services/syncbase/server/util/glob.go

// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package util

import (
	"strings"

	"v.io/syncbase/x/ref/services/syncbase/store"
	"v.io/v23/context"
	"v.io/v23/naming"
	"v.io/v23/rpc"
	"v.io/v23/verror"
	"v.io/x/lib/vlog"
	"v.io/x/ref/lib/glob"
)

// globPatternToPrefix takes "foo*" and returns "foo". It returns ErrBadArg for
// inputs that are not valid glob patterns as well as for inputs that are valid
// glob patterns but not valid prefixes.
func globPatternToPrefix(pattern string) (string, error) {
	if _, err := glob.Parse(pattern); err != nil {
		return "", verror.NewErrBadArg(nil)
	}
	if pattern == "" {
		return "", verror.NewErrBadArg(nil)
	}
	if pattern[len(pattern)-1] != '*' {
		return "", verror.NewErrBadArg(nil)
	}
	res := pattern[:len(pattern)-1]
	// Disallow chars and char sequences that have special meaning in glob, since
	// our Glob() does not support these.
	if strings.ContainsAny(res, "/*?[") {
		return "", verror.NewErrBadArg(nil)
	}
	if strings.Contains(res, "...") {
		return "", verror.NewErrBadArg(nil)
	}
	return res, nil
}

// TODO(sadovsky): It sucks that Glob must be implemented differently from other
// streaming RPC handlers. I don't have much confidence that I've implemented
// both types of streaming correctly.
func Glob(ctx *context.T, call rpc.ServerCall, pattern string, sn store.Snapshot, stKeyPrefix string) (<-chan naming.GlobReply, error) {
	// TODO(sadovsky): Support glob with non-prefix pattern.
	prefix, err := globPatternToPrefix(pattern)
	if err != nil {
		sn.Close()
		if verror.ErrorID(err) == verror.ErrBadArg.ID {
			return nil, verror.NewErrNotImplemented(ctx)
		} else {
			return nil, verror.New(verror.ErrInternal, ctx, err)
		}
	}
	it := sn.Scan(ScanPrefixArgs(stKeyPrefix, prefix))
	ch := make(chan naming.GlobReply)
	go func() {
		defer sn.Close()
		defer close(ch)
		key := []byte{}
		for it.Advance() {
			key = it.Key(key)
			parts := SplitKeyParts(string(key))
			ch <- naming.GlobReplyEntry{naming.MountEntry{Name: parts[len(parts)-1]}}
		}
		if err := it.Err(); err != nil {
			vlog.VI(1).Infof("Glob(%q) failed: %v", pattern, err)
			ch <- naming.GlobReplyError{naming.GlobError{
				Error: verror.New(verror.ErrInternal, ctx, err),
			}}
		}
	}()
	return ch, nil
}