utils: fs, new memory filesystem (#108)

* utils: fs, new memory filesystem

* utils: fs, renamed os.NewOS to os.New

* utils: fs, memory changes requested by @alcortes

1 files changed, 354 insertions, 0 deletions

diff --git a/utils/fs/memory/memory.go b/utils/fs/memory/memory.go
new file mode 100644
index 0000000..08a9599
--- /dev/null
+++ b/utils/fs/memory/memory.go
@@ -0,0 +1,354 @@
+package memory
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"gopkg.in/src-d/go-git.v4/utils/fs"
+)
+
+const separator = '/'
+
+// Memory a very convenient filesystem based on memory files
+type Memory struct {
+	base      string
+	s         *storage
+	tempCount int
+}
+
+//New returns a new Memory filesystem
+func New() *Memory {
+	return &Memory{
+		base: "/",
+		s:    &storage{make(map[string]*file, 0)},
+	}
+}
+
+func (fs *Memory) Create(filename string) (fs.File, error) {
+	return fs.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0)
+}
+
+func (fs *Memory) Open(filename string) (fs.File, error) {
+	return fs.OpenFile(filename, os.O_RDONLY, 0)
+}
+
+func (fs *Memory) OpenFile(filename string, flag int, perm os.FileMode) (fs.File, error) {
+	fullpath := fs.Join(fs.base, filename)
+	f, ok := fs.s.files[fullpath]
+	if !ok && !isCreate(flag) {
+		return nil, os.ErrNotExist
+	}
+
+	if f == nil {
+		fs.s.files[fullpath] = newFile(fs.base, fullpath, flag)
+		return fs.s.files[fullpath], nil
+	}
+
+	n := newFile(fs.base, fullpath, flag)
+	n.content = f.content
+
+	if isAppend(flag) {
+		n.position = int64(n.content.Len())
+	}
+
+	if isTruncate(flag) {
+		n.content.Truncate()
+	}
+
+	return n, nil
+}
+
+func (fs *Memory) Stat(filename string) (fs.FileInfo, error) {
+	fullpath := fs.Join(fs.base, filename)
+
+	if _, ok := fs.s.files[filename]; ok {
+		return newFileInfo(fs.base, fullpath, fs.s.files[filename].content.Len()), nil
+	}
+
+	info, err := fs.ReadDir(filename)
+	if err == nil && len(info) != 0 {
+		return newFileInfo(fs.base, fullpath, len(info)), nil
+	}
+
+	return nil, os.ErrNotExist
+}
+
+func (fs *Memory) ReadDir(base string) (entries []fs.FileInfo, err error) {
+	base = fs.Join(fs.base, base)
+
+	appendedDirs := make(map[string]bool, 0)
+	for fullpath, f := range fs.s.files {
+		if !strings.HasPrefix(fullpath, base) {
+			continue
+		}
+
+		fullpath, _ = filepath.Rel(base, fullpath)
+		parts := strings.Split(fullpath, string(separator))
+
+		if len(parts) == 1 {
+			entries = append(entries, newFileInfo(fs.base, fullpath, f.content.Len()))
+			continue
+		}
+
+		if _, ok := appendedDirs[parts[0]]; ok {
+			continue
+		}
+
+		entries = append(entries, &fileInfo{name: parts[0], isDir: true})
+		appendedDirs[parts[0]] = true
+	}
+
+	return
+}
+
+var maxTempFiles = 1024 * 4
+
+func (fs *Memory) TempFile(dir, prefix string) (fs.File, error) {
+	var fullpath string
+	for {
+		if fs.tempCount >= maxTempFiles {
+			return nil, errors.New("max. number of tempfiles reached")
+		}
+
+		fullpath = fs.getTempFilename(dir, prefix)
+		if _, ok := fs.s.files[fullpath]; !ok {
+			break
+		}
+	}
+
+	return fs.Create(fullpath)
+}
+
+func (fs *Memory) getTempFilename(dir, prefix string) string {
+	fs.tempCount++
+	filename := fmt.Sprintf("%s_%d_%d", prefix, fs.tempCount, time.Now().UnixNano())
+	return fs.Join(fs.base, dir, filename)
+}
+
+func (fs *Memory) Rename(from, to string) error {
+	from = fs.Join(fs.base, from)
+	to = fs.Join(fs.base, to)
+
+	if _, ok := fs.s.files[from]; !ok {
+		return os.ErrNotExist
+	}
+
+	fs.s.files[to] = fs.s.files[from]
+	fs.s.files[to].BaseFilename = to
+	delete(fs.s.files, from)
+
+	return nil
+}
+
+func (fs *Memory) Remove(filename string) error {
+	fullpath := fs.Join(fs.base, filename)
+	if _, ok := fs.s.files[fullpath]; !ok {
+		return os.ErrNotExist
+	}
+
+	delete(fs.s.files, fullpath)
+	return nil
+}
+
+func (fs *Memory) Join(elem ...string) string {
+	return filepath.Join(elem...)
+}
+
+func (fs *Memory) Dir(path string) fs.Filesystem {
+	return &Memory{
+		base: fs.Join(fs.base, path),
+		s:    fs.s,
+	}
+}
+
+func (fs *Memory) Base() string {
+	return fs.base
+}
+
+type file struct {
+	fs.BaseFile
+
+	content  *content
+	position int64
+	flag     int
+}
+
+func newFile(base, fullpath string, flag int) *file {
+	filename, _ := filepath.Rel(base, fullpath)
+
+	return &file{
+		BaseFile: fs.BaseFile{BaseFilename: filename},
+		content:  &content{},
+		flag:     flag,
+	}
+}
+
+func (f *file) Read(b []byte) (int, error) {
+	if f.IsClosed() {
+		return 0, fs.ErrClosed
+	}
+
+	if !isReadAndWrite(f.flag) && !isReadOnly(f.flag) {
+		return 0, errors.New("read not supported")
+	}
+
+	n, err := f.content.ReadAt(b, f.position)
+	f.position += int64(n)
+
+	return n, err
+}
+
+func (f *file) Seek(offset int64, whence int) (int64, error) {
+	if f.IsClosed() {
+		return 0, fs.ErrClosed
+	}
+
+	switch whence {
+	case io.SeekCurrent:
+		f.position += offset
+	case io.SeekStart:
+		f.position = offset
+	case io.SeekEnd:
+		f.position = int64(f.content.Len()) - offset
+	}
+
+	return f.position, nil
+}
+
+func (f *file) Write(p []byte) (int, error) {
+	if f.IsClosed() {
+		return 0, fs.ErrClosed
+	}
+
+	if !isReadAndWrite(f.flag) && !isWriteOnly(f.flag) {
+		return 0, errors.New("write not supported")
+	}
+
+	n, err := f.content.WriteAt(p, f.position)
+	f.position += int64(n)
+
+	return n, err
+}
+
+func (f *file) Close() error {
+	if f.IsClosed() {
+		return errors.New("file already closed")
+	}
+
+	f.Closed = true
+	return nil
+}
+
+func (f *file) Open() error {
+	f.Closed = false
+	return nil
+}
+
+type fileInfo struct {
+	name  string
+	size  int
+	isDir bool
+}
+
+func newFileInfo(base, fullpath string, size int) *fileInfo {
+	filename, _ := filepath.Rel(base, fullpath)
+
+	return &fileInfo{
+		name: filename,
+		size: size,
+	}
+}
+
+func (fi *fileInfo) Name() string {
+	return fi.name
+}
+
+func (fi *fileInfo) Size() int64 {
+	return int64(fi.size)
+}
+
+func (fi *fileInfo) Mode() os.FileMode {
+	return os.FileMode(0)
+}
+
+func (*fileInfo) ModTime() time.Time {
+	return time.Now()
+}
+
+func (fi *fileInfo) IsDir() bool {
+	return fi.isDir
+}
+
+func (*fileInfo) Sys() interface{} {
+	return nil
+}
+
+type storage struct {
+	files map[string]*file
+}
+
+type content struct {
+	bytes []byte
+}
+
+func (c *content) WriteAt(p []byte, off int64) (int, error) {
+	prev := len(c.bytes)
+	c.bytes = append(c.bytes[:off], p...)
+	if len(c.bytes) < prev {
+		c.bytes = c.bytes[:prev]
+	}
+
+	return len(p), nil
+}
+
+func (c *content) ReadAt(b []byte, off int64) (int, error) {
+	size := int64(len(c.bytes))
+	if off >= size {
+		return 0, io.EOF
+	}
+
+	l := int64(len(b))
+	if off+l > size {
+		l = size - off
+	}
+
+	n := copy(b, c.bytes[off:off+l])
+	return n, nil
+}
+
+func (c *content) Truncate() {
+	c.bytes = make([]byte, 0)
+}
+
+func (c *content) Len() int {
+	return len(c.bytes)
+}
+
+func isCreate(flag int) bool {
+	return flag&os.O_CREATE != 0
+}
+
+func isAppend(flag int) bool {
+	return flag&os.O_APPEND != 0
+}
+
+func isTruncate(flag int) bool {
+	return flag&os.O_TRUNC != 0
+}
+
+func isReadAndWrite(flag int) bool {
+	return flag&os.O_RDWR != 0
+}
+
+func isReadOnly(flag int) bool {
+	return flag == os.O_RDONLY
+}
+
+func isWriteOnly(flag int) bool {
+	return flag&os.O_WRONLY != 0
+}