Module types

WASI filesystem is a filesystem API primarily intended to let users run WASI programs that access their files on their existing filesystems, without significant overhead.

It is intended to be roughly portable between Unix-family platforms and Windows, though it does not hide many of the major differences.

Paths are passed as interface-type strings, meaning they must consist of a sequence of Unicode Scalar Values (USVs). Some filesystems may contain paths which are not accessible by this API.

The directory separator in WASI is always the forward-slash (/).

All paths in WASI are relative paths, and are interpreted relative to a descriptor referring to a base directory. If a path argument to any WASI function starts with /, or if any step of resolving a path, including .. and symbolic link steps, reaches a directory outside of the base directory, or reaches a symlink to an absolute or rooted path in the underlying filesystem, the function fails with error-code::not-permitted.

For more information about WASI path resolution and sandboxing, see WASI filesystem path resolution.

Structs

Descriptor

A descriptor is a reference to a filesystem object, which may be a file, directory, named pipe, special file, or other object on which filesystem calls may be made.

DescriptorFlags

Descriptor flags.

DescriptorStat

File attributes.

DirectoryEntry

A directory entry.

DirectoryEntryStream

A stream of directory entries.

MetadataHashValue

A 128-bit hash value, split into parts because wasm doesn’t have a 128-bit integer type.

OpenFlags

Open flags used by open-at.

PathFlags

Flags determining the method of how paths are resolved.

Enums

Advice

File or memory access pattern advisory information.

DescriptorType

The type of a filesystem object referenced by a descriptor.

ErrorCode

Error codes returned by functions, similar to errno in POSIX. 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.

NewTimestamp

When setting a timestamp, this gives the value to set it to.

Functions

filesystem_error_code

Attempts to extract a filesystem-related error-code from the stream error provided.

Type Aliases

Datetime

Error

Filesize

File size or length of a region within a file.

InputStream

LinkCount

Number of hard links to an inode.

OutputStream