psi: completed writing Bytes() for PSI table

stream/mts/psi/psi.go

@@ -1,5 +1,10 @@
 package psi
 
+import (
+	"hash/crc32"
+	"math/bits"
+)
+
 const (
 	ESSDDefLen = 5
 	DescDefLen = 2
@@ -81,8 +86,13 @@ func (p *PSI) Bytes() []byte {
 	out[l+1] = 0x80 | 0x40 | 0x30 | (0x03 & byte(p.sl>>8))
 	out[l+2] = byte(p.sl)
 	out = append(out, p.tss.Bytes()...)
-	crc32 := crc32_op()
-	return nil
+	crc32 := crc32_Update(0xffffffff, crc32_MakeTable(bits.Reverse32(crc32.IEEE)), out[l:])
+	out = append(out, make([]byte, 0, 4)...)
+	out = append(out, byte(crc32>>24))
+	out = append(out, byte(crc32>>16))
+	out = append(out, byte(crc32>>8))
+	out = append(out, byte(crc32))
+	return out
 }
 
 func (t *TSS) Bytes() []byte {
@@ -147,3 +157,26 @@ func boolToByte(b bool) byte {
 	}
 	return 0x00
 }
+
+func crc32_MakeTable(poly uint32) *crc32.Table {
+	var t crc32.Table
+	for i := range t {
+		crc := uint32(i) << 24
+		for j := 0; j < 8; j++ {
+			if crc&0x80000000 != 0 {
+				crc = (crc << 1) ^ poly
+			} else {
+				crc <<= 1
+			}
+		}
+		t[i] = crc
+	}
+	return &t
+}
+
+func crc32_Update(crc uint32, tab *crc32.Table, p []byte) uint32 {
+	for _, v := range p {
+		crc = tab[byte(crc>>24)^v] ^ (crc << 8)
+	}
+	return crc
+}