[Lldb-commits] [lldb] [LLDB] Add Lexer (with tests) for DIL (Data Inspection Language). (PR #123521)

[via lldb-commits]

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+//===-- DILLexer.h ----------------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLDB_VALUEOBJECT_DILLEXER_H_
+#define LLDB_VALUEOBJECT_DILLEXER_H_
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/iterator_range.h"
+#include "llvm/Support/Error.h"
+#include <cstdint>
+#include <limits.h>
+#include <memory>
+#include <string>
+#include <vector>
+
+namespace lldb_private::dil {
+
+/// Class defining the tokens generated by the DIL lexer and used by the
+/// DIL parser.
+class Token {
+public:
+  enum Kind {
+    coloncolon,
+    eof,
+    identifier,
+    l_paren,
+    r_paren,
+    unknown,
+  };
+
+  Token(Kind kind, std::string spelling, uint32_t start)
+      : m_kind(kind), m_spelling(spelling), m_start_pos(start) {}
+
+  Kind GetKind() const { return m_kind; }
+
+  std::string GetSpelling() const { return m_spelling; }
+
+  bool Is(Kind kind) const { return m_kind == kind; }
+
+  bool IsNot(Kind kind) const { return m_kind != kind; }
+
+  bool IsOneOf(Kind kind1, Kind kind2) const { return Is(kind1) || Is(kind2); }
+
+  template <typename... Ts> bool IsOneOf(Kind kind, Ts... Ks) const {
+    return Is(kind) || IsOneOf(Ks...);
+  }
+
+  uint32_t GetLocation() const { return m_start_pos; }
+
+  static llvm::StringRef GetTokenName(Kind kind);
+
+private:
+  Kind m_kind;
+  std::string m_spelling;
+  uint32_t m_start_pos; // within entire expression string
+};
+
+/// Class for doing the simple lexing required by DIL.
+class DILLexer {
+public:
+  /// Lexes all the tokens in expr and calls the private constructor
+  /// with the lexed tokens.
+  static llvm::Expected<DILLexer> Create(llvm::StringRef expr);
+
+  /// Return the current token to be handled by the DIL parser.
+  const Token &GetCurrentToken() { return m_lexed_tokens[m_tokens_idx]; }
+
+  /// Advance the current token position by N.
+  void Advance(uint32_t N = 1) {
+    // UINT_MAX means uninitialized, no "current" position, so move to start.
+    if (m_tokens_idx == UINT_MAX)
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cmtice wrote:

Not really...this index indicates which token the parser is currently working on.  We shouldn't set the index to zero until the parser asks for the first token (& starts parsing with it).

https://github.com/llvm/llvm-project/pull/123521