cc: extend c++ api for hash table

This commit extends the api for hash tables allowing to get, update and
delete elements

Signed-off-by: Mauricio Vasquez B <[email protected]>

src/cc/BPFTable.h

@@ -16,6 +16,7 @@
 
 #pragma once
 
+#include <cstring>
 #include <sys/epoll.h>
 #include <exception>
 #include <map>
@@ -70,16 +71,37 @@ template <class KeyType, class ValueType>
 class BPFHashTable : protected BPFTableBase<KeyType, ValueType> {
  public:
  explicit BPFHashTable(const TableDesc& desc)
- : BPFTableBase<KeyType, ValueType>(desc) {}
+ : BPFTableBase<KeyType, ValueType>(desc) {
+ if (desc.type != BPF_MAP_TYPE_HASH &&
+ desc.type != BPF_MAP_TYPE_PERCPU_HASH &&
+ desc.type != BPF_MAP_TYPE_LRU_HASH &&
+ desc.type != BPF_MAP_TYPE_LRU_PERCPU_HASH)
+ throw std::invalid_argument("Table '" + desc.name + "' is not a hash table");
+ }
 
- ValueType get_value(const KeyType& key) {
- ValueType res;
- if (!this->lookup(const_cast<KeyType*>(&key), &res))
- throw std::invalid_argument("Key does not exist in the table");
- return res;
+ StatusTuple get_value(const KeyType& key, ValueType& value) {
+ if (!this->lookup(const_cast<KeyType*>(&key), &value))
+ return StatusTuple(-1, "Error getting value: %s", std::strerror(errno));
+ return StatusTuple(0);
+ }
+
+ StatusTuple update_value(const KeyType& key, const ValueType& value) {
+ if (!this->update(const_cast<KeyType*>(&key), const_cast<ValueType*>(&value)))
+ return StatusTuple(-1, "Error updating value: %s", std::strerror(errno));
+ return StatusTuple(0);
  }
 
- ValueType operator[](const KeyType& key) { return get_value(key); }
+ StatusTuple remove_value(const KeyType& key) {
+ if (!this->remove(const_cast<KeyType*>(&key)))
+ return StatusTuple(-1, "Error removing value: %s", std::strerror(errno));
+ return StatusTuple(0);
+ }
+
+ ValueType operator[](const KeyType& key) {
+ ValueType value;
+ get_value(key, value);
+ return value;
+ }
 
  std::vector<std::pair<KeyType, ValueType>> get_table_offline() {
  std::vector<std::pair<KeyType, ValueType>> res;

tests/cc/CMakeLists.txt

@@ -11,6 +11,7 @@ add_test(NAME c_test_static COMMAND ${TEST_WRAPPER} c_test_static sudo ${CMAKE_C
 add_executable(test_libbcc
  test_libbcc.cc
  test_c_api.cc
+ test_hash_table.cc
  test_usdt_args.cc
  test_usdt_probes.cc)
 

tests/cc/test_hash_table.cc

@@ -0,0 +1,74 @@
+/*
+ * Copyright (c) 2017 Politecnico di Torino
+ *
+ * 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: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.
+ */
+
+#include "BPF.h"
+
+#include "catch.hpp"
+
+TEST_CASE("test hash table", "[hash_table]") {
+ const std::string BPF_PROGRAM = R"(
+ BPF_TABLE("hash", int, int, myhash, 1024);
+ BPF_TABLE("array", int, int, myarray, 1024);
+ )";
+
+ ebpf::BPF bpf;
+ ebpf::StatusTuple res(0);
+ res = bpf.init(BPF_PROGRAM);
+ REQUIRE(res.code() == 0);
+
+ ebpf::BPFHashTable<int, int> t = bpf.get_hash_table<int, int>("myhash");
+
+ SECTION("bad table type") {
+ // try to get table of wrong type
+ auto f1 = [&](){
+ bpf.get_hash_table<int, int>("myarray");
+ };
+
+ REQUIRE_THROWS(f1());
+ }
+
+ SECTION("standard methods") {
+ int k, v1, v2;
+ k = 1;
+ v1 = 42;
+ // create new element
+ res = t.update_value(k, v1);
+ REQUIRE(res.code() == 0);
+ res = t.get_value(k, v2);
+ REQUIRE(res.code() == 0);
+ REQUIRE(v2 == 42);
+
+ // update existing element
+ v1 = 69;
+ res = t.update_value(k, v1);
+ REQUIRE(res.code() == 0);
+ res = t.get_value(k, v2);
+ REQUIRE(res.code() == 0);
+ REQUIRE(v2 == 69);
+
+ // remove existing element
+ res = t.remove_value(k);
+ REQUIRE(res.code() == 0);
+
+ // remove non existing element
+ res = t.remove_value(k);
+ REQUIRE(res.code() != 0);
+
+ // get non existing element
+ res = t.get_value(k, v2);
+ REQUIRE(res.code() != 0);
+ }
+}