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The IC Polyfill library

Tests Coverage

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++.
init_with_memory(seed: &[u8], env_pairs: &[(&str, &str)]), memory: Memory) Initialization on top of custom memory provided by user.
init_with_memory_manager(seed: &[u8], env_pairs: &[(&str, &str)]), memory_manager: &MemoryManager, memory_index_range: Range<u8>) Initialization with the provided memory manager and a range of memory indices to be used by the stable storage.
mount_memory_file(file_name: &str, memory: Box<dyn Memory>) mount memory onto a given file_name. Any read and write calls will be forwarded to reading and writing in the memory provided.
unmount_memory_file(file_name: &str) unmount memory from a host file file_name. The file will work as usual.
init_memory_file(file_name: &str) Initialize memory contents with the contents of the file.
store_memory_file(file_name: &str) Store memory contents into the file.

Project features

The polyfill library's behavior can be configured using the following 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.