Refactoring trace_state to reuse common functionality in baggage (#638)

Author: nikhil1511

api/include/opentelemetry/common/kv_properties.h

@@ -0,0 +1,270 @@
+// Copyright 2021, OpenTelemetry Authors
+//
+// 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
+//
+//     http://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.
+
+#include "opentelemetry/common/key_value_iterable_view.h"
+#include "opentelemetry/common/string_util.h"
+#include "opentelemetry/nostd/function_ref.h"
+#include "opentelemetry/nostd/shared_ptr.h"
+#include "opentelemetry/nostd/string_view.h"
+#include "opentelemetry/nostd/unique_ptr.h"
+#include "opentelemetry/version.h"
+
+#include <string>
+#include <type_traits>
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace common
+{
+
+// Constructor parameter for KeyValueStringTokenizer
+struct KeyValueStringTokenizerOptions
+{
+  char member_separator     = ',';
+  char key_value_separator  = '=';
+  bool ignore_empty_members = true;
+};
+
+// Tokenizer for key-value headers
+class KeyValueStringTokenizer
+{
+public:
+  KeyValueStringTokenizer(
+      nostd::string_view str,
+      const KeyValueStringTokenizerOptions &opts = KeyValueStringTokenizerOptions())
+      : str_(str), opts_(opts), index_(0)
+  {}
+
+  // Returns next key value in the string header
+  // @param valid_kv : if the found kv pair is valid or not
+  // @param key : key in kv pair
+  // @param key : value in kv pair
+  // @returns true if next kv pair was found, false otherwise.
+  bool next(bool &valid_kv, nostd::string_view &key, nostd::string_view &value)
+  {
+    valid_kv = true;
+    while (index_ < str_.size())
+    {
+      size_t end = str_.find(opts_.member_separator, index_);
+      if (end == std::string::npos)
+      {
+        end = str_.size() - 1;
+      }
+      else
+      {
+        end--;
+      }
+
+      auto list_member = StringUtil::Trim(str_, index_, end);
+      if (list_member.size() == 0)
+      {
+        // empty list member
+        index_ = end + 2;
+        if (opts_.ignore_empty_members)
+        {
+          continue;
+        }
+
+        valid_kv = true;
+        key      = "";
+        value    = "";
+        return true;
+      }
+
+      auto key_end_pos = list_member.find(opts_.key_value_separator);
+      if (key_end_pos == std::string::npos)
+      {
+        // invalid member
+        valid_kv = false;
+      }
+      else
+      {
+        key   = list_member.substr(0, key_end_pos);
+        value = list_member.substr(key_end_pos + 1);
+      }
+
+      index_ = end + 2;
+
+      return true;
+    }
+
+    // no more entries remaining
+    return false;
+  }
+
+  // Returns total number of tokens in header string
+  size_t NumTokens() const noexcept
+  {
+    size_t cnt = 0, begin = 0;
+    while (begin < str_.size())
+    {
+      ++cnt;
+      size_t end = str_.find(opts_.member_separator, begin);
+      if (end == std::string::npos)
+      {
+        break;
+      }
+
+      begin = end + 1;
+    }
+
+    return cnt;
+  }
+
+  // Resets the iterator
+  void reset() noexcept { index_ = 0; }
+
+private:
+  nostd::string_view str_;
+  KeyValueStringTokenizerOptions opts_;
+  size_t index_;
+};
+
+// Class to store fixed size array of key-value pairs of string type
+class KeyValueProperties
+{
+  // Class to store key-value pairs of string types
+public:
+  class Entry
+  {
+  public:
+    Entry() : key_(nullptr), value_(nullptr) {}
+
+    // Copy constructor
+    Entry(const Entry &copy)
+    {
+      key_   = CopyStringToPointer(copy.key_.get());
+      value_ = CopyStringToPointer(copy.value_.get());
+    }
+
+    // Copy assignment operator
+    Entry &operator=(Entry &other)
+    {
+      key_   = CopyStringToPointer(other.key_.get());
+      value_ = CopyStringToPointer(other.value_.get());
+      return *this;
+    }
+
+    // Move contructor and assignment operator
+    Entry(Entry &&other) = default;
+    Entry &operator=(Entry &&other) = default;
+
+    // Creates an Entry for a given key-value pair.
+    Entry(nostd::string_view key, nostd::string_view value)
+    {
+      key_   = CopyStringToPointer(key);
+      value_ = CopyStringToPointer(value);
+    }
+
+    // Gets the key associated with this entry.
+    nostd::string_view GetKey() const { return key_.get(); }
+
+    // Gets the value associated with this entry.
+    nostd::string_view GetValue() const { return value_.get(); }
+
+    // Sets the value for this entry. This overrides the previous value.
+    void SetValue(nostd::string_view value) { value_ = CopyStringToPointer(value); }
+
+  private:
+    // Store key and value as raw char pointers to avoid using std::string.
+    nostd::unique_ptr<const char[]> key_;
+    nostd::unique_ptr<const char[]> value_;
+
+    // Copies string into a buffer and returns a unique_ptr to the buffer.
+    // This is a workaround for the fact that memcpy doesn't accept a const destination.
+    nostd::unique_ptr<const char[]> CopyStringToPointer(nostd::string_view str)
+    {
+      char *temp = new char[str.size() + 1];
+      memcpy(temp, str.data(), str.size());
+      temp[str.size()] = '\0';
+      return nostd::unique_ptr<const char[]>(temp);
+    }
+  };
+
+  // Maintain the number of entries in entries_.
+  size_t num_entries_;
+
+  // Max size of allocated array
+  size_t max_num_entries_;
+
+  // Store entries in a C-style array to avoid using std::array or std::vector.
+  nostd::unique_ptr<Entry[]> entries_;
+
+public:
+  // Create Key-value list of given size
+  // @param size : Size of list.
+  KeyValueProperties(size_t size)
+      : num_entries_(0), max_num_entries_(size), entries_(new Entry[size])
+  {}
+
+  // Create Empty Key-Value list
+  KeyValueProperties() : num_entries_(0), max_num_entries_(0), entries_(nullptr) {}
+
+  template <class T, class = typename std::enable_if<detail::is_key_value_iterable<T>::value>::type>
+  KeyValueProperties(const T &keys_and_values)
+      : num_entries_(0),
+        max_num_entries_(keys_and_values.size()),
+        entries_(new Entry[max_num_entries_])
+  {
+    for (auto &e : keys_and_values)
+    {
+      Entry entry(e.first, e.second);
+      (entries_.get())[num_entries_++] = std::move(entry);
+    }
+  }
+
+  // Adds new kv pair into kv properties
+  void AddEntry(const nostd::string_view &key, const nostd::string_view &value)
+  {
+    if (num_entries_ < max_num_entries_)
+    {
+      Entry entry(key, value);
+      (entries_.get())[num_entries_++] = std::move(entry);
+    }
+  }
+
+  // Returns all kv pair entries
+  bool GetAllEntries(
+      nostd::function_ref<bool(nostd::string_view, nostd::string_view)> callback) const
+  {
+    for (size_t i = 0; i < num_entries_; i++)
+    {
+      auto &entry = (entries_.get())[i];
+      if (!callback(entry.GetKey(), entry.GetValue()))
+      {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  // Return value for key if exists, return false otherwise
+  bool GetValue(const nostd::string_view key, std::string &value) const
+  {
+    for (size_t i = 0; i < num_entries_; i++)
+    {
+      auto &entry = (entries_.get())[i];
+      if (entry.GetKey() == key)
+      {
+        const auto &entry_value = entry.GetValue();
+        value                   = std::string(entry_value.data(), entry_value.size());
+        return true;
+      }
+    }
+    return false;
+  }
+
+  size_t Size() const noexcept { return num_entries_; }
+};
+}  // namespace common
+OPENTELEMETRY_END_NAMESPACE

api/include/opentelemetry/common/string_util.h

@@ -0,0 +1,42 @@
+// Copyright 2021, OpenTelemetry Authors
+//
+// 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
+//
+//     http://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.
+
+#pragma once
+
+#include "opentelemetry/nostd/string_view.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace common
+{
+
+class StringUtil
+{
+public:
+  static nostd::string_view Trim(nostd::string_view str, size_t left, size_t right)
+  {
+    while (str[static_cast<std::size_t>(left)] == ' ' && left <= right)
+    {
+      left++;
+    }
+    while (str[static_cast<std::size_t>(right)] == ' ' && left <= right)
+    {
+      right--;
+    }
+    return str.substr(left, 1 + right - left);
+  }
+};
+
+}  // namespace common
+
+OPENTELEMETRY_END_NAMESPACE