object/header: Add

4 files changed, 80 insertions, 0 deletions

diff --git a/object/header/append.go b/object/header/append.go
new file mode 100644
index 00000000..5b062e05
--- /dev/null
+++ b/object/header/append.go
@@ -0,0 +1,29 @@
+package header
+
+import (
+	"strconv"
+
+	"codeberg.org/lindenii/furgit/object/typ"
+)
+
+// Append appends a canonical loose-object header ("type size\x00") to dst.
+func Append(dst []byte, ty typ.Type, size int64) ([]byte, bool) {
+	if size < 0 {
+		return nil, false
+	}
+
+	tyName, ok := ty.Name()
+	if !ok {
+		return nil, false
+	}
+
+	sizeStr := strconv.FormatInt(size, 10)
+	out := make([]byte, 0, len(dst)+len(tyName)+len(sizeStr)+2)
+	out = append(out, dst...)
+	out = append(out, tyName...)
+	out = append(out, ' ')
+	out = append(out, sizeStr...)
+	out = append(out, 0)
+
+	return out, true
+}
diff --git a/object/header/doc.go b/object/header/doc.go
new file mode 100644
index 00000000..e9003a8f
--- /dev/null
+++ b/object/header/doc.go
@@ -0,0 +1,3 @@
+// Package header parses and serializes loose-object headers
+// ("type size\x00").
+package header
diff --git a/object/header/encode.go b/object/header/encode.go
new file mode 100644
index 00000000..4cd8599c
--- /dev/null
+++ b/object/header/encode.go
@@ -0,0 +1,8 @@
+package header
+
+import "codeberg.org/lindenii/furgit/object/typ"
+
+// Encode returns a canonical loose-object header ("type size\x00").
+func Encode(ty typ.Type, size int64) ([]byte, bool) {
+	return Append(nil, ty, size)
+}
diff --git a/object/header/parse.go b/object/header/parse.go
new file mode 100644
index 00000000..77deef38
--- /dev/null
+++ b/object/header/parse.go
@@ -0,0 +1,40 @@
+package header
+
+import (
+	"bytes"
+	"strconv"
+
+	"codeberg.org/lindenii/furgit/object/typ"
+)
+
+// Parse parses a canonical loose-object header ("type size\x00").
+func Parse(data []byte) (ty typ.Type, size int64, consumed int, ok bool) {
+	space := bytes.IndexByte(data, ' ')
+	if space <= 0 {
+		return typ.TypeInvalid, 0, 0, false
+	}
+
+	nulRel := bytes.IndexByte(data[space+1:], 0)
+	if nulRel < 0 {
+		return typ.TypeInvalid, 0, 0, false
+	}
+
+	nul := space + 1 + nulRel
+
+	ty, ok = typ.Parse(string(data[:space]))
+	if !ok {
+		return typ.TypeInvalid, 0, 0, false
+	}
+
+	sizeBytes := data[space+1 : nul]
+	if len(sizeBytes) == 0 {
+		return typ.TypeInvalid, 0, 0, false
+	}
+
+	size, err := strconv.ParseInt(string(sizeBytes), 10, 64)
+	if err != nil || size < 0 {
+		return typ.TypeInvalid, 0, 0, false
+	}
+
+	return ty, size, nul + 1, true
+}