IU2um( aPad->GetSize().y ),
                      IU2um( rect.GetWidth() ), IU2um( rect.GetHeight() ),
-                     (int)polygonal_shape.size() );
+                     (int)polygonal_shape.size(), hash.Format( true ).c_str() );
             name[ sizeof(name)-1 ] = 0;
 
             padstack->SetPadstackId( name );