From 34c34fd1f4fb4cfcf01968d704ac03a56153b114 Mon Sep 17 00:00:00 2001
From: qydysky <qydysky@foxmail.com>
Date: Sun, 4 Aug 2024 16:44:39 +0800
Subject: [PATCH] 1

---
 decoder/tool/B_I.go      |  2 +-
 decoder/tool/sue.go      | 30 ++++++++++++++++++++++++++++++
 decoder/tool/sue_test.go | 20 ++++++++++++++++++++
 3 files changed, 51 insertions(+), 1 deletion(-)
 create mode 100644 decoder/tool/sue.go
 create mode 100644 decoder/tool/sue_test.go

diff --git a/decoder/tool/B_I.go b/decoder/tool/B_I.go
index a8d1498..c33750d 100644
--- a/decoder/tool/B_I.go
+++ b/decoder/tool/B_I.go
@@ -1,4 +1,4 @@
-package mp4
+package tool
 
 /*
 整数 字节转换区
diff --git a/decoder/tool/sue.go b/decoder/tool/sue.go
new file mode 100644
index 0000000..2abe55a
--- /dev/null
+++ b/decoder/tool/sue.go
@@ -0,0 +1,30 @@
+package tool
+
+// unsigned integer Exp-Golomb-coded syntax element with the left bit first
+func ue(d int) (r, move int) {
+	for d&0b10000000 == 0b00000000 {
+		move += 1
+		d = d << 1
+	}
+	for i := move; i >= 0; i-- {
+		r |= d & 0b10000000 >> (7 - i)
+		d = d << 1
+	}
+	return r - 1, 2*move + 1
+}
+
+// signed integer Exp-Golomb-coded syntax element with the left bit first
+func se(d int) (r, move int) {
+	for d&0b10000000 == 0b00000000 {
+		move += 1
+		d = d << 1
+	}
+	for i := move; i > 0; i-- {
+		r |= d & 0b10000000 >> (8 - i)
+		d = d << 1
+	}
+	if d&0b10000000 == 0b00000000 {
+		r = -r
+	}
+	return r, 2*move + 1
+}
diff --git a/decoder/tool/sue_test.go b/decoder/tool/sue_test.go
new file mode 100644
index 0000000..139cf07
--- /dev/null
+++ b/decoder/tool/sue_test.go
@@ -0,0 +1,20 @@
+package tool
+
+import (
+	"testing"
+)
+
+func Test_ue(t *testing.T) {
+	if r, m := ue(0b01101100); r != 2 || m != 3 {
+		t.Fatal()
+	}
+}
+
+func Test_se(t *testing.T) {
+	if r, m := se(0b00101000); r != 2 || m != 5 {
+		t.Fatal()
+	}
+	if r, m := se(0b00100000); r != -2 || m != 5 {
+		t.Fatal()
+	}
+}
-- 
2.39.2