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Package sysfs

import "github.com/tetratelabs/wazero/experimental/sysfs"
Overview
Index
Examples

Overview ▾

Package sysfs includes a low-level filesystem interface and utilities needed for WebAssembly host functions (ABI) such as WASI and runtime.GOOS=js.

The name sysfs was chosen because wazero's public API has a "sys" package, which was named after https://github.com/golang/sys.

This tracked in https://github.com/tetratelabs/wazero/issues/1013

func DirFS 

func DirFS(dir string) experimentalsys.FS

DirFS is like os.DirFS except it returns sys.FS, which has more features.

▾ Example

This example shows how to configure a sysfs.DirFS

Code:

root := sysfs.DirFS(".")

moduleConfig = wazero.NewModuleConfig().
    WithFSConfig(wazero.NewFSConfig().(sysfs.FSConfig).WithSysFSMount(root, "/"))

type AdaptFS

AdaptFS adapts the input to sys.FS. Use DirFS instead of adapting an os.DirFS as it handles interop issues such as windows support.

Note: This performs no flag verification on OpenFile. sys.FS cannot read flags as there is no parameter to pass them through with. Moreover, sys.FS documentation does not require the file to be present. In summary, we can't enforce flag behavior. 

type AdaptFS = sysfs.AdaptFS

▾ Example

This example shows how to adapt a fs.FS to a sys.FS

Code:

m := fstest.MapFS{
    "a/b.txt": &fstest.MapFile{Mode: 0o666},
    ".":       &fstest.MapFile{Mode: 0o777 | fs.ModeDir},
}
root := &sysfs.AdaptFS{FS: m}

moduleConfig = wazero.NewModuleConfig().
    WithFSConfig(wazero.NewFSConfig().(sysfs.FSConfig).WithSysFSMount(root, "/"))

type FSConfig

FSConfig extends wazero.FSConfig, allowing access to the experimental sys.FS until it is moved to the "sys" package. 

type FSConfig interface {
    // WithSysFSMount assigns a sys.FS file system for any paths beginning at
    // `guestPath`.
    //
    // This is an alternative to WithFSMount, allowing more features.
    WithSysFSMount(fs experimentalsys.FS, guestPath string) wazero.FSConfig
}

type ReadFS

ReadFS is used to mask an existing sys.FS for reads. Notably, this allows the CLI to do read-only mounts of directories the host user can write, but doesn't want the guest wasm to. For example, Python libraries shouldn't be written to at runtime by the python wasm file.

Note: This implements read-only by returning sys.EROFS or sys.EBADF, depending on the operation that require write access. 

type ReadFS = sysfs.ReadFS

▾ Example

This example shows how to configure a sysfs.ReadFS

Code:

root := sysfs.DirFS(".")
readOnly := &sysfs.ReadFS{FS: root}

moduleConfig = wazero.NewModuleConfig().
    WithFSConfig(wazero.NewFSConfig().(sysfs.FSConfig).WithSysFSMount(readOnly, "/"))