os: add os.{get,set}Priority()

doc/api/os.md

@@ -192,6 +192,19 @@ added: v0.3.3
 The `os.freemem()` method returns the amount of free system memory in bytes as
 an integer.
 
+## os.getPriority([pid])
+<!-- YAML
+added: REPLACEME
+-->
+
+* `pid` {integer} The process ID to retrieve scheduling priority for.
+  **Default** `0`.
+* Returns: {integer}
+
+The `os.getPriority()` method returns the scheduling priority for the process
+specified by `pid`. If `pid` is not provided, or is `0`, the priority of the
+current process is returned.
+
 ## os.homedir()
 <!-- YAML
 added: v2.3.0
@@ -338,6 +351,26 @@ On POSIX systems, the operating system release is determined by calling
 [uname(3)][]. On Windows, `GetVersionExW()` is used. Please see
 https://en.wikipedia.org/wiki/Uname#Examples for more information.
 
+## os.setPriority([pid, ]priority)
+<!-- YAML
+added: REPLACEME
+-->
+
+* `pid` {integer} The process ID to set scheduling priority for.
+  **Default** `0`.
+* `priority` {integer} The scheduling priority to assign to the process.
+
+The `os.setPriority()` method attempts to set the scheduling priority for the
+process specified by `pid`. If `pid` is not provided, or is `0`, the priority
+of the current process is used.
+
+The `priority` input must be an integer between `-20` (high priority) and `19`
+(low priority). Due to differences between Unix priority levels and Windows
+priority classes, `priority` is mapped to one of six priority constants in
+`os.constants.priority`. When retrieving a process priority level, this range
+mapping may cause the return value to be slightly different on Windows. To avoid
+confusion, it is recommended to set `priority` to one of the priority constants.
+
 ## os.tmpdir()
 <!-- YAML
 added: v0.9.9
@@ -1208,6 +1241,60 @@ information.
   </tr>
 </table>
 
+### Priority Constants
+<!-- YAML
+added: REPLACEME
+-->
+
+The following process scheduling constants are exported by
+`os.constants.priority`:
+
+<table>
+  <tr>
+    <th>Constant</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_LOW</code></td>
+    <td>The lowest process scheduling priority. This corresponds to
+    <code>IDLE_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>19</code> on all other platforms.</td>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_BELOW_NORMAL</code></td>
+    <td>The process scheduling priority above <code>PRIORITY_LOW</code> and
+    below <code>PRIORITY_NORMAL</code>. This corresponds to
+    <code>BELOW_NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>10</code> on all other platforms.</td>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_NORMAL</code></td>
+    <td>The default process scheduling priority. This corresponds to
+    <code>NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>0</code> on all other platforms.</td>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_ABOVE_NORMAL</code></td>
+    <td>The process scheduling priority above <code>PRIORITY_NORMAL</code> and
+    below <code>PRIORITY_HIGH</code>. This corresponds to
+    <code>ABOVE_NORMAL_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>-7</code> on all other platforms.</td>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_HIGH</code></td>
+    <td>The process scheduling priority above <code>PRIORITY_ABOVE_NORMAL</code>
+    and below <code>PRIORITY_HIGHEST</code>. This corresponds to
+    <code>HIGH_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>-14</code> on all other platforms.</td>
+  </tr>
+  <tr>
+    <td><code>PRIORITY_HIGHEST</code></td>
+    <td>The highest process scheduling priority. This corresponds to
+    <code>REALTIME_PRIORITY_CLASS</code> on Windows, and a nice value of
+    <code>-20</code> on all other platforms.</td>
+  </tr>
+</table>
+
 ### libuv Constants
 
 <table>

lib/constants.js

@@ -29,6 +29,7 @@ const constants = process.binding('constants');
 Object.assign(exports,
               constants.os.dlopen,
               constants.os.errno,
+              constants.os.priority,
               constants.os.signals,
               constants.fs,
               constants.crypto);

lib/os.js

@@ -27,6 +27,7 @@ const { deprecate } = require('internal/util');
 const isWindows = process.platform === 'win32';
 
 const { codes: { ERR_SYSTEM_ERROR } } = require('internal/errors');
+const { validateInt32 } = require('internal/validators');
 
 const {
   getCPUs,
@@ -37,10 +38,12 @@ const {
   getLoadAvg,
   getOSRelease: _getOSRelease,
   getOSType: _getOSType,
+  getPriority: _getPriority,
   getTotalMem,
   getUserInfo: _getUserInfo,
   getUptime,
-  isBigEndian
+  isBigEndian,
+  setPriority: _setPriority
 } = process.binding('os');
 
 function getCheckedFunction(fn) {
@@ -206,17 +209,49 @@ function networkInterfaces() {
   return interfaceAddresses;
 }
 
+function setPriority(pid, priority) {
+  if (priority === undefined) {
+    priority = pid;
+    pid = 0;
+  }
+
+  validateInt32(pid, 'pid');
+  validateInt32(priority, 'priority', -20, 19);
+
+  const ctx = {};
+
+  if (_setPriority(pid, priority, ctx) !== 0)
+    throw new ERR_SYSTEM_ERROR(ctx);
+}
+
+function getPriority(pid) {
+  if (pid === undefined)
+    pid = 0;
+  else
+    validateInt32(pid, 'pid');
+
+  const ctx = {};
+  const priority = _getPriority(pid, ctx);
+
+  if (priority === undefined)
+    throw new ERR_SYSTEM_ERROR(ctx);
+
+  return priority;
+}
+
 module.exports = {
   arch,
   cpus,
   endianness,
   freemem: getFreeMem,
+  getPriority,
   homedir: getHomeDirectory,
   hostname: getHostname,
   loadavg,
   networkInterfaces,
   platform,
   release: getOSRelease,
+  setPriority,
   tmpdir,
   totalmem: getTotalMem,
   type: getOSType,

src/node_constants.cc

@@ -758,6 +758,44 @@ void DefineSignalConstants(Local<Object> target) {
 #endif
 }
 
+void DefinePriorityConstants(Local<Object> target) {
+#ifdef UV_PRIORITY_LOW
+# define PRIORITY_LOW UV_PRIORITY_LOW
+  NODE_DEFINE_CONSTANT(target, PRIORITY_LOW);
+# undef PRIORITY_LOW
+#endif
+
+#ifdef UV_PRIORITY_BELOW_NORMAL
+# define PRIORITY_BELOW_NORMAL UV_PRIORITY_BELOW_NORMAL
+  NODE_DEFINE_CONSTANT(target, PRIORITY_BELOW_NORMAL);
+# undef PRIORITY_BELOW_NORMAL
+#endif
+
+#ifdef UV_PRIORITY_NORMAL
+# define PRIORITY_NORMAL UV_PRIORITY_NORMAL
+  NODE_DEFINE_CONSTANT(target, PRIORITY_NORMAL);
+# undef PRIORITY_NORMAL
+#endif
+
+#ifdef UV_PRIORITY_ABOVE_NORMAL
+# define PRIORITY_ABOVE_NORMAL UV_PRIORITY_ABOVE_NORMAL
+  NODE_DEFINE_CONSTANT(target, PRIORITY_ABOVE_NORMAL);
+# undef PRIORITY_ABOVE_NORMAL
+#endif
+
+#ifdef UV_PRIORITY_HIGH
+# define PRIORITY_HIGH UV_PRIORITY_HIGH
+  NODE_DEFINE_CONSTANT(target, PRIORITY_HIGH);
+# undef PRIORITY_HIGH
+#endif
+
+#ifdef UV_PRIORITY_HIGHEST
+# define PRIORITY_HIGHEST UV_PRIORITY_HIGHEST
+  NODE_DEFINE_CONSTANT(target, PRIORITY_HIGHEST);
+# undef PRIORITY_HIGHEST
+#endif
+}
+
 void DefineOpenSSLConstants(Local<Object> target) {
 #ifdef OPENSSL_VERSION_NUMBER
     NODE_DEFINE_CONSTANT(target, OPENSSL_VERSION_NUMBER);
@@ -1338,6 +1376,10 @@ void DefineConstants(v8::Isolate* isolate, Local<Object> target) {
   CHECK(sig_constants->SetPrototype(env->context(),
                                     Null(env->isolate())).FromJust());
 
+  Local<Object> priority_constants = Object::New(isolate);
+  CHECK(priority_constants->SetPrototype(env->context(),
+                                         Null(env->isolate())).FromJust());
+
   Local<Object> fs_constants = Object::New(isolate);
   CHECK(fs_constants->SetPrototype(env->context(),
                                    Null(env->isolate())).FromJust());
@@ -1361,6 +1403,7 @@ void DefineConstants(v8::Isolate* isolate, Local<Object> target) {
   DefineErrnoConstants(err_constants);
   DefineWindowsErrorConstants(err_constants);
   DefineSignalConstants(sig_constants);
+  DefinePriorityConstants(priority_constants);
   DefineSystemConstants(fs_constants);
   DefineOpenSSLConstants(crypto_constants);
   DefineCryptoConstants(crypto_constants);
@@ -1374,6 +1417,7 @@ void DefineConstants(v8::Isolate* isolate, Local<Object> target) {
   os_constants->Set(OneByteString(isolate, "dlopen"), dlopen_constants);
   os_constants->Set(OneByteString(isolate, "errno"), err_constants);
   os_constants->Set(OneByteString(isolate, "signals"), sig_constants);
+  os_constants->Set(OneByteString(isolate, "priority"), priority_constants);
   target->Set(OneByteString(isolate, "os"), os_constants);
   target->Set(OneByteString(isolate, "fs"), fs_constants);
   target->Set(OneByteString(isolate, "crypto"), crypto_constants);

src/node_os.cc

@@ -52,6 +52,7 @@ using v8::Context;
 using v8::Float64Array;
 using v8::Function;
 using v8::FunctionCallbackInfo;
+using v8::Int32;
 using v8::Integer;
 using v8::Local;
 using v8::MaybeLocal;
@@ -405,6 +406,46 @@ static void GetUserInfo(const FunctionCallbackInfo<Value>& args) {
 }
 
 
+static void SetPriority(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  CHECK_EQ(args.Length(), 3);
+  CHECK(args[0]->IsInt32());
+  CHECK(args[1]->IsInt32());
+
+  const int pid = args[0].As<Int32>()->Value();
+  const int priority = args[1].As<Int32>()->Value();
+  const int err = uv_os_setpriority(pid, priority);
+
+  if (err) {
+    CHECK(args[2]->IsObject());
+    env->CollectUVExceptionInfo(args[2], err, "uv_os_setpriority");
+  }
+
+  args.GetReturnValue().Set(err);
+}
+
+
+static void GetPriority(const FunctionCallbackInfo<Value>& args) {
+  Environment* env = Environment::GetCurrent(args);
+
+  CHECK_EQ(args.Length(), 2);
+  CHECK(args[0]->IsInt32());
+
+  const int pid = args[0].As<Int32>()->Value();
+  int priority;
+  const int err = uv_os_getpriority(pid, &priority);
+
+  if (err) {
+    CHECK(args[1]->IsObject());
+    env->CollectUVExceptionInfo(args[1], err, "uv_os_getpriority");
+    return;
+  }
+
+  args.GetReturnValue().Set(priority);
+}
+
+
 void Initialize(Local<Object> target,
                 Local<Value> unused,
                 Local<Context> context) {
@@ -420,6 +461,8 @@ void Initialize(Local<Object> target,
   env->SetMethod(target, "getInterfaceAddresses", GetInterfaceAddresses);
   env->SetMethod(target, "getHomeDirectory", GetHomeDirectory);
   env->SetMethod(target, "getUserInfo", GetUserInfo);
+  env->SetMethod(target, "setPriority", SetPriority);
+  env->SetMethod(target, "getPriority", GetPriority);
   target->Set(FIXED_ONE_BYTE_STRING(env->isolate(), "isBigEndian"),
               Boolean::New(env->isolate(), IsBigEndian()));
 }

test/parallel/test-binding-constants.js

@@ -10,7 +10,7 @@ assert.deepStrictEqual(
 
 assert.deepStrictEqual(
   Object.keys(constants.os).sort(), ['UV_UDP_REUSEADDR', 'dlopen', 'errno',
-                                     'signals']
+                                     'priority', 'signals']
 );
 
 // Make sure all the constants objects don't inherit from Object.prototype