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252 lines
7.4 KiB
C++
252 lines
7.4 KiB
C++
//
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// ApplePartitionMap.hpp
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// Clock Signal
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//
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// Created by Thomas Harte on 23/08/2022.
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// Copyright © 2022 Thomas Harte. All rights reserved.
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//
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#ifndef ApplePartitionMap_hpp
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#define ApplePartitionMap_hpp
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#include <cstddef>
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#include <cstdint>
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#include <cstring>
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#include <sys/types.h>
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#include <vector>
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namespace Storage::MassStorage::Encodings::Apple {
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enum class DriveType {
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SCSI
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};
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/*!
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Implements a device to volume mapping with an Apple Partition Map.
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The @c VolumeProvider provides both the volume to be embedded into a device,
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and device driver information if applicable.
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*/
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template <typename VolumeProvider> class PartitionMap {
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public:
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/*!
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Sets the drive type to map to and the number of blocks in the underlying partition.
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*/
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void set_drive_type(DriveType drive_type, size_t number_of_blocks) {
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drive_type_ = drive_type;
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number_of_blocks_ = number_of_blocks;
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}
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/*!
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@returns The total number of blocks on the entire volume.
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*/
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size_t get_number_of_blocks() const {
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return
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number_of_blocks_ + // Size of the volume.
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size_t(non_volume_blocks()); // Size of everything else.
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}
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/*!
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Maps from a mass-storage device address to an address
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in the underlying volume.
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*/
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ssize_t to_source_address(size_t address) const {
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// The embedded volume is always the last thing on the device.
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return ssize_t(address) - ssize_t(non_volume_blocks());
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}
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/*!
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Converts from a source data block to one properly encoded for the drive type.
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Expected usage:
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const size_t source_address = mapper.to_source_address(unit_address);
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if(is_in_range_for_partition(source_address)) {
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return mapper.convert_source_block(source_address, get_block_contents(source_address));
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} else {
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return mapper.convert_source_block(source_address);
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}
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*/
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std::vector<uint8_t> convert_source_block(ssize_t source_address, std::vector<uint8_t> source_data = {}) {
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// Addresses greater than or equal to zero map to the actual disk image.
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if(source_address >= 0) return source_data;
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// Switch to mapping relative to 0, for personal sanity.
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source_address += non_volume_blocks();
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// Block 0 is the device descriptor, which lists the total number of blocks,
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// and provides an offset to the driver, if any.
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if(!source_address) {
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const uint32_t total_device_blocks = uint32_t(get_number_of_blocks());
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const auto driver_size = uint16_t(driver_block_size());
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const auto driver_offset = uint16_t(predriver_blocks());
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const uint8_t driver_count = driver_size > 0 ? 1 : 0;
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/* The driver descriptor. */
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std::vector<uint8_t> driver_description = {
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0x45, 0x52, /* device signature */
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0x02, 0x00, /* block size, in bytes */
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uint8_t(total_device_blocks >> 24),
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uint8_t(total_device_blocks >> 16),
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uint8_t(total_device_blocks >> 8),
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uint8_t(total_device_blocks),
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/* number of blocks on device */
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0x00, 0x01, /* reserved (formerly: device type) */
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0x00, 0x01, /* reserved (formerly: device ID) */
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0x00, 0x00,
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0x00, 0x00, /* reserved ('sbData', no further explanation given) */
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0x00, driver_count, /* number of device descriptor entries */
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0x00, 0x00,
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/* first device descriptor's starting block */
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uint8_t(driver_offset >> 8), uint8_t(driver_offset),
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/* size of device driver */
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uint8_t(driver_size >> 8), uint8_t(driver_size),
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0x00, 0x01, /*
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More modern documentation: operating system (MacOS = 1)
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Inside Macintosh IV: system type (Mac Plus = 1)
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*/
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};
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driver_description.resize(512);
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return driver_description;
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}
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// Blocks 1 and 2 contain entries of the partition map; there's also possibly an entry
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// for the driver.
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if(source_address < 3 + volume_provider_.HasDriver) {
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struct Partition {
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const char *name, *type;
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uint32_t start_block, size;
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uint8_t status;
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} partitions[3] = {
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{
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volume_provider_.name(),
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volume_provider_.type(),
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uint32_t(non_volume_blocks()),
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uint32_t(number_of_blocks_),
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0xb7
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},
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{
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"Apple",
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"Apple_partition_map",
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0x01,
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uint32_t(predriver_blocks()) - 1,
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0x37
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},
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{
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"Macintosh",
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"Apple_Driver",
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uint32_t(predriver_blocks()),
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uint32_t(driver_block_size()),
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0x7f
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},
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};
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std::vector<uint8_t> partition(512);
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// Fill in the fixed fields.
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partition[0] = 'P'; partition[1] = 'M'; /* Signature. */
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partition[7] = 3; /* Number of partitions. */
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const Partition &details = partitions[source_address-1];
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partition[8] = uint8_t(details.start_block >> 24);
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partition[9] = uint8_t(details.start_block >> 16);
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partition[10] = uint8_t(details.start_block >> 8);
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partition[11] = uint8_t(details.start_block);
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partition[84] = partition[12] = uint8_t(details.size >> 24);
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partition[85] = partition[13] = uint8_t(details.size >> 16);
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partition[86] = partition[14] = uint8_t(details.size >> 8);
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partition[87] = partition[15] = uint8_t(details.size);
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// 32 bytes are allocated for each of the following strings.
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memcpy(&partition[16], details.name, strlen(details.name));
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memcpy(&partition[48], details.type, strlen(details.type));
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partition[91] = details.status;
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// The third entry in this constructed partition map is the driver;
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// add some additional details.
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if constexpr (VolumeProvider::HasDriver) {
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if(source_address == 3) {
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const auto driver_size = uint16_t(volume_provider_.driver_size());
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const auto driver_checksum = uint16_t(volume_provider_.driver_checksum());
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/* Driver size in bytes. */
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partition[98] = uint8_t(driver_size >> 8);
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partition[99] = uint8_t(driver_size);
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/* Driver checksum. */
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partition[118] = uint8_t(driver_checksum >> 8);
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partition[119] = uint8_t(driver_checksum);
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/* Driver target processor. */
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const char *driver_target = volume_provider_.driver_target();
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memcpy(&partition[120], driver_target, strlen(driver_target));
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// Various non-zero values that Apple HD SC Tool wrote are below; they are
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// documented as reserved officially, so I don't know their meaning.
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partition[137] = 0x01;
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partition[138] = 0x06;
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partition[143] = 0x01;
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partition[147] = 0x02;
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partition[149] = 0x07;
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}
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}
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return partition;
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}
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if constexpr (VolumeProvider::HasDriver) {
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// The remainder of the non-volume area is the driver.
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if(source_address >= predriver_blocks() && source_address < non_volume_blocks()) {
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const uint8_t *driver = volume_provider_.driver();
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const auto offset = (source_address - predriver_blocks()) * 512;
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return std::vector<uint8_t>(&driver[offset], &driver[offset + 512]);
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}
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}
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// Default: return an empty block.
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return std::vector<uint8_t>(512);
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}
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private:
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DriveType drive_type_;
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size_t number_of_blocks_;
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VolumeProvider volume_provider_;
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ssize_t predriver_blocks() const {
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return
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0x40; // Holding:
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// (i) the driver descriptor;
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// (ii) the partition table; and
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// (iii) the partition entries.
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}
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ssize_t non_volume_blocks() const {
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return
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predriver_blocks() +
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driver_block_size(); // Size of device driver (if any).
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}
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ssize_t driver_block_size() const {
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if constexpr (VolumeProvider::HasDriver) {
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return (volume_provider_.driver_size() + 511) >> 9;
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} else {
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return 0;
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}
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}
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};
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}
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#endif /* ApplePartitionMap_hpp */
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