Don’t hard-code escape sequences

Instead of hard-coding VT100-compatible escape sequences, parse the
system terminfo database and read escape sequences from it. This is
both more flexible (it should work well on more terminals) and more
efficient (it won’t insert padding on terminals that don’t need it).

1 files changed, 106 insertions, 0 deletions

diff --git a/goldfishterm/internal/emit.h b/goldfishterm/internal/emit.h
new file mode 100644
index 0000000..371f6b0
--- /dev/null
+++ b/goldfishterm/internal/emit.h
@@ -0,0 +1,106 @@
+// Copyright 2021 Benjamin Barenblat
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+// An extremely simple EDSL for describing output to the terminal. It supports
+// exactly two instructions: "send some bytes to the terminal" and "sleep". The
+// string capability interpreter produces terms in this EDSL, which makes it
+// easier to test.
+
+#ifndef EC_GOLDFISHTERM_INTERNAL_EMIT_H_
+#define EC_GOLDFISHTERM_INTERNAL_EMIT_H_
+
+#include <stdint.h>
+
+#include <memory>
+#include <ostream>
+#include <string>
+#include <utility>
+
+#include "third_party/abseil/absl/strings/str_cat.h"
+#include "third_party/abseil/absl/strings/string_view.h"
+#include "third_party/abseil/absl/time/time.h"
+#include "third_party/abseil/absl/types/span.h"
+
+namespace goldfishterm_internal {
+
+class EmitTerm {
+ public:
+  virtual void Emit(std::ostream&) const = 0;
+
+  virtual ~EmitTerm() noexcept = default;
+};
+
+class EmitBytes final : public EmitTerm {
+ public:
+  explicit EmitBytes() noexcept = default;
+
+  explicit EmitBytes(absl::string_view bytes) noexcept : bytes_(bytes) {}
+
+  EmitBytes(const EmitBytes&) = default;
+  EmitBytes& operator=(const EmitBytes&) = default;
+  EmitBytes(EmitBytes&&) noexcept = default;
+  EmitBytes& operator=(EmitBytes&&) noexcept = default;
+
+  bool empty() const noexcept { return bytes_.empty(); }
+
+  void Append(absl::string_view more) noexcept {
+    absl::StrAppend(&bytes_, more);
+  }
+
+  void Emit(std::ostream&) const override;
+
+  bool operator==(const EmitBytes& other) const noexcept {
+    return bytes_ == other.bytes_;
+  }
+
+  friend std::ostream& operator<<(std::ostream& out,
+                                  const EmitBytes& emit) noexcept {
+    return out << "EmitBytes(" << emit.bytes_ << ')';
+  }
+
+ private:
+  std::string bytes_;
+};
+
+class EmitDelay final : public EmitTerm {
+ public:
+  explicit EmitDelay() noexcept = default;
+
+  explicit EmitDelay(absl::Duration delay) : delay_(std::move(delay)) {}
+
+  EmitDelay(const EmitDelay&) = default;
+  EmitDelay& operator=(const EmitDelay&) = default;
+  EmitDelay(EmitDelay&&) noexcept = default;
+  EmitDelay& operator=(EmitDelay&&) noexcept = default;
+
+  bool zero() const noexcept { return delay_ == absl::ZeroDuration(); }
+
+  void Increase(absl::Duration more) noexcept { delay_ += more; }
+
+  void Emit(std::ostream&) const noexcept override;
+
+  bool operator==(const EmitDelay& other) const noexcept {
+    return delay_ == other.delay_;
+  }
+
+ private:
+  absl::Duration delay_;
+};
+
+// Runs an entire program in the emitter EDSL.
+void Emit(absl::Span<const std::shared_ptr<const EmitTerm>>, std::ostream&);
+
+}  // namespace goldfishterm_internal
+
+#endif  // EC_GOLDFISHTERM_INTERNAL_EMIT_H_