uvwasi

uvwasi implements the WASI system call API, so that WebAssembly runtimes can easily implement WASI calls. Under the hood, uvwasi leverages libuv where possible for maximum portability.

                              |
WebAssembly code              |      WebAssembly application code
                              |                 |
                              |                 v
                              | WASI syscalls (inserted by compiler toolchain)
                              |                 |
------------------------------+                 |
                              |                 v
WebAssembly runtime (Node.js) |    uvwasi (implementation of WASI)
                              |                 |
                              |                 v
                              |               libuv
                              |                 |
                              |                 v
                              |        platform-specific calls
                              |

(Hence uvwasi isn't for making C-programs-that-use-libuv-APIs execute on WASI runtimes. That would either be a new platform added by libuv, or done through POSIX emulation by the Emscripten or wasi-sdk toolchains.)

Building Locally

To build with CMake:

$ mkdir -p out/cmake ; cd out/cmake   # create build directory
$ cmake ../.. -DBUILD_TESTING=ON      # generate project with test
$ cmake --build .                     # build
$ ctest -C Debug --output-on-failure  # run tests

Example Usage

#include <stdlib.h>
#include <assert.h>
#include "uv.h"
#include "uvwasi.h"

int main(void) {
  uvwasi_t uvwasi;
  uvwasi_options_t init_options;
  uvwasi_errno_t err;

  /* Setup the initialization options. */
  init_options.in = 0;
  init_options.out = 1;
  init_options.err = 2;
  init_options.fd_table_size = 3;
  init_options.argc = 3;
  init_options.argv = calloc(3, sizeof(char*));
  init_options.argv[0] = "--foo=bar";
  init_options.argv[1] = "-baz";
  init_options.argv[2] = "100";
  init_options.envp = NULL;
  init_options.preopenc = 1;
  init_options.preopens = calloc(1, sizeof(uvwasi_preopen_t));
  init_options.preopens[0].mapped_path = "/var";
  init_options.preopens[0].real_path = ".";
  init_options.allocator = NULL;

  /* Initialize the sandbox. */
  err = uvwasi_init(&uvwasi, &init_options);
  assert(err == UVWASI_ESUCCESS);

  /* TODO(cjihrig): Show an example system call or two. */

  /* Clean up resources. */
  uvwasi_destroy(&uvwasi);
  return 0;
}

API

The WASI API is versioned. This documentation is based on the WASI preview 1 snapshot. uvwasi implements the WASI system call API with the following additions/modifications:

• Each system call takes an additional uvwasi_t* as its first argument. The uvwasi_t is the sandbox under which system calls are issued. Each uvwasi_t can have different command line arguments, environment variables, preopened directories, file descriptor mappings, etc. This allows one controlling process to host multiple WASI applications simultaneously.
• Each system call returns a uvwasi_errno_t. This appears to be expected of WASI system calls, but it is not explicitly part of the official API docs. This detail is explicitly documented here.
• Additional functions and data types are provided for interacting with WASI sandboxes and the uvwasi library. These APIs are documented in the Unofficial APIs section below.

Unofficial APIs

This section contains data types and functions for working with uvwasi. They are not part of the official WASI API, but are used to embed uvwasi.

UVWASI_VERSION_MAJOR

The major release version of the uvwasi library. uvwasi follows semantic versioning. Changes to this value represent breaking changes in the public API.

UVWASI_VERSION_MINOR

The minor release version of the uvwasi library. uvwasi follows semantic versioning. Changes to this value represent feature additions in the public API.

UVWASI_VERSION_PATCH

The patch release version of the uvwasi library. uvwasi follows semantic versioning. Changes to this value represent bug fixes in the public API.

UVWASI_VERSION_HEX

The major, minor, and patch versions of the uvwasi library encoded as a single integer value.

UVWASI_VERSION_STRING

The major, minor, and patch versions of the uvwasi library encoded as a version string.

UVWASI_VERSION_WASI

The version of the WASI API targeted by uvwasi.

uvwasi_t

An individual WASI sandbox instance.

typedef struct uvwasi_s {
  struct uvwasi_fd_table_t fds;
  uvwasi_size_t argc;
  char** argv;
  char* argv_buf;
  uvwasi_size_t argv_buf_size;
  uvwasi_size_t envc;
  char** env;
  char* env_buf;
  uvwasi_size_t env_buf_size;
} uvwasi_t;

uvwasi_preopen_t

A data structure used to map a directory path within a WASI sandbox to a directory path on the WASI host platform.

typedef struct uvwasi_preopen_s {
  char* mapped_path;
  char* real_path;
} uvwasi_preopen_t;

uvwasi_options_t

A data structure used to pass configuration options to uvwasi_init().

typedef struct uvwasi_options_s {
  uvwasi_size_t fd_table_size;
  uvwasi_size_t preopenc;
  uvwasi_preopen_t* preopens;
  uvwasi_size_t argc;
  char** argv;
  char** envp;
  uvwasi_fd_t in;
  uvwasi_fd_t out;
  uvwasi_fd_t err;
  const uvwasi_mem_t* allocator;
} uvwasi_options_t;

uvwasi_init()

Initializes a sandbox represented by a uvwasi_t using the options represented by a uvwasi_options_t.

Inputs:

• __wasi_t uvwasi

  The sandbox to initialize.

• __wasi_options_t options

  Configuration options used when initializing the sandbox.

Outputs:

• None

Returns:

• __wasi_errno_t errno

  A WASI errno.

uvwasi_destroy()

Cleans up resources related to a WASI sandbox. This function notably does not return an error code.

Inputs:

• __wasi_t uvwasi

  The sandbox to clean up.

Outputs:

• None

Returns:

• None

System Calls

This section has been adapted from the official WASI API documentation.

• uvwasi_args_get()
• uvwasi_args_sizes_get()
• uvwasi_clock_res_get()
• uvwasi_clock_time_get()
• uvwasi_environ_get()
• uvwasi_environ_sizes_get()
• uvwasi_fd_advise()
• uvwasi_fd_allocate()
• uvwasi_fd_close()
• uvwasi_fd_datasync()
• uvwasi_fd_fdstat_get()
• uvwasi_fd_fdstat_set_flags()
• uvwasi_fd_fdstat_set_rights()
• uvwasi_fd_filestat_get()
• uvwasi_fd_filestat_set_size()
• uvwasi_fd_filestat_set_times()
• uvwasi_fd_pread()
• uvwasi_fd_prestat_get()
• uvwasi_fd_prestat_dir_name()
• uvwasi_fd_pwrite()
• uvwasi_fd_read()
• uvwasi_fd_readdir()
• uvwasi_fd_renumber()
• uvwasi_fd_seek()
• uvwasi_fd_sync()
• uvwasi_fd_tell()
• uvwasi_fd_write()
• uvwasi_path_create_directory()
• uvwasi_path_filestat_get()
• uvwasi_path_filestat_set_times()
• uvwasi_path_link()
• uvwasi_path_open()
• uvwasi_path_readlink()
• uvwasi_path_remove_directory()
• uvwasi_path_rename()
• uvwasi_path_symlink()
• uvwasi_path_unlink_file()
• uvwasi_poll_oneoff()
• uvwasi_proc_exit()
• uvwasi_proc_raise()
• uvwasi_random_get()
• uvwasi_sched_yield()
• uvwasi_sock_recv()
• uvwasi_sock_send()
• uvwasi_sock_shutdown()

uvwasi_args_get()

Read command-line argument data.

The sizes of the buffers should match that returned by uvwasi_args_sizes_get().

Inputs:

• char **argv

  A pointer to a buffer to write the argument pointers.

• char *argv_buf

  A pointer to a buffer to write the argument string data.

uvwasi_args_sizes_get()

Return command-line argument data sizes.

Outputs:

• __wasi_size_t *argc

  The number of arguments.

• __wasi_size_t *argv_buf_size

  The size of the argument string data.

uvwasi_clock_res_get()

Return the resolution of a clock.

Implementations are required to provide a non-zero value for supported clocks. For unsupported clocks, return UVWASI_EINVAL.

Note: This is similar to clock_getres in POSIX.

Inputs:

• __wasi_clockid_t clock_id

  The clock for which to return the resolution.

Outputs:

• __wasi_timestamp_t resolution

  The resolution of the clock.

uvwasi_clock_time_get()

Return the time value of a clock.

Note: This is similar to clock_gettime in POSIX.

Inputs:

• __wasi_clockid_t clock_id

  The clock for which to return the time.

• __wasi_timestamp_t precision

  The maximum lag (exclusive) that the returned time value may have, compared to its actual value.

Outputs:

• __wasi_timestamp_t time

  The time value of the clock.

uvwasi_environ_get()

Read environment variable data.

The sizes of the buffers should match that returned by uvwasi_environ_sizes_get().

Inputs:

• char **environ

  A pointer to a buffer to write the environment variable pointers.

• char *environ_buf

  A pointer to a buffer to write the environment variable string data.

uvwasi_environ_sizes_get()

Return command-line argument data sizes.

Outputs:

• __wasi_size_t *environ_count

  The number of environment variables.

• __wasi_size_t *environ_buf_size

  The size of the environment variable string data.

uvwasi_fd_advise()

Provide file advisory information on a file descriptor.

Note: This is similar to posix_fadvise in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor for the file for which to provide file advisory information.

• __wasi_filesize_t offset

  The offset within the file to which the advisory applies.

• __wasi_filesize_t len

  The length of the region to which the advisory applies.

• __wasi_advice_t advice

  The advice.

uvwasi_fd_allocate()

Force the allocation of space in a file.

Note: This is similar to posix_fallocate in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor for the file in which to allocate space.

• __wasi_filesize_t offset

  The offset at which to start the allocation.

• __wasi_filesize_t len

  The length of the area that is allocated.

uvwasi_fd_close()

Close a file descriptor.

Note: This is similar to close in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to close.

uvwasi_fd_datasync()

Synchronize the data of a file to disk.

Note: This is similar to fdatasync in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor of the file to synchronize to disk.

uvwasi_fd_fdstat_get()

Get the attributes of a file descriptor.

Note: This returns similar flags to fsync(fd, F_GETFL) in POSIX, as well as additional fields.

Inputs:

• __wasi_fd_t fd

  The file descriptor to inspect.

• __wasi_fdstat_t *buf

  The buffer where the file descriptor's attributes are stored.

uvwasi_fd_fdstat_set_flags()

Adjust the flags associated with a file descriptor.

Note: This is similar to fcntl(fd, F_SETFL, flags) in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to operate on.

• __wasi_fdflags_t flags

  The desired values of the file descriptor flags.

uvwasi_fd_fdstat_set_rights()

Adjust the rights associated with a file descriptor.

This can only be used to remove rights, and returns UVWASI_ENOTCAPABLE if called in a way that would attempt to add rights.

Inputs:

• __wasi_fd_t fd

  The file descriptor to operate on.

• __wasi_rights_t fs_rights_base and __wasi_rights_t fs_rights_inheriting

  The desired rights of the file descriptor.

uvwasi_fd_filestat_get()

Return the attributes of an open file.

Inputs:

• __wasi_fd_t fd

  The file descriptor to inspect.

• __wasi_filestat_t *buf

  The buffer where the file's attributes are stored.

uvwasi_fd_filestat_set_size()

Adjust the size of an open file. If this increases the file's size, the extra bytes are filled with zeros.

Note: This is similar to ftruncate in POSIX.

Inputs:

• __wasi_fd_t fd

  A file descriptor for the file to adjust.

• __wasi_filesize_t st_size

  The desired file size.

uvwasi_fd_filestat_set_times()

Adjust the timestamps of an open file or directory.

Note: This is similar to futimens in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to operate on.

• __wasi_timestamp_t st_atim

  The desired values of the data access timestamp.

• __wasi_timestamp_t st_mtim

  The desired values of the data modification timestamp.

• __wasi_fstflags_t fst_flags

  A bitmask indicating which timestamps to adjust.

uvwasi_fd_pread()

Read from a file descriptor, without using and updating the file descriptor's offset.

Note: This is similar to preadv in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor from which to read data.

• const __wasi_iovec_t *iovs and __wasi_size_t iovs_len

  List of scatter/gather vectors in which to store data.

• __wasi_filesize_t offset

  The offset within the file at which to read.

Outputs:

• __wasi_size_t nread

  The number of bytes read.

uvwasi_fd_prestat_get()

Return a description of the given preopened file descriptor.

Inputs:

• __wasi_fd_t fd

  The file descriptor about which to retrieve information.

• __wasi_prestat_t *buf

  The buffer where the description is stored.

uvwasi_fd_prestat_dir_name()

Return a description of the given preopened file descriptor.

Inputs:

• __wasi_fd_t fd

  The file descriptor about which to retrieve information.

• const char *path and __wasi_size_t path_len

  A buffer into which to write the preopened directory name.

uvwasi_fd_pwrite()

Write to a file descriptor, without using and updating the file descriptor's offset.

Note: This is similar to pwritev in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to which to write data.

• const __wasi_ciovec_t *iovs and __wasi_size_t iovs_len

  List of scatter/gather vectors from which to retrieve data.

• __wasi_filesize_t offset

  The offset within the file at which to write.

Outputs:

• __wasi_size_t nwritten

  The number of bytes written.

uvwasi_fd_read()

Read from a file descriptor.

Note: This is similar to readv in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor from which to read data.

• const __wasi_iovec_t *iovs and __wasi_size_t iovs_len

  List of scatter/gather vectors to which to store data.

Outputs:

• __wasi_size_t nread

  The number of bytes read.

uvwasi_fd_readdir()

Read directory entries from a directory.

When successful, the contents of the output buffer consist of a sequence of directory entries. Each directory entry consists of a uvwasi_dirent_t object, followed by uvwasi_dirent_t::d_namlen bytes holding the name of the directory entry.

This function fills the output buffer as much as possible, potentially truncating the last directory entry. This allows the caller to grow its read buffer size in case it's too small to fit a single large directory entry, or skip the oversized directory entry.

Inputs:

• __wasi_fd_t fd

  The directory from which to read the directory entries.

• void *buf and __wasi_size_t buf_len

  The buffer where directory entries are stored.

• __wasi_dircookie_t cookie

  The location within the directory to start reading.

Outputs:

• __wasi_size_t bufused

  The number of bytes stored in the read buffer. If less than the size of the read buffer, the end of the directory has been reached.

uvwasi_fd_renumber()

Atomically replace a file descriptor by renumbering another file descriptor.

Due to the strong focus on thread safety, this environment does not provide a mechanism to duplicate or renumber a file descriptor to an arbitrary number, like dup2(). This would be prone to race conditions, as an actual file descriptor with the same number could be allocated by a different thread at the same time.

This function provides a way to atomically renumber file descriptors, which would disappear if dup2() were to be removed entirely.

Inputs:

• __wasi_fd_t from

  The file descriptor to renumber.

• __wasi_fd_t to

  The file descriptor to overwrite.

uvwasi_fd_seek()

Move the offset of a file descriptor.

Note: This is similar to lseek in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to operate on.

• __wasi_filedelta_t offset

  The number of bytes to move.

• __wasi_whence_t whence

  The base from which the offset is relative.

Outputs:

• __wasi_filesize_t newoffset

  The new offset of the file descriptor, relative to the start of the file.

uvwasi_fd_sync()

Synchronize the data and metadata of a file to disk.

Note: This is similar to fsync in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor of the file containing the data and metadata to synchronize to disk.

uvwasi_fd_tell()

Return the current offset of a file descriptor.

Note: This is similar to lseek(fd, 0, SEEK_CUR) in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to inspect.

Outputs:

• __wasi_filesize_t offset

  The current offset of the file descriptor, relative to the start of the file.

uvwasi_fd_write()

Write to a file descriptor.

Note: This is similar to writev in POSIX.

Inputs:

• __wasi_fd_t fd

  The file descriptor to which to write data.

• const __wasi_ciovec_t *iovs and __wasi_size_t iovs_len

  List of scatter/gather vectors from which to retrieve data.

Outputs:

• __wasi_size_t nwritten

  The number of bytes written.

uvwasi_path_create_directory()

Create a directory.

Note: This is similar to mkdirat in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *path and __wasi_size_t path_len

  The path at which to create the directory.

uvwasi_path_filestat_get()

Return the attributes of a file or directory.

Note: This is similar to stat in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• __wasi_lookupflags_t flags

  Flags determining the method of how the path is resolved.

• const char *path and __wasi_size_t path_len

  The path of the file or directory to inspect.

• __wasi_filestat_t *buf

  The buffer where the file's attributes are stored.

uvwasi_path_filestat_set_times()

Adjust the timestamps of a file or directory.

Note: This is similar to utimensat in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• __wasi_lookupflags_t flags

  Flags determining the method of how the path is resolved.

• const char *path and __wasi_size_t path_len

  The path of the file or directory to operate on.

• __wasi_timestamp_t st_atim

  The desired values of the data access timestamp.

• __wasi_timestamp_t st_mtim

  The desired values of the data modification timestamp.

• __wasi_fstflags_t fst_flags

  A bitmask indicating which timestamps to adjust.

uvwasi_path_link()

Create a hard link.

Note: This is similar to linkat in POSIX.

Inputs:

• __wasi_fd_t old_fd

  The working directory at which the resolution of the old path starts.

• __wasi_lookupflags_t old_flags

  Flags determining the method of how the path is resolved.

• const char *old_path and __wasi_size_t old_path_len

  The source path from which to link.

• __wasi_fd_t new_fd

  The working directory at which the resolution of the new path starts.

• const char *new_path and __wasi_size_t new_path_len

  The destination path at which to create the hard link.

uvwasi_path_open()

Open a file or directory.

The returned file descriptor is not guaranteed to be the lowest-numbered file descriptor not currently open; it is randomized to prevent applications from depending on making assumptions about indexes, since this is error-prone in multi-threaded contexts. The returned file descriptor is guaranteed to be less than 2³¹.

Note: This is similar to openat in POSIX.

Inputs:

• __wasi_fd_t dirfd

  The working directory at which the resolution of the path starts.

• __wasi_lookupflags_t dirflags

  Flags determining the method of how the path is resolved.

• const char *path and __wasi_size_t path_len

  The relative path of the file or directory to open, relative to the dirfd directory.

• __wasi_oflags_t o_flags

  The method by which to open the file.

• __wasi_rights_t fs_rights_base and __wasi_rights_t fs_rights_inheriting

  The initial rights of the newly created file descriptor. The implementation is allowed to return a file descriptor with fewer rights than specified, if and only if those rights do not apply to the type of file being opened.

  The base rights are rights that will apply to operations using the file descriptor itself, while the inheriting rights are rights that apply to file descriptors derived from it.

• __wasi_fdflags_t fs_flags

  The initial flags of the file descriptor.

Outputs:

• __wasi_fd_t fd

  The file descriptor of the file that has been opened.

uvwasi_path_readlink()

Read the contents of a symbolic link.

Note: This is similar to readlinkat in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *path and __wasi_size_t path_len

  The path of the symbolic link from which to read.

• char *buf and __wasi_size_t buf_len

  The buffer to which to write the contents of the symbolic link.

Outputs:

• __wasi_size_t bufused

  The number of bytes placed in the buffer.

uvwasi_path_remove_directory()

Remove a directory.

Return UVWASI_ENOTEMPTY if the directory is not empty.

Note: This is similar to unlinkat(fd, path, AT_REMOVEDIR) in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *path and __wasi_size_t path_len

  The path to a directory to remove.

uvwasi_path_rename()

Rename a file or directory.

Note: This is similar to renameat in POSIX.

Inputs:

• __wasi_fd_t old_fd

  The working directory at which the resolution of the old path starts.

• const char *old_path and __wasi_size_t old_path_len

  The source path of the file or directory to rename.

• __wasi_fd_t new_fd

  The working directory at which the resolution of the new path starts.

• const char *new_path and __wasi_size_t new_path_len

  The destination path to which to rename the file or directory.

uvwasi_path_symlink()

Create a symbolic link.

Note: This is similar to symlinkat in POSIX.

Inputs:

• const char *old_path and __wasi_size_t old_path_len

  The contents of the symbolic link.

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *new_path and __wasi_size_t new_path_len

  The destination path at which to create the symbolic link.

uvwasi_path_unlink_file()

Unlink a file.

Return UVWASI_EISDIR if the path refers to a directory.

Note: This is similar to unlinkat(fd, path, 0) in POSIX.

Inputs:

• __wasi_fd_t fd

  The working directory at which the resolution of the path starts.

• const char *path and __wasi_size_t path_len

  The path to a file to unlink.

uvwasi_poll_oneoff()

Concurrently poll for the occurrence of a set of events.

Inputs:

• const __wasi_subscription_t *in

  The events to which to subscribe.

• __wasi_event_t *out

  The events that have occurred.

• __wasi_size_t nsubscriptions

  Both the number of subscriptions and events.

Outputs:

• __wasi_size_t nevents

  The number of events stored.

uvwasi_proc_exit()

Terminate the process normally. An exit code of 0 indicates successful termination of the program. The meanings of other values is dependent on the environment.

Note: This is similar to _Exit in POSIX.

Inputs:

• __wasi_exitcode_t rval

  The exit code returned by the process.

Does not return.

uvwasi_proc_raise()

Send a signal to the process of the calling thread.

Note: This is similar to raise in POSIX.

Inputs:

• __wasi_signal_t sig

  The signal condition to trigger.

uvwasi_random_get()

Write high-quality random data into a buffer.

This function blocks when the implementation is unable to immediately provide sufficient high-quality random data.

This function may execute slowly, so when large mounts of random data are required, it's advisable to use this function to seed a pseudo-random number generator, rather than to provide the random data directly.

Inputs:

• void *buf and __wasi_size_t buf_len

  The buffer to fill with random data.

uvwasi_sched_yield()

Temporarily yield execution of the calling thread.

Note: This is similar to sched_yield in POSIX.

uvwasi_sock_recv()

Receive a message from a socket.

Note: This is similar to recv in POSIX, though it also supports reading the data into multiple buffers in the manner of readv.

Inputs:

• __wasi_fd_t sock

  The socket on which to receive data.

• const __wasi_iovec_t *ri_data and __wasi_size_t ri_data_len

  List of scatter/gather vectors to which to store data.

• __wasi_riflags_t ri_flags

  Message flags.

Outputs:

• __wasi_size_t ro_datalen

  Number of bytes stored in ri_data.

• __wasi_roflags_t ro_flags

  Message flags.

uvwasi_sock_send()

Send a message on a socket.

Note: This is similar to send in POSIX, though it also supports writing the data from multiple buffers in the manner of writev.

Inputs:

• __wasi_fd_t sock

  The socket on which to send data.

• const __wasi_ciovec_t *si_data and __wasi_size_t si_data_len

  List of scatter/gather vectors to which to retrieve data

• __wasi_siflags_t si_flags

  Message flags.

Outputs:

• __wasi_size_t so_datalen

  Number of bytes transmitted.

uvwasi_sock_shutdown()

Shut down socket send and receive channels.

Note: This is similar to shutdown in POSIX.

Inputs:

• __wasi_fd_t sock

  The socket on which to shutdown channels.

• __wasi_sdflags_t how

  Which channels on the socket to shut down.

Types

uvwasi_advice_t (uint8_t)

File or memory access pattern advisory information.

Used by uvwasi_fd_advise().

Possible values:

• UVWASI_ADVICE_DONTNEED

  The application expects that it will not access the specified data in the near future.

• UVWASI_ADVICE_NOREUSE

  The application expects to access the specified data once and then not reuse it thereafter.

• UVWASI_ADVICE_NORMAL

  The application has no advice to give on its behavior with respect to the specified data.

• UVWASI_ADVICE_RANDOM

  The application expects to access the specified data in a random order.

• UVWASI_ADVICE_SEQUENTIAL

  The application expects to access the specified data sequentially from lower offsets to higher offsets.

• UVWASI_ADVICE_WILLNEED

  The application expects to access the specified data in the near future.

uvwasi_ciovec_t (struct)

A region of memory for scatter/gather writes.

Used by uvwasi_fd_pwrite(), uvwasi_fd_write(), and uvwasi_sock_send().

Members:

• const void *buf and __wasi_size_t buf_len

  The address and length of the buffer to be written.

uvwasi_clockid_t (uint32_t)

Identifiers for clocks.

Used by uvwasi_subscription_t, uvwasi_clock_res_get(), and uvwasi_clock_time_get().

Possible values:

• UVWASI_CLOCK_MONOTONIC

  The store-wide monotonic clock, which is defined as a clock measuring real time, whose value cannot be adjusted and which cannot have negative clock jumps.

  The epoch of this clock is undefined. The absolute time value of this clock therefore has no meaning.

• UVWASI_CLOCK_PROCESS_CPUTIME_ID

  The CPU-time clock associated with the current process.

• UVWASI_CLOCK_REALTIME

  The clock measuring real time. Time value zero corresponds with 1970-01-01T00:00:00Z.

• UVWASI_CLOCK_THREAD_CPUTIME_ID

  The CPU-time clock associated with the current thread.

uvwasi_device_t (uint64_t)

Identifier for a device containing a file system. Can be used in combination with uvwasi_inode_t to uniquely identify a file or directory in the filesystem.

Used by uvwasi_filestat_t.

uvwasi_dircookie_t (uint64_t)

A reference to the offset of a directory entry.

Used by uvwasi_dirent_t and uvwasi_fd_readdir().

Special values:

• UVWASI_DIRCOOKIE_START

  Permanent reference to the first directory entry within a directory.

uvwasi_dirent_t (struct)

A directory entry.

Members:

• __wasi_dircookie_t d_next

  The offset of the next directory entry stored in this directory.

• __wasi_inode_t d_ino

  The serial number of the file referred to by this directory entry.

• uint32_t d_namlen

  The length of the name of the directory entry.

• __wasi_filetype_t d_type

  The type of the file referred to by this directory entry.

uvwasi_errno_t (uint16_t)

Error codes returned by functions.

Not all of these error codes are returned by the functions provided by this API; some are used in higher-level library layers, and others are provided merely for alignment with POSIX.

Used by uvwasi_event_t.

Possible values:

• UVWASI_ESUCCESS

  No error occurred. System call completed successfully.

• UVWASI_E2BIG

  Argument list too long.

• UVWASI_EACCES

  Permission denied.

• UVWASI_EADDRINUSE

  Address in use.

• UVWASI_EADDRNOTAVAIL

  Address not available.

• UVWASI_EAFNOSUPPORT

  Address family not supported.

• UVWASI_EAGAIN

  Resource unavailable, or operation would block.

• UVWASI_EALREADY

  Connection already in progress.

• UVWASI_EBADF

  Bad file descriptor.

• UVWASI_EBADMSG

  Bad message.

• UVWASI_EBUSY

  Device or resource busy.

• UVWASI_ECANCELED

  Operation canceled.

• UVWASI_ECHILD

  No child processes.

• UVWASI_ECONNABORTED

  Connection aborted.

• UVWASI_ECONNREFUSED

  Connection refused.

• UVWASI_ECONNRESET

  Connection reset.

• UVWASI_EDEADLK

  Resource deadlock would occur.

• UVWASI_EDESTADDRREQ

  Destination address required.

• UVWASI_EDOM

  Mathematics argument out of domain of function.

• UVWASI_EDQUOT

  Reserved.

• UVWASI_EEXIST

  File exists.

• UVWASI_EFAULT

  Bad address.

• UVWASI_EFBIG

  File too large.

• UVWASI_EHOSTUNREACH

  Host is unreachable.

• UVWASI_EIDRM

  Identifier removed.

• UVWASI_EILSEQ

  Illegal byte sequence.

• UVWASI_EINPROGRESS

  Operation in progress.

• UVWASI_EINTR

  Interrupted function.

• UVWASI_EINVAL

  Invalid argument.

• UVWASI_EIO

  I/O error.

• UVWASI_EISCONN

  Socket is connected.

• UVWASI_EISDIR

  Is a directory.

• UVWASI_ELOOP

  Too many levels of symbolic links.

• UVWASI_EMFILE

  File descriptor value too large.

• UVWASI_EMLINK

  Too many links.

• UVWASI_EMSGSIZE

  Message too large.

• UVWASI_EMULTIHOP

  Reserved.

• UVWASI_ENAMETOOLONG

  Filename too long.

• UVWASI_ENETDOWN

  Network is down.

• UVWASI_ENETRESET

  Connection aborted by network.

• UVWASI_ENETUNREACH

  Network unreachable.

• UVWASI_ENFILE

  Too many files open in system.

• UVWASI_ENOBUFS

  No buffer space available.

• UVWASI_ENODEV

  No such device.

• UVWASI_ENOENT

  No such file or directory.

• UVWASI_ENOEXEC

  Executable file format error.

• UVWASI_ENOLCK

  No locks available.

• UVWASI_ENOLINK

  Reserved.

• UVWASI_ENOMEM

  Not enough space.

• UVWASI_ENOMSG

  No message of the desired type.

• UVWASI_ENOPROTOOPT

  Protocol not available.

• UVWASI_ENOSPC

  No space left on device.

• UVWASI_ENOSYS

  Function not supported.

• UVWASI_ENOTCONN

  The socket is not connected.

• UVWASI_ENOTDIR

  Not a directory or a symbolic link to a directory.

• UVWASI_ENOTEMPTY

  Directory not empty.

• UVWASI_ENOTRECOVERABLE

  State not recoverable.

• UVWASI_ENOTSOCK

  Not a socket.

• UVWASI_ENOTSUP

  Not supported, or operation not supported on socket.

• UVWASI_ENOTTY

  Inappropriate I/O control operation.

• UVWASI_ENXIO

  No such device or address.

• UVWASI_EOVERFLOW

  Value too large to be stored in data type.

• UVWASI_EOWNERDEAD

  Previous owner died.

• UVWASI_EPERM

  Operation not permitted.

• UVWASI_EPIPE

  Broken pipe.

• UVWASI_EPROTO

  Protocol error.

• UVWASI_EPROTONOSUPPORT

  Protocol not supported.

• UVWASI_EPROTOTYPE

  Protocol wrong type for socket.

• UVWASI_ERANGE

  Result too large.

• UVWASI_EROFS

  Read-only file system.

• UVWASI_ESPIPE

  Invalid seek.

• UVWASI_ESRCH

  No such process.

• UVWASI_ESTALE

  Reserved.

• UVWASI_ETIMEDOUT

  Connection timed out.

• UVWASI_ETXTBSY

  Text file busy.

• UVWASI_EXDEV

  Cross-device link.

• UVWASI_ENOTCAPABLE

  Extension: Capabilities insufficient.

uvwasi_event_t (struct)

An event that occurred.

Used by uvwasi_poll_oneoff().

Members:

• __wasi_userdata_t userdata

  User-provided value that got attached to uvwasi_subscription_t::userdata.

• __wasi_errno_t error

  If non-zero, an error that occurred while processing the subscription request.

• __wasi_eventtype_t type

  The type of the event that occurred.

• When type is UVWASI_EVENTTYPE_FD_READ or UVWASI_EVENTTYPE_FD_WRITE:

  • u.fd_readwrite

    • __wasi_filesize_t nbytes

      The number of bytes available for reading or writing.

    • __wasi_eventrwflags_t flags

      The state of the file descriptor.

uvwasi_eventrwflags_t (uint16_t bitfield)

The state of the file descriptor subscribed to with UVWASI_EVENTTYPE_FD_READ or UVWASI_EVENTTYPE_FD_WRITE.

Used by uvwasi_event_t.

Possible values:

• UVWASI_EVENT_FD_READWRITE_HANGUP

  The peer of this socket has closed or disconnected.

uvwasi_eventtype_t (uint8_t)

Type of a subscription to an event or its occurrence.

Used by uvwasi_event_t and uvwasi_subscription_t.

Possible values:

• UVWASI_EVENTTYPE_CLOCK

  The time value of clock uvwasi_subscription_t::u.clock.clock_id has reached timestamp uvwasi_subscription_t::u.clock.timeout.

• UVWASI_EVENTTYPE_FD_READ

  File descriptor uvwasi_subscription_t::u.fd_readwrite.fd has data available for reading. This event always triggers for regular files.

• UVWASI_EVENTTYPE_FD_WRITE

  File descriptor uvwasi_subscription_t::u.fd_readwrite.fd has capacity available for writing. This event always triggers for regular files.

uvwasi_exitcode_t (uint32_t)

Exit code generated by a process when exiting.

Used by uvwasi_proc_exit().

uvwasi_fd_t (uint32_t)

A file descriptor number.

Used by many functions in this API.

As in POSIX, three file descriptor numbers are provided to instances on startup -- 0, 1, and 2, (a.k.a. STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO).

Other than these, WASI implementations are not required to allocate new file descriptors in ascending order.

uvwasi_fdflags_t (uint16_t bitfield)

File descriptor flags.

Used by uvwasi_fdstat_t, uvwasi_fd_fdstat_set_flags(), and uvwasi_path_open().

Possible values:

• UVWASI_FDFLAG_APPEND

  Append mode: Data written to the file is always appended to the file's end.

• UVWASI_FDFLAG_DSYNC

  Write according to synchronized I/O data integrity completion. Only the data stored in the file is synchronized.

• UVWASI_FDFLAG_NONBLOCK

  Non-blocking mode.

• UVWASI_FDFLAG_RSYNC

  Synchronized read I/O operations.

• UVWASI_FDFLAG_SYNC

  Write according to synchronized I/O file integrity completion. In addition to synchronizing the data stored in the file, the implementation may also synchronously update the file's metadata.

uvwasi_fdstat_t (struct)

File descriptor attributes.

Used by uvwasi_fd_fdstat_get().

Members:

• __wasi_filetype_t fs_filetype

  File type.

• __wasi_fdflags_t fs_flags

  File descriptor flags.

• __wasi_rights_t fs_rights_base

  Rights that apply to this file descriptor.

• __wasi_rights_t fs_rights_inheriting

  Maximum set of rights that may be installed on new file descriptors that are created through this file descriptor, e.g., through uvwasi_path_open().

uvwasi_filedelta_t (int64_t)

Relative offset within a file.

Used by uvwasi_fd_seek().

uvwasi_filesize_t (uint64_t)

Non-negative file size or length of a region within a file.

Used by uvwasi_event_t, uvwasi_filestat_t, uvwasi_fd_pread(), uvwasi_fd_pwrite(), uvwasi_fd_seek(), uvwasi_path_tell(), uvwasi_fd_advise(), uvwasi_fd_allocate(), and uvwasi_fd_filestat_set_size().

uvwasi_filestat_t (struct)

File attributes.

Used by uvwasi_fd_filestat_get() and uvwasi_path_filestat_get().

Members:

• __wasi_device_t st_dev

  Device ID of device containing the file.

• __wasi_inode_t st_ino

  File serial number.

• __wasi_filetype_t st_filetype

  File type.

• __wasi_linkcount_t st_nlink

  Number of hard links to the file.

• __wasi_filesize_t st_size

  For regular files, the file size in bytes. For symbolic links, the length in bytes of the pathname contained in the symbolic link.

• __wasi_timestamp_t st_atim

  Last data access timestamp.

• __wasi_timestamp_t st_mtim

  Last data modification timestamp.

• __wasi_timestamp_t st_ctim

  Last file status change timestamp.

uvwasi_filetype_t (uint8_t)

The type of a file descriptor or file.

Used by uvwasi_dirent_t, uvwasi_fdstat_t, and uvwasi_filestat_t.

Possible values:

• UVWASI_FILETYPE_UNKNOWN

  The type of the file descriptor or file is unknown or is different from any of the other types specified.

• UVWASI_FILETYPE_BLOCK_DEVICE

  The file descriptor or file refers to a block device inode.

• UVWASI_FILETYPE_CHARACTER_DEVICE

  The file descriptor or file refers to a character device inode.

• UVWASI_FILETYPE_DIRECTORY

  The file descriptor or file refers to a directory inode.

• UVWASI_FILETYPE_REGULAR_FILE

  The file descriptor or file refers to a regular file inode.

• UVWASI_FILETYPE_SOCKET_DGRAM

  The file descriptor or file refers to a datagram socket.

• UVWASI_FILETYPE_SOCKET_STREAM

  The file descriptor or file refers to a byte-stream socket.

• UVWASI_FILETYPE_SYMBOLIC_LINK

  The file refers to a symbolic link inode.

uvwasi_fstflags_t (uint16_t bitfield)

Which file time attributes to adjust.

Used by uvwasi_fd_filestat_set_times() and uvwasi_path_filestat_set_times().

Possible values:

• UVWASI_FILESTAT_SET_ATIM

  Adjust the last data access timestamp to the value stored in uvwasi_filestat_t::st_atim.

• UVWASI_FILESTAT_SET_ATIM_NOW

  Adjust the last data access timestamp to the time of clock UVWASI_CLOCK_REALTIME.

• UVWASI_FILESTAT_SET_MTIM

  Adjust the last data modification timestamp to the value stored in uvwasi_filestat_t::st_mtim.

• UVWASI_FILESTAT_SET_MTIM_NOW

  Adjust the last data modification timestamp to the time of clock UVWASI_CLOCK_REALTIME.

uvwasi_inode_t (uint64_t)

File serial number that is unique within its file system.

Used by uvwasi_dirent_t and uvwasi_filestat_t.

uvwasi_iovec_t (struct)

A region of memory for scatter/gather reads.

Used by uvwasi_fd_pread(), uvwasi_fd_read(), and uvwasi_sock_recv().

Members:

• void *buf and __wasi_size_t buf_len

  The address and length of the buffer to be filled.

uvwasi_linkcount_t (uint64_t)

Number of hard links to an inode.

Used by uvwasi_filestat_t.

uvwasi_lookupflags_t (uint32_t bitfield)

Flags determining the method of how paths are resolved.

Used by uvwasi_path_filestat_get(), uvwasi_path_filestat_set_times(), uvwasi_path_link(), and uvwasi_path_open().

Possible values:

• UVWASI_LOOKUP_SYMLINK_FOLLOW

  As long as the resolved path corresponds to a symbolic link, it is expanded.

uvwasi_oflags_t (uint16_t bitfield)

Open flags used by uvwasi_path_open().

Used by uvwasi_path_open().

Possible values:

• UVWASI_O_CREAT

  Create file if it does not exist.

• UVWASI_O_DIRECTORY

  Fail if not a directory.

• UVWASI_O_EXCL

  Fail if file already exists.

• UVWASI_O_TRUNC

  Truncate file to size 0.

uvwasi_riflags_t (uint16_t bitfield)

Flags provided to uvwasi_sock_recv().

Used by uvwasi_sock_recv().

Possible values:

• UVWASI_SOCK_RECV_PEEK

  Returns the message without removing it from the socket's receive queue.

• UVWASI_SOCK_RECV_WAITALL

  On byte-stream sockets, block until the full amount of data can be returned.

uvwasi_rights_t (uint64_t bitfield)

File descriptor rights, determining which actions may be performed.

Used by uvwasi_fdstat_t, uvwasi_fd_fdstat_set_rights(), and uvwasi_path_open().

Possible values:

• UVWASI_RIGHT_FD_DATASYNC

  The right to invoke uvwasi_fd_datasync().

  If UVWASI_RIGHT_PATH_OPEN is set, includes the right to invoke uvwasi_path_open() with UVWASI_FDFLAG_DSYNC.

• UVWASI_RIGHT_FD_READ

  The right to invoke uvwasi_fd_read() and uvwasi_sock_recv().

  If UVWASI_RIGHT_FD_SEEK is set, includes the right to invoke uvwasi_fd_pread().

• UVWASI_RIGHT_FD_SEEK

  The right to invoke uvwasi_fd_seek(). This flag implies UVWASI_RIGHT_FD_TELL.

• UVWASI_RIGHT_FD_FDSTAT_SET_FLAGS

  The right to invoke uvwasi_fd_fdstat_set_flags().

• UVWASI_RIGHT_FD_SYNC

  The right to invoke uvwasi_fd_sync().

  If UVWASI_RIGHT_PATH_OPEN is set, includes the right to invoke uvwasi_path_open() with UVWASI_FDFLAG_RSYNC and UVWASI_FDFLAG_DSYNC.

• UVWASI_RIGHT_FD_TELL

  The right to invoke uvwasi_fd_seek() in such a way that the file offset remains unaltered (i.e., UVWASI_WHENCE_CUR with offset zero), or to invoke uvwasi_fd_tell().

• UVWASI_RIGHT_FD_WRITE

  The right to invoke uvwasi_fd_write() and uvwasi_sock_send().

  If UVWASI_RIGHT_FD_SEEK is set, includes the right to invoke uvwasi_fd_pwrite().

• UVWASI_RIGHT_FD_ADVISE

  The right to invoke uvwasi_fd_advise().

• UVWASI_RIGHT_FD_ALLOCATE

  The right to invoke uvwasi_fd_allocate().

• UVWASI_RIGHT_PATH_CREATE_DIRECTORY

  The right to invoke uvwasi_path_create_directory().

• UVWASI_RIGHT_PATH_CREATE_FILE

  If UVWASI_RIGHT_PATH_OPEN is set, the right to invoke uvwasi_path_open() with UVWASI_O_CREAT.

• UVWASI_RIGHT_PATH_LINK_SOURCE

  The right to invoke uvwasi_path_link() with the file descriptor as the source directory.

• UVWASI_RIGHT_PATH_LINK_TARGET

  The right to invoke uvwasi_path_link() with the file descriptor as the target directory.

• UVWASI_RIGHT_PATH_OPEN

  The right to invoke uvwasi_path_open().

• UVWASI_RIGHT_FD_READDIR

  The right to invoke uvwasi_fd_readdir().

• UVWASI_RIGHT_PATH_READLINK

  The right to invoke uvwasi_path_readlink().

• UVWASI_RIGHT_PATH_RENAME_SOURCE

  The right to invoke uvwasi_path_rename() with the file descriptor as the source directory.

• UVWASI_RIGHT_PATH_RENAME_TARGET

  The right to invoke uvwasi_path_rename() with the file descriptor as the target directory.

• UVWASI_RIGHT_PATH_FILESTAT_GET

  The right to invoke uvwasi_path_filestat_get().

• UVWASI_RIGHT_PATH_FILESTAT_SET_SIZE

  The right to change a file's size (there is no uvwasi_path_filestat_set_size()).

  If UVWASI_RIGHT_PATH_OPEN is set, includes the right to invoke uvwasi_path_open() with UVWASI_O_TRUNC.

• UVWASI_RIGHT_PATH_FILESTAT_SET_TIMES

  The right to invoke uvwasi_path_filestat_set_times().

• UVWASI_RIGHT_FD_FILESTAT_GET

  The right to invoke uvwasi_fd_filestat_get().

• UVWASI_RIGHT_FD_FILESTAT_SET_SIZE

  The right to invoke uvwasi_fd_filestat_set_size().

• UVWASI_RIGHT_FD_FILESTAT_SET_TIMES

  The right to invoke uvwasi_fd_filestat_set_times().

• UVWASI_RIGHT_PATH_SYMLINK

  The right to invoke uvwasi_path_symlink().

• UVWASI_RIGHT_PATH_UNLINK_FILE

  The right to invoke uvwasi_path_unlink_file().

• UVWASI_RIGHT_PATH_REMOVE_DIRECTORY

  The right to invoke uvwasi_path_remove_directory().

• UVWASI_RIGHT_POLL_FD_READWRITE

  If UVWASI_RIGHT_FD_READ is set, includes the right to invoke uvwasi_poll_oneoff() to subscribe to UVWASI_EVENTTYPE_FD_READ.

  If UVWASI_RIGHT_FD_WRITE is set, includes the right to invoke uvwasi_poll_oneoff() to subscribe to UVWASI_EVENTTYPE_FD_WRITE.

• UVWASI_RIGHT_SOCK_SHUTDOWN

  The right to invoke uvwasi_sock_shutdown().

uvwasi_roflags_t (uint16_t bitfield)

Flags returned by uvwasi_sock_recv().

Used by uvwasi_sock_recv().

Possible values:

• UVWASI_SOCK_RECV_DATA_TRUNCATED

  Returned by uvwasi_sock_recv(): Message data has been truncated.

uvwasi_sdflags_t (uint8_t bitfield)

Which channels on a socket to shut down.

Used by uvwasi_sock_shutdown().

Possible values:

• UVWASI_SHUT_RD

  Disables further receive operations.

• UVWASI_SHUT_WR

  Disables further send operations.

uvwasi_siflags_t (uint16_t bitfield)

Flags provided to uvwasi_sock_send(). As there are currently no flags defined, it must be set to zero.

Used by uvwasi_sock_send().

uvwasi_signal_t (uint8_t)

Signal condition.

Used by uvwasi_proc_raise().

Possible values:

• UVWASI_SIGABRT

  Process abort signal.

  Action: Terminates the process.

• UVWASI_SIGALRM

  Alarm clock.

  Action: Terminates the process.

• UVWASI_SIGBUS

  Access to an undefined portion of a memory object.

  Action: Terminates the process.

• UVWASI_SIGCHLD

  Child process terminated, stopped, or continued.

  Action: Ignored.

• UVWASI_SIGCONT

  Continue executing, if stopped.

  Action: Continues executing, if stopped.

• UVWASI_SIGFPE

  Erroneous arithmetic operation.

  Action: Terminates the process.

• UVWASI_SIGHUP

  Hangup.

  Action: Terminates the process.

• UVWASI_SIGILL

  Illegal instruction.

  Action: Terminates the process.

• UVWASI_SIGINT

  Terminate interrupt signal.

  Action: Terminates the process.

• UVWASI_SIGKILL

  Kill.

  Action: Terminates the process.

• UVWASI_SIGPIPE

  Write on a pipe with no one to read it.

  Action: Ignored.

• UVWASI_SIGQUIT

  Terminal quit signal.

  Action: Terminates the process.

• UVWASI_SIGSEGV

  Invalid memory reference.

  Action: Terminates the process.

• UVWASI_SIGSTOP

  Stop executing.

  Action: Stops executing.

• UVWASI_SIGSYS

  Bad system call.

  Action: Terminates the process.

• UVWASI_SIGTERM

  Termination signal.

  Action: Terminates the process.

• UVWASI_SIGTRAP

  Trace/breakpoint trap.

  Action: Terminates the process.

• UVWASI_SIGTSTP

  Terminal stop signal.

  Action: Stops executing.

• UVWASI_SIGTTIN

  Background process attempting read.

  Action: Stops executing.

• UVWASI_SIGTTOU

  Background process attempting write.

  Action: Stops executing.

• UVWASI_SIGURG

  High bandwidth data is available at a socket.

  Action: Ignored.

• UVWASI_SIGUSR1

  User-defined signal 1.

  Action: Terminates the process.

• UVWASI_SIGUSR2

  User-defined signal 2.

  Action: Terminates the process.

• UVWASI_SIGVTALRM

  Virtual timer expired.

  Action: Terminates the process.

• UVWASI_SIGXCPU

  CPU time limit exceeded.

  Action: Terminates the process.

• UVWASI_SIGXFSZ

  File size limit exceeded.

  Action: Terminates the process.

uvwasi_subclockflags_t (uint16_t bitfield)

Flags determining how to interpret the timestamp provided in uvwasi_subscription_t::u.clock.timeout.

Used by uvwasi_subscription_t.

Possible values:

• UVWASI_SUBSCRIPTION_CLOCK_ABSTIME

  If set, treat the timestamp provided in uvwasi_subscription_t::u.clock.timeout as an absolute timestamp of clock uvwasi_subscription_t::u.clock.clock_id.

  If clear, treat the timestamp provided in uvwasi_subscription_t::u.clock.timeout relative to the current time value of clock uvwasi_subscription_t::u.clock.clock_id.

uvwasi_subscription_t (struct)

Subscription to an event.

Used by uvwasi_poll_oneoff().

Members:

• __wasi_userdata_t userdata

  User-provided value that is attached to the subscription in the implementation and returned through uvwasi_event_t::userdata.

• __wasi_eventtype_t type

  The type of the event to which to subscribe.

• When type is UVWASI_EVENTTYPE_CLOCK:

  • u.clock

    • __wasi_clockid_t clock_id

      The clock against which to compare the timestamp.

    • __wasi_timestamp_t timeout

      The absolute or relative timestamp.

    • __wasi_timestamp_t precision

      The amount of time that the implementation may wait additionally to coalesce with other events.

    • __wasi_subclockflags_t flags

      Flags specifying whether the timeout is absolute or relative.

• When type is UVWASI_EVENTTYPE_FD_READ or UVWASI_EVENTTYPE_FD_WRITE:

  • u.fd_readwrite

    • __wasi_fd_t fd

      The file descriptor on which to wait for it to become ready for reading or writing.

uvwasi_timestamp_t (uint64_t)

Timestamp in nanoseconds.

Used by uvwasi_filestat_t, uvwasi_subscription_t, uvwasi_clock_res_get(), uvwasi_clock_time_get(), uvwasi_fd_filestat_set_times(), and uvwasi_path_filestat_set_times().

uvwasi_userdata_t (uint64_t)

User-provided value that may be attached to objects that is retained when extracted from the implementation.

Used by uvwasi_event_t and uvwasi_subscription_t.

uvwasi_whence_t (uint8_t)

The position relative to which to set the offset of the file descriptor.

Used by uvwasi_fd_seek().

Possible values:

• UVWASI_WHENCE_CUR

  Seek relative to current position.

• UVWASI_WHENCE_END

  Seek relative to end-of-file.

• UVWASI_WHENCE_SET

  Seek relative to start-of-file.

Doing a release

To do a release complete the following steps:

• Look at the list of changes - https://github.com/nodejs/uvwasi/commits/main.
• Put together a list of notable changes. See https://github.com/nodejs/uvwasi/releases/tag/v0.0.14 or any of the other releases for example. Use that list in the release commit, the GitHub release, and the PR to update uvwasi in Node.js (or any other projects where you update it)
• Update the version in the CMake file. Specifically: https://github.com/nodejs/uvwasi/blob/main/CMakeLists.txt#L5
• Create a release commit. This should just involve changing one line and adding the notable changes. See https://github.com/nodejs/uvwasi/commit/6ad5fc996420d0e4e75983ce3deb65f327321f33 as an example.
• PR the release commit. Once it lands, create a GitHub release with the same notable changes. When doing the GitHub release you will need to select Choose a tag and type in the new tag. That should result in Create new tag: vX.Y.Z on publish where vX.Y.Z matches the tag you specified.
• Update uvwasi in Node.js or any projects you want to update - there are several other projects that use uvwasi.