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