fixed ROM_COPY to use a relative region name, so it can be used in a device. [smf]

src/emu/emumem.cpp

@@ -1077,6 +1077,64 @@ memory_region::memory_region(running_machine &machine, std::string name, u32 len
 	assert(width == 1 || width == 2 || width == 4 || width == 8);
 }
 
+std::string memory_region::sibling(std::string_view tag) const
+{
+	std::string result;
+	if (!tag.empty() && (tag[0] == ':'))
+	{
+		// if the tag begins with a colon, ignore our path and start from the root
+		tag.remove_prefix(1);
+		result.assign(":");
+	}
+	else
+	{
+		// otherwise, start relative to current path
+		std::string::size_type lastcolon = m_name.find_last_of(':');
+		if (lastcolon != std::string::npos)
+			result.assign(m_name, 0, lastcolon + 1);
+	}
+
+	// iterate over the tag, look for special path characters to resolve
+	std::string_view::size_type delimiter;
+	while ((delimiter = tag.find_first_of("^:")) != std::string_view::npos)
+	{
+		// copy everything up to there
+		bool const parent = tag[delimiter] == '^';
+		result.append(tag, 0, delimiter);
+		tag.remove_prefix(delimiter + 1);
+
+		if (parent)
+		{
+			// strip trailing colons
+			std::string::size_type len = result.length();
+			while ((len > 1) && (result[--len] == ':'))
+				result.resize(len);
+
+			// remove the last path part, leaving the last colon
+			if (result != ":")
+			{
+				std::string::size_type lastcolon = result.find_last_of(':');
+				if (lastcolon != std::string::npos)
+					result.resize(lastcolon + 1);
+			}
+		}
+		else
+		{
+			// collapse successive colons
+			if (result.back() != ':')
+				result.append(1, ':');
+			delimiter = tag.find_first_not_of(':');
+			if (delimiter != std::string_view::npos)
+				tag.remove_prefix(delimiter);
+		}
+	}
+
+	// copy everything else
+	result.append(tag);
+
+	return result;
+}
+
 std::string memory_share::compare(u8 width, size_t bytes, endianness_t endianness) const
 {
 	if (width != m_bitwidth)

src/emu/emumem.h

@@ -2589,6 +2589,7 @@ public:
 	u8 *end() { return base() + m_buffer.size(); }
 	u32 bytes() const { return m_buffer.size(); }
 	const std::string &name() const { return m_name; }
+	std::string sibling(std::string_view tag) const;
 
 	// flag expansion
 	endianness_t endianness() const { return m_endianness; }

src/emu/romload.cpp

@@ -963,7 +963,7 @@ void rom_load_manager::fill_rom_data(memory_region &region, const rom_entry *rom
 void rom_load_manager::copy_rom_data(memory_region &region, const rom_entry *romp)
 {
 	u8 *base = region.base() + ROM_GETOFFSET(romp);
-	const std::string &srcrgntag = romp->name();
+	const std::string srcrgntag = region.sibling(romp->name());
 	u32 numbytes = ROM_GETLENGTH(romp);
 	u32 srcoffs = u32(strtol(romp->hashdata().c_str(), nullptr, 0));  /* srcoffset in place of hashdata */