Migrate to error constants in glacier

lib/glacier/status/error.h

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stdint.h>
+
+namespace glcr {
+
+typedef uint64_t ErrorCode;
+
+#define RET_ERR(expr)           \
+  {                             \
+    z_err_t _tmp_err = expr;    \
+    if (_tmp_err != glcr::OK) { \
+      return _tmp_err;          \
+    }                           \
+  }
+
+static const uint64_t OK = 0x0;
+
+// First set of error codes generally indicate user errors.
+static const uint64_t INVALID_ARGUMENT = 0x1;
+static const uint64_t NOT_FOUND = 0x2;
+static const uint64_t PERMISSION_DENIED = 0x3;
+static const uint64_t NULL_PTR = 0x4;
+static const uint64_t EMPTY = 0x5;
+static const uint64_t ALREADY_EXISTS = 0x6;
+static const uint64_t BUFFER_SIZE = 0x7;
+static const uint64_t FAILED_PRECONDITION = 0x8;
+
+// Second set of error codes generally indicate service errors.
+static const uint64_t INTERNAL = 0x100;
+static const uint64_t UNIMPLEMENTED = 0x101;
+static const uint64_t EXHAUSTED = 0x102;
+
+// Kernel specific error codes (relating to capabilities).
+static const uint64_t CAP_NOT_FOUND = 0x1000;
+static const uint64_t CAP_WRONG_TYPE = 0x1001;
+static const uint64_t CAP_PERMISSION_DENIED = 0x1002;
+
+}  // namespace glcr

lib/glacier/status/error_or.h

@@ -0,0 +1,41 @@
+#pragma once
+
+#include <glacier/status/error.h>
+
+namespace glcr {
+
+template <typename T>
+class ErrorOr {
+ public:
+  ErrorOr() = delete;
+  ErrorOr(const ErrorOr&) = delete;
+  ErrorOr(ErrorOr&&) = delete;
+
+  ErrorOr(ErrorCode code) : error_(code), ok_(false) {}
+  ErrorOr(T obj) : obj_(obj), ok_(true) {}
+  ErrorOr(T&& obj) : obj_(obj), ok_(true) {}
+
+  bool ok() { return ok_; }
+  operator bool() { return ok_; }
+
+  T& value() { return obj_; }
+
+  ErrorCode error() { return error_; }
+
+ private:
+  union {
+    ErrorCode error_;
+    T obj_;
+  };
+  bool ok_;
+};
+
+#define ASSIGN_OR_RETURN(lhs, rhs) \
+                                   \
+  auto e##__LINE__ = rhs;          \
+  if (!e##__LINE__.ok()) {         \
+    return e##__LINE__.error();    \
+  }                                \
+  lhs = rhs.value();
+
+}  // namespace glcr