more fs

src/block_device.cpp

@@ -1,4 +1,5 @@
 #include "block_device.hpp"
+#include <cassert>
 #include <cstdint>
 #include <cstring>
 #include <fstream>
@@ -20,6 +21,7 @@ auto FileDisk::block_count() -> uint16_t
 {
     m_file.seekg(0, std::ios_base::end);
     std::streamsize location = m_file.tellg();
+    assert(location != -1);
     return location / block_size & 0xffff;
 }
 
@@ -27,10 +29,12 @@ void FileDisk::read(uint8_t* data, uint16_t block)
 {
     m_file.seekg(block * block_size);
     m_file.read(reinterpret_cast<char*>(data), block_size);
+    assert(m_file.good());
 }
 
 void FileDisk::write(const uint8_t* data, uint16_t block)
 {
     m_file.seekg(block * block_size);
     m_file.write(reinterpret_cast<const char*>(data), block_size);
+    assert(m_file.good());
 }

src/fs.cpp

@@ -1,75 +1,360 @@
 #include "fs.hpp"
+#include <cassert>
 #include <cstdint>
+#include <cstring>
+#include <optional>
+#include <string_view>
+#include <tuple>
 
 namespace vc5::filesys {
 
-constexpr auto Ok = Status::Ok;
+using BlockData = std::array<u8, block_size>;
 
-using BlockData = std::array<uint8_t, block_size>;
+namespace {
 
-void Fs::init()
-{
-    m_super = SuperBlockData {
-        .block_bitmap = {},
-        .inode_bitmap = {},
-        .inode_blocks = {},
-    };
-    write_superblock();
-}
-
-Status Fs::make_directory()
-{
-    uint16_t id;
-    if (auto result = next_inode_id(id); result != Ok) {
-        return result;
+    auto inode_mode(INodeType type) -> u16
+    {
+        u16 mode = 0;
+        mode |= std::to_underlying(type) << inode_type_bitoffset;
+        return mode;
     }
 
-    auto node = INodeData {
-        .id = id,
-        .flags = static_cast<uint16_t>(INodeType::Directory),
+    auto inode_mode_type(u16 mode) -> INodeType
+    {
+        return static_cast<INodeType>(
+            mode >> inode_type_bitoffset & inode_type_bitmask);
+    }
+
+    auto unwrap_inode_id(u16 inode_id) -> std::tuple<u16, u16>
+    {
+        u16 inode_block_idx = inode_id / inodes_per_block;
+        u16 block_offset = inode_id % inodes_per_block * inode_size;
+
+        assert(inode_block_idx * inodes_per_block + block_offset / inode_size
+                == inode_id
+            && "calculation wrong");
+
+        return { inode_block_idx, block_offset };
+    }
+
+}
+
+auto Fs::init_new(u16 volume_id, u16 block_count) -> Result<void>
+{
+    m_superblock = Superblock {
+        .volume_id = volume_id,
+        .fs_version = 1,
+        .blocks_count = block_count,
+        .blocks_free = block_count,
+        .root_inode = 0,
+        .inode_blocks_count = 0,
+        .iblocks = {},
+        .inode_bitmap = {},
+    };
+
+    auto root_inode_id = make_directory_inode();
+    if (not root_inode_id)
+        return std::unexpected(root_inode_id.error());
+
+    m_superblock.root_inode = *root_inode_id;
+
+    if (auto result = sync_to_disk(); not result)
+        return result;
+
+    return {};
+}
+
+auto Fs::make_file(u16 dir_inode_id, std::string_view name) -> Result<u16>
+{
+    if (name.size() > name_max_len)
+        return std::unexpected("invalid filename");
+
+    auto dir_inode_result = read_inode(dir_inode_id);
+    if (not dir_inode_result)
+        return std::unexpected(dir_inode_result.error());
+    auto& dir_inode = *dir_inode_result;
+
+    if (inode_mode_type(dir_inode.mode) != INodeType::Dir)
+        return std::unexpected("incorrect inode type");
+
+    auto inode_id = allocate_inode();
+    if (not inode_id)
+        return inode_id;
+
+    auto inode = INode {
+        .mode = inode_mode(INodeType::File),
         .blocks_count = 0,
+        .links_count = 0,
+        .last_block_size = 0,
+        .size = 0,
         .blocks = {},
     };
+
+    auto entry = DirEntry {
+        .inode = *inode_id,
+        .next = 0,
+        .name_len = static_cast<u16>(name.size()),
+        .name = {},
+    };
+
+    std::memcpy(entry.name.data(), name.data(), name.size());
+
+    if (auto result = append_to_directory(dir_inode, entry); not result)
+        return std::unexpected(result.error());
 }
 
-Status Fs::write_new_inode(INodeData& data)
+auto Fs::init_from_existing() -> Result<void>
 {
-    uint16_t block_id = data.id / inodes_per_block;
-    uint16_t offset = data.id % inodes_per_block * inode_size;
-
-    BlockData block;
-    m_disk->read(&block[0], block_id);
+    return sync_from_disk();
 }
 
-Status Fs::next_inode_id(uint16_t& id)
+auto Fs::append_to_directory(INode& dir_inode, const DirEntry& entry)
+    -> Result<void>
 {
-    for (uint16_t map_idx = 0; map_idx < sb_inode_bitmap_count; ++map_idx) {
-        auto& map = m_super.inode_bitmap[map_idx];
 
-        for (uint16_t bit_idx = 0; bit_idx < 16; ++bit_idx) {
+    for (u16 i = 0; i < inode_ndir_blocks; ++i) {
+        auto dir_entry_block = dir_inode.blocks[i];
 
-            if ((map >> bit_idx & 1) == 0) {
-                id = map_idx * sb_inode_bitmap_count + bit_idx;
-                return Ok;
-            }
+        auto block = read_block<BlockData>(dir_entry_block);
+        if (not block)
+            return std::unexpected(block.error());
+    }
+
+    return {};
+}
+
+auto Fs::make_directory_inode() -> Result<u16>
+{
+    auto inode_id = allocate_inode();
+    if (not inode_id)
+        return inode_id;
+
+    auto inode = INode {
+        .mode = inode_mode(INodeType::Dir),
+        .blocks_count = 0,
+        .links_count = 0,
+        .last_block_size = 0,
+        .size = 0,
+        .blocks = {},
+    };
+
+    if (auto result = write_inode(*inode_id, inode); not result)
+        return std::unexpected(result.error());
+
+    return inode_id;
+}
+
+auto Fs::inode_last_block_id(const INode& inode) -> Result<u16>
+{
+    if (inode.blocks_count < inode_ndir_blocks) {
+        return inode.blocks_count - 1;
+
+    } else if (inode.blocks_count >= inode_ind_block
+        && inode.blocks_count <= inode_ind_block + block_size) {
+
+        auto block_id = inode.blocks[inode_ind_block];
+        assert(block_id != 0);
+
+        auto ind_block = read_block<BlockData>(block_id);
+        if (not ind_block)
+            return std::unexpected(ind_block.error());
+
+        return ind_block.value()[inode.blocks_count - inode_ind_block];
+
+    } else if (inode.blocks_count == inode_dind_block) {
+
+        u16 first_id = inode_dind_block;
+        u16 second_id = inode.blocks_count - inode_dind_block;
+
+        auto first_block_id = inode.blocks[inode_dind_block];
+        assert(first_block_id != 0);
+
+        auto first_ind_block = read_block<BlockData>(first_block_id);
+        if (not first_ind_block)
+            return std::unexpected(first_ind_block.error());
+
+        auto second_block_id
+            = first_ind_block.value()[inode.blocks_count - inode_dind_block];
+
+        auto second_ind_block = read_block<BlockData>(second_block_id);
+        if (not second_ind_block)
+            return std::unexpected(second_ind_block.error());
+
+        return second_ind_block.value()[inode.blocks_count - inode_dind_block];
+
+    } else {
+        return std::unexpected("inode at capacity");
+    }
+}
+
+auto Fs::read_inode(u16 inode_id) -> Result<INode>
+{
+    auto [inode_block_idx, block_offset] = unwrap_inode_id(inode_id);
+
+    if (inode_block_idx >= m_superblock.inode_blocks_count)
+        return std::unexpected("inode lookup failed");
+
+    auto block_id = m_superblock.iblocks[inode_block_idx];
+
+    struct INodeData {
+        u16 mode;
+        u16 blocks_count;
+        u16 links_count;
+        u16 last_block_size;
+        u32 size;
+        std::array<u16, inode_blocks_count> blocks;
+    };
+    static_assert(sizeof(INodeData) == sizeof(INode));
+
+    return read_block_part<INode>(block_id, block_offset);
+}
+
+auto Fs::write_inode(u16 inode_id, const INode& inode) -> Result<void>
+{
+    auto [inode_block_idx, block_offset] = unwrap_inode_id(inode_id);
+
+    if (inode_block_idx >= m_superblock.inode_blocks_count)
+        return std::unexpected("inode lookup failed");
+
+    auto block_id = m_superblock.iblocks[inode_block_idx];
+
+    if (auto result = write_block_part(block_id, inode, block_offset);
+        not result)
+        return result;
+
+    return {};
+}
+
+auto Fs::allocate_inode() -> Result<u16>
+{
+    auto inode_id = std::optional<u16>();
+    auto& sb = m_superblock;
+    for (u16 i = 0; i < sb.inode_blocks_count * 16; ++i) {
+        if (sb.inode_bitmap[i]) {
+            inode_id = i;
+            break;
         }
     }
-    return Status::INodeAllocFail;
+
+    if (not inode_id) {
+        if (sb.inode_blocks_count >= iblocks_max_count) {
+            return std::unexpected("inode allocate failed");
+        }
+        auto new_block_id = allocate_block();
+        if (not new_block_id)
+            return new_block_id;
+
+        sb.iblocks[sb.inode_blocks_count] = *new_block_id;
+        inode_id = sb.inode_blocks_count * 16;
+        sb.inode_blocks_count += 1;
+    }
+
+    sb.inode_bitmap[*inode_id] = true;
+    return *inode_id;
 }
 
-Status Fs::read_superblock()
+auto Fs::allocate_block() -> Result<u16>
 {
-    BlockData block;
-    m_disk->read(&block[0], super_block_location);
-    m_super = *reinterpret_cast<SuperBlockData*>(&block[0]);
-    return Ok;
+    u16 block_id = 0;
+
+    // data/inode blocks start at 4
+    for (u16 i = 4; i < blocks_max_count; ++i) {
+        if (not m_blocks_bitmap.bitmap[i]) {
+            block_id = i;
+            break;
+        }
+    }
+    if (block_id == 0) {
+        return std::unexpected("allocate block failed");
+    }
+    m_blocks_bitmap.bitmap[block_id] = true;
+    return block_id;
 }
 
-Status Fs::write_superblock()
+auto Fs::sync_from_disk() -> Result<void>
 {
-    m_disk->write(
-        reinterpret_cast<const uint8_t*>(&m_super), super_block_location);
-    return Ok;
+    auto superblock = read_block<Superblock>(sb_loc);
+    if (not superblock)
+        return std::unexpected(superblock.error());
+
+    auto blocks_bitmap = read_block<BlocksBitmap>(blocks_bitmap_loc);
+    if (not blocks_bitmap)
+        return std::unexpected(superblock.error());
+
+    m_superblock = *superblock;
+    m_blocks_bitmap = *blocks_bitmap;
+
+    return {};
+}
+
+auto Fs::sync_to_disk() -> Result<void>
+{
+    if (auto result = write_block(m_superblock, sb_loc); not result)
+        return result;
+
+    if (auto result = write_block(m_blocks_bitmap, blocks_bitmap_loc);
+        not result)
+        return result;
+
+    return {};
+}
+
+template <typename Data>
+    requires(sizeof(Data) <= block_size)
+auto Fs::read_block_part(u16 block_id, u16 offset) -> Result<Data>
+{
+    assert(sizeof(Data) + offset <= block_size);
+
+    BlockData block = {};
+    m_disk->read(block.data(), block_id);
+
+    Data data;
+    std::memcpy(
+        reinterpret_cast<uint8_t*>(&data) + offset, block.data(), sizeof(Data));
+
+    return data;
+}
+
+template <typename Data>
+    requires(sizeof(Data) <= block_size)
+auto Fs::write_block_part(u16 block_id, const Data& data, u16 offset)
+    -> Result<void>
+{
+    assert(sizeof(Data) + offset <= block_size);
+
+    BlockData block = {};
+    m_disk->read(block.data(), block_id);
+
+    std::memcpy(block.data(),
+        reinterpret_cast<const uint8_t*>(&data) + offset,
+        sizeof(Data));
+    m_disk->write(block.data(), block_id);
+
+    return {};
+}
+
+template <typename Data>
+    requires(sizeof(Data) <= block_size)
+auto Fs::read_block(u16 block_id) -> Result<Data>
+{
+    BlockData block = {};
+    m_disk->read(block.data(), block_id);
+
+    Data data;
+    std::memcpy(reinterpret_cast<uint8_t*>(&data), block.data(), sizeof(Data));
+
+    return data;
+}
+
+template <typename Data>
+    requires(sizeof(Data) <= block_size)
+auto Fs::write_block(const Data& data, u16 block_id) -> Result<void>
+{
+    BlockData block = {};
+    std::memcpy(
+        block.data(), reinterpret_cast<const uint8_t*>(&data), sizeof(Data));
+    m_disk->write(block.data(), block_id);
+    return {};
 }
 
 }

src/fs.hpp

@@ -1,53 +1,80 @@
 #pragma once
 
 #include "block_device.hpp"
+#include "types.hpp"
+#include <bitset>
 #include <cstddef>
-#include <cstdint>
+#include <expected>
+#include <string_view>
+#include <type_traits>
+#include <utility>
 
 namespace vc5::filesys {
 
-enum class Status : uint16_t {
-    Ok,
-    INodeAllocFail,
+constexpr u16 block_size = 0x200;
+
+constexpr u16 name_max_len = 256;
+
+struct DirEntry {
+    u16 inode;
+    u16 next;
+    u16 name_len;
+    std::array<char, name_max_len> name;
 };
 
-constexpr uint16_t block_size = 0x200;
-constexpr uint16_t name_max_len = 255;
+constexpr u16 inode_size = 32;
+constexpr u16 inodes_per_block = block_size / inode_size;
 
-struct DirEntryData {
-    uint16_t inode;
-    uint16_t name_len;
-    std::array<uint8_t, name_max_len> name;
-};
-
-enum class INodeType : uint16_t {
+enum class INodeType : u16 {
     File = 0,
-    Directory = 1,
-    Symlink = 2,
+    Dir = 1,
+    Link = 2,
 };
 
-constexpr uint16_t inode_size = 32;
-constexpr uint16_t inodes_per_block = block_size / inode_size;
-constexpr uint16_t inode_blocks_count = 8;
+constexpr u16 inode_type_bitoffset = 0;
+constexpr u16 inode_type_bitmask = 0b11;
 
-struct INodeData {
-    uint16_t id;
-    uint16_t flags;
-    uint16_t blocks_count;
-    std::array<uint16_t, inode_blocks_count> blocks;
+constexpr u16 inode_ndir_blocks = 8;
+constexpr u16 inode_ind_block = inode_ndir_blocks;
+constexpr u16 inode_dind_block = inode_ind_block + 1;
+constexpr u16 inode_blocks_count = inode_dind_block + 1;
+
+struct INode {
+    u16 mode;
+    u16 blocks_count;
+    u16 links_count;
+    u16 last_block_size;
+    u32 size;
+    std::array<u16, inode_blocks_count> blocks;
 };
 
-constexpr uint16_t super_block_location = 0x400;
-constexpr uint16_t sb_block_bitmap_count = 8;
-constexpr uint16_t sb_inode_bitmap_count = 8;
-constexpr uint16_t sb_inode_blocks_count = 16;
+static_assert(sizeof(INode) <= inode_size);
 
-struct SuperBlockData {
-    std::array<uint16_t, sb_block_bitmap_count> block_bitmap;
-    std::array<uint16_t, sb_inode_bitmap_count> inode_bitmap;
-    std::array<uint16_t, sb_inode_blocks_count> inode_blocks;
+constexpr u16 sb_loc = 3;
+constexpr u16 blocks_bitmap_loc = 4;
+constexpr u16 blocks_max_count = block_size * 8;
+constexpr u16 iblocks_max_count = 32;
+constexpr u16 inodes_max_count = block_size / inode_size * iblocks_max_count;
+
+struct Superblock {
+    u16 volume_id;
+    u16 fs_version;
+    u16 blocks_count;
+    u16 blocks_free;
+    u16 root_inode;
+    u16 inode_blocks_count;
+    std::array<u16, iblocks_max_count> iblocks;
+    std::bitset<inodes_max_count> inode_bitmap;
 };
 
+static_assert(sizeof(Superblock) <= block_size);
+
+struct BlocksBitmap {
+    std::bitset<blocks_max_count> bitmap;
+};
+
+static_assert(sizeof(BlocksBitmap) <= block_size);
+
 class Fs {
 public:
     explicit Fs(BlockDevice& disk)
@@ -55,19 +82,115 @@ public:
     {
     }
 
-    void init();
+    template <typename T> using Result = std::expected<T, std::string_view>;
+
+    static auto init_new(BlockDevice& disk, u16 volume_id, u16 block_count)
+        -> Result<Fs>
+    {
+        auto fs = Fs(disk);
+        if (auto result = fs.init_new(volume_id, block_count); not result)
+            return std::unexpected(result.error());
+        return fs;
+    }
+
+    static auto load(BlockDevice& disk) -> Result<Fs>
+    {
+        auto fs = Fs(disk);
+        if (auto result = fs.init_from_existing(); not result)
+            return std::unexpected(result.error());
+        return fs;
+    }
+
+    auto root_inode_id() const -> Result<u16>
+    {
+        return m_superblock.root_inode;
+    }
+
+    auto make_file(u16 dir_inode_id, std::string_view name) -> Result<u16>;
 
 private:
-    Status make_directory();
+    auto init_new(u16 volume_id, u16 block_count) -> Result<void>;
+    auto init_from_existing() -> Result<void>;
 
-    Status write_new_inode(INodeData& data);
-    Status next_inode_id(uint16_t& id);
+    auto append_to_directory(INode& dir_inode, const DirEntry& entry)
+        -> Result<void>;
+    auto make_directory_inode() -> Result<u16>;
 
-    Status read_superblock();
-    Status write_superblock();
+    auto inode_last_block_id(const INode& inode) -> Result<u16>;
+
+    auto write_inode(u16 inode_id, const INode& inode) -> Result<void>;
+    auto read_inode(u16 inode_id) -> Result<INode>;
+    auto allocate_inode() -> Result<u16>;
+
+    auto allocate_block() -> Result<u16>;
+
+    auto sync_from_disk() -> Result<void>;
+    auto sync_to_disk() -> Result<void>;
+
+    // templates declared here to get private access
+
+    template <typename Data>
+        requires(sizeof(Data) <= block_size)
+    auto read_block_part(u16 block_id, u16 offset) -> Result<Data>;
+    template <typename Data>
+        requires(sizeof(Data) <= block_size)
+    auto write_block_part(u16 block_id, const Data& data, u16 offset)
+        -> Result<void>;
+
+    template <typename Data>
+        requires(sizeof(Data) <= block_size)
+    auto read_block(u16 block_id) -> Result<Data>;
+    template <typename Data>
+        requires(sizeof(Data) <= block_size)
+    auto write_block(const Data& data, u16 block_id) -> Result<void>;
 
     BlockDevice* m_disk;
-    SuperBlockData m_super;
+    Superblock m_superblock = {};
+    BlocksBitmap m_blocks_bitmap = {};
+};
+
+class ByteReader {
+public:
+    template <typename Data>
+    ByteReader(const Data* data)
+        : m_data(reinterpret_cast<const u8*>(data)) {};
+
+    template <typename Data>
+        requires std::is_integral_v<Data>
+    auto operator>>(Data& v) -> ByteReader&
+    {
+        v = 0;
+        for (std::size_t i = 0; i < sizeof(Data); ++i) {
+            v |= *m_data << (sizeof(Data) - i - 1) * 8;
+            m_data++;
+        }
+        return *this;
+    }
+
+private:
+    const u8* m_data;
+};
+
+class ByteWriter {
+public:
+    template <typename Data>
+    ByteWriter(Data* data)
+        : m_data(reinterpret_cast<u8*>(data)) {};
+
+    template <typename Data>
+        requires std::is_integral_v<Data>
+    auto operator>>(Data& v) -> ByteWriter&
+    {
+        v = 0;
+        for (std::size_t i = 0; i < sizeof(Data); ++i) {
+            *m_data = v >> (sizeof(Data) - i - 1) * 8 & 0xff;
+            m_data++;
+        }
+        return *this;
+    }
+
+private:
+    u8* m_data;
 };
 
 }

src/types.hpp

@@ -0,0 +1,17 @@
+#pragma once
+
+#include <cstdint>
+
+namespace vc5 {
+
+using u8 = std::uint8_t;
+using u16 = std::uint16_t;
+using u32 = std::uint32_t;
+using u64 = std::uint64_t;
+
+using i8 = std::int8_t;
+using i16 = std::int16_t;
+using i32 = std::int32_t;
+using i64 = std::int64_t;
+
+}

src/vm_main.cpp

@@ -1,12 +1,16 @@
 #include "block_device.hpp"
 #include "builder.hpp"
+#include "fs.hpp"
 #include "io_device.hpp"
+#include "types.hpp"
 #include "vm.hpp"
 #include <SDL2/SDL_main.h>
+#include <array>
 #include <cstdint>
 #include <cstdlib>
 #include <print>
 #include <string>
+#include <string_view>
 
 using namespace std::chrono_literals;
 
@@ -22,7 +26,25 @@ int main(int argc, char** argv)
         return EXIT_FAILURE;
     }
 
-    auto disk = FileDisk(argv[1]);
+    auto file_disk = FileDisk(argv[1]);
+    auto disk = MemoryDisk(128);
+
+    auto block = std::array<uint8_t, 512> {};
+
+    for (u16 i = 0; i < 2; ++i) {
+        file_disk.read(block.data(), i);
+        disk.write(block.data(), i);
+    }
+
+    try {
+        auto fs = filesys::Fs::init_new(disk, 0, 128).value();
+
+        auto root = fs.root_inode_id().value();
+
+    } catch (std::bad_expected_access<std::string_view>& ex) {
+        std::println(stderr, "error: {}", ex.error());
+        return EXIT_FAILURE;
+    }
 
     auto vm = VM(*device, disk);
     vm.run();