memory index enumerate support. untested.

Change-Id: I28df97ed6385675545a74a6e01e779cc627ef033

lib/go/camli/index/enumstat.go

@@ -18,14 +18,29 @@ package index
 
 import (
 	"os"
+	"strconv"
+	"strings"
 
 	"camli/blobref"
 )
 
 func (ix *Index) EnumerateBlobs(dest chan<- blobref.SizedBlobRef, after string, limit uint, waitSeconds int) os.Error {
 	defer close(dest)
-	panic("TODO")
-	return nil
+	it := ix.s.Find("have:"+after)
+	n := uint(0)
+	for n < limit && it.Next() {
+		k := it.Key()
+		if !strings.HasPrefix(k, "have:") {
+			break
+		}
+		n++
+		br := blobref.Parse(k[len("have:"):])
+		size, err := strconv.Atoi64(it.Value())
+		if br != nil && err == nil {
+			dest <- blobref.SizedBlobRef{br, size}
+		}
+	}
+	return it.Close()
 }
 
 func (ix *Index) StatBlobs(dest chan<- blobref.SizedBlobRef, blobs []*blobref.BlobRef, waitSeconds int) os.Error {

lib/go/camli/index/index.go

@@ -31,6 +31,42 @@ type IndexStorage interface {
 
 	BeginBatch() BatchMutation
 	CommitBatch(b BatchMutation) os.Error
+
+	// Find returns an iterator positioned before the first key/value pair
+	// whose key is 'greater than or equal to' the given key. There may be no
+	// such pair, in which case the iterator will return false on Next.
+	//
+	// Any error encountered will be implicitly returned via the iterator. An
+	// error-iterator will yield no key/value pairs and closing that iterator
+	// will return that error.
+	Find(key string) Iterator
+}
+
+// Iterator iterates over an index Storage's key/value pairs in key order.
+//
+// An iterator must be closed after use, but it is not necessary to read an
+// iterator until exhaustion.
+//
+// An iterator is not necessarily goroutine-safe, but it is safe to use
+// multiple iterators concurrently, with each in a dedicated goroutine.
+type Iterator interface {
+	// Next moves the iterator to the next key/value pair.
+	// It returns whether the iterator is exhausted.
+	Next() bool
+
+	// Key returns the key of the current key/value pair.
+	// Only valid after a call to Next returns true.
+	Key() string
+
+	// Value returns the value of the current key/value pair.
+	// Only valid after a call to Next returns true.
+	Value() string
+
+	// Close closes the iterator and returns any accumulated error. Exhausting
+	// all the key/value pairs in a table is not considered to be an error.
+	// It is valid to call Close multiple times. Other methods should not be
+	// called after the iterator has been closed.
+	Close() os.Error
 }
 
 type BatchMutation interface {

lib/go/camli/index/memindex.go

@@ -38,6 +38,28 @@ type memKeys struct {
 	db db.DB
 }
 
+// stringIterator converts from leveldb's db.Iterator interface, which
+// operates on []byte, to Camlistore's index.Iterator, which operates
+// on string.
+type stringIterator struct {
+	db.Iterator
+}
+
+func (s stringIterator) Key() string {
+	return string(s.Iterator.Key())
+}
+
+func (s stringIterator) Value() string {
+	return string(s.Iterator.Value())
+}
+
+func (mk *memKeys) Find(key string) Iterator {
+	mk.mu.Lock()
+	defer mk.mu.Unlock()
+	dit := mk.db.Find([]byte(key))
+	return stringIterator{dit}
+}
+
 func (mk *memKeys) Set(key, value string) os.Error {
 	mk.mu.Lock()
 	defer mk.mu.Unlock()