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 //===- llvm/Support/Process.h -----------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 /// \file
 ///
 /// Provides a library for accessing information about this process and other
 /// processes on the operating system. Also provides means of spawning
 /// subprocess for commands. The design of this library is modeled after the
 /// proposed design of the Boost.Process library, and is design specifically to
 /// follow the style of standard libraries and potentially become a proposal
 /// for a standard library.
 ///
 /// This file declares the llvm::sys::Process class which contains a collection
 /// of legacy static interfaces for extracting various information about the
 /// current process. The goal is to migrate users of this API over to the new
 /// interfaces.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_SUPPORT_PROCESS_H
 #define LLVM_SUPPORT_PROCESS_H
 
 #include "llvm/Support/Chrono.h"
 #include "llvm/Support/DataTypes.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/Program.h"
 #include <optional>
 #include <system_error>
 
 namespace llvm {
 template <typename T> class ArrayRef;
 class StringRef;
 
 namespace sys {
 
 
 /// A collection of legacy interfaces for querying information about the
 /// current executing process.
 class Process {
 public:
   using Pid = int32_t;
 
   /// Get the process's identifier.
   static Pid getProcessId();
 
   /// Get the process's page size.
   /// This may fail if the underlying syscall returns an error. In most cases,
   /// page size information is used for optimization, and this error can be
   /// safely discarded by calling consumeError, and an estimated page size
   /// substituted instead.
   static Expected<unsigned> getPageSize();
 
   /// Get the process's estimated page size.
   /// This function always succeeds, but if the underlying syscall to determine
   /// the page size fails then this will silently return an estimated page size.
   /// The estimated page size is guaranteed to be a power of 2.
   static unsigned getPageSizeEstimate() {
     if (auto PageSize = getPageSize())
       return *PageSize;
     else {
       consumeError(PageSize.takeError());
       return 4096;
     }
   }
 
   /// Return process memory usage.
   /// This static function will return the total amount of memory allocated
   /// by the process. This only counts the memory allocated via the malloc,
   /// calloc and realloc functions and includes any "free" holes in the
   /// allocated space.
   static size_t GetMallocUsage();
 
   /// This static function will set \p user_time to the amount of CPU time
   /// spent in user (non-kernel) mode and \p sys_time to the amount of CPU
   /// time spent in system (kernel) mode.  If the operating system does not
   /// support collection of these metrics, a zero duration will be for both
   /// values.
   /// \param elapsed Returns the system_clock::now() giving current time
   /// \param user_time Returns the current amount of user time for the process
   /// \param sys_time Returns the current amount of system time for the process
   static void GetTimeUsage(TimePoint<> &elapsed,
                            std::chrono::nanoseconds &user_time,
                            std::chrono::nanoseconds &sys_time);
 
   /// This function makes the necessary calls to the operating system to
   /// prevent core files or any other kind of large memory dumps that can
   /// occur when a program fails.
   /// Prevent core file generation.
   static void PreventCoreFiles();
 
   /// true if PreventCoreFiles has been called, false otherwise.
   static bool AreCoreFilesPrevented();
 
   // This function returns the environment variable \arg name's value as a UTF-8
   // string. \arg Name is assumed to be in UTF-8 encoding too.
   static std::optional<std::string> GetEnv(StringRef name);
 
   /// This function searches for an existing file in the list of directories
   /// in a PATH like environment variable, and returns the first file found,
   /// according to the order of the entries in the PATH like environment
   /// variable.  If an ignore list is specified, then any folder which is in
   /// the PATH like environment variable but is also in IgnoreList is not
   /// considered.
   static std::optional<std::string>
   FindInEnvPath(StringRef EnvName, StringRef FileName,
                 ArrayRef<std::string> IgnoreList,
                 char Separator = EnvPathSeparator);
 
   static std::optional<std::string>
   FindInEnvPath(StringRef EnvName, StringRef FileName,
                 char Separator = EnvPathSeparator);
 
   // This functions ensures that the standard file descriptors (input, output,
   // and error) are properly mapped to a file descriptor before we use any of
   // them.  This should only be called by standalone programs, library
   // components should not call this.
   static std::error_code FixupStandardFileDescriptors();
 
   // This function safely closes a file descriptor.  It is not safe to retry
   // close(2) when it returns with errno equivalent to EINTR; this is because
   // *nixen cannot agree if the file descriptor is, in fact, closed when this
   // occurs.
   //
   // N.B. Some operating systems, due to thread cancellation, cannot properly
   // guarantee that it will or will not be closed one way or the other!
   static std::error_code SafelyCloseFileDescriptor(int FD);
 
   /// This function determines if the standard input is connected directly
   /// to a user's input (keyboard probably), rather than coming from a file
   /// or pipe.
   static bool StandardInIsUserInput();
 
   /// This function determines if the standard output is connected to a
   /// "tty" or "console" window. That is, the output would be displayed to
   /// the user rather than being put on a pipe or stored in a file.
   static bool StandardOutIsDisplayed();
 
   /// This function determines if the standard error is connected to a
   /// "tty" or "console" window. That is, the output would be displayed to
   /// the user rather than being put on a pipe or stored in a file.
   static bool StandardErrIsDisplayed();
 
   /// This function determines if the given file descriptor is connected to
   /// a "tty" or "console" window. That is, the output would be displayed to
   /// the user rather than being put on a pipe or stored in a file.
   static bool FileDescriptorIsDisplayed(int fd);
 
   /// This function determines if the given file descriptor is displayd and
   /// supports colors.
   static bool FileDescriptorHasColors(int fd);
 
   /// This function determines the number of columns in the window
   /// if standard output is connected to a "tty" or "console"
   /// window. If standard output is not connected to a tty or
   /// console, or if the number of columns cannot be determined,
   /// this routine returns zero.
   static unsigned StandardOutColumns();
 
   /// This function determines the number of columns in the window
   /// if standard error is connected to a "tty" or "console"
   /// window. If standard error is not connected to a tty or
   /// console, or if the number of columns cannot be determined,
   /// this routine returns zero.
   static unsigned StandardErrColumns();
 
   /// This function determines whether the terminal connected to standard
   /// output supports colors. If standard output is not connected to a
   /// terminal, this function returns false.
   static bool StandardOutHasColors();
 
   /// This function determines whether the terminal connected to standard
   /// error supports colors. If standard error is not connected to a
   /// terminal, this function returns false.
   static bool StandardErrHasColors();
 
   /// Enables or disables whether ANSI escape sequences are used to output
   /// colors. This only has an effect on Windows.
   /// Note: Setting this option is not thread-safe and should only be done
   /// during initialization.
   static void UseANSIEscapeCodes(bool enable);
 
   /// Whether changing colors requires the output to be flushed.
   /// This is needed on systems that don't support escape sequences for
   /// changing colors.
   static bool ColorNeedsFlush();
 
   /// This function returns the colorcode escape sequences.
   /// If ColorNeedsFlush() is true then this function will change the colors
   /// and return an empty escape sequence. In that case it is the
   /// responsibility of the client to flush the output stream prior to
   /// calling this function.
   static const char *OutputColor(char c, bool bold, bool bg);
 
   /// Same as OutputColor, but only enables the bold attribute.
   static const char *OutputBold(bool bg);
 
   /// This function returns the escape sequence to reverse forground and
   /// background colors.
   static const char *OutputReverse();
 
   /// Resets the terminals colors, or returns an escape sequence to do so.
   static const char *ResetColor();
 
   /// Get the result of a process wide random number generator. The
   /// generator will be automatically seeded in non-deterministic fashion.
   static unsigned GetRandomNumber();
 
   /// Equivalent to ::exit(), except when running inside a CrashRecoveryContext.
   /// In that case, the control flow will resume after RunSafely(), like for a
   /// crash, rather than exiting the current process.
   /// Use \arg NoCleanup for calling _exit() instead of exit().
   [[noreturn]] static void Exit(int RetCode, bool NoCleanup = false);
 
 private:
   [[noreturn]] static void ExitNoCleanup(int RetCode);
 };
 
 }
 }
 
 #endif

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