libc/src/stdlib/getenv.cpp

   1 //===-- Implementation of getenv ------------------------------------------===//
   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 #include "src/stdlib/getenv.h"
  10 #include "config/app.h"
  11 #include "src/__support/CPP/string_view.h"
  12 #include "src/__support/common.h"
  13 #include "src/__support/macros/config.h"
  14
  15 #include <stddef.h> // For size_t.
  16
  17 namespace LIBC_NAMESPACE_DECL {
  18
  19 LLVM_LIBC_FUNCTION(char *, getenv, (const char *name)) {
  20   char **env_ptr = reinterpret_cast<char **>(LIBC_NAMESPACE::app.env_ptr);
  21
  22   if (name == nullptr || env_ptr == nullptr)
  23     return nullptr;
  24
  25   LIBC_NAMESPACE::cpp::string_view env_var_name(name);
  26   if (env_var_name.size() == 0)
  27     return nullptr;
  28   for (char **env = env_ptr; *env != nullptr; env++) {
  29     LIBC_NAMESPACE::cpp::string_view cur(*env);
  30     if (!cur.starts_with(env_var_name))
  31       continue;
  32
  33     if (cur[env_var_name.size()] != '=')
  34       continue;
  35
  36     // Remove the name and the equals sign.
  37     cur.remove_prefix(env_var_name.size() + 1);
  38     // We know that data is null terminated, so this is safe.
  39     return const_cast<char *>(cur.data());
  40   }
  41
  42   return nullptr;
  43 }
  44
  45 } // namespace LIBC_NAMESPACE_DECL