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diff third_party/libuv/docs/src/misc.rst @ 160:948de3f54cea
[ThirdParty] Added libuv
| author | June Park <parkjune1995@gmail.com> |
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| date | Wed, 14 Jan 2026 19:39:52 -0800 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/third_party/libuv/docs/src/misc.rst Wed Jan 14 19:39:52 2026 -0800 @@ -0,0 +1,940 @@ + +.. _misc: + +Miscellaneous utilities +======================= + +This section contains miscellaneous functions that don't really belong in any +other section. + + +Data types +---------- + +.. c:type:: uv_buf_t + + Buffer data type. + + .. c:member:: char* uv_buf_t.base + + Pointer to the base of the buffer. + + .. c:member:: size_t uv_buf_t.len + + Total bytes in the buffer. + + .. note:: + On Windows this field is ULONG. + +.. c:type:: void* (*uv_malloc_func)(size_t size) + + Replacement function for :man:`malloc(3)`. + See :c:func:`uv_replace_allocator`. + +.. c:type:: void* (*uv_realloc_func)(void* ptr, size_t size) + + Replacement function for :man:`realloc(3)`. + See :c:func:`uv_replace_allocator`. + +.. c:type:: void* (*uv_calloc_func)(size_t count, size_t size) + + Replacement function for :man:`calloc(3)`. + See :c:func:`uv_replace_allocator`. + +.. c:type:: void (*uv_free_func)(void* ptr) + + Replacement function for :man:`free(3)`. + See :c:func:`uv_replace_allocator`. + +.. c:type:: void (*uv_random_cb)(uv_random_t* req, int status, void* buf, size_t buflen) + + Callback passed to :c:func:`uv_random`. `status` is non-zero in case of + error. The `buf` pointer is the same pointer that was passed to + :c:func:`uv_random`. + +.. c:type:: uv_file + + Cross platform representation of a file handle. + +.. c:type:: uv_os_sock_t + + Cross platform representation of a socket handle. + +.. c:type:: uv_os_fd_t + + Abstract representation of a file descriptor. On Unix systems this is a + `typedef` of `int` and on Windows a `HANDLE`. + +.. c:type:: uv_pid_t + + Cross platform representation of a `pid_t`. + + .. versionadded:: 1.16.0 + +.. c:type:: uv_timeval_t + + Y2K38-unsafe data type for storing times with microsecond resolution. + Will be replaced with :c:type:`uv_timeval64_t` in libuv v2.0. + + :: + + typedef struct { + long tv_sec; + long tv_usec; + } uv_timeval_t; + +.. c:type:: uv_timeval64_t + + Y2K38-safe data type for storing times with microsecond resolution. + + :: + + typedef struct { + int64_t tv_sec; + int32_t tv_usec; + } uv_timeval64_t; + +.. c:type:: uv_timespec64_t + + Y2K38-safe data type for storing times with nanosecond resolution. + + :: + + typedef struct { + int64_t tv_sec; + int32_t tv_nsec; + } uv_timespec64_t; + +.. c:enum:: uv_clock_id + + Clock source for :c:func:`uv_clock_gettime`. + + :: + + typedef enum { + UV_CLOCK_MONOTONIC, + UV_CLOCK_REALTIME + } uv_clock_id; + +.. c:type:: uv_rusage_t + + Data type for resource usage results. + + :: + + typedef struct { + uv_timeval_t ru_utime; /* user CPU time used */ + uv_timeval_t ru_stime; /* system CPU time used */ + uint64_t ru_maxrss; /* maximum resident set size */ + uint64_t ru_ixrss; /* integral shared memory size (X) */ + uint64_t ru_idrss; /* integral unshared data size (X) */ + uint64_t ru_isrss; /* integral unshared stack size (X) */ + uint64_t ru_minflt; /* page reclaims (soft page faults) (X) */ + uint64_t ru_majflt; /* page faults (hard page faults) */ + uint64_t ru_nswap; /* swaps (X) */ + uint64_t ru_inblock; /* block input operations */ + uint64_t ru_oublock; /* block output operations */ + uint64_t ru_msgsnd; /* IPC messages sent (X) */ + uint64_t ru_msgrcv; /* IPC messages received (X) */ + uint64_t ru_nsignals; /* signals received (X) */ + uint64_t ru_nvcsw; /* voluntary context switches (X) */ + uint64_t ru_nivcsw; /* involuntary context switches (X) */ + } uv_rusage_t; + + Members marked with `(X)` are unsupported on Windows. + See :man:`getrusage(2)` for supported fields on UNIX-like platforms. + + The maximum resident set size is reported in kilobytes, the unit most + platforms use natively. + +.. c:type:: uv_cpu_info_t + + Data type for CPU information. + + :: + + typedef struct uv_cpu_info_s { + char* model; + int speed; + struct uv_cpu_times_s { + uint64_t user; /* milliseconds */ + uint64_t nice; /* milliseconds */ + uint64_t sys; /* milliseconds */ + uint64_t idle; /* milliseconds */ + uint64_t irq; /* milliseconds */ + } cpu_times; + } uv_cpu_info_t; + +.. c:type:: uv_interface_address_t + + Data type for interface addresses. + + :: + + typedef struct uv_interface_address_s { + char* name; + char phys_addr[6]; + int is_internal; + union { + struct sockaddr_in address4; + struct sockaddr_in6 address6; + } address; + union { + struct sockaddr_in netmask4; + struct sockaddr_in6 netmask6; + } netmask; + } uv_interface_address_t; + +.. c:type:: uv_passwd_t + + Data type for password file information. + + :: + + typedef struct uv_passwd_s { + char* username; + long uid; + long gid; + char* shell; + char* homedir; + } uv_passwd_t; + +.. c:type:: uv_group_t + + Data type for group file information. + + :: + + typedef struct uv_group_s { + char* groupname; + unsigned long gid; + char** members; + } uv_group_t; + +.. c:type:: uv_utsname_t + + Data type for operating system name and version information. + + :: + + typedef struct uv_utsname_s { + char sysname[256]; + char release[256]; + char version[256]; + char machine[256]; + } uv_utsname_t; + +.. c:type:: uv_env_item_t + + Data type for environment variable storage. + + :: + + typedef struct uv_env_item_s { + char* name; + char* value; + } uv_env_item_t; + +.. c:type:: uv_random_t + + Random data request type. + +API +--- + +.. c:function:: uv_handle_type uv_guess_handle(uv_file file) + + Used to detect what type of stream should be used with a given file + descriptor. Usually this will be used during initialization to guess the + type of the stdio streams. + + For :man:`isatty(3)` equivalent functionality use this function and test + for `UV_TTY`. + +.. c:function:: int uv_replace_allocator(uv_malloc_func malloc_func, uv_realloc_func realloc_func, uv_calloc_func calloc_func, uv_free_func free_func) + + .. versionadded:: 1.6.0 + + Override the use of the standard library's :man:`malloc(3)`, + :man:`calloc(3)`, :man:`realloc(3)`, :man:`free(3)`, memory allocation + functions. + + This function must be called before any other libuv function is called or + after all resources have been freed and thus libuv doesn't reference + any allocated memory chunk. + + On success, it returns 0, if any of the function pointers is `NULL` it + returns `UV_EINVAL`. + + .. warning:: There is no protection against changing the allocator multiple + times. If the user changes it they are responsible for making + sure the allocator is changed while no memory was allocated with + the previous allocator, or that they are compatible. + + .. warning:: Allocator must be thread-safe. + +.. c:function:: void uv_library_shutdown(void); + + .. versionadded:: 1.38.0 + + Release any global state that libuv is holding onto. Libuv will normally + do so automatically when it is unloaded but it can be instructed to perform + cleanup manually. + + .. warning:: Only call :c:func:`uv_library_shutdown()` once. + + .. warning:: Don't call :c:func:`uv_library_shutdown()` when there are + still event loops or I/O requests active. + + .. warning:: Don't call libuv functions after calling + :c:func:`uv_library_shutdown()`. + +.. c:function:: uv_buf_t uv_buf_init(char* base, unsigned int len) + + Constructor for :c:type:`uv_buf_t`. + + Due to platform differences the user cannot rely on the ordering of the + `base` and `len` members of the uv_buf_t struct. The user is responsible for + freeing `base` after the uv_buf_t is done. Return struct passed by value. + +.. c:function:: char** uv_setup_args(int argc, char** argv) + + Store the program arguments. Required for getting / setting the process title + or the executable path. Libuv may take ownership of the memory that `argv` + points to. This function should be called exactly once, at program start-up. + + Example: + + :: + + argv = uv_setup_args(argc, argv); /* May return a copy of argv. */ + + +.. c:function:: int uv_get_process_title(char* buffer, size_t size) + + Gets the title of the current process. You *must* call `uv_setup_args` + before calling this function on Unix and AIX systems. If `uv_setup_args` + has not been called on systems that require it, then `UV_ENOBUFS` is + returned. If `buffer` is `NULL` or `size` is zero, `UV_EINVAL` is returned. + If `size` cannot accommodate the process title and terminating `nul` + character, the function returns `UV_ENOBUFS`. + + .. note:: + On BSD systems, `uv_setup_args` is needed for getting the initial process + title. The process title returned will be an empty string until either + `uv_setup_args` or `uv_set_process_title` is called. + + .. versionchanged:: 1.18.1 now thread-safe on all supported platforms. + + .. versionchanged:: 1.39.0 now returns an error if `uv_setup_args` is needed + but hasn't been called. + +.. c:function:: int uv_set_process_title(const char* title) + + Sets the current process title. You *must* call `uv_setup_args` before + calling this function on Unix and AIX systems. If `uv_setup_args` has not + been called on systems that require it, then `UV_ENOBUFS` is returned. On + platforms with a fixed size buffer for the process title the contents of + `title` will be copied to the buffer and truncated if larger than the + available space. Other platforms will return `UV_ENOMEM` if they cannot + allocate enough space to duplicate the contents of `title`. + + .. versionchanged:: 1.18.1 now thread-safe on all supported platforms. + + .. versionchanged:: 1.39.0 now returns an error if `uv_setup_args` is needed + but hasn't been called. + +.. c:function:: int uv_resident_set_memory(size_t* rss) + + Gets the resident set size (RSS) for the current process. + +.. c:function:: int uv_uptime(double* uptime) + + Gets the current system uptime. Depending on the system full or fractional seconds are returned. + +.. c:function:: int uv_getrusage(uv_rusage_t* rusage) + + Gets the resource usage measures for the current process. + + .. note:: + On Windows not all fields are set, the unsupported fields are filled with zeroes. + See :c:type:`uv_rusage_t` for more details. + +.. c:function:: int uv_getrusage_thread(uv_rusage_t* rusage) + + Gets the resource usage measures for the calling thread. + + .. versionadded:: 1.50.0 + + .. note:: + Not supported on all platforms. May return `UV_ENOTSUP`. + On macOS and Windows not all fields are set, the unsupported fields are filled with zeroes. + See :c:type:`uv_rusage_t` for more details. + +.. c:function:: uv_pid_t uv_os_getpid(void) + + Returns the current process ID. + + .. versionadded:: 1.18.0 + +.. c:function:: uv_pid_t uv_os_getppid(void) + + Returns the parent process ID. + + .. versionadded:: 1.16.0 + +.. c:function:: unsigned int uv_available_parallelism(void) + + Returns an estimate of the default amount of parallelism a program should + use. Always returns a non-zero value. + + On Linux, inspects the calling thread's CPU affinity mask to determine if + it has been pinned to specific CPUs. + + On Windows, the available parallelism may be underreported on systems with + more than 64 logical CPUs. + + On other platforms, reports the number of CPUs that the operating system + considers to be online. + + .. versionadded:: 1.44.0 + +.. c:function:: int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count) + + Gets information about the CPUs on the system. The `cpu_infos` array will + have `count` elements and needs to be freed with :c:func:`uv_free_cpu_info`. + + Use :c:func:`uv_available_parallelism` if you need to know how many CPUs + are available for threads or child processes. + +.. c:function:: void uv_free_cpu_info(uv_cpu_info_t* cpu_infos, int count) + + Frees the `cpu_infos` array previously allocated with :c:func:`uv_cpu_info`. + +.. c:function:: int uv_cpumask_size(void) + + Returns the maximum size of the mask used for process/thread affinities, + or `UV_ENOTSUP` if affinities are not supported on the current platform. + + .. versionadded:: 1.45.0 + +.. c:function:: int uv_interface_addresses(uv_interface_address_t** addresses, int* count) + + Gets address information about the network interfaces on the system. An + array of `count` elements is allocated and returned in `addresses`. It must + be freed by the user, calling :c:func:`uv_free_interface_addresses`. + +.. c:function:: void uv_free_interface_addresses(uv_interface_address_t* addresses, int count) + + Free an array of :c:type:`uv_interface_address_t` which was returned by + :c:func:`uv_interface_addresses`. + +.. c:function:: void uv_loadavg(double avg[3]) + + Gets the load average. See: `<https://en.wikipedia.org/wiki/Load_(computing)>`_ + + .. note:: + Returns [0,0,0] on Windows (i.e., it's not implemented). + +.. c:function:: int uv_ip4_addr(const char* ip, int port, struct sockaddr_in* addr) + + Convert a string containing an IPv4 addresses to a binary structure. + +.. c:function:: int uv_ip6_addr(const char* ip, int port, struct sockaddr_in6* addr) + + Convert a string containing an IPv6 addresses to a binary structure. + +.. c:function:: int uv_ip4_name(const struct sockaddr_in* src, char* dst, size_t size) + + Convert a binary structure containing an IPv4 address to a string. + +.. c:function:: int uv_ip6_name(const struct sockaddr_in6* src, char* dst, size_t size) + + Convert a binary structure containing an IPv6 address to a string. + +.. c:function:: int uv_ip_name(const struct sockaddr *src, char *dst, size_t size) + + Convert a binary structure containing an IPv4 address or an IPv6 address to a string. + +.. c:function:: int uv_inet_ntop(int af, const void* src, char* dst, size_t size) +.. c:function:: int uv_inet_pton(int af, const char* src, void* dst) + + Cross-platform IPv6-capable implementation of :man:`inet_ntop(3)` + and :man:`inet_pton(3)`. On success they return 0. In case of error + the target `dst` pointer is unmodified. + +.. c:macro:: UV_IF_NAMESIZE + + Maximum IPv6 interface identifier name length. Defined as + `IFNAMSIZ` on Unix and `IF_NAMESIZE` on Linux and Windows. + + .. versionadded:: 1.16.0 + +.. c:function:: int uv_if_indextoname(unsigned int ifindex, char* buffer, size_t* size) + + IPv6-capable implementation of :man:`if_indextoname(3)`. When called, + `*size` indicates the length of the `buffer`, which is used to store the + result. + On success, zero is returned, `buffer` contains the interface name, and + `*size` represents the string length of the `buffer`, excluding the NUL + terminator byte from `*size`. On error, a negative result is + returned. If `buffer` is not large enough to hold the result, + `UV_ENOBUFS` is returned, and `*size` represents the necessary size in + bytes, including the NUL terminator byte into the `*size`. + + On Unix, the returned interface name can be used directly as an + interface identifier in scoped IPv6 addresses, e.g. + `fe80::abc:def1:2345%en0`. + + On Windows, the returned interface cannot be used as an interface + identifier, as Windows uses numerical interface identifiers, e.g. + `fe80::abc:def1:2345%5`. + + To get an interface identifier in a cross-platform compatible way, + use `uv_if_indextoiid()`. + + Example: + + :: + + char ifname[UV_IF_NAMESIZE]; + size_t size = sizeof(ifname); + uv_if_indextoname(sin6->sin6_scope_id, ifname, &size); + + .. versionadded:: 1.16.0 + +.. c:function:: int uv_if_indextoiid(unsigned int ifindex, char* buffer, size_t* size) + + Retrieves a network interface identifier suitable for use in an IPv6 scoped + address. On Windows, returns the numeric `ifindex` as a string. On all other + platforms, `uv_if_indextoname()` is called. The result is written to + `buffer`, with `*size` indicating the length of `buffer`. If `buffer` is not + large enough to hold the result, then `UV_ENOBUFS` is returned, and `*size` + represents the size, including the NUL byte, required to hold the + result. + + See `uv_if_indextoname` for further details. + + .. versionadded:: 1.16.0 + +.. c:function:: int uv_exepath(char* buffer, size_t* size) + + Gets the executable path. You *must* call `uv_setup_args` before calling + this function. + +.. c:function:: int uv_cwd(char* buffer, size_t* size) + + Gets the current working directory, and stores it in `buffer`. If the + current working directory is too large to fit in `buffer`, this function + returns `UV_ENOBUFS`, and sets `size` to the required length, including the + null terminator. + + .. versionchanged:: 1.1.0 + + On Unix the path no longer ends in a slash. + + .. versionchanged:: 1.9.0 the returned length includes the terminating null + byte on `UV_ENOBUFS`, and the buffer is null terminated + on success. + + +.. c:function:: int uv_chdir(const char* dir) + + Changes the current working directory. + +.. c:function:: int uv_os_homedir(char* buffer, size_t* size) + + Gets the current user's home directory. On Windows, `uv_os_homedir()` first + checks the `USERPROFILE` environment variable using + `GetEnvironmentVariableW()`. If `USERPROFILE` is not set, + `GetUserProfileDirectoryW()` is called. On all other operating systems, + `uv_os_homedir()` first checks the `HOME` environment variable using + :man:`getenv(3)`. If `HOME` is not set, :man:`getpwuid_r(3)` is called. The + user's home directory is stored in `buffer`. When `uv_os_homedir()` is + called, `size` indicates the maximum size of `buffer`. On success `size` is set + to the string length of `buffer`. On `UV_ENOBUFS` failure `size` is set to the + required length for `buffer`, including the null byte. + + .. warning:: + `uv_os_homedir()` is not thread safe. + + .. versionadded:: 1.6.0 + +.. c:function:: int uv_os_tmpdir(char* buffer, size_t* size) + + Gets the temp directory. On Windows, `uv_os_tmpdir()` uses `GetTempPathW()`. + On all other operating systems, `uv_os_tmpdir()` uses the first environment + variable found in the ordered list `TMPDIR`, `TMP`, `TEMP`, and `TEMPDIR`. + If none of these are found, the path `"/tmp"` is used, or, on Android, + `"/data/local/tmp"` is used. The temp directory is stored in `buffer`. When + `uv_os_tmpdir()` is called, `size` indicates the maximum size of `buffer`. + On success `size` is set to the string length of `buffer` (which does not + include the terminating null). On `UV_ENOBUFS` failure `size` is set to the + required length for `buffer`, including the null byte. + + .. warning:: + `uv_os_tmpdir()` is not thread safe. + + .. versionadded:: 1.9.0 + +.. c:function:: int uv_os_get_passwd(uv_passwd_t* pwd) + + Gets a subset of the password file entry for the current effective uid (not + the real uid). The populated data includes the username, euid, gid, shell, + and home directory. On non-Windows systems, all data comes from + :man:`getpwuid_r(3)`. On Windows, uid and gid are set to -1 and have no + meaning, and shell is `NULL`. After successfully calling this function, the + memory allocated to `pwd` needs to be freed with + :c:func:`uv_os_free_passwd`. + + .. versionadded:: 1.9.0 + +.. c:function:: int uv_os_get_passwd2(uv_passwd_t* pwd, uv_uid_t uid) + + Gets a subset of the password file entry for the provided uid. + The populated data includes the username, euid, gid, shell, + and home directory. On non-Windows systems, all data comes from + :man:`getpwuid_r(3)`. On Windows, uid and gid are set to -1 and have no + meaning, and shell is `NULL`. After successfully calling this function, the + memory allocated to `pwd` needs to be freed with + :c:func:`uv_os_free_passwd`. + + .. versionadded:: 1.45.0 + +.. c:function:: int uv_os_get_group(uv_group_t* group, uv_uid_t gid) + + Gets a subset of the group file entry for the provided uid. + The populated data includes the group name, gid, and members. On non-Windows + systems, all data comes from :man:`getgrgid_r(3)`. On Windows, uid and gid + are set to -1 and have no meaning. After successfully calling this function, + the memory allocated to `group` needs to be freed with + :c:func:`uv_os_free_group`. + + .. versionadded:: 1.45.0 + +.. c:function:: void uv_os_free_group(uv_passwd_t* pwd) + + Frees the memory previously allocated with :c:func:`uv_os_get_group`. + + .. versionadded:: 1.45.0 + +.. c:function:: void uv_os_free_passwd(uv_passwd_t* pwd) + + Frees the `pwd` memory previously allocated with :c:func:`uv_os_get_passwd`. + + .. versionadded:: 1.9.0 + +.. c:function:: uint64_t uv_get_free_memory(void) + + Gets the amount of free memory available in the system, as reported by + the kernel (in bytes). Returns 0 when unknown. + +.. c:function:: uint64_t uv_get_total_memory(void) + + Gets the total amount of physical memory in the system (in bytes). + Returns 0 when unknown. + +.. c:function:: uint64_t uv_get_constrained_memory(void) + + Gets the total amount of memory available to the process (in bytes) based on + limits imposed by the OS. If there is no such constraint, or the constraint + is unknown, `0` is returned. If there is a constraining mechanism, but there + is no constraint set, `UINT64_MAX` is returned. Note that it is not unusual + for this value to be less than or greater than :c:func:`uv_get_total_memory`. + + .. note:: + This function currently only returns a non-zero value on Linux, based + on cgroups if it is present, and on z/OS based on RLIMIT_MEMLIMIT. + + .. versionadded:: 1.29.0 + +.. c:function:: uint64_t uv_get_available_memory(void) + + Gets the amount of free memory that is still available to the process (in bytes). + This differs from :c:func:`uv_get_free_memory` in that it takes into account any + limits imposed by the OS. If there is no such constraint, or the constraint + is unknown, the amount returned will be identical to :c:func:`uv_get_free_memory`. + + .. note:: + This function currently only returns a value that is different from + what :c:func:`uv_get_free_memory` reports on Linux, based + on cgroups if it is present. + + .. versionadded:: 1.45.0 + +.. c:function:: uint64_t uv_hrtime(void) + + Returns the current high-resolution timestamp. This is expressed in + nanoseconds. It is relative to an arbitrary time in the past. It is not + related to the time of day and therefore not subject to clock drift. The + primary use is for measuring performance between intervals. + + .. note:: + Not every platform can support nanosecond resolution; however, this value will always + be in nanoseconds. + +.. c:function:: int uv_clock_gettime(uv_clock_id clock_id, uv_timespec64_t* ts) + + Obtain the current system time from a high-resolution real-time or monotonic + clock source. + + The real-time clock counts from the UNIX epoch (1970-01-01) and is subject + to time adjustments; it can jump back in time. + + The monotonic clock counts from an arbitrary point in the past and never + jumps back in time. + + .. versionadded:: 1.45.0 + +.. c:function:: void uv_print_all_handles(uv_loop_t* loop, FILE* stream) + + Prints all handles associated with the given `loop` to the given `stream`. + + Example: + + :: + + uv_print_all_handles(uv_default_loop(), stderr); + /* + [--I] signal 0x1a25ea8 + [-AI] async 0x1a25cf0 + [R--] idle 0x1a7a8c8 + */ + + The format is `[flags] handle-type handle-address`. For `flags`: + + - `R` is printed for a handle that is referenced + - `A` is printed for a handle that is active + - `I` is printed for a handle that is internal + + .. warning:: + This function is meant for ad hoc debugging, there is no API/ABI + stability guarantees. + + .. versionadded:: 1.8.0 + +.. c:function:: void uv_print_active_handles(uv_loop_t* loop, FILE* stream) + + This is the same as :c:func:`uv_print_all_handles` except only active handles + are printed. + + .. warning:: + This function is meant for ad hoc debugging, there is no API/ABI + stability guarantees. + + .. versionadded:: 1.8.0 + +.. c:function:: int uv_os_environ(uv_env_item_t** envitems, int* count) + + Retrieves all environment variables. This function will allocate memory + which must be freed by calling :c:func:`uv_os_free_environ`. + + .. warning:: + This function is not thread safe. + + .. versionadded:: 1.31.0 + +.. c:function:: void uv_os_free_environ(uv_env_item_t* envitems, int count); + + Frees the memory allocated for the environment variables by + :c:func:`uv_os_environ`. + + .. versionadded:: 1.31.0 + +.. c:function:: int uv_os_getenv(const char* name, char* buffer, size_t* size) + + Retrieves the environment variable specified by `name`, copies its value + into `buffer`, and sets `size` to the string length of the value. When + calling this function, `size` must be set to the amount of storage available + in `buffer`, including the null terminator. If the environment variable + exceeds the storage available in `buffer`, `UV_ENOBUFS` is returned, and + `size` is set to the amount of storage required to hold the value. If no + matching environment variable exists, `UV_ENOENT` is returned. + + .. warning:: + This function is not thread safe. + + .. versionadded:: 1.12.0 + +.. c:function:: int uv_os_setenv(const char* name, const char* value) + + Creates or updates the environment variable specified by `name` with + `value`. + + .. warning:: + This function is not thread safe. + + .. versionadded:: 1.12.0 + +.. c:function:: int uv_os_unsetenv(const char* name) + + Deletes the environment variable specified by `name`. If no such environment + variable exists, this function returns successfully. + + .. warning:: + This function is not thread safe. + + .. versionadded:: 1.12.0 + +.. c:function:: int uv_os_gethostname(char* buffer, size_t* size) + + Returns the hostname as a null-terminated string in `buffer`, and sets + `size` to the string length of the hostname. When calling this function, + `size` must be set to the amount of storage available in `buffer`, including + the null terminator. If the hostname exceeds the storage available in + `buffer`, `UV_ENOBUFS` is returned, and `size` is set to the amount of + storage required to hold the value. + + .. versionadded:: 1.12.0 + + .. versionchanged:: 1.26.0 `UV_MAXHOSTNAMESIZE` is available and represents + the maximum `buffer` size required to store a + hostname and terminating `nul` character. + +.. c:function:: int uv_os_getpriority(uv_pid_t pid, int* priority) + + Retrieves the scheduling priority of the process specified by `pid`. The + returned value of `priority` is between -20 (high priority) and 19 (low + priority). + + .. note:: + On Windows, the returned priority will equal one of the `UV_PRIORITY` + constants. + + .. versionadded:: 1.23.0 + +.. c:function:: int uv_os_setpriority(uv_pid_t pid, int priority) + + Sets the scheduling priority of the process specified by `pid`. The + `priority` value range is between -20 (high priority) and 19 (low priority). + The constants `UV_PRIORITY_LOW`, `UV_PRIORITY_BELOW_NORMAL`, + `UV_PRIORITY_NORMAL`, `UV_PRIORITY_ABOVE_NORMAL`, `UV_PRIORITY_HIGH`, and + `UV_PRIORITY_HIGHEST` are also provided for convenience. + + .. note:: + On Windows, this function utilizes `SetPriorityClass()`. The `priority` + argument is mapped to a Windows priority class. When retrieving the + process priority, the result will equal one of the `UV_PRIORITY` + constants, and not necessarily the exact value of `priority`. + + .. note:: + On Windows, setting `PRIORITY_HIGHEST` will only work for elevated user, + for others it will be silently reduced to `PRIORITY_HIGH`. + + .. note:: + On IBM i PASE, the highest process priority is -10. The constant + `UV_PRIORITY_HIGHEST` is -10, `UV_PRIORITY_HIGH` is -7, + `UV_PRIORITY_ABOVE_NORMAL` is -4, `UV_PRIORITY_NORMAL` is 0, + `UV_PRIORITY_BELOW_NORMAL` is 15 and `UV_PRIORITY_LOW` is 39. + + .. note:: + On IBM i PASE, you are not allowed to change your priority unless you + have the \*JOBCTL special authority (even to lower it). + + .. versionadded:: 1.23.0 + +.. c:function:: int uv_os_uname(uv_utsname_t* buffer) + + Retrieves system information in `buffer`. The populated data includes the + operating system name, release, version, and machine. On non-Windows + systems, `uv_os_uname()` is a thin wrapper around :man:`uname(2)`. Returns + zero on success, and a non-zero error value otherwise. + + .. versionadded:: 1.25.0 + +.. c:function:: int uv_gettimeofday(uv_timeval64_t* tv) + + Cross-platform implementation of :man:`gettimeofday(2)`. The timezone + argument to `gettimeofday()` is not supported, as it is considered obsolete. + + .. versionadded:: 1.28.0 + +.. c:function:: int uv_random(uv_loop_t* loop, uv_random_t* req, void* buf, size_t buflen, unsigned int flags, uv_random_cb cb) + + Fill `buf` with exactly `buflen` cryptographically strong random bytes + acquired from the system CSPRNG. `flags` is reserved for future extension + and must currently be 0. + + Short reads are not possible. When less than `buflen` random bytes are + available, a non-zero error value is returned or passed to the callback. + + The synchronous version may block indefinitely when not enough entropy + is available. The asynchronous version may not ever finish when the system + is low on entropy. + + Sources of entropy: + + - Windows: `RtlGenRandom <https://docs.microsoft.com/en-us/windows/desktop/api/ntsecapi/nf-ntsecapi-rtlgenrandom>_`. + - Linux, Android: :man:`getrandom(2)` if available, or :man:`urandom(4)` + after reading from `/dev/random` once, or the `KERN_RANDOM` + :man:`sysctl(2)`. + - FreeBSD: `getrandom(2) <https://www.freebsd.org/cgi/man.cgi?query=getrandom&sektion=2>_`, + or `/dev/urandom` after reading from `/dev/random` once. + - NetBSD: `KERN_ARND` `sysctl(7) <https://man.netbsd.org/sysctl.7>_` + - macOS, OpenBSD: `getentropy(2) <https://man.openbsd.org/getentropy.2>_` + if available, or `/dev/urandom` after reading from `/dev/random` once. + - AIX: `/dev/random`. + - IBM i: `/dev/urandom`. + - Other UNIX: `/dev/urandom` after reading from `/dev/random` once. + + :returns: 0 on success, or an error code < 0 on failure. The contents of + `buf` is undefined after an error. + + .. note:: + When using the synchronous version, both `loop` and `req` parameters + are not used and can be set to `NULL`. + + .. versionadded:: 1.33.0 + +.. c:function:: void uv_sleep(unsigned int msec) + + Causes the calling thread to sleep for `msec` milliseconds. + + .. versionadded:: 1.34.0 + +String manipulation functions +----------------------------- + +These string utilities are needed internally for dealing with Windows, and are +exported to allow clients to work uniformly with this data when the libuv API +is not complete. + +.. c:function:: size_t uv_utf16_length_as_wtf8(const uint16_t* utf16, ssize_t utf16_len) + + Get the length of a UTF-16 (or UCS-2) `utf16` value after converting it to + WTF-8. If `utf16` is NUL terminated, `utf16_len` can be set to -1, + otherwise it must be specified. + + .. versionadded:: 1.47.0 + +.. c:function:: int uv_utf16_to_wtf8(const uint16_t* utf16, ssize_t utf16_len, char** wtf8_ptr, size_t* wtf8_len_ptr) + + Convert UTF-16 (or UCS-2) data in `utf16` to WTF-8 data in `*wtf8_ptr`. The + `utf16_len` count (in characters) gives the length of `utf16`. If `utf16` + is NUL terminated, `utf16_len` can be set to -1, otherwise it must be + specified. If `wtf8_ptr` is `NULL`, no result will be computed, but the + length (equal to `uv_utf16_length_as_wtf8`) will be stored in `wtf8_ptr`. + If `*wtf8_ptr` is `NULL`, space for the conversion will be allocated and + returned in `wtf8_ptr` and the length will be returned in `wtf8_len_ptr`. + Otherwise, the length of `*wtf8_ptr` must be passed in `wtf8_len_ptr`. The + `wtf8_ptr` must contain an extra space for an extra NUL after the result. + If the result is truncated, `UV_ENOBUFS` will be returned and + `wtf8_len_ptr` will be the length of the required `wtf8_ptr` to contain the + whole result. + + .. versionadded:: 1.47.0 + +.. c:function:: ssize_t uv_wtf8_length_as_utf16(const char* wtf8) + + Get the length in characters of a NUL-terminated WTF-8 `wtf8` value + after converting it to UTF-16 (or UCS-2), including NUL terminator. + + .. versionadded:: 1.47.0 + +.. c:function:: void uv_wtf8_to_utf16(const char* utf8, uint16_t* utf16, size_t utf16_len) + + Convert NUL-terminated WTF-8 data in `wtf8` to UTF-16 (or UCS-2) data + in `utf16`. The `utf16_len` count (in characters) must include space + for the NUL terminator. + + .. versionadded:: 1.47.0