mojo/public/c/system/quota.h

// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MOJO_PUBLIC_C_SYSTEM_QUOTA_H_
#define MOJO_PUBLIC_C_SYSTEM_QUOTA_H_

#include <stdint.h>

#include "mojo/public/c/system/macros.h"
#include "mojo/public/c/system/system_export.h"
#include "mojo/public/c/system/types.h"

// Flags passed to |MojoSetQuota| via |MojoSetQuotaOptions|.
typedef uint32_t MojoSetQuotaFlags;

// No flags.
#define MOJO_SET_QUOTA_FLAG_NONE ((MojoSetQuotaFlags)0)

// Options passed to |MojoSetQuota()|.
struct MOJO_ALIGNAS(8) MojoSetQuotaOptions {
  // The size of this structure, used for versioning.
  uint32_t struct_size;

  // See |MojoSetQuotaFlags| above.
  MojoSetQuotaFlags flags;
};
MOJO_STATIC_ASSERT(sizeof(struct MojoSetQuotaOptions) == 8,
                   "MojoSetQuotaOptions has wrong size.");

// Flags passed to |MojoQueryQuota| via |MojoQueryQuotaOptions|.
typedef uint32_t MojoQueryQuotaFlags;

// No flags.
#define MOJO_QUERY_QUOTA_FLAG_NONE ((MojoQueryQuotaFlags)0)

// Options passed to |MojoQueryQuota()|.
struct MOJO_ALIGNAS(8) MojoQueryQuotaOptions {
  // The size of this structure, used for versioning.
  uint32_t struct_size;

  // See |MojoQueryQuotaFlags| above.
  MojoQueryQuotaFlags flags;
};
MOJO_STATIC_ASSERT(sizeof(struct MojoQueryQuotaOptions) == 8,
                   "MojoQueryQuotaOptions has wrong size.");

// The maximum value any quota can be set to. Effectively means "no quota".
#define MOJO_QUOTA_LIMIT_NONE ((uint64_t)0xffffffffffffffff)

// An enumeration of different types of quotas that can be set on a handle.
typedef uint32_t MojoQuotaType;

// Limits the number of unread messages which can be queued on a message pipe
// endpoint before raising a |MOJO_HANDLE_SIGNAL_QUOTA_EXCEEDED| signal on that
// endpoint. May only be set on message pipe handles.
#define MOJO_QUOTA_TYPE_RECEIVE_QUEUE_LENGTH ((MojoQuotaType)0)

// Limits the total size (in bytes) of unread messages which can be queued on a
// message pipe endpoint before raising a |MOJO_HANDLE_SIGNAL_QUOTA_EXCEEDED|
// signal on that endpoint. May only be set on message pipe handles.
#define MOJO_QUOTA_TYPE_RECEIVE_QUEUE_MEMORY_SIZE ((MojoQuotaType)1)

// Limits the number of sent, unread messages which can be queued on a message
// pipe endpoint before raising a |MOJO_HANDLE_SIGNAL_QUOTA_EXCEEDED| signal on
// that  endpoint. May only be set on message pipe handles.
#define MOJO_QUOTA_TYPE_UNREAD_MESSAGE_COUNT ((MojoQuotaType)2)

#ifdef __cplusplus
extern "C" {
#endif

// Sets a quota on a given handle which will cause that handle to raise the
// |MOJO_HANDLE_SIGNAL_QUOTA_EXCEEDED| signal if the quota is exceeded. Signals
// can be trapped using |MojoCreateTrap()| and related APIs (see trap.h).
//
// All quota limits on a handle default to |MOJO_QUOTA_LIMIT_NONE|, meaning that
// the resource is unlimited.
//
// NOTE: A handle's quota is only enforced as long as the handle remains within
// the process which set the quota.
//
// Parameters:
//   |handle|: The handle on which a quota should be set.
//   |type|: The type of quota to set. Certain types of quotas may only be set
//       on certain types of handles. See notes on individual quota type
//       definitions above for meaning and restrictions.
//   |limit|: The limiting value of the quota. The meaning of this is determined
//       by |type|. See notes on individual quota type definitions above.
//   |options|: Additional options; may be null.
//
//  Returns:
//    |MOJO_RESULT_OK| if the quota was successfully set.
//    |MOJO_RESULT_INVALID_ARGUMENT| if |handle| is not a valid handle value,
//        |type| is not a known quota type, |options| is non-null but
//        |*options| is malformed, or the quota |type| cannot be set on |handle|
//        because the quota does not apply to that type of handle.
MOJO_SYSTEM_EXPORT MojoResult
MojoSetQuota(MojoHandle handle,
             MojoQuotaType type,
             uint64_t limit,
             const struct MojoSetQuotaOptions* options);

// Queries a handle for information about a specific quota.
//
// Parameters:
//   |handle|: The handle to query.
//   |type|: The type of quota to query.
//   |limit|: Receives the quota's currently set limit if non-null.
//   |usage|: Receives the quota's current usage if non-null.
//
// Returns:
//   |MOJO_RESULT_OK| if the quota was successfully queried on |handle|. Upon
//       return, |*limit| contains the quota's current limit if |limit| is
//       non-null, and |*usage| contains the quota's current usage if |usage| is
//       non-null.
//   |MOJO_RESULT_INVALID_ARGUMENT| if |handle| is not a valid handle value or
//       quota |type| does not apply to the type of object referenced by
//       |handle|.
MOJO_SYSTEM_EXPORT MojoResult
MojoQueryQuota(MojoHandle handle,
               MojoQuotaType type,
               const struct MojoQueryQuotaOptions* options,
               uint64_t* limit,
               uint64_t* usage);

#ifdef __cplusplus
}  // extern "C"
#endif

#endif  // MOJO_PUBLIC_C_SYSTEM_QUOTA_H_