1 files changed, 375 insertions, 0 deletions
diff --git a/modules/assetfs/embed.go b/modules/assetfs/embed.go
new file mode 100644
index 0000000000..95176372d1
--- /dev/null
+++ b/modules/assetfs/embed.go
@@ -0,0 +1,375 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package assetfs
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/util"
+)
+
+type EmbeddedFile interface {
+	io.ReadSeeker
+	fs.ReadDirFile
+	ReadDir(n int) ([]fs.DirEntry, error)
+}
+
+type EmbeddedFileInfo interface {
+	fs.FileInfo
+	fs.DirEntry
+	GetGzipContent() ([]byte, bool)
+}
+
+type decompressor interface {
+	io.Reader
+	Close() error
+	Reset(io.Reader) error
+}
+
+type embeddedFileInfo struct {
+	fs       *embeddedFS
+	fullName string
+	data     []byte
+
+	BaseName   string              `json:"n"`
+	OriginSize int64               `json:"s,omitempty"`
+	DataBegin  int64               `json:"b,omitempty"`
+	DataLen    int64               `json:"l,omitempty"`
+	Children   []*embeddedFileInfo `json:"c,omitempty"`
+}
+
+func (fi *embeddedFileInfo) GetGzipContent() ([]byte, bool) {
+	// when generating the bindata, if the compressed data equals or is larger than the original data, we store the original data
+	if fi.DataLen == fi.OriginSize {
+		return nil, false
+	}
+	return fi.data, true
+}
+
+type EmbeddedFileBase struct {
+	info       *embeddedFileInfo
+	dataReader io.ReadSeeker
+	seekPos    int64
+}
+
+func (f *EmbeddedFileBase) ReadDir(n int) ([]fs.DirEntry, error) {
+	// this method is used to satisfy the "func (f ioFile) ReadDir(...)" in httpfs
+	l, err := f.info.fs.ReadDir(f.info.fullName)
+	if err != nil {
+		return nil, err
+	}
+	if n < 0 || n > len(l) {
+		return l, nil
+	}
+	return l[:n], nil
+}
+
+type EmbeddedOriginFile struct {
+	EmbeddedFileBase
+}
+
+type EmbeddedCompressedFile struct {
+	EmbeddedFileBase
+	decompressor    decompressor
+	decompressorPos int64
+}
+
+type embeddedFS struct {
+	meta func() *EmbeddedMeta
+
+	files   map[string]*embeddedFileInfo
+	filesMu sync.RWMutex
+
+	data []byte
+}
+
+type EmbeddedMeta struct {
+	Root *embeddedFileInfo
+}
+
+func NewEmbeddedFS(data []byte) fs.ReadDirFS {
+	efs := &embeddedFS{data: data, files: make(map[string]*embeddedFileInfo)}
+	efs.meta = sync.OnceValue(func() *EmbeddedMeta {
+		var meta EmbeddedMeta
+		p := bytes.LastIndexByte(data, '\n')
+		if p < 0 {
+			return &meta
+		}
+		if err := json.Unmarshal(data[p+1:], &meta); err != nil {
+			panic("embedded file is not valid")
+		}
+		return &meta
+	})
+	return efs
+}
+
+var _ fs.ReadDirFS = (*embeddedFS)(nil)
+
+func (e *embeddedFS) ReadDir(name string) (l []fs.DirEntry, err error) {
+	fi, err := e.getFileInfo(name)
+	if err != nil {
+		return nil, err
+	}
+	if !fi.IsDir() {
+		return nil, fs.ErrNotExist
+	}
+	l = make([]fs.DirEntry, len(fi.Children))
+	for i, child := range fi.Children {
+		l[i], err = e.getFileInfo(name + "/" + child.BaseName)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return l, nil
+}
+
+func (e *embeddedFS) getFileInfo(fullName string) (*embeddedFileInfo, error) {
+	// no need to do heavy "path.Clean()" because we don't want to support "foo/../bar" or absolute paths
+	fullName = strings.TrimPrefix(fullName, "./")
+	if fullName == "" {
+		fullName = "."
+	}
+
+	e.filesMu.RLock()
+	fi := e.files[fullName]
+	e.filesMu.RUnlock()
+	if fi != nil {
+		return fi, nil
+	}
+
+	fields := strings.Split(fullName, "/")
+	fi = e.meta().Root
+	if fullName != "." {
+		found := true
+		for _, field := range fields {
+			for _, child := range fi.Children {
+				if found = child.BaseName == field; found {
+					fi = child
+					break
+				}
+			}
+			if !found {
+				return nil, fs.ErrNotExist
+			}
+		}
+	}
+
+	e.filesMu.Lock()
+	defer e.filesMu.Unlock()
+	if fi != nil {
+		fi.fs = e
+		fi.fullName = fullName
+		fi.data = e.data[fi.DataBegin : fi.DataBegin+fi.DataLen]
+		e.files[fullName] = fi // do not cache nil, otherwise keeping accessing random non-existing file will cause OOM
+		return fi, nil
+	}
+	return nil, fs.ErrNotExist
+}
+
+func (e *embeddedFS) Open(name string) (fs.File, error) {
+	info, err := e.getFileInfo(name)
+	if err != nil {
+		return nil, err
+	}
+	base := EmbeddedFileBase{info: info}
+	base.dataReader = bytes.NewReader(base.info.data)
+	if info.DataLen != info.OriginSize {
+		decomp, err := gzip.NewReader(base.dataReader)
+		if err != nil {
+			return nil, err
+		}
+		return &EmbeddedCompressedFile{EmbeddedFileBase: base, decompressor: decomp}, nil
+	}
+	return &EmbeddedOriginFile{base}, nil
+}
+
+var (
+	_ EmbeddedFileInfo = (*embeddedFileInfo)(nil)
+	_ EmbeddedFile     = (*EmbeddedOriginFile)(nil)
+	_ EmbeddedFile     = (*EmbeddedCompressedFile)(nil)
+)
+
+func (f *EmbeddedOriginFile) Read(p []byte) (n int, err error) {
+	return f.dataReader.Read(p)
+}
+
+func (f *EmbeddedCompressedFile) Read(p []byte) (n int, err error) {
+	if f.decompressorPos > f.seekPos {
+		if err = f.decompressor.Reset(bytes.NewReader(f.info.data)); err != nil {
+			return 0, err
+		}
+		f.decompressorPos = 0
+	}
+	if f.decompressorPos < f.seekPos {
+		if _, err = io.CopyN(io.Discard, f.decompressor, f.seekPos-f.decompressorPos); err != nil {
+			return 0, err
+		}
+		f.decompressorPos = f.seekPos
+	}
+	n, err = f.decompressor.Read(p)
+	f.decompressorPos += int64(n)
+	f.seekPos = f.decompressorPos
+	return n, err
+}
+
+func (f *EmbeddedFileBase) Seek(offset int64, whence int) (int64, error) {
+	switch whence {
+	case io.SeekStart:
+		f.seekPos = offset
+	case io.SeekCurrent:
+		f.seekPos += offset
+	case io.SeekEnd:
+		f.seekPos = f.info.OriginSize + offset
+	}
+	return f.seekPos, nil
+}
+
+func (f *EmbeddedFileBase) Stat() (fs.FileInfo, error) {
+	return f.info, nil
+}
+
+func (f *EmbeddedOriginFile) Close() error {
+	return nil
+}
+
+func (f *EmbeddedCompressedFile) Close() error {
+	return f.decompressor.Close()
+}
+
+func (fi *embeddedFileInfo) Name() string {
+	return fi.BaseName
+}
+
+func (fi *embeddedFileInfo) Size() int64 {
+	return fi.OriginSize
+}
+
+func (fi *embeddedFileInfo) Mode() fs.FileMode {
+	return util.Iif(fi.IsDir(), fs.ModeDir|0o555, 0o444)
+}
+
+func (fi *embeddedFileInfo) ModTime() time.Time {
+	return getExecutableModTime()
+}
+
+func (fi *embeddedFileInfo) IsDir() bool {
+	return fi.Children != nil
+}
+
+func (fi *embeddedFileInfo) Sys() any {
+	return nil
+}
+
+func (fi *embeddedFileInfo) Type() fs.FileMode {
+	return util.Iif(fi.IsDir(), fs.ModeDir, 0)
+}
+
+func (fi *embeddedFileInfo) Info() (fs.FileInfo, error) {
+	return fi, nil
+}
+
+// getExecutableModTime returns the modification time of the executable file.
+// In bindata, we can't use the ModTime of the files because we need to make the build reproducible
+var getExecutableModTime = sync.OnceValue(func() (modTime time.Time) {
+	exePath, err := os.Executable()
+	if err != nil {
+		return modTime
+	}
+	exePath, err = filepath.Abs(exePath)
+	if err != nil {
+		return modTime
+	}
+	exePath, err = filepath.EvalSymlinks(exePath)
+	if err != nil {
+		return modTime
+	}
+	st, err := os.Stat(exePath)
+	if err != nil {
+		return modTime
+	}
+	return st.ModTime()
+})
+
+func GenerateEmbedBindata(fsRootPath, outputFile string) error {
+	output, err := os.OpenFile(outputFile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.ModePerm)
+	if err != nil {
+		return err
+	}
+	defer output.Close()
+
+	meta := &EmbeddedMeta{}
+	meta.Root = &embeddedFileInfo{}
+	var outputOffset int64
+	var embedFiles func(parent *embeddedFileInfo, fsPath, embedPath string) error
+	embedFiles = func(parent *embeddedFileInfo, fsPath, embedPath string) error {
+		dirEntries, err := os.ReadDir(fsPath)
+		if err != nil {
+			return err
+		}
+		for _, dirEntry := range dirEntries {
+			if err != nil {
+				return err
+			}
+			if dirEntry.IsDir() {
+				child := &embeddedFileInfo{
+					BaseName: dirEntry.Name(),
+					Children: []*embeddedFileInfo{}, // non-nil means it's a directory
+				}
+				parent.Children = append(parent.Children, child)
+				if err = embedFiles(child, filepath.Join(fsPath, dirEntry.Name()), path.Join(embedPath, dirEntry.Name())); err != nil {
+					return err
+				}
+			} else {
+				data, err := os.ReadFile(filepath.Join(fsPath, dirEntry.Name()))
+				if err != nil {
+					return err
+				}
+				var compressed bytes.Buffer
+				gz, _ := gzip.NewWriterLevel(&compressed, gzip.BestCompression)
+				if _, err = gz.Write(data); err != nil {
+					return err
+				}
+				if err = gz.Close(); err != nil {
+					return err
+				}
+
+				// only use the compressed data if it is smaller than the original data
+				outputBytes := util.Iif(len(compressed.Bytes()) < len(data), compressed.Bytes(), data)
+				child := &embeddedFileInfo{
+					BaseName:   dirEntry.Name(),
+					OriginSize: int64(len(data)),
+					DataBegin:  outputOffset,
+					DataLen:    int64(len(outputBytes)),
+				}
+				if _, err = output.Write(outputBytes); err != nil {
+					return err
+				}
+				outputOffset += child.DataLen
+				parent.Children = append(parent.Children, child)
+			}
+		}
+		return nil
+	}
+
+	if err = embedFiles(meta.Root, fsRootPath, ""); err != nil {
+		return err
+	}
+	jsonBuf, err := json.Marshal(meta) // can't use json.NewEncoder here because it writes extra EOL
+	if err != nil {
+		return err
+	}
+	_, _ = output.Write([]byte{'\n'})
+	_, err = output.Write(jsonBuf)
+	return err
+}