Documentation
¶
Index ¶
- Constants
- Variables
- type Context
- func (c *Context) Args() [][]byte
- func (c *Context) ArgsSize() uint32
- func (c *Context) Environ() [][]byte
- func (c *Context) EnvironSize() uint32
- func (c *Context) FS() *FSContext
- func (c *Context) Nanosleep(ns int64)
- func (c *Context) Nanotime() int64
- func (c *Context) NanotimeResolution() sys.ClockResolution
- func (c *Context) RandSource() io.Reader
- func (c *Context) Walltime() (sec int64, nsec int32)
- func (c *Context) WalltimeResolution() sys.ClockResolution
- type FSContext
- func (c *FSContext) Close(context.Context) (err error)
- func (c *FSContext) CloseFile(fd uint32) bool
- func (c *FSContext) FdReader(fd uint32) io.Reader
- func (c *FSContext) FdWriter(fd uint32) io.Writer
- func (c *FSContext) Mkdir(name string, perm fs.FileMode) (newFD uint32, err error)
- func (c *FSContext) OpenFile(name string, flags int, perm fs.FileMode) (newFD uint32, err error)
- func (c *FSContext) OpenedFile(fd uint32) (*FileEntry, bool)
- func (c *FSContext) Rename(from, to string) (err error)
- func (c *FSContext) Rmdir(name string) (err error)
- func (c *FSContext) StatFile(fd uint32) (fs.FileInfo, error)
- func (c *FSContext) StatPath(name string) (fs.FileInfo, error)
- func (c *FSContext) Unlink(name string) (err error)
- func (c *FSContext) Utimes(name string, atimeNsec, mtimeNsec int64) (err error)
- type FileEntry
- type FileTable
- func (t *FileTable) Delete(fd uint32)
- func (t *FileTable) Grow(n int)
- func (t *FileTable) Insert(file *FileEntry) (fd uint32)
- func (t *FileTable) Len() (n int)
- func (t *FileTable) Lookup(fd uint32) (file *FileEntry, found bool)
- func (t *FileTable) Range(f func(uint32, *FileEntry) bool)
- func (t *FileTable) Reset()
- type ReadDir
Constants ¶
const ( FdStdin uint32 = iota FdStdout FdStderr // FdRoot is the file descriptor of the root ("/") filesystem. // // # Why file descriptor 3? // // While not specified, the most common WASI implementation, wasi-libc, expects // POSIX style file descriptor allocation, where the lowest available number is // used to open the next file. Since 1 and 2 are taken by stdout and stderr, // `root` is assigned 3. // - https://github.com/WebAssembly/WASI/issues/122 // - https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_14 // - https://github.com/WebAssembly/wasi-libc/blob/wasi-sdk-16/libc-bottom-half/sources/preopens.c#L215 FdRoot )
Variables ¶
var EmptyFS = &emptyFS{}
EmptyFS is exported to special-case an empty file system.
Functions ¶
This section is empty.
Types ¶
type Context ¶
type Context struct {
// contains filtered or unexported fields
}
Context holds module-scoped system resources currently only supported by built-in host functions.
func DefaultContext ¶
DefaultContext returns Context with no values set except a possibly nil fs.FS
func NewContext ¶
func NewContext( max uint32, args, environ [][]byte, stdin io.Reader, stdout, stderr io.Writer, randSource io.Reader, walltime *sys.Walltime, walltimeResolution sys.ClockResolution, nanotime *sys.Nanotime, nanotimeResolution sys.ClockResolution, nanosleep *sys.Nanosleep, fs fs.FS, ) (sysCtx *Context, err error)
NewContext is a factory function which helps avoid needing to know defaults or exporting all fields. Note: max is exposed for testing. max is only used for env/args validation.
func (*Context) Args ¶
Args is like os.Args and defaults to nil.
Note: The count will never be more than math.MaxUint32. See wazero.ModuleConfig WithArgs
func (*Context) ArgsSize ¶
ArgsSize is the size to encode Args as Null-terminated strings.
Note: To get the size without null-terminators, subtract the length of Args from this value. See wazero.ModuleConfig WithArgs See https://en.wikipedia.org/wiki/Null-terminated_string
func (*Context) Environ ¶
Environ are "key=value" entries like os.Environ and default to nil.
Note: The count will never be more than math.MaxUint32. See wazero.ModuleConfig WithEnv
func (*Context) EnvironSize ¶
EnvironSize is the size to encode Environ as Null-terminated strings.
Note: To get the size without null-terminators, subtract the length of Environ from this value. See wazero.ModuleConfig WithEnv See https://en.wikipedia.org/wiki/Null-terminated_string
func (*Context) NanotimeResolution ¶
func (c *Context) NanotimeResolution() sys.ClockResolution
NanotimeResolution returns resolution of Nanotime.
func (*Context) RandSource ¶
RandSource is a source of random bytes and defaults to a deterministic source. see wazero.ModuleConfig WithRandSource
func (*Context) WalltimeResolution ¶
func (c *Context) WalltimeResolution() sys.ClockResolution
WalltimeResolution returns resolution of Walltime.
type FSContext ¶
type FSContext struct {
// contains filtered or unexported fields
}
func NewFSContext ¶
func NewFSContext(stdin io.Reader, stdout, stderr io.Writer, root fs.FS) (fsc *FSContext, err error)
NewFSContext creates a FSContext, using the `root` parameter for any paths beginning at "/". If the input is EmptyFS, there is no root filesystem. Otherwise, `root` is assigned file descriptor FdRoot and the returned context can open files in that file system. Any error on opening "." is returned.
func (*FSContext) CloseFile ¶
CloseFile returns true if a file was opened and closed without error, or false if syscall.EBADF.
func (*FSContext) FdReader ¶
FdReader returns a valid reader for the given file descriptor or nil if syscall.EBADF.
func (*FSContext) FdWriter ¶
FdWriter returns a valid writer for the given file descriptor or nil if syscall.EBADF.
func (*FSContext) Mkdir ¶
Mkdir is like syscall.Mkdir and returns the file descriptor of the new directory or an error.
func (*FSContext) OpenFile ¶
OpenFile is like syscall.Open and returns the file descriptor of the new file or an error.
func (*FSContext) OpenedFile ¶
OpenedFile returns a file and true if it was opened or nil and false, if syscall.EBADF.
type FileEntry ¶
type FileEntry struct {
// Name is the basename of the file, at the time it was opened. When the
// file is root "/" (fd = FdRoot), this is "/".
//
// Note: This must match fs.FileInfo.
Name string
// File is always non-nil, even when root "/" (fd = FdRoot).
File fs.File
// ReadDir is present when this File is a fs.ReadDirFile and `ReadDir`
// was called.
ReadDir *ReadDir
}
FileEntry maps a path to an open file in a file system.
type FileTable ¶
type FileTable struct {
// contains filtered or unexported fields
}
FileTable is a data structure mapping 32 bit file descriptor to file objects.
The data structure optimizes for memory density and lookup performance, trading off compute at insertion time. This is a useful compromise for the use cases we employ it with: files are usually read or written a lot more often than they are opened, each operation requires a table lookup so we are better off spending extra compute to insert files in the table in order to get cheaper lookups. Memory efficiency is also crucial to support scaling with programs that open thousands of files: having a high or non-linear memory-to-item ratio could otherwise be used as an attack vector by malicous applications attempting to damage performance of the host.
func (*FileTable) Grow ¶
Grow ensures that t has enough room for n files, potentially reallocating the internal buffers if their capacity was too small to hold this many files.
func (*FileTable) Insert ¶
Insert inserts the given file to the table, returning the fd that it is mapped to.
The method does not perform deduplication, it is possible for the same file to be inserted multiple times, each insertion will return a different fd.
type ReadDir ¶
type ReadDir struct {
// CountRead is the total count of files read including Entries.
CountRead uint64
// Entries is the contents of the last fs.ReadDirFile call. Notably,
// directory listing are not rewindable, so we keep entries around in case
// the caller mis-estimated their buffer and needs a few still cached.
Entries []fs.DirEntry
}
ReadDir is the status of a prior fs.ReadDirFile call.
Source Files