path: root/src/libutil/util.hh

#pragma once

#include "types.hh"
#include "error.hh"
#include "logging.hh"
#include "ansicolor.hh"

#include <sys/types.h>
#include <sys/stat.h>
#include <dirent.h>
#include <unistd.h>
#include <signal.h>

#include <functional>
#include <map>
#include <sstream>
#include <optional>

#ifndef HAVE_STRUCT_DIRENT_D_TYPE
#define DT_UNKNOWN 0
#define DT_REG 1
#define DT_LNK 2
#define DT_DIR 3
#endif

namespace nix {

struct Sink;
struct Source;


/* The system for which Nix is compiled. */
extern const std::string nativeSystem;


/* Return an environment variable. */
std::optional<std::string> getEnv(const std::string & key);

/* Get the entire environment. */
std::map<std::string, std::string> getEnv();

/* Clear the environment. */
void clearEnv();

/* Return an absolutized path, resolving paths relative to the
   specified directory, or the current directory otherwise.  The path
   is also canonicalised. */
Path absPath(Path path,
    std::optional<Path> dir = {},
    bool resolveSymlinks = false);

/* Canonicalise a path by removing all `.' or `..' components and
   double or trailing slashes.  Optionally resolves all symlink
   components such that each component of the resulting path is *not*
   a symbolic link. */
Path canonPath(const Path & path, bool resolveSymlinks = false);

/* Return the directory part of the given canonical path, i.e.,
   everything before the final `/'.  If the path is the root or an
   immediate child thereof (e.g., `/foo'), this means `/'
   is returned.*/
Path dirOf(const Path & path);

/* Return the base name of the given canonical path, i.e., everything
   following the final `/' (trailing slashes are removed). */
std::string_view baseNameOf(std::string_view path);

/* Check whether 'path' is a descendant of 'dir'. */
bool isInDir(const Path & path, const Path & dir);

/* Check whether 'path' is equal to 'dir' or a descendant of 'dir'. */
bool isDirOrInDir(const Path & path, const Path & dir);

/* Get status of `path'. */
struct stat lstat(const Path & path);

/* Return true iff the given path exists. */
bool pathExists(const Path & path);

/* Read the contents (target) of a symbolic link.  The result is not
   in any way canonicalised. */
Path readLink(const Path & path);

bool isLink(const Path & path);

/* Read the contents of a directory.  The entries `.' and `..' are
   removed. */
struct DirEntry
{
    string name;
    ino_t ino;
    unsigned char type; // one of DT_*
    DirEntry(const string & name, ino_t ino, unsigned char type)
        : name(name), ino(ino), type(type) { }
};

typedef vector<DirEntry> DirEntries;

DirEntries readDirectory(const Path & path);

unsigned char getFileType(const Path & path);

/* Read the contents of a file into a string. */
string readFile(int fd);
string readFile(const Path & path);
void readFile(const Path & path, Sink & sink);

/* Write a string to a file. */
void writeFile(const Path & path, std::string_view s, mode_t mode = 0666);

void writeFile(const Path & path, Source & source, mode_t mode = 0666);

/* Read a line from a file descriptor. */
string readLine(int fd);

/* Write a line to a file descriptor. */
void writeLine(int fd, string s);

/* Delete a path; i.e., in the case of a directory, it is deleted
   recursively. It's not an error if the path does not exist. The
   second variant returns the number of bytes and blocks freed. */
void deletePath(const Path & path);

void deletePath(const Path & path, uint64_t & bytesFreed);

std::string getUserName();

/* Return $HOME or the user's home directory from /etc/passwd. */
Path getHome();

/* Return $XDG_CACHE_HOME or $HOME/.cache. */
Path getCacheDir();

/* Return $XDG_CONFIG_HOME or $HOME/.config. */
Path getConfigDir();

/* Return the directories to search for user configuration files */
std::vector<Path> getConfigDirs();

/* Return $XDG_DATA_HOME or $HOME/.local/share. */
Path getDataDir();

/* Create a directory and all its parents, if necessary.  Returns the
   list of created directories, in order of creation. */
Paths createDirs(const Path & path);

/* Create a symlink. */
void createSymlink(const Path & target, const Path & link,
    std::optional<time_t> mtime = {});

/* Atomically create or replace a symlink. */
void replaceSymlink(const Path & target, const Path & link,
    std::optional<time_t> mtime = {});


/* Wrappers arount read()/write() that read/write exactly the
   requested number of bytes. */
void readFull(int fd, char * buf, size_t count);
void writeFull(int fd, std::string_view s, bool allowInterrupts = true);

MakeError(EndOfFile, Error);


/* Read a file descriptor until EOF occurs. */
string drainFD(int fd, bool block = true, const size_t reserveSize=0);

void drainFD(int fd, Sink & sink, bool block = true);


/* Automatic cleanup of resources. */


class AutoDelete
{
    Path path;
    bool del;
    bool recursive;
public:
    AutoDelete();
    AutoDelete(const Path & p, bool recursive = true);
    ~AutoDelete();
    void cancel();
    void reset(const Path & p, bool recursive = true);
    operator Path() const { return path; }
};


class AutoCloseFD
{
    int fd;
    void close();
public:
    AutoCloseFD();
    AutoCloseFD(int fd);
    AutoCloseFD(const AutoCloseFD & fd) = delete;
    AutoCloseFD(AutoCloseFD&& fd);
    ~AutoCloseFD();
    AutoCloseFD& operator =(const AutoCloseFD & fd) = delete;
    AutoCloseFD& operator =(AutoCloseFD&& fd);
    int get() const;
    explicit operator bool() const;
    int release();
};


/* Create a temporary directory. */
Path createTempDir(const Path & tmpRoot = "", const Path & prefix = "nix",
    bool includePid = true, bool useGlobalCounter = true, mode_t mode = 0755);

/* Create a temporary file, returning a file handle and its path. */
std::pair<AutoCloseFD, Path> createTempFile(const Path & prefix = "nix");


class Pipe
{
public:
    AutoCloseFD readSide, writeSide;
    void create();
};


struct DIRDeleter
{
    void operator()(DIR * dir) const {
        closedir(dir);
    }
};

typedef std::unique_ptr<DIR, DIRDeleter> AutoCloseDir;


class Pid
{
    pid_t pid = -1;
    bool separatePG = false;
    int killSignal = SIGKILL;
public:
    Pid();
    Pid(pid_t pid);
    ~Pid();
    void operator =(pid_t pid);
    operator pid_t();
    int kill();
    int wait();

    void setSeparatePG(bool separatePG);
    void setKillSignal(int signal);
    pid_t release();
};


/* Kill all processes running under the specified uid by sending them
   a SIGKILL. */
void killUser(uid_t uid);


/* Fork a process that runs the given function, and return the child
   pid to the caller. */
struct ProcessOptions
{
    string errorPrefix = "error: ";
    bool dieWithParent = true;
    bool runExitHandlers = false;
    bool allowVfork = true;
};

pid_t startProcess(std::function<void()> fun, const ProcessOptions &