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tdtl/td/tl/tl_simple_parser.h

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+/*
+    This file is part of TON Blockchain Library.
+
+    TON Blockchain Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    TON Blockchain Library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2017-2019 Telegram Systems LLP
+*/
+#pragma once
+
+#include <cassert>
+#include <cstdint>
+#include <cstring>
+#include <string>
+
+namespace td {
+namespace tl {
+
+class tl_simple_parser {
+  const char *data;
+  const char *data_begin;
+  std::size_t data_len;
+  const char *error;
+  std::size_t error_pos;
+
+  void set_error(const char *error_message) {
+    if (error == NULL) {
+      assert(error_message != NULL);
+      error = error_message;
+      error_pos = static_cast<std::size_t>(data - data_begin);
+      data = "\x00\x00\x00\x00\x00\x00\x00\x00";
+      data_len = 0;
+    } else {
+      data = "\x00\x00\x00\x00\x00\x00\x00\x00";
+      assert(data_len == 0);
+    }
+  }
+
+  void check_len(const std::size_t len) {
+    if (data_len < len) {
+      set_error("Not enough data to read");
+    } else {
+      data_len -= len;
+    }
+  }
+
+  tl_simple_parser(const tl_simple_parser &other);
+  tl_simple_parser &operator=(const tl_simple_parser &other);
+
+ public:
+  tl_simple_parser(const char *data, std::size_t data_len)
+      : data(data), data_begin(data), data_len(data_len), error(), error_pos() {
+  }
+
+  const char *get_error() const {
+    return error;
+  }
+
+  std::size_t get_error_pos() const {
+    return error_pos;
+  }
+
+  std::int32_t fetch_int() {
+    check_len(sizeof(std::int32_t));
+    std::int32_t result = *reinterpret_cast<const std::int32_t *>(data);
+    data += sizeof(std::int32_t);
+    return result;
+  }
+
+  std::int64_t fetch_long() {
+    check_len(sizeof(std::int64_t));
+    std::int64_t result;
+    std::memcpy(&result, data, sizeof(std::int64_t));
+    data += sizeof(std::int64_t);
+    return result;
+  }
+
+  std::string fetch_string() {
+    check_len(4);
+    int result_len = static_cast<unsigned char>(data[0]);
+    if (result_len < 254) {
+      check_len((result_len >> 2) * 4);
+      std::string result(data + 1, result_len);
+      data += ((result_len >> 2) + 1) * 4;
+      return result;
+    }
+
+    if (result_len == 254) {
+      result_len = static_cast<unsigned char>(data[1]) + (static_cast<unsigned char>(data[2]) << 8) +
+                   (static_cast<unsigned char>(data[3]) << 16);
+      check_len(((result_len + 3) >> 2) * 4);
+      std::string result(data + 4, result_len);
+      data += ((result_len + 7) >> 2) * 4;
+      return result;
+    }
+
+    set_error("Can't fetch string, 255 found");
+    return std::string();
+  }
+
+  void fetch_end() {
+    if (data_len) {
+      set_error("Too much data to fetch");
+    }
+  }
+};
+
+}  // namespace tl
+}  // namespace td