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package nnet
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import (
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"context"
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"fmt"
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protocolpkg "github.com/noahlann/nnet/pkg/protocol"
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)
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// NNetVersionIdentifier NNet协议版本识别器
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// 从协议帧头中读取版本字段（偏移4的位置，1字节）
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type NNetVersionIdentifier struct {
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// versionMapping 版本映射：byte值 -> 版本字符串
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// 例如：{1: "1.0", 2: "2.0"}
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versionMapping map[byte]string
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}
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// NewNNetVersionIdentifier 创建NNet协议版本识别器
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func NewNNetVersionIdentifier(versionMapping map[byte]string) protocolpkg.VersionIdentifier {
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if versionMapping == nil {
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// 默认映射
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versionMapping = map[byte]string{
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1: "1.0",
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2: "2.0",
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}
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}
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return &NNetVersionIdentifier{
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versionMapping: versionMapping,
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}
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}
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// Identify 识别协议版本
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func (i *NNetVersionIdentifier) Identify(data []byte, ctx context.Context) (string, error) {
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// NNet协议格式：[Magic(4)][Version(1)][Length(4)][Data(N)][Checksum(2)]
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// 版本字段在偏移4的位置（Magic 4字节之后）
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versionOffset := 4
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minRequiredBytes := versionOffset + 1
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// 检查数据长度
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if len(data) < minRequiredBytes {
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return "", protocolpkg.NewError(fmt.Sprintf("data too short: need at least %d bytes, got %d", minRequiredBytes, len(data)))
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}
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// 检查Magic
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magic := string(data[0:4])
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if magic != "NNET" {
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return "", protocolpkg.NewError(fmt.Sprintf("invalid magic: %s", magic))
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}
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// 读取版本字段
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versionByte := data[versionOffset]
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// 查找版本映射
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version, ok := i.versionMapping[versionByte]
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if !ok {
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return "", protocolpkg.NewError(fmt.Sprintf("unknown version byte: %d", versionByte))
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}
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return version, nil
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}
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