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filemetadata.go
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filemetadata.go
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// Package filemetadata contains types of metadata for files, to be used for caching.
package filemetadata
import (
"fmt"
"os"
"github.com/bazelbuild/remote-apis-sdks/go/pkg/digest"
)
// Metadata contains details for a particular file.
type Metadata struct {
Digest digest.Digest
IsExecutable bool
Err error
}
// FileError is the error returned by the Compute function.
type FileError struct {
IsDirectory bool
IsNotFound bool
IsInvalidSymlink bool
Err error
}
// Error returns the error message.
func (e *FileError) Error() string {
return e.Err.Error()
}
func isSymlink(filename string) (bool, error) {
file, err := os.Lstat(filename)
if err != nil {
return false, err
}
return file.Mode()&os.ModeSymlink != 0, nil
}
// Compute computes a Metadata from a given file path.
// If an error is returned, it will be of type *FileError.
func Compute(filename string) *Metadata {
md := &Metadata{Digest: digest.Empty}
file, err := os.Stat(filename)
if err != nil {
fe := &FileError{Err: err}
if s, err := isSymlink(filename); err == nil && s {
fe.IsInvalidSymlink = true
}
if os.IsNotExist(err) {
fe.IsNotFound = true
}
md.Err = fe
return md
}
mode := file.Mode()
md.IsExecutable = (mode & 0100) != 0
if mode.IsDir() {
md.Err = &FileError{IsDirectory: true, Err: fmt.Errorf("%s is a directory", filename)}
return md
}
md.Digest, md.Err = digest.NewFromFile(filename)
return md
}
// Cache is a cache for file contents->Metadata.
type Cache interface {
Get(path string) *Metadata
Delete(filename string) error
Update(path string, cacheEntry *Metadata) error
Reset()
GetCacheHits() uint64
GetCacheMisses() uint64
}
type noopCache struct{}
// Get computes the metadata from the file contents.
// If an error is returned, it will be in Metadata.Err of type *FileError.
func (c *noopCache) Get(path string) *Metadata {
return Compute(path)
}
// Delete removes an entry from the cache. It is a noop for the Noop cache.
func (c *noopCache) Delete(string) error {
return nil
}
// Update updates a cache entry with the given value. It is a noop for Noop cache.
func (c *noopCache) Update(string, *Metadata) error {
return nil
}
// Reset clears the cache. It is a noop for the Noop cache.
func (c *noopCache) Reset() {}
// GetCacheHits returns the number of cache hits. It returns 0 for Noop cache.
func (c *noopCache) GetCacheHits() uint64 {
return 0
}
// GetCacheMisses returns the number of cache misses.
// It returns 0 for Noop cache.
func (c *noopCache) GetCacheMisses() uint64 {
return 0
}
// NewNoopCache returns a cache that doesn't cache (evaluates on every Get).
func NewNoopCache() Cache {
return &noopCache{}
}