From 6fa4e379d22a8959d4361615aa8797c09c678f23 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 30 Aug 2022 16:07:44 -0400
Subject: [PATCH] Make a hacky and blunt offer of drive data.

---
 Storage/Disk/DiskImage/Formats/2MG.cpp | 57 ++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/Storage/Disk/DiskImage/Formats/2MG.cpp b/Storage/Disk/DiskImage/Formats/2MG.cpp
index b48590b60..f68c3c090 100644
--- a/Storage/Disk/DiskImage/Formats/2MG.cpp
+++ b/Storage/Disk/DiskImage/Formats/2MG.cpp
@@ -9,11 +9,67 @@
 #include "2MG.hpp"
 
 #include "MacintoshIMG.hpp"
+#include "../../../MassStorage/Encodings/AppleIIVolume.hpp"
+
 
 #include <cstring>
 
 using namespace Storage::Disk;
 
+namespace {
+
+// TODO: I've boxed myself into a corner on this stuff by not using factories more generally;
+// volume to device mappers are not themselves mass storage devices because then their use
+// can't currently be private to file types and relevant knowledge would need to be pushed up into
+// the static analyser.
+//
+// So, I guess: go factory, pervasively. And probably stop the strict disk/mass storage/tape
+// distinction, given that clearly some platforms just capture volumes abstractly from media.
+class MassStorage2MG: public Storage::MassStorage::MassStorageDevice {
+	public:
+		MassStorage2MG(const std::string &file_name, long start, long size):
+			file_(file_name),
+			file_start_(start),
+			image_size_(size)
+		{
+			mapper_.set_drive_type(
+				Storage::MassStorage::Encodings::Apple::DriveType::SCSI,
+				size_t(size / 512)
+			);
+		}
+
+	private:
+		Storage::FileHolder file_;
+		long file_start_, image_size_;
+		Storage::MassStorage::Encodings::AppleII::Mapper mapper_;
+
+		/* MassStorageDevices overrides. */
+		size_t get_block_size() final {
+			return 512;
+		}
+		size_t get_number_of_blocks() final {
+			return mapper_.get_number_of_blocks();
+		}
+		std::vector<uint8_t> get_block(size_t address) final {
+			const auto source_address = mapper_.to_source_address(address);
+
+			if(source_address >= 0 && long(source_address*512) < image_size_) {
+				const long file_offset = 512 * source_address;
+				file_.seek(file_offset, SEEK_SET);
+				return mapper_.convert_source_block(source_address, file_.read(get_block_size()));
+			} else {
+				return mapper_.convert_source_block(source_address);
+			}
+		}
+		void set_block(size_t address, const std::vector<uint8_t> &data) final {
+			// TODO.
+//			file_.seek(file_start_ + address * 512, SEEK_SET);
+//			file_.write(data);
+		}
+};
+
+}
+
 Disk2MG::DiskOrMassStorageDevice Disk2MG::open(const std::string &file_name) {
 	FileHolder file(file_name);
 
@@ -74,6 +130,7 @@ Disk2MG::DiskOrMassStorageDevice Disk2MG::open(const std::string &file_name) {
 			// TODO: Apple II-style.
 
 			// TODO: hard-disk image.
+			return new MassStorage2MG(file_name, data_start, data_size);
 		break;
 		case 2:
 			// TODO: NIB data (yuck!).