6bcb40fe01
This allows applications to mount filesystems in the os package. This is useful for mounting external flash filesystems, for example.
85 строки
3 КиБ
Go
85 строки
3 КиБ
Go
package os
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import (
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"strings"
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)
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// mounts lists the mount points currently mounted in the filesystem provided by
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// the os package. To resolve a path to a mount point, it is scanned from top to
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// bottom looking for the first prefix match.
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var mounts []mountPoint
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type mountPoint struct {
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// prefix is a filesystem prefix, that always starts and ends with a forward
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// slash. To denote the root filesystem, use a single slash: "/".
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// This allows fast checking whether a path lies within a mount point.
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prefix string
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// filesystem is the Filesystem implementation that is mounted at this mount
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// point.
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filesystem Filesystem
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}
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// Filesystem provides an interface for generic filesystem drivers mounted in
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// the os package. The errors returned must be one of the os.Err* errors, or a
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// custom error if one doesn't exist. It should not be a *PathError because
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// errors will be wrapped with a *PathError by the filesystem abstraction.
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//
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// WARNING: this interface is not finalized and may change in a future version.
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type Filesystem interface {
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// OpenFile opens the named file.
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OpenFile(name string, flag int, perm FileMode) (FileHandle, error)
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// Mkdir creates a new directoy with the specified permission (before
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// umask). Some filesystems may not support directories or permissions.
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Mkdir(name string, perm FileMode) error
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// Remove removes the named file or (empty) directory.
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Remove(name string) error
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}
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// FileHandle is an interface that should be implemented by filesystems
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// implementing the Filesystem interface.
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//
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// WARNING: this interface is not finalized and may change in a future version.
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type FileHandle interface {
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// Read reads up to len(b) bytes from the file.
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Read(b []byte) (n int, err error)
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// Write writes up to len(b) bytes to the file.
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Write(b []byte) (n int, err error)
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// Close closes the file, making it unusable for further writes.
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Close() (err error)
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}
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// findMount returns the appropriate (mounted) filesystem to use for a given
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// filename plus the path relative to that filesystem.
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func findMount(path string) (Filesystem, string) {
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for i := len(mounts) - 1; i >= 0; i-- {
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mount := mounts[i]
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if strings.HasPrefix(path, mount.prefix) {
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return mount.filesystem, path[len(mount.prefix)-1:]
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}
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}
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if isOS {
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// Assume that the first entry in the mounts slice is the OS filesystem
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// at the root of the directory tree. Use it as-is, to support relative
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// paths.
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return mounts[0].filesystem, path
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}
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return nil, path
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}
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// Mount mounts the given filesystem in the filesystem abstraction layer of the
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// os package. It is not possible to unmount filesystems. Filesystems added
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// later will override earlier filesystems.
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//
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// The provided prefix must start and end with a forward slash. This is true for
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// the root directory ("/") for example.
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func Mount(prefix string, filesystem Filesystem) {
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if prefix[0] != '/' || prefix[len(prefix)-1] != '/' {
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panic("os.Mount: invalid prefix")
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}
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mounts = append(mounts, mountPoint{prefix, filesystem})
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}
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