libc/src/__support/StringUtil/message_mapper.h

   1 //===-- A class for number to string mappings -------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef LLVM_LIBC_SRC___SUPPORT_STRINGUTIL_MESSAGE_MAPPER_H
  10 #define LLVM_LIBC_SRC___SUPPORT_STRINGUTIL_MESSAGE_MAPPER_H
  11
  12 #include "src/__support/CPP/array.h"
  13 #include "src/__support/CPP/optional.h"
  14 #include "src/__support/CPP/string_view.h"
  15 #include "src/__support/macros/config.h"
  16 #include <stddef.h>
  17
  18 namespace LIBC_NAMESPACE_DECL {
  19
  20 struct MsgMapping {
  21   int num;
  22   cpp::string_view msg;
  23
  24   constexpr MsgMapping() : num(0), msg() { ; }
  25
  26   constexpr MsgMapping(int init_num, const char *init_msg)
  27       : num(init_num), msg(init_msg) {
  28     ;
  29   }
  30 };
  31
  32 template <size_t N> using MsgTable = cpp::array<MsgMapping, N>;
  33
  34 template <size_t N> constexpr size_t total_str_len(const MsgTable<N> &table) {
  35   size_t total = 0;
  36   for (size_t i = 0; i < table.size(); ++i) {
  37     // add 1 for the null terminator.
  38     total += table[i].msg.size() + 1;
  39   }
  40   return total;
  41 }
  42
  43 template <size_t N> constexpr size_t max_key_val(const MsgTable<N> &table) {
  44   int max = 0;
  45   for (size_t i = 0; i < table.size(); ++i) {
  46     if (table[i].num > max) {
  47       max = table[i].num;
  48     }
  49   }
  50   // max will never be negative since the starting value is 0. This is good,
  51   // since it's used as a length.
  52   return static_cast<size_t>(max);
  53 }
  54
  55 template <size_t ARR_SIZE, size_t TOTAL_STR_LEN> class MessageMapper {
  56   int msg_offsets[ARR_SIZE] = {-1};
  57   char string_array[TOTAL_STR_LEN] = {'\0'};
  58
  59 public:
  60   template <size_t N> constexpr MessageMapper(const MsgTable<N> &table) {
  61     cpp::string_view string_mappings[ARR_SIZE] = {""};
  62     for (size_t i = 0; i < table.size(); ++i)
  63       string_mappings[table[i].num] = table[i].msg;
  64
  65     int string_array_index = 0;
  66     for (size_t cur_num = 0; cur_num < ARR_SIZE; ++cur_num) {
  67       if (string_mappings[cur_num].size() != 0) {
  68         msg_offsets[cur_num] = string_array_index;
  69         // No need to replace with proper strcpy, this is evaluated at compile
  70         // time.
  71         for (size_t i = 0; i < string_mappings[cur_num].size() + 1;
  72              ++i, ++string_array_index) {
  73           string_array[string_array_index] = string_mappings[cur_num][i];
  74         }
  75       } else {
  76         msg_offsets[cur_num] = -1;
  77       }
  78     }
  79   }
  80
  81   cpp::optional<cpp::string_view> get_str(int num) const {
  82     if (num >= 0 && static_cast<size_t>(num) < ARR_SIZE &&
  83         msg_offsets[num] != -1) {
  84       return {string_array + msg_offsets[num]};
  85     } else {
  86       return cpp::optional<cpp::string_view>();
  87     }
  88   }
  89 };
  90
  91 template <size_t N1, size_t N2>
  92 constexpr MsgTable<N1 + N2> operator+(const MsgTable<N1> &t1,
  93                                       const MsgTable<N2> &t2) {
  94   MsgTable<N1 + N2> res{};
  95   for (size_t i = 0; i < N1; ++i)
  96     res[i] = t1[i];
  97   for (size_t i = 0; i < N2; ++i)
  98     res[N1 + i] = t2[i];
  99   return res;
 100 }
 101
 102 } // namespace LIBC_NAMESPACE_DECL
 103
 104 #endif // LLVM_LIBC_SRC___SUPPORT_STRINGUTIL_MESSAGE_MAPPER_H