Initial interface

.github/workflows/main.yml

@@ -11,4 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: WebAssembly/wit-abi-up-to-date@v19
+    - uses: WebAssembly/wit-abi-up-to-date@v22
+      with:
+        wit-bindgen: '0.33.0'
+        wasm-tools: '1.218.0'

wit/deps.lock

@@ -0,0 +1,4 @@
+[io]
+url = "https://github.com/WebAssembly/wasi-io/archive/main.tar.gz"
+sha256 = "1cccbfe4122686ea57a25cd368e8cdfc408cbcad089f47fb6685b6f92e96f050"
+sha512 = "7a95f964c13da52611141acd89bc8876226497f128e99dd176a4270c5b5efbd8cc847b5fbd1a91258d028c646db99e0424d72590cf1caf20f9f3a3343fad5017"

wit/deps.toml

@@ -0,0 +1 @@
+io = "https://github.com/WebAssembly/wasi-io/archive/main.tar.gz"

wit/deps/io/error.wit

@@ -0,0 +1,34 @@
+package wasi:io@0.2.3;
+
+@since(version = 0.2.0)
+interface error {
+    /// A resource which represents some error information.
+    ///
+    /// The only method provided by this resource is `to-debug-string`,
+    /// which provides some human-readable information about the error.
+    ///
+    /// In the `wasi:io` package, this resource is returned through the
+    /// `wasi:io/streams/stream-error` type.
+    ///
+    /// To provide more specific error information, other interfaces may
+    /// offer functions to "downcast" this error into more specific types. For example,
+    /// errors returned from streams derived from filesystem types can be described using
+    /// the filesystem's own error-code type. This is done using the function
+    /// `wasi:filesystem/types/filesystem-error-code`, which takes a `borrow<error>`
+    /// parameter and returns an `option<wasi:filesystem/types/error-code>`.
+    ///
+    /// The set of functions which can "downcast" an `error` into a more
+    /// concrete type is open.
+    @since(version = 0.2.0)
+    resource error {
+        /// Returns a string that is suitable to assist humans in debugging
+        /// this error.
+        ///
+        /// WARNING: The returned string should not be consumed mechanically!
+        /// It may change across platforms, hosts, or other implementation
+        /// details. Parsing this string is a major platform-compatibility
+        /// hazard.
+        @since(version = 0.2.0)
+        to-debug-string: func() -> string;
+    }
+}

wit/deps/io/poll.wit

@@ -0,0 +1,47 @@
+package wasi:io@0.2.3;
+
+/// A poll API intended to let users wait for I/O events on multiple handles
+/// at once.
+@since(version = 0.2.0)
+interface poll {
+    /// `pollable` represents a single I/O event which may be ready, or not.
+    @since(version = 0.2.0)
+    resource pollable {
+
+      /// Return the readiness of a pollable. This function never blocks.
+      ///
+      /// Returns `true` when the pollable is ready, and `false` otherwise.
+      @since(version = 0.2.0)
+      ready: func() -> bool;
+
+      /// `block` returns immediately if the pollable is ready, and otherwise
+      /// blocks until ready.
+      ///
+      /// This function is equivalent to calling `poll.poll` on a list
+      /// containing only this pollable.
+      @since(version = 0.2.0)
+      block: func();
+    }
+
+    /// Poll for completion on a set of pollables.
+    ///
+    /// This function takes a list of pollables, which identify I/O sources of
+    /// interest, and waits until one or more of the events is ready for I/O.
+    ///
+    /// The result `list<u32>` contains one or more indices of handles in the
+    /// argument list that is ready for I/O.
+    ///
+    /// This function traps if either:
+    /// - the list is empty, or:
+    /// - the list contains more elements than can be indexed with a `u32` value.
+    ///
+    /// A timeout can be implemented by adding a pollable from the
+    /// wasi-clocks API to the list.
+    ///
+    /// This function does not return a `result`; polling in itself does not
+    /// do any I/O so it doesn't fail. If any of the I/O sources identified by
+    /// the pollables has an error, it is indicated by marking the source as
+    /// being ready for I/O.
+    @since(version = 0.2.0)
+    poll: func(in: list<borrow<pollable>>) -> list<u32>;
+}

wit/deps/io/streams.wit

@@ -0,0 +1,290 @@
+package wasi:io@0.2.3;
+
+/// WASI I/O is an I/O abstraction API which is currently focused on providing
+/// stream types.
+///
+/// In the future, the component model is expected to add built-in stream types;
+/// when it does, they are expected to subsume this API.
+@since(version = 0.2.0)
+interface streams {
+    @since(version = 0.2.0)
+    use error.{error};
+    @since(version = 0.2.0)
+    use poll.{pollable};
+
+    /// An error for input-stream and output-stream operations.
+    @since(version = 0.2.0)
+    variant stream-error {
+        /// The last operation (a write or flush) failed before completion.
+        ///
+        /// More information is available in the `error` payload.
+        ///
+        /// After this, the stream will be closed. All future operations return
+        /// `stream-error::closed`.
+        last-operation-failed(error),
+        /// The stream is closed: no more input will be accepted by the
+        /// stream. A closed output-stream will return this error on all
+        /// future operations.
+        closed
+    }
+
+    /// An input bytestream.
+    ///
+    /// `input-stream`s are *non-blocking* to the extent practical on underlying
+    /// platforms. I/O operations always return promptly; if fewer bytes are
+    /// promptly available than requested, they return the number of bytes promptly
+    /// available, which could even be zero. To wait for data to be available,
+    /// use the `subscribe` function to obtain a `pollable` which can be polled
+    /// for using `wasi:io/poll`.
+    @since(version = 0.2.0)
+    resource input-stream {
+        /// Perform a non-blocking read from the stream.
+        ///
+        /// When the source of a `read` is binary data, the bytes from the source
+        /// are returned verbatim. When the source of a `read` is known to the
+        /// implementation to be text, bytes containing the UTF-8 encoding of the
+        /// text are returned.
+        ///
+        /// This function returns a list of bytes containing the read data,
+        /// when successful. The returned list will contain up to `len` bytes;
+        /// it may return fewer than requested, but not more. The list is
+        /// empty when no bytes are available for reading at this time. The
+        /// pollable given by `subscribe` will be ready when more bytes are
+        /// available.
+        ///
+        /// This function fails with a `stream-error` when the operation
+        /// encounters an error, giving `last-operation-failed`, or when the
+        /// stream is closed, giving `closed`.
+        ///
+        /// When the caller gives a `len` of 0, it represents a request to
+        /// read 0 bytes. If the stream is still open, this call should
+        /// succeed and return an empty list, or otherwise fail with `closed`.
+        ///
+        /// The `len` parameter is a `u64`, which could represent a list of u8 which
+        /// is not possible to allocate in wasm32, or not desirable to allocate as
+        /// as a return value by the callee. The callee may return a list of bytes
+        /// less than `len` in size while more bytes are available for reading.
+        @since(version = 0.2.0)
+        read: func(
+            /// The maximum number of bytes to read
+            len: u64
+        ) -> result<list<u8>, stream-error>;
+
+        /// Read bytes from a stream, after blocking until at least one byte can
+        /// be read. Except for blocking, behavior is identical to `read`.
+        @since(version = 0.2.0)
+        blocking-read: func(
+            /// The maximum number of bytes to read
+            len: u64
+        ) -> result<list<u8>, stream-error>;
+
+        /// Skip bytes from a stream. Returns number of bytes skipped.
+        ///
+        /// Behaves identical to `read`, except instead of returning a list
+        /// of bytes, returns the number of bytes consumed from the stream.
+        @since(version = 0.2.0)
+        skip: func(
+            /// The maximum number of bytes to skip.
+            len: u64,
+        ) -> result<u64, stream-error>;
+
+        /// Skip bytes from a stream, after blocking until at least one byte
+        /// can be skipped. Except for blocking behavior, identical to `skip`.
+        @since(version = 0.2.0)
+        blocking-skip: func(
+            /// The maximum number of bytes to skip.
+            len: u64,
+        ) -> result<u64, stream-error>;
+
+        /// Create a `pollable` which will resolve once either the specified stream
+        /// has bytes available to read or the other end of the stream has been
+        /// closed.
+        /// The created `pollable` is a child resource of the `input-stream`.
+        /// Implementations may trap if the `input-stream` is dropped before
+        /// all derived `pollable`s created with this function are dropped.
+        @since(version = 0.2.0)
+        subscribe: func() -> pollable;
+    }
+
+
+    /// An output bytestream.
+    ///
+    /// `output-stream`s are *non-blocking* to the extent practical on
+    /// underlying platforms. Except where specified otherwise, I/O operations also
+    /// always return promptly, after the number of bytes that can be written
+    /// promptly, which could even be zero. To wait for the stream to be ready to
+    /// accept data, the `subscribe` function to obtain a `pollable` which can be
+    /// polled for using `wasi:io/poll`.
+    ///
+    /// Dropping an `output-stream` while there's still an active write in
+    /// progress may result in the data being lost. Before dropping the stream,
+    /// be sure to fully flush your writes.
+    @since(version = 0.2.0)
+    resource output-stream {
+        /// Check readiness for writing. This function never blocks.
+        ///
+        /// Returns the number of bytes permitted for the next call to `write`,
+        /// or an error. Calling `write` with more bytes than this function has
+        /// permitted will trap.
+        ///
+        /// When this function returns 0 bytes, the `subscribe` pollable will
+        /// become ready when this function will report at least 1 byte, or an
+        /// error.
+        @since(version = 0.2.0)
+        check-write: func() -> result<u64, stream-error>;
+
+        /// Perform a write. This function never blocks.
+        ///
+        /// When the destination of a `write` is binary data, the bytes from
+        /// `contents` are written verbatim. When the destination of a `write` is
+        /// known to the implementation to be text, the bytes of `contents` are
+        /// transcoded from UTF-8 into the encoding of the destination and then
+        /// written.
+        ///
+        /// Precondition: check-write gave permit of Ok(n) and contents has a
+        /// length of less than or equal to n. Otherwise, this function will trap.
+        ///
+        /// returns Err(closed) without writing if the stream has closed since
+        /// the last call to check-write provided a permit.
+        @since(version = 0.2.0)
+        write: func(
+            contents: list<u8>
+        ) -> result<_, stream-error>;
+
+        /// Perform a write of up to 4096 bytes, and then flush the stream. Block
+        /// until all of these operations are complete, or an error occurs.
+        ///
+        /// This is a convenience wrapper around the use of `check-write`,
+        /// `subscribe`, `write`, and `flush`, and is implemented with the
+        /// following pseudo-code:
+        ///
+        /// ```text
+        /// let pollable = this.subscribe();
+        /// while !contents.is_empty() {
+        ///     // Wait for the stream to become writable
+        ///     pollable.block();
+        ///     let Ok(n) = this.check-write(); // eliding error handling
+        ///     let len = min(n, contents.len());
+        ///     let (chunk, rest) = contents.split_at(len);
+        ///     this.write(chunk  );            // eliding error handling
+        ///     contents = rest;
+        /// }
+        /// this.flush();
+        /// // Wait for completion of `flush`
+        /// pollable.block();
+        /// // Check for any errors that arose during `flush`
+        /// let _ = this.check-write();         // eliding error handling
+        /// ```
+        @since(version = 0.2.0)
+        blocking-write-and-flush: func(
+            contents: list<u8>
+        ) -> result<_, stream-error>;
+
+        /// Request to flush buffered output. This function never blocks.
+        ///
+        /// This tells the output-stream that the caller intends any buffered
+        /// output to be flushed. the output which is expected to be flushed
+        /// is all that has been passed to `write` prior to this call.
+        ///
+        /// Upon calling this function, the `output-stream` will not accept any
+        /// writes (`check-write` will return `ok(0)`) until the flush has
+        /// completed. The `subscribe` pollable will become ready when the
+        /// flush has completed and the stream can accept more writes.
+        @since(version = 0.2.0)
+        flush: func() -> result<_, stream-error>;
+
+        /// Request to flush buffered output, and block until flush completes
+        /// and stream is ready for writing again.
+        @since(version = 0.2.0)
+        blocking-flush: func() -> result<_, stream-error>;
+
+        /// Create a `pollable` which will resolve once the output-stream
+        /// is ready for more writing, or an error has occurred. When this
+        /// pollable is ready, `check-write` will return `ok(n)` with n>0, or an
+        /// error.
+        ///
+        /// If the stream is closed, this pollable is always ready immediately.
+        ///
+        /// The created `pollable` is a child resource of the `output-stream`.
+        /// Implementations may trap if the `output-stream` is dropped before
+        /// all derived `pollable`s created with this function are dropped.
+        @since(version = 0.2.0)
+        subscribe: func() -> pollable;
+
+        /// Write zeroes to a stream.
+        ///
+        /// This should be used precisely like `write` with the exact same
+        /// preconditions (must use check-write first), but instead of
+        /// passing a list of bytes, you simply pass the number of zero-bytes
+        /// that should be written.
+        @since(version = 0.2.0)
+        write-zeroes: func(
+            /// The number of zero-bytes to write
+            len: u64
+        ) -> result<_, stream-error>;
+
+        /// Perform a write of up to 4096 zeroes, and then flush the stream.
+        /// Block until all of these operations are complete, or an error
+        /// occurs.
+        ///
+        /// This is a convenience wrapper around the use of `check-write`,
+        /// `subscribe`, `write-zeroes`, and `flush`, and is implemented with
+        /// the following pseudo-code:
+        ///
+        /// ```text
+        /// let pollable = this.subscribe();
+        /// while num_zeroes != 0 {
+        ///     // Wait for the stream to become writable
+        ///     pollable.block();
+        ///     let Ok(n) = this.check-write(); // eliding error handling
+        ///     let len = min(n, num_zeroes);
+        ///     this.write-zeroes(len);         // eliding error handling
+        ///     num_zeroes -= len;
+        /// }
+        /// this.flush();
+        /// // Wait for completion of `flush`
+        /// pollable.block();
+        /// // Check for any errors that arose during `flush`
+        /// let _ = this.check-write();         // eliding error handling
+        /// ```
+        @since(version = 0.2.0)
+        blocking-write-zeroes-and-flush: func(
+            /// The number of zero-bytes to write
+            len: u64
+        ) -> result<_, stream-error>;
+
+        /// Read from one stream and write to another.
+        ///
+        /// The behavior of splice is equivalent to:
+        /// 1. calling `check-write` on the `output-stream`
+        /// 2. calling `read` on the `input-stream` with the smaller of the
+        /// `check-write` permitted length and the `len` provided to `splice`
+        /// 3. calling `write` on the `output-stream` with that read data.
+        ///
+        /// Any error reported by the call to `check-write`, `read`, or
+        /// `write` ends the splice and reports that error.
+        ///
+        /// This function returns the number of bytes transferred; it may be less
+        /// than `len`.
+        @since(version = 0.2.0)
+        splice: func(
+            /// The stream to read from
+            src: borrow<input-stream>,
+            /// The number of bytes to splice
+            len: u64,
+        ) -> result<u64, stream-error>;
+
+        /// Read from one stream and write to another, with blocking.
+        ///
+        /// This is similar to `splice`, except that it blocks until the
+        /// `output-stream` is ready for writing, and the `input-stream`
+        /// is ready for reading, before performing the `splice`.
+        @since(version = 0.2.0)
+        blocking-splice: func(
+            /// The stream to read from
+            src: borrow<input-stream>,
+            /// The number of bytes to splice
+            len: u64,
+        ) -> result<u64, stream-error>;
+    }
+}