Add redis parser + test

server/redis_parser.h

@@ -0,0 +1,91 @@
+// Copyright 2021, Beeri 15.  All rights reserved.
+// Author: Roman Gershman (romange@gmail.com)
+//
+#pragma once
+
+#include <absl/container/inlined_vector.h>
+
+#include "resp_expr.h"
+
+namespace dfly {
+
+/**
+ * @brief Zero-copy (best-effort) parser.
+ *
+ */
+class RedisParser {
+ public:
+  enum Result {
+    OK,
+    INPUT_PENDING,
+    BAD_ARRAYLEN,
+    BAD_BULKLEN,
+    BAD_STRING,
+    BAD_INT
+  };
+  using Buffer = RespExpr::Buffer;
+
+  explicit RedisParser() {
+  }
+
+  /**
+   * @brief Parses str into res. "consumed" stores number of bytes consumed from str.
+   *
+   * A caller should not invalidate str if the parser returns RESP_OK as long as he continues
+   * accessing res. However, if parser returns MORE_INPUT a caller may discard consumed
+   * part of str because parser caches the intermediate state internally according to 'consumed'
+   * result.
+   *
+   * Note: A parser does not always guarantee progress, i.e. if a small buffer was passed it may
+   * returns MORE_INPUT with consumed == 0.
+   *
+   */
+
+  Result Parse(Buffer str, uint32_t* consumed, RespVec* res);
+
+  size_t stash_size() const { return stash_.size(); }
+  const std::vector<std::unique_ptr<RespVec>>& stash() const { return stash_;}
+
+ private:
+  void InitStart(uint8_t prefix_b, RespVec* res);
+  void StashState(RespVec* res);
+
+  // Skips the first character (*).
+  Result ConsumeArrayLen(Buffer str);
+  Result ParseArg(Buffer str);
+  Result ConsumeBulk(Buffer str);
+  Result ParseInline(Buffer str);
+
+  // Updates last_consumed_
+  Result ParseNum(Buffer str, int64_t* res);
+  void HandleFinishArg();
+  void ExtendLastString(Buffer str);
+
+  enum State : uint8_t {
+    INIT_S = 0,
+    INLINE_S,
+    ARRAY_LEN_S,
+    PARSE_ARG_S,  // Parse [$:+-]string\r\n
+    BULK_STR_S,
+    FINISH_ARG_S,
+    CMD_COMPLETE_S,
+  };
+
+  State state_ = INIT_S;
+  Result last_result_ = OK;
+
+  uint32_t last_consumed_ = 0;
+  uint32_t bulk_len_ = 0;
+  uint32_t last_stashed_level_ = 0, last_stashed_index_ = 0;
+
+  // expected expression length, pointer to expression vector.
+  absl::InlinedVector<std::pair<uint32_t, RespVec*>, 4> parse_stack_;
+  std::vector<std::unique_ptr<RespVec>> stash_;
+
+  using BlobPtr = std::unique_ptr<uint8_t[]>;
+  std::vector<BlobPtr> buf_stash_;
+  RespVec* cached_expr_ = nullptr;
+  bool is_broken_token_ = false;
+};
+
+}  // namespace dfly