1 //
2 // Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2021
3 //
4 // Distributed under the Boost Software License, Version 1.0. (See accompanying
5 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6 //
7 #pragma once
8 
9 #include "td/utils/common.h"
10 #include "td/utils/logging.h"
11 #include "td/utils/Slice.h"
12 
13 #include <atomic>
14 #include <cstdio>
15 #include <cstring>
16 
17 namespace td {
18 
19 template <int buffer_size = 32 * (1 << 10)>
20 class MemoryLog final : public LogInterface {
21   static constexpr size_t MAX_OUTPUT_SIZE = buffer_size / 16 < (8 << 10) ? buffer_size / 16 : (8 << 10);
22 
23   static_assert((buffer_size & (buffer_size - 1)) == 0, "Buffer size must be power of 2");
24   static_assert(buffer_size >= (8 << 10), "Too small buffer size");
25 
26  public:
MemoryLog()27   MemoryLog() {
28     std::memset(buffer_, ' ', sizeof(buffer_));
29   }
30 
get_buffer()31   Slice get_buffer() const {
32     return Slice(buffer_, sizeof(buffer_));
33   }
34 
get_pos()35   size_t get_pos() const {
36     return pos_ & (buffer_size - 1);
37   }
38 
39  private:
do_append(int log_level,CSlice new_slice)40   void do_append(int log_level, CSlice new_slice) final {
41     Slice slice = new_slice;
42     slice.truncate(MAX_OUTPUT_SIZE);
43     while (!slice.empty() && slice.back() == '\n') {
44       slice.remove_suffix(1);
45     }
46     size_t slice_size = slice.size();
47     CHECK(slice_size * 3 < buffer_size);
48     size_t pad_size = ((slice_size + 15) & ~15) - slice_size;
49     constexpr size_t MAGIC_SIZE = 16;
50     auto total_size = static_cast<uint32>(slice_size + pad_size + MAGIC_SIZE);
51     auto real_pos = pos_.fetch_add(total_size, std::memory_order_relaxed);
52     CHECK((total_size & 15) == 0);
53 
54     uint32 start_pos = real_pos & (buffer_size - 1);
55     uint32 end_pos = start_pos + total_size;
56     if (likely(end_pos <= buffer_size)) {
57       std::memcpy(&buffer_[start_pos + MAGIC_SIZE], slice.data(), slice_size);
58       std::memcpy(&buffer_[start_pos + MAGIC_SIZE + slice_size], "               ", pad_size);
59     } else {
60       size_t first = buffer_size - start_pos - MAGIC_SIZE;
61       size_t second = slice_size - first;
62       std::memcpy(&buffer_[start_pos + MAGIC_SIZE], slice.data(), first);
63       std::memcpy(&buffer_[0], slice.data() + first, second);
64       std::memcpy(&buffer_[second], "               ", pad_size);
65     }
66 
67     CHECK((start_pos & 15) == 0);
68     CHECK(start_pos <= buffer_size - MAGIC_SIZE);
69     buffer_[start_pos] = '\n';
70     size_t printed = std::snprintf(&buffer_[start_pos + 1], MAGIC_SIZE - 1, "LOG:%08x: ", real_pos);
71     CHECK(printed == MAGIC_SIZE - 2);
72     buffer_[start_pos + MAGIC_SIZE - 1] = ' ';
73   }
74 
75   char buffer_[buffer_size];
76   std::atomic<uint32> pos_{0};
77 };
78 
79 }  // namespace td
80