Switch env var APIs to std::string_view

Author: pitrou

cpp/src/arrow/util/io_util.cc

@@ -1758,32 +1758,30 @@ Status FileTruncate(int fd, const int64_t size) {
 // Environment variables
 //
 
-Result<std::string> GetEnvVar(const char* name) {
+Result<std::string> GetEnvVar(std::string_view name) {
 #ifdef _WIN32
   // On Windows, getenv() reads an early copy of the process' environment
   // which doesn't get updated when SetEnvironmentVariable() is called.
   constexpr int32_t bufsize = 2000;
   char c_str[bufsize];
-  auto res = GetEnvironmentVariableA(name, c_str, bufsize);
+  auto res = GetEnvironmentVariableA(name.data(), c_str, bufsize);
   if (res >= bufsize) {
     return Status::CapacityError("environment variable value too long");
   } else if (res == 0) {
     return Status::KeyError("environment variable '", name, "'undefined");
   }
   return std::string(c_str);
 #else
-  char* c_str = getenv(name);
+  char* c_str = getenv(name.data());
   if (c_str == nullptr) {
     return Status::KeyError("environment variable '", name, "'undefined");
   }
   return std::string(c_str);
 #endif
 }
 
-Result<std::string> GetEnvVar(const std::string& name) { return GetEnvVar(name.c_str()); }
-
 #ifdef _WIN32
-Result<NativePathString> GetEnvVarNative(const std::string& name) {
+Result<NativePathString> GetEnvVarNative(std::string_view name) {
   NativePathString w_name;
   constexpr int32_t bufsize = 2000;
   wchar_t w_str[bufsize];
@@ -1798,57 +1796,46 @@ Result<NativePathString> GetEnvVarNative(const std::string& name) {
   return NativePathString(w_str);
 }
 
-Result<NativePathString> GetEnvVarNative(const char* name) {
-  return GetEnvVarNative(std::string(name));
-}
-
 #else
 
-Result<NativePathString> GetEnvVarNative(const std::string& name) {
+Result<NativePathString> GetEnvVarNative(std::string_view name) {
   return GetEnvVar(name);
 }
 
-Result<NativePathString> GetEnvVarNative(const char* name) { return GetEnvVar(name); }
 #endif
 
-Status SetEnvVar(const char* name, const char* value) {
+Status SetEnvVar(std::string_view name, std::string_view value) {
 #ifdef _WIN32
-  if (SetEnvironmentVariableA(name, value)) {
+  if (SetEnvironmentVariableA(name.data(), value.data())) {
     return Status::OK();
   } else {
     return Status::Invalid("failed setting environment variable");
   }
 #else
-  if (setenv(name, value, 1) == 0) {
+  if (setenv(name.data(), value.data(), 1) == 0) {
     return Status::OK();
   } else {
     return Status::Invalid("failed setting environment variable");
   }
 #endif
 }
 
-Status SetEnvVar(const std::string& name, const std::string& value) {
-  return SetEnvVar(name.c_str(), value.c_str());
-}
-
-Status DelEnvVar(const char* name) {
+Status DelEnvVar(std::string_view name) {
 #ifdef _WIN32
-  if (SetEnvironmentVariableA(name, nullptr)) {
+  if (SetEnvironmentVariableA(name.data(), nullptr)) {
     return Status::OK();
   } else {
     return Status::Invalid("failed deleting environment variable");
   }
 #else
-  if (unsetenv(name) == 0) {
+  if (unsetenv(name.data()) == 0) {
     return Status::OK();
   } else {
     return Status::Invalid("failed deleting environment variable");
   }
 #endif
 }
 
-Status DelEnvVar(const std::string& name) { return DelEnvVar(name.c_str()); }
-
 //
 // Temporary directories
 //

cpp/src/arrow/util/io_util.h

@@ -25,6 +25,7 @@
 #include <memory>
 #include <optional>
 #include <string>
+#include <string_view>
 #include <utility>
 #include <vector>
 
@@ -238,23 +239,16 @@ Status MemoryMapRemap(void* addr, size_t old_size, size_t new_size, int fildes,
 ARROW_EXPORT
 Status MemoryAdviseWillNeed(const std::vector<MemoryRegion>& regions);
 
+// Returns KeyError if the environment variable doesn't exist
 ARROW_EXPORT
-Result<std::string> GetEnvVar(const char* name);
+Result<std::string> GetEnvVar(std::string_view name);
 ARROW_EXPORT
-Result<std::string> GetEnvVar(const std::string& name);
-ARROW_EXPORT
-Result<NativePathString> GetEnvVarNative(const char* name);
-ARROW_EXPORT
-Result<NativePathString> GetEnvVarNative(const std::string& name);
+Result<NativePathString> GetEnvVarNative(std::string_view name);
 
 ARROW_EXPORT
-Status SetEnvVar(const char* name, const char* value);
-ARROW_EXPORT
-Status SetEnvVar(const std::string& name, const std::string& value);
-ARROW_EXPORT
-Status DelEnvVar(const char* name);
+Status SetEnvVar(std::string_view name, std::string_view value);
 ARROW_EXPORT
-Status DelEnvVar(const std::string& name);
+Status DelEnvVar(std::string_view name);
 
 ARROW_EXPORT
 std::string ErrnoMessage(int errnum);