init: 自 zomaintain/backend/rdplib 平移独立成库; module path 从上游 github.com/nakagami/grdp 改为 git.zeroonesoft.cn/golib/rdplib

2026-09-19 18:55:43 +08:00
commit 1096fbce9d
94 changed files with 36790 additions and 0 deletions
@@ -0,0 +1,67 @@
+package rdpgfx
+
+import "bytes"
+
+// ScanResult holds the IDR-presence flag and SPS/PPS NAL boundaries (offsets
+// into the original packet, including Annex B start code) discovered during a
+// single linear walk of an Annex B H.264 packet.
+type ScanResult struct {
+	HasKeyFrame      bool
+	SPSStart, SPSEnd int
+	PPSStart, PPSEnd int
+}
+
+// ScanH264Packet walks an Annex B H.264 packet exactly once, returning
+// whether it contains any IDR slice (NAL type 5) or SPS (NAL type 7) NAL
+// unit and recording the byte ranges for the most recent SPS/PPS NALs found.
+func ScanH264Packet(data []byte) ScanResult {
+	var r ScanResult
+	startCode := []byte{0, 0, 1}
+	pos := 0
+	for pos < len(data) {
+		off := bytes.Index(data[pos:], startCode)
+		if off < 0 {
+			break
+		}
+		i := pos + off
+		scLen := 3
+		if i > 0 && data[i-1] == 0 {
+			i--
+			scLen = 4
+		}
+		if i+scLen >= len(data) {
+			break
+		}
+		nalType := data[i+scLen] & 0x1F
+		if nalType == 5 || nalType == 7 {
+			r.HasKeyFrame = true
+		}
+		if nalType == 7 || nalType == 8 {
+			searchFrom := i + scLen + 1
+			j := len(data)
+			if searchFrom < len(data) {
+				if next := bytes.Index(data[searchFrom:], startCode); next >= 0 {
+					j = searchFrom + next
+					if j > 0 && data[j-1] == 0 {
+						j--
+					}
+				}
+			}
+			if nalType == 7 {
+				r.SPSStart, r.SPSEnd = i, j
+			} else {
+				r.PPSStart, r.PPSEnd = i, j
+			}
+			pos = j
+			continue
+		}
+		pos = i + scLen + 1
+	}
+	return r
+}
+
+// h264PacketHasIDR reports whether an Annex B H.264 packet contains an IDR
+// (keyframe) NAL unit.
+func h264PacketHasIDR(data []byte) bool {
+	return ScanH264Packet(data).HasKeyFrame
+}