83 lines
1.7 KiB
Go
83 lines
1.7 KiB
Go
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package telegram
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import (
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"io"
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"regexp"
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"strings"
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"sync"
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)
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const (
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endTag = "NNNN"
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expression = "(?s)ZCZC.*?NNNN"
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maxBufferSize = 65536
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bufferTrimSize = 32768
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)
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// Parser handles telegram extraction from raw serial data.
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type Parser struct {
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mu sync.Mutex
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buffer strings.Builder
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exp *regexp.Regexp
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rawLog io.Writer
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}
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// New creates a new Parser.
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func New(rawLog io.Writer) *Parser {
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return &Parser{
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exp: regexp.MustCompile(expression),
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rawLog: rawLog,
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}
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}
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// Append adds raw data to the internal buffer and returns any complete
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// telegrams that were found. Returns nil if no complete telegram is ready.
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func (p *Parser) Append(data string) []string {
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p.mu.Lock()
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defer p.mu.Unlock()
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if p.buffer.Len() > maxBufferSize {
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// Truncate to prevent unbounded growth
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existing := p.buffer.String()
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p.buffer.Reset()
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p.buffer.WriteString(existing[len(existing)-bufferTrimSize:])
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}
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p.buffer.WriteString(data)
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p.buffer.WriteByte('\n')
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return p.extract()
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}
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// extract finds and returns all complete telegrams in the buffer.
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func (p *Parser) extract() []string {
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content := p.buffer.String()
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if !strings.Contains(content, endTag) {
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return nil
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}
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loc := p.exp.FindStringIndex(content)
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if loc == nil {
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return nil
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}
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telegram := content[loc[0]:loc[1]]
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telegram = removeEmpty(telegram) + "\n\n\n"
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// Write raw log
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if p.rawLog != nil {
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p.rawLog.Write([]byte(telegram + "\n"))
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}
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// Keep remaining data after the matched telegram
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remaining := content[loc[1]:]
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p.buffer.Reset()
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p.buffer.WriteString(remaining)
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return []string{telegram}
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}
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func removeEmpty(s string) string {
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return regexp.MustCompile(`[\t\r\n]+`).ReplaceAllString(strings.TrimSpace(s), "\n")
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}
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