Initial commit

15 files changed, 1334 insertions, 0 deletions

diff --git a/src/args.cc b/src/args.cc
new file mode 100644
index 0000000..1794941
--- /dev/null
+++ b/src/args.cc
@@ -0,0 +1,389 @@
+#include "args.hh"
+
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <format>
+#include <iostream>
+#include <map>
+#include <memory>
+#include <optional>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+namespace {
+
+std::string kEmpty;
+
+class OptionImpl : public Args::OptionArgument {
+ public:
+  enum Type : uint8_t {
+    NoArgument,
+    RequiredArgument,
+    OptionalArgument,
+  };
+
+  OptionImpl(Type type, char shortname, std::string longname, std::string arg,
+             std::string help)
+      : type(type),
+        shortname(shortname),
+        longname(std::move(longname)),
+        arg(std::move(arg)),
+        help(std::move(help)) {}
+
+  const Type type;
+  const char shortname;
+  const std::string longname;
+  const std::string arg;
+  const std::string help;
+
+  [[nodiscard]] bool is_set() const override { return is_set_; }
+
+  [[nodiscard]] bool has_argument() const override {
+    return value_.has_value();
+  }
+
+  [[nodiscard]] const std::string& argument() const override {
+    if (value_.has_value())
+      return value_.value();
+    assert(false);
+    return kEmpty;
+  }
+
+  void clear() {
+    is_set_ = false;
+    value_.reset();
+  }
+
+  void set_argument(std::string value) {
+    assert(type == Type::RequiredArgument || type == Type::OptionalArgument);
+    is_set_ = true;
+    value_ = std::move(value);
+  }
+
+  void set_no_argument() {
+    assert(type == Type::NoArgument || type == Type::OptionalArgument);
+    is_set_ = true;
+    value_.reset();
+  }
+
+ private:
+  bool is_set_{false};
+  std::optional<std::string> value_;
+};
+
+class ArgsImpl : public Args {
+ public:
+  explicit ArgsImpl(std::string prgname) : prgname_(std::move(prgname)) {}
+
+  std::shared_ptr<Option> option(char shortname, std::string longname,
+                                 std::string help) override {
+    auto opt = std::make_shared<OptionImpl>(
+        OptionImpl::Type::NoArgument, shortname, std::move(longname),
+        /* arg */ std::string(), std::move(help));
+    add(opt);
+    return opt;
+  }
+
+  std::shared_ptr<OptionArgument> option_argument(char shortname,
+                                                  std::string longname,
+                                                  std::string arg,
+                                                  std::string help,
+                                                  bool required) override {
+    auto opt = std::make_shared<OptionImpl>(
+        required ? OptionImpl::Type::RequiredArgument
+                 : OptionImpl::Type::OptionalArgument,
+        shortname, std::move(longname), std::move(arg), std::move(help));
+    add(opt);
+    return opt;
+  }
+
+  bool run(int argc, char** argv,
+           std::vector<std::string_view>* arguments = nullptr) override {
+    last_error_.clear();
+    for (auto& opt : options_) {
+      opt->clear();
+    }
+
+    std::string_view prgname;
+    if (prgname_.empty()) {
+      if (argc > 0)
+        prgname = argv[0];
+    } else {
+      prgname = prgname_;
+    }
+
+    for (int a = 1; a < argc; ++a) {
+      assert(argv[a]);
+      if (argv[a][0] == '-' && argv[a][1] != '\0') {
+        if (argv[a][1] == '-') {
+          // long option
+          size_t eq = 2;
+          while (argv[a][eq] != '=' && argv[a][eq] != '\0')
+            ++eq;
+          size_t end = eq;
+          while (argv[a][end] != '\0')
+            ++end;
+
+          if (end == 2) {
+            // "--", no more options signal
+            if (arguments) {
+              for (++a; a < argc; ++a)
+                arguments->emplace_back(argv[a]);
+            }
+            break;
+          }
+
+          auto name = std::string_view(argv[a] + 2, eq - 2);
+          auto it = long_.find(name);
+          if (it == long_.end()) {
+            last_error_ =
+                std::format("{}: unrecognized option '--{}'", prgname, name);
+            return false;
+          }
+          auto& opt = options_[it->second];
+
+          if (eq < end) {
+            // long option with argument after equal sign
+            switch (opt->type) {
+              case OptionImpl::Type::NoArgument:
+                last_error_ =
+                    std::format("{}: option '--{}' doesn't allow an argument",
+                                prgname, name);
+                return false;
+              case OptionImpl::Type::RequiredArgument:
+              case OptionImpl::Type::OptionalArgument:
+                opt->set_argument(
+                    std::string(argv[a] + eq + 1, end - (eq + 1)));
+                break;
+            }
+          } else {
+            switch (opt->type) {
+              case OptionImpl::Type::NoArgument:
+              case OptionImpl::Type::OptionalArgument:
+                opt->set_no_argument();
+                break;
+              case OptionImpl::Type::RequiredArgument:
+                if (++a >= argc) {
+                  last_error_ = std::format(
+                      "{}: option '--{}' requires an argument", prgname, name);
+                  return false;
+                }
+                opt->set_argument(argv[a]);
+                break;
+            }
+          }
+        } else {
+          // short options
+          char* current = argv[a] + 1;
+          for (; *current; ++current) {
+            auto it = short_.find(*current);
+            if (it == short_.end()) {
+              last_error_ =
+                  std::format("{}: invalid option -- '{}'", prgname, *current);
+              return false;
+            }
+
+            auto& opt = options_[it->second];
+            switch (opt->type) {
+              case OptionImpl::Type::NoArgument:
+              case OptionImpl::Type::OptionalArgument:
+                opt->set_no_argument();
+                break;
+              case OptionImpl::Type::RequiredArgument:
+                if (++a >= argc) {
+                  last_error_ =
+                      std::format("{}: option requires an argument -- '{}'",
+                                  prgname, *current);
+                  return false;
+                }
+                opt->set_argument(argv[a]);
+                break;
+            }
+          }
+        }
+      } else {
+        if (arguments)
+          arguments->emplace_back(argv[a]);
+      }
+    }
+    return true;
+  }
+
+  void print_error(std::ostream& out) const override {
+    if (last_error_.empty())
+      return;
+
+    out << last_error_ << '\n';
+  }
+
+  void print_help(std::ostream& out, uint32_t width = 79) const override {
+    if (options_.empty())
+      return;
+
+    uint32_t indent = 0;
+    const uint32_t max_need = width / 2;
+    std::vector<uint32_t> option_need;
+    for (auto const& opt : options_) {
+      uint32_t need;
+      if (opt->longname.empty()) {
+        need = 4;  // -O
+        switch (opt->type) {
+          case OptionImpl::Type::NoArgument:
+          case OptionImpl::Type::OptionalArgument:
+            break;
+          case OptionImpl::Type::RequiredArgument:
+            need += 1 + (opt->arg.empty() ? 3 : opt->arg.size());
+            break;
+        }
+      } else {
+        need = 8 + opt->longname.size();  // -O, --option
+        switch (opt->type) {
+          case OptionImpl::Type::NoArgument:
+            break;
+          case OptionImpl::Type::RequiredArgument:
+            // =ARG
+            need += 1 + (opt->arg.empty() ? 3 : opt->arg.size());
+            break;
+          case OptionImpl::Type::OptionalArgument:
+            // [=ARG]
+            need += 3 + (opt->arg.empty() ? 3 : opt->arg.size());
+            break;
+        }
+      }
+      need += 2;  // margin
+
+      option_need.emplace_back(need);
+      if (need <= max_need) {
+        indent = std::max(indent, need);
+      }
+    }
+
+    print_wrap(out, width, /* indent */ 0,
+               "Mandatory arguments to long options"
+               " are mandatory for short options too.");
+    auto need_it = option_need.begin();
+    for (auto const& opt : options_) {
+      if (opt->longname.empty()) {
+        out << "  -" << opt->shortname;
+        switch (opt->type) {
+          case OptionImpl::Type::NoArgument:
+          case OptionImpl::Type::OptionalArgument:
+            break;
+          case OptionImpl::Type::RequiredArgument:
+            out << " " << (opt->arg.empty() ? "ARG" : opt->arg);
+            break;
+        }
+      } else {
+        if (opt->shortname != '\0') {
+          out << "  -" << opt->shortname << ", --";
+        } else {
+          out << "      --";
+        }
+        out << opt->longname;
+        switch (opt->type) {
+          case OptionImpl::Type::NoArgument:
+            break;
+          case OptionImpl::Type::RequiredArgument:
+            out << "=" << (opt->arg.empty() ? "ARG" : opt->arg);
+            break;
+          case OptionImpl::Type::OptionalArgument:
+            out << "=[" << (opt->arg.empty() ? "ARG" : opt->arg) << ']';
+            break;
+        }
+      }
+
+      auto need = *need_it++;
+      if (need > max_need) {
+        out << '\n';
+        if (!opt->help.empty()) {
+          print_wrap(out, width, 0, opt->help);
+        }
+      } else {
+        if (opt->help.empty()) {
+          out << '\n';
+        } else {
+          out << "  ";  // add margin, already included in need
+          while (need++ < indent)
+            out << ' ';
+          print_wrap(out, width, indent, opt->help);
+        }
+      }
+    }
+  }
+
+ private:
+  void add(std::shared_ptr<OptionImpl> opt) {
+    if (opt->shortname == '\0' && opt->longname.empty()) {
+      assert(false);
+    } else {
+      auto idx = options_.size();
+      if (opt->shortname != '\0')
+        short_.emplace(opt->shortname, idx);
+      if (!opt->longname.empty())
+        long_.emplace(opt->longname, idx);
+    }
+    options_.emplace_back(std::move(opt));
+  }
+
+  static inline bool is_whitespace(char c) { return c == ' ' || c == '\t'; }
+
+  static void print_wrap(std::ostream& out, uint32_t width, uint32_t indent,
+                         const std::string& str) {
+    if (indent + str.size() <= width) {
+      out << str << '\n';
+      return;
+    }
+    if (width <= indent || indent + 10 > width) {
+      out << '\n';
+      out << str << '\n';
+      return;
+    }
+    const std::string indent_str(indent, ' ');
+    const uint32_t avail = width - indent;
+    size_t offset = 0;
+    while (offset + avail < str.size()) {
+      uint32_t i = avail;
+      while (i > 0 && !is_whitespace(str[offset + i]))
+        --i;
+      if (i == 0) {
+        out << str.substr(offset, avail - 1);
+        out << "-\n";
+        offset += avail - 1;
+      } else {
+        out << str.substr(offset, i);
+        out << '\n';
+        offset += i;
+      }
+      out << indent_str;
+    }
+    out << str.substr(offset);
+    out << '\n';
+  }
+
+  const std::string prgname_;
+  std::vector<std::shared_ptr<OptionImpl>> options_;
+  std::map<char, size_t> short_;
+  std::map<std::string_view, size_t> long_;
+  std::string last_error_;
+};
+
+}  // namespace
+
+std::shared_ptr<Args::Option> Args::option(std::string longname,
+                                           std::string help) {
+  return option(/* shortname */ '\0', std::move(longname), std::move(help));
+}
+
+std::shared_ptr<Args::OptionArgument> Args::option_argument(
+    std::string longname, std::string arg, std::string help, bool required) {
+  return option_argument(/* shortname */ '\0', std::move(longname),
+                         std::move(arg), std::move(help), required);
+}
+
+std::unique_ptr<Args> Args::create(std::string prgname) {
+  return std::make_unique<ArgsImpl>(std::move(prgname));
+}
diff --git a/src/args.hh b/src/args.hh
new file mode 100644
index 0000000..14f3716
--- /dev/null
+++ b/src/args.hh
@@ -0,0 +1,64 @@
+#ifndef ARGS_HH
+#define ARGS_HH
+
+#include <cstdint>
+#include <iosfwd>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <vector>
+
+class Args {
+ public:
+  virtual ~Args() = default;
+
+  class Option {
+   public:
+    virtual ~Option() = default;
+
+    [[nodiscard]] virtual bool is_set() const = 0;
+
+   protected:
+    Option() = default;
+    Option(Option const&) = delete;
+    Option& operator=(Option const&) = delete;
+  };
+
+  class OptionArgument : public Option {
+   public:
+    [[nodiscard]] virtual bool has_argument() const = 0;
+    [[nodiscard]] virtual const std::string& argument() const = 0;
+  };
+
+  static std::unique_ptr<Args> create(std::string prgname = std::string());
+
+  virtual std::shared_ptr<Option> option(char shortname,
+                                         std::string longname = std::string(),
+                                         std::string help = std::string()) = 0;
+
+  std::shared_ptr<Option> option(std::string longname,
+                                 std::string help = std::string());
+
+  virtual std::shared_ptr<OptionArgument> option_argument(
+      char shortname, std::string longname = std::string(),
+      std::string arg = std::string(), std::string help = std::string(),
+      bool required = true) = 0;
+
+  std::shared_ptr<OptionArgument> option_argument(
+      std::string longname, std::string arg = std::string(),
+      std::string help = std::string(), bool required = true);
+
+  virtual bool run(int argc, char** argv,
+                   std::vector<std::string_view>* arguments = nullptr) = 0;
+
+  virtual void print_error(std::ostream& out) const = 0;
+
+  virtual void print_help(std::ostream& out, uint32_t width = 79) const = 0;
+
+ protected:
+  Args() = default;
+  Args(Args const&) = delete;
+  Args& operator=(Args const&) = delete;
+};
+
+#endif  // ARGS_HH
diff --git a/src/buffer.cc b/src/buffer.cc
new file mode 100644
index 0000000..18913a5
--- /dev/null
+++ b/src/buffer.cc
@@ -0,0 +1,213 @@
+#include "buffer.hh"
+
+#include <algorithm>
+#include <cassert>
+#include <cstring>
+#include <memory>
+#include <utility>
+
+namespace {
+
+class FixedBuffer : public Buffer {
+ public:
+  explicit FixedBuffer(size_t size) : size_(size) {}
+
+  void const* rptr(size_t& avail, size_t need) override {
+    if (rptr_ < wptr_) {
+      avail = wptr_ - rptr_;
+    } else if (rptr_ == wptr_ && !full_) {
+      avail = 0;
+    } else {
+      avail = (data_.get() + size_) - rptr_;
+      if (avail < need && rptr_ > data_.get()) {
+        rotate();
+        return rptr(avail, need);
+      }
+    }
+    return rptr_;
+  }
+
+  void consume(size_t size) override {
+    if (size == 0)
+      return;
+    if (rptr_ < wptr_) {
+      assert(std::cmp_greater_equal(wptr_ - rptr_, size));
+      rptr_ += size;
+      if (rptr_ == wptr_)
+        reset();
+    } else {
+      assert(rptr_ != wptr_ || full_);
+      assert(std::cmp_greater_equal((data_.get() + size_) - rptr_, size));
+      rptr_ += size;
+      if (rptr_ == data_.get() + size_) {
+        rptr_ = data_.get();
+        if (rptr_ == wptr_)
+          reset();
+      }
+    }
+  }
+
+  void* wptr(size_t& avail, size_t need) override {
+    if (wptr_ == nullptr) {
+      data_ = std::make_unique_for_overwrite<char[]>(size_);
+      rptr_ = wptr_ = data_.get();
+    }
+
+    if (wptr_ < rptr_) {
+      avail = rptr_ - wptr_;
+    } else if (rptr_ == wptr_ && full_) {
+      avail = 0;
+    } else {
+      avail = (data_.get() + size_) - wptr_;
+      if (avail < need && rptr_ > data_.get()) {
+        rotate();
+        return wptr(avail, need);
+      }
+    }
+    return wptr_;
+  }
+
+  void commit(size_t size) override {
+    if (size == 0)
+      return;
+    if (wptr_ < rptr_) {
+      assert(std::cmp_greater_equal(rptr_ - wptr_, size));
+      wptr_ += size;
+      if (wptr_ == rptr_) {
+        full_ = true;
+      }
+    } else {
+      assert(rptr_ != wptr_ || !full_);
+      assert(std::cmp_greater_equal((data_.get() + size_) - wptr_, size));
+      wptr_ += size;
+      if (wptr_ == data_.get() + size_) {
+        wptr_ = data_.get();
+        if (wptr_ == rptr_)
+          full_ = true;
+      }
+    }
+  }
+
+  [[nodiscard]] bool full() const override { return rptr_ == wptr_ && full_; }
+
+  [[nodiscard]] bool empty() const override { return rptr_ == wptr_ && !full_; }
+
+ private:
+  void reset() {
+    rptr_ = wptr_ = data_.get();
+    full_ = false;
+  }
+
+  void rotate() {
+    if (rptr_ < wptr_) {
+      size_t size = wptr_ - rptr_;
+      memmove(data_.get(), rptr_, size);
+      wptr_ = data_.get() + size;
+    } else {
+      size_t to_move = (data_.get() + size_) - rptr_;
+      if (wptr_ + to_move > rptr_) {
+        auto tmp = std::make_unique_for_overwrite<char[]>(to_move);
+        memcpy(tmp.get(), rptr_, to_move);
+        memmove(data_.get() + to_move, data_.get(), wptr_ - data_.get());
+        memcpy(data_.get(), tmp.get(), to_move);
+      } else {
+        memmove(data_.get() + to_move, data_.get(), wptr_ - data_.get());
+        memcpy(data_.get(), rptr_, to_move);
+      }
+      wptr_ += to_move;
+    }
+    rptr_ = data_.get();
+  }
+
+  size_t const size_;
+  std::unique_ptr<char[]> data_;
+  char* rptr_{nullptr};
+  char* wptr_{nullptr};
+  bool full_{false};
+};
+
+class DynamicBuffer : public Buffer {
+ public:
+  DynamicBuffer(size_t start_size, size_t max_size)
+      : start_size_(start_size), max_size_(max_size) {}
+
+  void const* rptr(size_t& avail, size_t /* need */) override {
+    avail = wptr_ - rptr_;
+    return rptr_;
+  }
+
+  void consume(size_t size) override {
+    assert(std::cmp_greater_equal(wptr_ - rptr_, size));
+    rptr_ += size;
+    if (rptr_ == wptr_) {
+      reset();
+    }
+  }
+
+  void* wptr(size_t& avail, size_t need) override {
+    avail = end_ - wptr_;
+    if (avail < need) {
+      if (end_ == nullptr) {
+        size_t size = std::min(max_size_, std::max(need, start_size_));
+        data_ = std::make_unique_for_overwrite<char[]>(size);
+        end_ = data_.get() + size;
+        rptr_ = wptr_ = data_.get();
+        avail = end_ - wptr_;
+      } else if (std::cmp_greater_equal(rptr_ - data_.get(), need - avail)) {
+        memmove(data_.get(), rptr_, wptr_ - rptr_);
+        wptr_ = data_.get() + (wptr_ - rptr_);
+        rptr_ = data_.get();
+        avail = end_ - wptr_;
+      } else if (std::cmp_less(end_ - data_.get(), max_size_)) {
+        size_t current_size = end_ - data_.get();
+        size_t new_size = std::min(
+            max_size_, current_size + std::max(need - avail, current_size));
+        auto tmp = std::make_unique_for_overwrite<char[]>(new_size);
+        memcpy(tmp.get(), rptr_, wptr_ - rptr_);
+        end_ = tmp.get() + new_size;
+        wptr_ = tmp.get() + (wptr_ - rptr_);
+        rptr_ = tmp.get();
+        data_ = std::move(tmp);
+        avail = end_ - wptr_;
+      }
+    }
+    return wptr_;
+  }
+
+  void commit(size_t size) override {
+    assert(std::cmp_greater_equal(end_ - wptr_, size));
+    wptr_ += size;
+  }
+
+  [[nodiscard]] bool full() const override {
+    return rptr_ == data_.get() && wptr_ == end_ &&
+           std::cmp_equal(end_ - data_.get(), max_size_);
+  }
+
+  [[nodiscard]] bool empty() const override { return rptr_ == wptr_; }
+
+ private:
+  void reset() {
+    if (std::cmp_greater(end_ - data_.get(), start_size_)) {
+      data_ = std::make_unique_for_overwrite<char[]>(start_size_);
+    }
+    rptr_ = wptr_ = data_.get();
+  }
+
+  size_t const start_size_;
+  size_t const max_size_;
+  std::unique_ptr<char[]> data_;
+  char* end_{nullptr};
+  char* rptr_{nullptr};
+  char* wptr_{nullptr};
+};
+
+}  // namespace
+
+std::unique_ptr<Buffer> Buffer::fixed(size_t size) {
+  return std::make_unique<FixedBuffer>(size);
+}
+
+std::unique_ptr<Buffer> Buffer::dynamic(size_t start_size, size_t max_size) {
+  return std::make_unique<DynamicBuffer>(start_size, max_size);
+}
diff --git a/src/buffer.hh b/src/buffer.hh
new file mode 100644
index 0000000..685cd36
--- /dev/null
+++ b/src/buffer.hh
@@ -0,0 +1,31 @@
+#ifndef BUFFER_HH
+#define BUFFER_HH
+
+#include <cstddef>
+#include <memory>
+
+class Buffer {
+ public:
+  virtual ~Buffer() = default;
+
+  virtual void const* rptr(size_t& avail, size_t need = 1) = 0;
+  virtual void consume(size_t size) = 0;
+
+  virtual void* wptr(size_t& avail, size_t need = 1) = 0;
+  virtual void commit(size_t size) = 0;
+
+  [[nodiscard]] virtual bool full() const = 0;
+  [[nodiscard]] virtual bool empty() const = 0;
+
+  [[nodiscard]]
+  static std::unique_ptr<Buffer> fixed(size_t size);
+  [[nodiscard]]
+  static std::unique_ptr<Buffer> dynamic(size_t start_size, size_t max_size);
+
+ protected:
+  Buffer() = default;
+  Buffer(Buffer const&) = delete;
+  Buffer& operator=(Buffer const&) = delete;
+};
+
+#endif  // BUFFER_HH
diff --git a/src/check.hh b/src/check.hh
new file mode 100644
index 0000000..91c1717
--- /dev/null
+++ b/src/check.hh
@@ -0,0 +1,39 @@
+#ifndef CHECK_HH
+#define CHECK_HH
+
+#include <cstdlib>
+#include <stdckdint.h>
+#include <type_traits>
+
+namespace check {
+
+template <typename T>
+  requires std::is_arithmetic_v<T>
+T add(T a, T b) {
+  T ret;
+  if (ckd_add(&ret, a, b))
+    abort();
+  return ret;
+}
+
+template <typename T>
+  requires std::is_arithmetic_v<T>
+T sub(T a, T b) {
+  T ret;
+  if (ckd_sub(&ret, a, b))
+    abort();
+  return ret;
+}
+
+template <typename T>
+  requires std::is_arithmetic_v<T>
+T mul(T a, T b) {
+  T ret;
+  if (ckd_mul(&ret, a, b))
+    abort();
+  return ret;
+}
+
+}  // namespace check
+
+#endif  // CHECK_HH
diff --git a/src/config.h.in b/src/config.h.in
new file mode 100644
index 0000000..eaab018
--- /dev/null
+++ b/src/config.h.in
@@ -0,0 +1 @@
+#define VERSION "@version@"
diff --git a/src/io.cc b/src/io.cc
new file mode 100644
index 0000000..99c0518
--- /dev/null
+++ b/src/io.cc
@@ -0,0 +1,232 @@
+#include "io.hh"
+
+#include "unique_fd.hh"
+
+#include <algorithm>
+#include <cerrno>
+#include <cstdio>
+#include <cstring>
+#include <expected>
+#include <fcntl.h>
+#include <limits>
+#include <memory>
+#include <optional>
+#include <string>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <utility>
+
+namespace io {
+
+namespace {
+
+class BasicReader : public Reader {
+ public:
+  explicit BasicReader(unique_fd fd) : fd_(std::move(fd)) {}
+
+  [[nodiscard]]
+  std::expected<size_t, ReadError> read(void* dst, size_t max) override {
+    ssize_t ret = ::read(
+        fd_.get(), dst,
+        std::min(static_cast<size_t>(std::numeric_limits<ssize_t>::max()),
+                 max));
+    if (ret < 0) {
+      switch (errno) {
+        case EINTR:
+          return read(dst, max);
+        default:
+          return std::unexpected(ReadError::Error);
+      }
+    } else if (ret == 0 && max > 0) {
+      return std::unexpected(ReadError::Eof);
+    }
+    offset_ += ret;
+    return ret;
+  }
+
+  [[nodiscard]]
+  std::expected<size_t, ReadError> skip(size_t max) override {
+    off_t ret;
+    if (sizeof(size_t) > sizeof(off_t)) {
+      ret = lseek(
+          fd_.get(),
+          // NOLINTNEXTLINE(bugprone-narrowing-conversions)
+          std::min(static_cast<size_t>(std::numeric_limits<off_t>::max()), max),
+          SEEK_CUR);
+    } else {
+      ret = lseek(fd_.get(), static_cast<off_t>(max), SEEK_CUR);
+    }
+    if (ret < 0) {
+      return std::unexpected(ReadError::Error);
+    }
+    // Don't want skip to go past (cached) file end.
+    if (!size_.has_value() || ret >= size_.value()) {
+      // When going past end, double check that it still is the end.
+      off_t ret2 = lseek(fd_.get(), 0, SEEK_END);
+      if (ret2 < 0) {
+        // We're screwed, but try to go back to original position and then
+        // return error.
+        size_.reset();
+        lseek(fd_.get(), offset_, SEEK_SET);
+        return std::unexpected(ReadError::Error);
+      }
+      size_ = ret2;
+      if (ret >= ret2) {
+        auto distance = ret2 - offset_;
+        offset_ = ret2;
+        if (distance == 0 && max > 0)
+          return std::unexpected(ReadError::Eof);
+        return distance;
+      }
+      // Seek back to where we should be
+      if (lseek(fd_.get(), ret, SEEK_SET) < 0) {
+        return std::unexpected(ReadError::Error);
+      }
+    }
+    auto distance = ret - offset_;
+    offset_ = ret;
+    return distance;
+  }
+
+ private:
+  unique_fd fd_;
+  off_t offset_{0};
+  std::optional<off_t> size_;
+};
+
+class MemoryReader : public Reader {
+ public:
+  MemoryReader(void* ptr, size_t size) : ptr_(ptr), size_(size) {}
+
+  [[nodiscard]]
+  std::expected<size_t, ReadError> read(void* dst, size_t max) override {
+    size_t avail = size_ - offset_;
+    if (avail == 0 && max > 0)
+      return std::unexpected(io::ReadError::Eof);
+    size_t ret = std::min(max, avail);
+    memcpy(dst, reinterpret_cast<char*>(ptr_) + offset_, ret);
+    offset_ += ret;
+    return ret;
+  }
+
+  [[nodiscard]]
+  std::expected<size_t, ReadError> skip(size_t max) override {
+    size_t avail = size_ - offset_;
+    size_t ret = std::min(max, avail);
+    offset_ += ret;
+    return ret;
+  }
+
+ protected:
+  void* ptr_;
+  size_t const size_;
+
+ private:
+  size_t offset_{0};
+};
+
+class MmapReader : public MemoryReader {
+ public:
+  MmapReader(unique_fd fd, void* ptr, size_t size)
+      : MemoryReader(ptr, size), fd_(std::move(fd)) {}
+
+  ~MmapReader() override { munmap(ptr_, size_); }
+
+ private:
+  unique_fd fd_;
+};
+
+class StringReader : public MemoryReader {
+ public:
+  explicit StringReader(std::string data)
+      : MemoryReader(nullptr, data.size()), data_(std::move(data)) {
+    ptr_ = data_.data();
+  }
+
+ private:
+  std::string data_;
+};
+
+}  // namespace
+
+std::expected<size_t, ReadError> Reader::repeat_read(void* dst, size_t max) {
+  auto ret = read(dst, max);
+  if (!ret.has_value() || ret.value() == max)
+    return ret;
+
+  char* d = reinterpret_cast<char*>(dst);
+  size_t offset = ret.value();
+  while (true) {
+    ret = read(d + offset, max - offset);
+    if (!ret.has_value())
+      break;
+    offset += ret.value();
+    if (offset == max)
+      break;
+  }
+  return offset;
+}
+
+std::expected<size_t, ReadError> Reader::repeat_skip(size_t max) {
+  auto ret = skip(max);
+  if (!ret.has_value() || ret.value() == max)
+    return ret;
+
+  size_t offset = ret.value();
+  while (true) {
+    ret = skip(max - offset);
+    if (!ret.has_value())
+      break;
+    offset += ret.value();
+    if (offset == max)
+      break;
+  }
+  return offset;
+}
+
+std::expected<std::unique_ptr<Reader>, OpenError> open(
+    const std::string& file_path) {
+  return openat(AT_FDCWD, file_path);
+}
+
+std::expected<std::unique_ptr<Reader>, OpenError> openat(
+    int dirfd, const std::string& file_path) {
+  unique_fd fd(::openat(dirfd, file_path.c_str(), O_RDONLY));
+  if (fd) {
+    struct stat buf;
+    if (fstat(fd.get(), &buf) == 0) {
+      if (std::cmp_less_equal(buf.st_size,
+                              std::numeric_limits<size_t>::max())) {
+        auto size = static_cast<size_t>(buf.st_size);
+        void* ptr = mmap(nullptr, size, PROT_READ, MAP_PRIVATE, fd.get(), 0);
+        if (ptr != MAP_FAILED) {
+          return std::make_unique<MmapReader>(std::move(fd), ptr, size);
+        }
+      }
+    }
+    return std::make_unique<BasicReader>(std::move(fd));
+  }
+  OpenError err;
+  switch (errno) {
+    case EINTR:
+      return openat(dirfd, file_path);
+    case EACCES:
+      err = OpenError::NoAccess;
+      break;
+    case ENOENT:
+      err = OpenError::NoSuchFile;
+      break;
+    default:
+      err = OpenError::Error;
+      break;
+  }
+  return std::unexpected(err);
+}
+
+std::unique_ptr<Reader> memory(std::string data) {
+  return std::make_unique<StringReader>(std::move(data));
+}
+
+}  // namespace io
diff --git a/src/io.hh b/src/io.hh
new file mode 100644
index 0000000..7c21028
--- /dev/null
+++ b/src/io.hh
@@ -0,0 +1,51 @@
+#ifndef IO_HH
+#define IO_HH
+
+#include <cstddef>
+#include <expected>
+#include <memory>
+#include <string>
+
+namespace io {
+
+enum class ReadError {
+  Error,
+  Eof,
+  InvalidData,  // invalid data read (not used by raw file)
+  MaxTooSmall,  // max argument needs to be bigger (not used by raw file)
+};
+
+enum class OpenError {
+  NoSuchFile,
+  NoAccess,
+  Error,
+};
+
+class Reader {
+ public:
+  virtual ~Reader() = default;
+
+  [[nodiscard]] virtual std::expected<size_t, ReadError> read(void* dst,
+                                                              size_t max) = 0;
+  [[nodiscard]] virtual std::expected<size_t, ReadError> skip(size_t max) = 0;
+
+  [[nodiscard]] std::expected<size_t, ReadError> repeat_read(void* dst,
+                                                             size_t max);
+  [[nodiscard]] std::expected<size_t, ReadError> repeat_skip(size_t max);
+
+ protected:
+  Reader() = default;
+
+  Reader(Reader const&) = delete;
+  Reader& operator=(Reader const&) = delete;
+};
+
+[[nodiscard]] std::expected<std::unique_ptr<Reader>, OpenError> open(
+    const std::string& file_path);
+[[nodiscard]] std::expected<std::unique_ptr<Reader>, OpenError> openat(
+    int dirfd, const std::string& file_path);
+[[nodiscard]] std::unique_ptr<Reader> memory(std::string data);
+
+}  // namespace io
+
+#endif  // IO_HH
diff --git a/src/line.cc b/src/line.cc
new file mode 100644
index 0000000..23370fc
--- /dev/null
+++ b/src/line.cc
@@ -0,0 +1,127 @@
+#include "line.hh"
+
+#include "check.hh"
+
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <expected>
+#include <memory>
+#include <string_view>
+#include <utility>
+
+namespace line {
+
+namespace {
+
+const char kLineTerminators[] = "\r\n";
+
+class ReaderImpl : public Reader {
+ public:
+  ReaderImpl(std::unique_ptr<io::Reader> reader, size_t max_len)
+      : reader_(std::move(reader)),
+        max_len_(max_len),
+        buffer_(std::make_unique_for_overwrite<char[]>(
+            check::add(max_len, static_cast<size_t>(2)))),
+        rptr_(buffer_.get()),
+        wptr_(buffer_.get()),
+        search_(rptr_),
+        end_(buffer_.get() + check::add(max_len, static_cast<size_t>(2))) {}
+
+  [[nodiscard]] std::expected<std::string_view, io::ReadError> read() override {
+    while (true) {
+      search_ = std::find_first_of(search_, wptr_, kLineTerminators,
+                                   kLineTerminators + 2);
+      if (search_ < wptr_) {
+        if (std::cmp_greater(search_ - rptr_, max_len_)) {
+          return line(max_len_, 0);
+        }
+
+        size_t tlen;
+        if (*search_ == '\n') {
+          tlen = 1;
+        } else {
+          if (search_ + 1 == wptr_) {
+            make_space_if_needed();
+            auto got = fill();
+            if (!got.has_value()) {
+              if (got.error() == io::ReadError::Eof) {
+                return line(search_ - rptr_, 1);
+              }
+              return std::unexpected(got.error());
+            }
+          }
+          if (search_[1] == '\n') {
+            tlen = 2;
+          } else {
+            tlen = 1;
+          }
+        }
+        return line(search_ - rptr_, tlen);
+      }
+      if (std::cmp_greater_equal(wptr_ - rptr_, max_len_)) {
+        return line(max_len_, 0);
+      }
+
+      make_space_if_needed();
+      auto got = fill();
+      if (!got.has_value()) {
+        if (got.error() == io::ReadError::Eof && rptr_ != wptr_) {
+          return line(wptr_ - rptr_, 0);
+        }
+        return std::unexpected(got.error());
+      }
+    }
+  }
+
+  [[nodiscard]] uint64_t number() const override { return number_; }
+
+ private:
+  std::string_view line(size_t len, size_t terminator_len) {
+    assert(len <= max_len_);
+    auto ret = std::string_view(rptr_, len);
+    rptr_ += len + terminator_len;
+    search_ = rptr_;
+    ++number_;
+    return ret;
+  }
+
+  void make_space_if_needed() {
+    size_t free = rptr_ - buffer_.get();
+    if (free == 0)
+      return;
+    size_t avail = end_ - wptr_;
+    if (avail > 1024)
+      return;
+    memmove(buffer_.get(), rptr_, wptr_ - rptr_);
+    search_ -= free;
+    wptr_ -= free;
+    rptr_ = buffer_.get();
+  }
+
+  std::expected<size_t, io::ReadError> fill() {
+    auto ret = reader_->read(wptr_, end_ - wptr_);
+    if (ret.has_value())
+      wptr_ += ret.value();
+    return ret;
+  }
+
+  std::unique_ptr<io::Reader> reader_;
+  size_t const max_len_;
+  uint64_t number_{0};
+  std::unique_ptr<char[]> buffer_;
+  char* rptr_;
+  char* wptr_;
+  char* search_;
+  char* const end_;
+};
+
+}  // namespace
+
+std::unique_ptr<Reader> open(std::unique_ptr<io::Reader> reader,
+                             size_t max_len) {
+  return std::make_unique<ReaderImpl>(std::move(reader), max_len);
+}
+
+}  // namespace line
diff --git a/src/line.hh b/src/line.hh
new file mode 100644
index 0000000..a8eeea8
--- /dev/null
+++ b/src/line.hh
@@ -0,0 +1,37 @@
+#ifndef LINE_HH
+#define LINE_HH
+
+#include "io.hh"  // IWYU pragma: export
+
+#include <cstddef>
+#include <expected>
+#include <memory>
+#include <optional>
+#include <string_view>
+
+namespace line {
+
+class Reader {
+ public:
+  virtual ~Reader() = default;
+
+  // Returned view is only valid until next call to read.
+  [[nodiscard]]
+  virtual std::expected<std::string_view, io::ReadError> read() = 0;
+  // Starts at zero. Returns next line.
+  // So, before first read it is zero, after first read it is one.
+  [[nodiscard]] virtual uint64_t number() const = 0;
+
+ protected:
+  Reader() = default;
+
+  Reader(Reader const&) = delete;
+  Reader& operator=(Reader const&) = delete;
+};
+
+[[nodiscard]] std::unique_ptr<Reader> open(std::unique_ptr<io::Reader> reader,
+                                           size_t max_len = 8192);
+
+}  // namespace line
+
+#endif  // LINE_HH
diff --git a/src/main.cc b/src/main.cc
new file mode 100644
index 0000000..e66f95a
--- /dev/null
+++ b/src/main.cc
@@ -0,0 +1,31 @@
+#include "args.hh"
+#include "config.h"
+
+#include <iostream>
+
+#ifndef VERSION
+# define VERSION "unknown"
+#endif
+
+int main(int argc, char** argv) {
+  auto args = Args::create();
+  auto opt_help = args->option('h', "help", "display this text and exit.");
+  auto opt_version = args->option('V', "version", "display version and exit.");
+  if (!args->run(argc, argv)) {
+    args->print_error(std::cerr);
+    std::cerr << "Try 'bluetooth-jukebox --help' for more information.\n";
+    return 1;
+  }
+  if (opt_help->is_set()) {
+    std::cout << "Usage: bluetooth-jukebox [OPTION...]\n"
+              << "\n";
+    args->print_help(std::cout);
+    return 0;
+  }
+  if (opt_version->is_set()) {
+    std::cout << "bluetooth-jukebox " << VERSION
+              << " written by Joel Klinghed <the_jk@spawned.biz>.\n";
+    return 0;
+  }
+  return 0;
+}
diff --git a/src/str.cc b/src/str.cc
new file mode 100644
index 0000000..44db3a6
--- /dev/null
+++ b/src/str.cc
@@ -0,0 +1,53 @@
+#include "str.hh"
+
+#include <cstddef>
+#include <string_view>
+#include <vector>
+
+namespace str {
+
+namespace {
+
+[[nodiscard]]
+inline bool is_space(char c) {
+  return c == ' ' || c == '\t' || c == '\r' || c == '\n';
+}
+
+}  // namespace
+
+void split(std::string_view str, std::vector<std::string_view>& out,
+           char separator, bool keep_empty) {
+  out.clear();
+
+  size_t offset = 0;
+  while (true) {
+    auto next = str.find(separator, offset);
+    if (next == std::string_view::npos) {
+      if (keep_empty || offset < str.size())
+        out.push_back(str.substr(offset));
+      break;
+    }
+    if (keep_empty || offset < next)
+      out.push_back(str.substr(offset, next - offset));
+    offset = next + 1;
+  }
+}
+
+std::vector<std::string_view> split(std::string_view str, char separator,
+                                    bool keep_empty) {
+  std::vector<std::string_view> vec;
+  split(str, vec, separator, keep_empty);
+  return vec;
+}
+
+std::string_view trim(std::string_view str) {
+  size_t s = 0;
+  size_t e = str.size();
+  while (s < e && is_space(str[s]))
+    ++s;
+  while (e > s && is_space(str[e - 1]))
+    --e;
+  return str.substr(s, e - s);
+}
+
+}  // namespace str
diff --git a/src/str.hh b/src/str.hh
new file mode 100644
index 0000000..e1ee549
--- /dev/null
+++ b/src/str.hh
@@ -0,0 +1,21 @@
+#ifndef STR_HH
+#define STR_HH
+
+#include <string_view>
+#include <vector>
+
+namespace str {
+
+void split(std::string_view str, std::vector<std::string_view>& out,
+           char separator = ' ', bool keep_empty = false);
+
+[[nodiscard]] std::vector<std::string_view> split(std::string_view str,
+                                                  char separator = ' ',
+                                                  bool keep_empty = false);
+
+[[nodiscard]]
+std::string_view trim(std::string_view str);
+
+}  // namespace str
+
+#endif  // STR_HH
diff --git a/src/unique_fd.cc b/src/unique_fd.cc
new file mode 100644
index 0000000..135a449
--- /dev/null
+++ b/src/unique_fd.cc
@@ -0,0 +1,9 @@
+#include "unique_fd.hh"
+
+#include <unistd.h>
+
+void unique_fd::reset(int fd) {
+  if (fd_ != -1)
+    close(fd_);
+  fd_ = fd;
+}
diff --git a/src/unique_fd.hh b/src/unique_fd.hh
new file mode 100644
index 0000000..2950905
--- /dev/null
+++ b/src/unique_fd.hh
@@ -0,0 +1,36 @@
+#ifndef UNIQUE_FD_HH
+#define UNIQUE_FD_HH
+
+class unique_fd {
+ public:
+  constexpr unique_fd() : fd_(-1) {}
+  explicit constexpr unique_fd(int fd) : fd_(fd) {}
+  unique_fd(unique_fd& fd) = delete;
+  unique_fd& operator=(unique_fd& fd) = delete;
+  unique_fd(unique_fd&& fd) : fd_(fd.release()) {}
+  unique_fd& operator=(unique_fd&& fd) {
+    reset(fd.release());
+    return *this;
+  }
+  ~unique_fd() { reset(); }
+
+  bool operator==(unique_fd const& fd) const { return get() == fd.get(); }
+  bool operator!=(unique_fd const& fd) const { return get() != fd.get(); }
+
+  int get() const { return fd_; }
+  explicit operator bool() const { return fd_ != -1; }
+  int operator*() const { return fd_; }
+
+  int release() {
+    int ret = fd_;
+    fd_ = -1;
+    return ret;
+  }
+
+  void reset(int fd = -1);
+
+ private:
+  int fd_;
+};
+
+#endif  // UNIQUE_FD_HH