corevm_guest/

c_stub.rs

//! This is the main API that exposes CoreVM-specific host-calls via exports with C linkage. At
//! present there are Rust and C convenience wrappers for this API available in this crate. In
//! future more languages might be added.
//!
//!
//! # Input
//!
//! ## Blocking vs. non-blocking behaviour
//!
//! Some of the host-calls might use blocking or non-blocking mode. In blocking mode (which is
//! usually the default) a host-call that can't complete within the space-time frame of the current
//! work package suspends VM execution. The builder then supplies the data that the host-call
//! needed and resumes execution in another work package. For the guest this happens
//! transparently, i.e. it's not possible to detect whether the VM was suspended in a host-call or
//! not.
//!
//! In a non-blocking mode VM is not suspended and host-call returns some special value to indicate
//! that it can't complete normally.
//!
//! For example, in blocking mode [`read_console_data`] suspends the VM if the standard input stream
//! is empty. In non-blocking mode the same host-call simply returns `u64::MAX` to indicate that the
//! stream is empty.
//!
//!
//! ## Retaining vs. discarding input on VM suspension
//!
//! When VM is suspended the unprocessed input data is discarded by default. This applies to video,
//! audio, console input and also host messages. Unprocessed inter-service messages, however, are
//! retained by the builder; they are supplied to the guest in the next work package as the input.
//!
//!
//! # Transactions
//!
//! ## Synchronous execution
//!
//! CoreVM implements synchronous transactions, i.e. transactions that are guaranteed to complete
//! within one time-slot. Each transaction involves two or more guests and is coordinated by a
//! single CoreVM service. To achieve synchronicity the service co-schedules all guests in a single
//! work package and executes them in lockstep until the transaction completes (successfully or
//! not). If either of the guests runs out of resources, the transaction is rolled back to be
//! re-executed in some subsequent time slot. This happens transaprently to the guests.
//!
//! ## Example
//!
//! Transaction initiator:
//! ```no_run,ignore
//! initiate_transaction(...);
//! // Do the changes here...
//! if commit_transaction().is_err() {
//!     // Rollback the changes here...
//! }
//! // Confirm that the transaction was finished successfully or was successfully rolled back.
//! end_transaction();
//! ```
//!
//! Transaction processor:
//! ```no_run,ignore
//! recv_transaction(...);
//! ...
//! if commit_transaction().is_err() {
//!     // Rollback the changes here...
//! }
//! // Confirm that the transaction was finished successfully or was successfully rolled back.
//! end_transaction();
//! ```

#![allow(unused_variables)]
#![allow(improper_ctypes_definitions)]
#![allow(clippy::missing_safety_doc)]

/// Get the current amount of gas.
pub unsafe extern "C" fn gas() -> u64 {
	0
}

/// Allocate memory block of the specified size.
///
/// - The size is rounded up to the next multiple of page size.
/// - The returned address is aligned at a page boundary.
///
/// Returns the address of the allocated memory region or `0` if the allocation was
/// unsuccessful.
pub unsafe extern "C" fn alloc(size: u64) -> u64 {
	0
}

/// Deallocate the memory block of the specified size starting at `address`.
///
/// Deallocates *all* the pages that overlap the memory block.
pub unsafe extern "C" fn free(address: u64, size: u64) {}

/// Append the data from `address..address + len` to the _console_ output stream.
///
/// The `stream` can be `1` for standard output and `2` for standard error.
pub unsafe extern "C" fn yield_console_data(stream: u64, address: u64, len: u64) {}

/// Append a video frame from `address..address + len` to the _video_ output stream.
///
/// `format` is frame encoding format; see [`VideoFrameFormat`](crate::VideoFrameFormat) for the
/// list of supported formats.
pub unsafe extern "C" fn yield_video_frame(address: u64, len: u64, format: u64) {}

/// Set video monitor output mode.
///
/// Parameters:
/// - `width` is frame width,
/// - `height` is frame height,
/// - `refresh_rate` is monitor refresh rate measured as the number of frames per second,
/// - `flags` additional flags that fine-tune video encoder.
///
/// Flags:
/// | Name | Bits | Description |
/// |------|------|-------------|
/// | `quantization_level` | 0-3 | Video codec quantization level. Non-zero value makes encoding lossy. |
/// | `chroma_subsampling` | 4 | Determines whether 4:2:0 chroma subsampling is enabled or not. Enabling this makes encoding lossy. |
/// | `raw` | 5 | Enables raw mode: every frame is recorded as is without any encoding. This is useful when running the code in a RISCV interpreter. |
///
/// By default video output is disabled.
///
///
/// # Lossy vs. lossless encoding
///
/// Lossy encoding works best for images with smooth color transitions (e.g. any depictions of
/// physical reality). For such images enabling lossy encoding might significantly reduce video
/// output size without noticeable change in quality.
///
/// Lossless encoding works best for images with sharp edges such as dialog boxes and vector
/// graphics in general. By default video encoding is lossless.
pub unsafe extern "C" fn video_mode(width: u64, height: u64, refresh_rate: u64, flags: u64) {}

/// Append audio samples from `address..address + len` to the _audio_ output stream.
///
/// The format of the sample is defined by [`audio_mode`](crate::audio_mode).
///
/// When both video and audio output is enabled the guest is expected to yield exactly _N_ video
/// frames worth of audio samples per second, where _N_ is the number of frames per second. To
/// improve synchrony approximately one video frame worth of audio samples should be yielded
/// together with the video frame, however this is not a strict requirement because the monitor
/// usually buffers video and audio streams. The following example shows a typical program
/// that yields both video and audio frames.
///
/// ```no_run,ignore
/// loop {
///     yield_video_frame(...);
///     yield_audio_samples(...);
/// }
/// ```
pub unsafe extern "C" fn yield_audio_samples(address: u64, len: u64) {}

/// Set audio output mode.
///
/// Parameters:
/// - `channels` is the number of channels,
/// - `sample_rate` is the number of samples per second per channel,
/// - `sample_format` is the audio sample format; see
///   [`AudioSampleFormat`](crate::AudioSampleFormat) for the list of supported formats.
///
/// By default audio output is disabled.
pub unsafe extern "C" fn audio_mode(channels: u64, sample_rate: u64, sample_format: u64) {}

/// Pop a message from another service from the queue.
///
/// Returns the length of the message in the first 32 bits and the ID of the sender in the second
/// 32 bits of the return value.
///
/// - If the message length is less than or equal to `len` the message is popped from the queue and
///   copied to `address..address + len`.
/// - If the message length is larger than `len` or the `address` is zero, then the message length
///   and source are returned but message isn't popped and its contents are not copied.
/// - If the queue is empty, then the call will block until new messages are pushed to the queue.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::RecvMessage::NON_BLOCKING). Setting this flag makes the
///   call non-blocking. If the queue is empty and this flag is set, then the call immediately
///   returns `u64::MAX` instead of waiting for new messages to arrive.
/// - [`DISCARD`](corevm_types::flags::RecvMessage::DISCARD). Setting this flag makes the call
///   silently discard messages longer than `len`.
///
///
/// # VM suspension behaviour
///
/// When VM is suspended the remaining messages are _retained_ in the queue by the builder and will
/// be available to the guest as soon as the VM is resumed.
pub unsafe extern "C" fn recv_message(address: u64, len: u64, flags: u64) -> u64 {
	u64::MAX
}

/// Send the message stored at `address..address + len` to the CoreVM service with id
/// `guest_id`.
pub unsafe extern "C" fn send_message(guest_id: u64, address: u64, len: u64) {}

/// Pop a message from the host from the queue.
///
/// The interface of this function is similar to [`recv_message`] but it does not return the ID of
/// the sender.
///
/// # VM suspension behaviour
///
/// When VM is suspended the remaining messages are _discarded_ by the builder.
pub unsafe extern "C" fn recv_host_message(address: u64, len: u64, flags: u64) -> u64 {
	u64::MAX
}

/// Wait for the data to appear in any of the specified input streams.
///
/// Parameters:
/// - `streams`: a bitset that specifies which [input streams](corevm_types::InputStreams) to wait
///   for.
/// - `flags`: a bitset with [polling options](corevm_types::flags::Poll). values.
///
/// Returns a bitset that specifies which streams are available for the input.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::Poll::NON_BLOCKING). Setting this flag makes the call
///   return immediately even if all streams are empty.
pub unsafe extern "C" fn poll(streams: u64, flags: u64) -> u64 {
	0
}

/// Read the data from _console_ input stream (standard input).
///
/// The data is copied to `address..address + len` and the host-call returns the number of bytes
/// copied. If console input stream is empty, the call blocks until new data arrives.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::ReadConsoleData::NON_BLOCKING). Setting this flag makes
///   the call non-blocking: if there is no data in the standard input, then the call immediately
///   returns `u64::MAX`.
///
/// # VM suspension behaviour
///
/// When VM is suspended the remaining console data is _discarded_ by the builder.
pub unsafe extern "C" fn read_console_data(address: u64, len: u64, flags: u64) -> u64 {
	0
}

/// Get video input mode.
///
/// The data is encoded as follows.
///
/// - `VideoMode::width`: bits `0..16`.
/// - `VideoMode::height`: bits `16..32`.
/// - `VideoMode::refresh_rate`: bits `32..48`.
/// - `VideoMode::format`: bits `48..56`. See [`VideoFrameFormat`](crate::VideoFrameFormat) for the
///   list of possible values.
///
/// Returns `0` if there is no video input.
pub unsafe extern "C" fn video_input_mode() -> u64 {
	0
}

/// Get the next frame from the video input.
///
/// The frame is copied to `address..address + len`. If the frame length is larger than
/// `len` or the `address` is zero, then the frame length is returned and nothing is
/// copied. If video input stream is empty, then the call blocks until new data arrives.
///
/// `format` is frame encoding format; see [`VideoFrameFormat`](crate::VideoFrameFormat)
/// for the list of supported formats.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::ReadVideoFrame::NON_BLOCKING). If the flag is set and
///   the video input is empty, then the call immediately returns `u64::MAX`.
///
/// # VM suspension behaviour
///
/// When VM is suspended the remaining video frames are _discarded_ by the builder.
pub unsafe extern "C" fn read_video_frame(address: u64, len: u64, format: u64, flags: u64) -> u64 {
	u64::MAX
}

/// Get audio input mode.
///
/// The data is encoded as follows.
///
/// - `AudioMode::sample_rate`: bits `0..32`.
/// - `AudioMode::channels`: bits `32..40`.
/// - `AudioMode::sample_format`: bits `40..48`.
///
/// Returns 0 if there is no audio input.
pub unsafe extern "C" fn audio_input_mode() -> u64 {
	0
}

/// Get the frames from the audio input.
///
/// The frames are copied to `address..address + len` and the host-call returns the number of bytes
/// copied. This host-call copies as many complete frames as can fit into `len` (a frame is an array
/// of samples, one sample for each channel). If audio input stream is empty, the call blocks until
/// new data arrives.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::ReadAudioFrames::NON_BLOCKING). Setting this flag makes
///   the call non-blocking. In this mode if there is no data in the audio input, then the call
///   immediately returns `u64::MAX`.
///
/// # VM suspension behaviour
///
/// When VM is suspended the remaining audio frames are _discarded_ by the builder.
pub unsafe extern "C" fn read_audio_frames(address: u64, len: u64, flags: u64) -> u64 {
	u64::MAX
}

/// Initiate a transaction with guest ID `target` with payload from `address..address + len`.
///
/// Blocks until the target guest copies the payload from `address..address + len` to the target
/// guest's address space via [`recv_transaction`].
///
/// Returns zero on success. Returns non-zero when any of the following is true:
/// - bad address supplied to [`recv_transaction`] or [`initiate_transaction`],
/// - target guest couldn't be found,
/// - any other low-level error is encountered.
///
/// # Transactions with more than two guests
///
/// To involve more than two guests in the transaction simply call `initiate_transaction` multiple
/// times  _before_ calling `commit_transaction` or `rollback_transaction`. You have to use a
/// different `target` each time and might use a different payload as well. All such transactions
/// will be combined into one and a subsequent call to `commit_transaction` or
/// `rollback_transaction` will affect all of them at once. For such transaction to succeed every
/// guest should call `commit_transaction`.
///
/// # Synchronous execution
///
/// This is synchronous operation, i.e. all guests that participate in the transaction are executed
/// in lockstep until the transaction completes.
pub unsafe extern "C" fn initiate_transaction(target: u64, address: u64, len: u64) -> u64 {
	0
}

/// Receive a transaction from the transaction initiator.
///
/// Returns the length of the payload in the first 32 bits and the guest ID of the sender in the
/// second 32 bits of the return value.
///
/// - If the payload length is less than or equal to `len` the payload copied to `address..address +
///   len`.
/// - If the payload length is larger than `len` or the `address` is zero, then the payload length
///   and source are returned but payload contents are not copied.
/// - If there is no pending transaction, then the call will block until some transaction is
///   initiated.
/// - If any low-level error occures the transaction is ignored and the next one is tried until the
///   call either succeeds or runs out of pending transactions.
///
/// # Flags
///
/// - [`NON_BLOCKING`](corevm_types::flags::RecvTransaction::NON_BLOCKING). Setting this flag makes
///   the call non-blocking. If the queue is empty and this flag is set, then the call immediately
///   returns `u64::MAX` instead of waiting for new messages to arrive.
///
/// # Synchronous execution
///
/// This is synchronous operation, i.e. all guests that participate in the transaction are executed
/// in lockstep until the transaction completes. The transaction is considered received when the
/// payload is copied to the guest address space.
pub unsafe extern "C" fn recv_transaction(address: u64, len: u64, flags: u64) -> u64 {
	u64::MAX
}

/// Commit the transaction that was started by either [`initiate_transaction`] or
/// [`recv_transaction`].
///
/// Blocks until the other guest either calls [`commit_transaction`], or [`rollback_transaction`],
/// or panics.
///
/// This call singnifies that the current guest finished its part of the transaction. Calling this
/// function without an active transaction will result in panic.
///
/// Returns zero on success. Returns non-zero when any of the following is true:
/// - the other side of this transaction panics or calls [`rollback_transaction`],
/// - any other low-level error is encountered.
///
/// # Synchronous execution
///
/// This is synchronous operation, i.e. all guests that participate in the transaction are executed
/// in lockstep until the transaction completes. The transaction is considered complete when either
/// both guests call [`end_transaction`] or one of the guests panics.
pub unsafe extern "C" fn commit_transaction() -> u64 {
	0
}

/// Cancel the transaction that was started by either [`initiate_transaction`] or
/// [`recv_transaction`].
///
/// This call singnifies that the current guest is unable to finish its part of the transaction.
/// Calling this function without an active transaction will result in panic.
///
/// # Synchronous execution
///
/// This is synchronous operation, i.e. all guests that participate in the transaction are executed
/// in lockstep until the transaction completes. The transaction is considered complete when either
/// both guests call [`end_transaction`] or one of the guests panics.
pub unsafe extern "C" fn rollback_transaction() {}

/// Finish the transaction.
///
/// This call confirms that either the transaction was finished successfully or the changes were
/// rolled back successfully.
///
/// # Synchronous execution
///
/// This is synchronous operation, i.e. all guests that participate in the transaction are executed
/// in lockstep until the transaction completes. The transaction is considered complete when either
/// both guests call [`end_transaction`] or one of the guests panics.
pub unsafe extern "C" fn end_transaction() {}