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file.go
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file.go
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// Copyright 2013 Tumblr, Inc.
// Use of this source code is governed by the license for
// The Go Circuit Project, found in the LICENSE file.
//
// Authors:
// 2013 Petar Maymounkov <p@gocircuit.org>
// Package file provides ways to pass open files to across circuit runtimes
package file
// XXX: Update this implementation to conform with and use xy/io
import (
"encoding/gob"
"os"
"runtime"
"github.com/hoijui/circuit/pkg/use/circuit"
"github.com/hoijui/circuit/pkg/use/errors"
)
func init() {
gob.Register(&os.PathError{})
}
// NewFileClient consumes a cross-interface, backed by a FileServer on a remote worker, and
// returns a local proxy object with convinient access methods
func NewFileClient(x circuit.X) *FileClient {
return &FileClient{X: x}
}
// FileClient is a convenience wrapper for using a cross-interface, referring to a FileServer remote object.
type FileClient struct {
circuit.X
}
func asError(x interface{}) error {
if x == nil {
return nil
}
return x.(error)
}
func asFileInfo(x interface{}) os.FileInfo {
if x == nil {
return nil
}
return x.(os.FileInfo)
}
func asFileInfoSlice(x interface{}) []os.FileInfo {
if x == nil {
return nil
}
return x.([]os.FileInfo)
}
func asBytes(x interface{}) []byte {
if x == nil {
return nil
}
return x.([]byte)
}
func fileRecover(pe *error) {
if p := recover(); p != nil {
*pe = errors.NewError("server died")
}
}
// Close closes this file.
func (fcli *FileClient) Close() (err error) {
defer fileRecover(&err)
return asError(fcli.Call("Close")[0])
}
// Stat returns meta-information about this file.
func (fcli *FileClient) Stat() (_ os.FileInfo, err error) {
defer fileRecover(&err)
r := fcli.Call("Stat")
return asFileInfo(r[0]), asError(r[1])
}
// Readdir returns a directory listing of this file, if it is a directory.
func (fcli *FileClient) Readdir(count int) (_ []os.FileInfo, err error) {
defer fileRecover(&err)
r := fcli.Call("Readdir", count)
return asFileInfoSlice(r[0]), asError(r[1])
}
// Read reads a slice of bytes from this file.
func (fcli *FileClient) Read(p []byte) (_ int, err error) {
defer fileRecover(&err)
r := fcli.Call("Read", len(p))
q, err := asBytes(r[0]), asError(r[1])
if len(q) > len(p) {
panic("corrupt file server")
}
copy(p, q)
return len(q), err
}
// Seek seeks the cursor of this file.
func (fcli *FileClient) Seek(offset int64, whence int) (_ int64, err error) {
defer fileRecover(&err)
r := fcli.Call("Seek", offset, whence)
return r[0].(int64), asError(r[1])
}
// Truncate truncates this file.
func (fcli *FileClient) Truncate(size int64) (err error) {
defer fileRecover(&err)
return asError(fcli.Call("Truncate", size)[0])
}
// Write writes a slice of bytes to this file.
func (fcli *FileClient) Write(p []byte) (_ int, err error) {
defer fileRecover(&err)
r := fcli.Call("Write", p)
return r[0].(int), asError(r[1])
}
// Sync flushes any unflushed write buffers.
func (fcli *FileClient) Sync() (err error) {
defer fileRecover(&err)
return asError(fcli.Call("Sync")[0])
}
// NewFileServer returns a file object which can be passed across runtimes.
// It makes sure to close the file if the no more references to the object remain in the circtui.
func NewFileServer(f *os.File) *FileServer {
fsrv := &FileServer{f: f}
runtime.SetFinalizer(fsrv, func(fsrv_ *FileServer) {
fsrv.f.Close()
})
return fsrv
}
// FileServer is an cross-worker exportable interface to a locally-open file.
type FileServer struct {
f *os.File
}
func init() {
circuit.RegisterValue(&FileServer{})
}
// Close closes this file.
func (fsrv *FileServer) Close() error {
return fsrv.f.Close()
}
// Stat returns meta-information about this file.
func (fsrv *FileServer) Stat() (os.FileInfo, error) {
fi, err := fsrv.f.Stat()
return NewFileInfoOS(fi), err
}
// Readdir lists the contents of this file, if it is a directory.
func (fsrv *FileServer) Readdir(count int) ([]os.FileInfo, error) {
ff, err := fsrv.f.Readdir(count)
for i, f := range ff {
ff[i] = NewFileInfoOS(f)
}
return ff, err
}
// Read reads a slice of bytes from this file.
func (fsrv *FileServer) Read(n int) ([]byte, error) {
p := make([]byte, min(n, 1e4))
m, err := fsrv.f.Read(p)
return p[:m], err
}
func min(x, y int) int {
if x < y {
return x
}
return y
}
// Seek changes the position of the cursor in this file.
func (fsrv *FileServer) Seek(offset int64, whence int) (int64, error) {
return fsrv.f.Seek(offset, whence)
}
// Truncate truncates this file.
func (fsrv *FileServer) Truncate(size int64) error {
return fsrv.f.Truncate(size)
}
// Write writes a slice of bytes to this file.
func (fsrv *FileServer) Write(p []byte) (int, error) {
return fsrv.f.Write(p)
}
// Sync flushes any unflushed write buffers.
func (fsrv *FileServer) Sync() error {
return fsrv.f.Sync()
}