Move the Environment portability header to the stdlib header

[folly.git] / folly / portability / Stdlib.cpp

diff --git a/folly/portability/Stdlib.cpp b/folly/portability/Stdlib.cpp
index 1a6a7520908af3caca6309f25e1d4f2a5fc23928..013a7d32539d0a2752d46db9a9d40831121572b9 100644 (file)
--- a/folly/portability/Stdlib.cpp
+++ b/folly/portability/Stdlib.cpp
@@ -70,5 +70,69 @@ char* realpath(const char* path, char* resolved_path) {
   // I sure hope the caller gave us _MAX_PATH space in the buffer....
   return _fullpath(resolved_path, path, _MAX_PATH);
 }
+
+int setenv(const char* name, const char* value, int overwrite) {
+  if (overwrite == 0 && getenv(name) != nullptr) {
+    return 0;
+  }
+
+  if (*value != '\0') {
+    auto e = _putenv_s(name, value);
+    if (e != 0) {
+      errno = e;
+      return -1;
+    }
+    return 0;
+  }
+
+  // We are trying to set the value to an empty string, but
+  // _putenv_s deletes entries if the value is an empty string,
+  // and just calling SetEnvironmentVariableA doesn't update
+  // _environ, so we have to do these terrible things.
+  if (_putenv_s(name, "  ") != 0) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  // Here lies the documentation we blatently ignore to make
+  // this work >_>...
+  *getenv(name) = '\0';
+  // This would result in a double null termination, which
+  // normally signifies the end of the environment variable
+  // list, so we stick a completely empty environment variable
+  // into the list instead.
+  *(getenv(name) + 1) = '=';
+
+  // If _wenviron is null, the wide environment has not been initialized
+  // yet, and we don't need to try to update it.
+  // We have to do this otherwise we'd be forcing the initialization and
+  // maintenance of the wide environment even though it's never actually
+  // used in most programs.
+  if (_wenviron != nullptr) {
+    wchar_t buf[_MAX_ENV + 1];
+    size_t len;
+    if (mbstowcs_s(&len, buf, _MAX_ENV + 1, name, _MAX_ENV) != 0) {
+      errno = EINVAL;
+      return -1;
+    }
+    *_wgetenv(buf) = u'\0';
+    *(_wgetenv(buf) + 1) = u'=';
+  }
+
+  // And now, we have to update the outer environment to have
+  // a proper empty value.
+  if (!SetEnvironmentVariableA(name, value)) {
+    errno = EINVAL;
+    return -1;
+  }
+  return 0;
+}
+
+int unsetenv(const char* name) {
+  if (_putenv_s(name, "") != 0) {
+    return -1;
+  }
+  return 0;
+}
 }
 #endif