1 files changed, 192 insertions, 0 deletions
diff --git a/utils/merkletrie/internal/fsnoder/new.go b/utils/merkletrie/internal/fsnoder/new.go
new file mode 100644
index 0000000..3ea4733
--- /dev/null
+++ b/utils/merkletrie/internal/fsnoder/new.go
@@ -0,0 +1,192 @@
+package fsnoder
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"gopkg.in/src-d/go-git.v4/utils/merkletrie/noder"
+)
+
+// New function creates a full merkle trie from the string description of
+// a filesystem tree.  See examples of the string format in the package
+// description.
+func New(s string) (noder.Noder, error) {
+	return decodeDir([]byte(s), root)
+}
+
+const (
+	root    = true
+	nonRoot = false
+)
+
+// Expected data: a fsnoder description, for example: A(foo bar qux ...).
+// When isRoot is true, unnamed dirs are supported, for example: (foo
+// bar qux ...)
+func decodeDir(data []byte, isRoot bool) (*dir, error) {
+	data = bytes.TrimSpace(data)
+	if len(data) == 0 {
+		return nil, io.EOF
+	}
+
+	// get the name of the dir (a single letter) and remove it from the
+	// data.  In case the there is no name and isRoot is true, just use
+	// "" as the name.
+	var name string
+	if data[0] == dirStartMark {
+		if isRoot {
+			name = ""
+		} else {
+			return nil, fmt.Errorf("inner unnamed dirs not allowed: %s", data)
+		}
+	} else {
+		name = string(data[0])
+		data = data[1:]
+	}
+
+	// check that data is enclosed in parents and it is big enough and
+	// remove them.
+	if len(data) < 2 {
+		return nil, fmt.Errorf("malformed data: too short")
+	}
+	if data[0] != dirStartMark {
+		return nil, fmt.Errorf("malformed data: first %q not found",
+			dirStartMark)
+	}
+	if data[len(data)-1] != dirEndMark {
+		return nil, fmt.Errorf("malformed data: last %q not found",
+			dirEndMark)
+	}
+	data = data[1 : len(data)-1] // remove initial '(' and last ')'
+
+	children, err := decodeChildren(data)
+	if err != nil {
+		return nil, err
+	}
+
+	return newDir(name, children)
+}
+
+func isNumber(b byte) bool {
+	return '0' <= b && b <= '9'
+}
+
+func isLetter(b byte) bool {
+	return ('a' <= b && b <= 'z') || ('A' <= b && b <= 'Z')
+}
+
+func decodeChildren(data []byte) ([]noder.Noder, error) {
+	data = bytes.TrimSpace(data)
+	if len(data) == 0 {
+		return nil, nil
+	}
+
+	chunks := split(data)
+	ret := make([]noder.Noder, len(chunks))
+	var err error
+	for i, c := range chunks {
+		ret[i], err = decodeChild(c)
+		if err != nil {
+			return nil, fmt.Errorf("malformed element %d (%s): %s", i, c, err)
+		}
+	}
+
+	return ret, nil
+}
+
+// returns the description of the elements of a dir.  It is just looking
+// for spaces if they are not part of inner dirs.
+func split(data []byte) [][]byte {
+	chunks := [][]byte{}
+
+	start := 0
+	dirDepth := 0
+	for i, b := range data {
+		switch b {
+		case dirStartMark:
+			dirDepth++
+		case dirEndMark:
+			dirDepth--
+		case dirElementSep:
+			if dirDepth == 0 {
+				chunks = append(chunks, data[start:i+1])
+				start = i + 1
+			}
+		}
+	}
+	chunks = append(chunks, data[start:])
+
+	return chunks
+}
+
+// A child can be a file or a dir.
+func decodeChild(data []byte) (noder.Noder, error) {
+	clean := bytes.TrimSpace(data)
+	if len(data) < 3 {
+		return nil, fmt.Errorf("element too short: %s", clean)
+	}
+
+	switch clean[1] {
+	case fileStartMark:
+		return decodeFile(clean)
+	case dirStartMark:
+		return decodeDir(clean, nonRoot)
+	default:
+		if clean[0] == dirStartMark {
+			return nil, fmt.Errorf("non-root unnamed dir are not allowed: %s",
+				clean)
+		}
+		return nil, fmt.Errorf("malformed dir element: %s", clean)
+	}
+}
+
+func decodeFile(data []byte) (noder.Noder, error) {
+	if len(data) == 3 {
+		return decodeEmptyFile(data)
+	}
+
+	if len(data) != 4 {
+		return nil, fmt.Errorf("length is not 4")
+	}
+	if !isLetter(data[0]) {
+		return nil, fmt.Errorf("name must be a letter")
+	}
+	if data[1] != '<' {
+		return nil, fmt.Errorf("wrong file start character")
+	}
+	if !isNumber(data[2]) {
+		return nil, fmt.Errorf("contents must be a number")
+	}
+	if data[3] != '>' {
+		return nil, fmt.Errorf("wrong file end character")
+	}
+
+	name := string(data[0])
+	contents := string(data[2])
+
+	return newFile(name, contents)
+}
+
+func decodeEmptyFile(data []byte) (noder.Noder, error) {
+	if len(data) != 3 {
+		return nil, fmt.Errorf("length is not 3: %s", data)
+	}
+	if !isLetter(data[0]) {
+		return nil, fmt.Errorf("name must be a letter: %s", data)
+	}
+	if data[1] != '<' {
+		return nil, fmt.Errorf("wrong file start character: %s", data)
+	}
+	if data[2] != '>' {
+		return nil, fmt.Errorf("wrong file end character: %s", data)
+	}
+
+	name := string(data[0])
+
+	return newFile(name, "")
+}
+
+// HashEqual returns if a and b have the same hash.
+func HashEqual(a, b noder.Hasher) bool {
+	return bytes.Equal(a.Hash(), b.Hash())
+}