The IC Polyfill library

The project provides polyfill implementation of wasi_unstable and wasi_snapshot_preview1 functions using IC System API.

Usage

The intended use is to add this library as a dependency to your rust project. And then run wasi2ic on the produced Wasm binary.

In your project you would need to call the init function. It makes sure the linker does not remove the functions and can be used to initialize the random seed and define some environment variables.

Example:

    init(&[12,3,54,1], &[("PATH", "/usr/bin"), ("UID", "1028"), ("HOME", "/home/user")]);

Supported WASI functions (wasi_unstable, wasi_snapshot_preview1)

Status	Description
Supported	Function is fully supported.
No-op	Empty implementation that does nothing but can be called without issues.
Not implemented	Function is not yet implemented - calling it causes the application to panic.
Not supported	Function is not planned to be implemented - calling it causes the application to panic.

WASI function	Status
args_get	No-op
args_sizes_get	No-op
clock_res_get	Supported
clock_time_get	Supported
environ_get	Supported
environ_sizes_get	Supported
fd_advise	No-op
fd_allocate	No-op
fd_close	Supported
fd_datasync	No-op
fd_fdstat_get	Supported
fd_fdstat_set_flags	Supported
fd_fdstat_set_rights	Supported
fd_filestat_get	Supported
fd_filestat_set_size	No-op
fd_filestat_set_times	Supported
fd_pread	Supported
fd_prestat_dir_name	Supported
fd_prestat_get	Supported
fd_pwrite	Supported
fd_read	Supported
fd_readdir	Supported
fd_renumber	Supported
fd_seek	Supported
fd_sync	Supported
fd_tell	Supported
fd_write	Supported
path_create_directory	Supported
path_filestat_get	Supported1
path_filestat_set_times	Supported1
path_link	Supported1
path_open	Supported1
path_readlink	Not implemented
path_remove_directory	Supported
path_rename	Supported
path_symlink	Not implemented
path_unlink_file	Supported
poll_oneoff	Not implemented
proc_exit	Supported
proc_raise	Not implemented
random_get	Supported2
sched_yield	No-op
sock_accept	Not supported
sock_recv	Not supported
sock_send	Not supported
sock_shutdown	Not supported

¹ - Currently symlinks are not supported by the file system, this affects a few path_ functions, the flags ("follow symlink") parameter is currently ignored.

² - The random_get function utilizes a synchronous pseudo-random number generator.

Additional library functions

Function	Description
init(seed: &[u8], env_pairs: &[(&str, &str)])	Initialization call.
raw_init(seed: *const u8, len: usize)	Similar to init, but has simpler parameters for calling from C or C++.
init_seed(seed: &[u8])	Convenience method to explicitly re-initialize the random seed.
raw_init_seed(seed: *const u8, len: usize)	Similar to init_seed, but has simpler parameters for calling from C or C++.

Project features

The polyfill library's behavior can be configured using the following Cargo features:

• transient use the transient file system implementation. This works faster but does not take the advantage of keeping the file system's state in stable memory (and the ability to keep FS state between canister upgrades).
• report_wasi_calls outputs statistical information of the called polyfill functions.
• skip_unimplemented_functions rather than throw exception on calling the unimplemented function, its implementation will be missing in the compilation. This can be useful if you want to provide custom implementations for those functions.