From a047b135ca416584178a6adde64cc156ab637431 Mon Sep 17 00:00:00 2001
From: Luke Shumaker <lukeshu@lukeshu.com>
Date: Mon, 27 Jan 2020 19:35:32 -0500
Subject: Have RRD.UnmarshalBinary() avoid parsing things repeatedly

---
 rrdformat/unmarshal_binary.go | 79 +++++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 29 deletions(-)

(limited to 'rrdformat/unmarshal_binary.go')

diff --git a/rrdformat/unmarshal_binary.go b/rrdformat/unmarshal_binary.go
index b9bafde..70c06b7 100644
--- a/rrdformat/unmarshal_binary.go
+++ b/rrdformat/unmarshal_binary.go
@@ -2,6 +2,7 @@ package rrdformat
 
 import (
 	"encoding"
+	"fmt"
 
 	"git.lukeshu.com/go/librrd/rrdformat/rrdbinary"
 )
@@ -16,44 +17,64 @@ func (rrd *RRD) UnmarshalBinary(data []byte) error {
 	if err != nil {
 		return err
 	}
-	var header Header
-	if err := rrdbinary.Unmarshal(arch, data, &header); err != nil {
-		return err
-	}
 
+	decoder := rrdbinary.NewDecoder(arch, data)
 	var parsed RRDv0005
-	parsed.DSDefs = make([]DSDef, header.DSCnt)
-	parsed.DSDefs = make([]DSDef, header.DSCnt)
-	parsed.RRADefs = make([]RRADef, header.RRACnt)
-	//LastUpdated
-	parsed.PDPPreps = make([]PDPPrep, header.DSCnt)
-	parsed.CDPPreps = make([]CDPPrep, header.DSCnt*header.RRACnt)
-	parsed.RRAPtrs = make([]RRAPtr, header.RRACnt)
-	//Values
 
-	switch header.Version {
+	if err := decoder.Decode(&parsed.Header, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "Header", err)
+	}
+	// allocate memory based on .Header values
+	parsed.DSDefs = make([]DSDef, parsed.Header.DSCnt)
+	parsed.DSDefs = make([]DSDef, parsed.Header.DSCnt)
+	parsed.RRADefs = make([]RRADef, parsed.Header.RRACnt)
+	parsed.PDPPreps = make([]PDPPrep, parsed.Header.DSCnt)
+	parsed.CDPPreps = make([]CDPPrep, parsed.Header.DSCnt*parsed.Header.RRACnt)
+	parsed.RRAPtrs = make([]RRAPtr, parsed.Header.RRACnt)
+	// resume decoding
+	if err := decoder.Decode(&parsed.DSDefs, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "DSDefs", err)
+	}
+	if err := decoder.Decode(&parsed.RRADefs, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "RRADefs", err)
+	}
+	// allocate memory based on .RRADefs
+	val_cnt := 0
+	for i := range parsed.RRADefs {
+		val_cnt += int(parsed.RRADefs[i].RowCnt * parsed.Header.DSCnt)
+	}
+	parsed.Values = make([]RRDValue, val_cnt)
+	// resume decoding
+	var lastUpdatedPtr interface{}
+	switch parsed.Header.Version {
 	case "0001", "0002":
-		_parsed := &RRDv0001{} //(*RRDv0001)(&parsed)
-		if err := rrdbinary.Unmarshal(arch, data, _parsed); err != nil {
-			return err
-		}
+		lastUpdatedPtr = &parsed.LastUpdated.Sec
 	case "0003", "0004", "0005":
-		if err := rrdbinary.Unmarshal(arch, data, &parsed); err != nil {
-			return err
-		}
+		lastUpdatedPtr = &parsed.LastUpdated
 	default:
-		// version number already validated by
-		// SniffArchitecture
+		// version number already validated by SniffArchitecture
 		panic("should not happen")
 	}
-
-	val_cnt := 0
-	for i := range parsed.RRADefs {
-		val_cnt += int(parsed.RRADefs[i].RowCnt * header.DSCnt)
+	if err := decoder.Decode(lastUpdatedPtr, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "LastUpdated", err)
 	}
-	parsed.Values = make([]RRDValue, val_cnt)
-	if err := rrdbinary.Unmarshal(arch, data, &parsed.Values); err != nil {
-		return err
+	if err := decoder.Decode(&parsed.LastUpdated, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "LastUpdated", err)
+	}
+	if err := decoder.Decode(&parsed.PDPPreps, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "PDPPreps", err)
+	}
+	if err := decoder.Decode(&parsed.CDPPreps, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "CDPPreps", err)
+	}
+	if err := decoder.Decode(&parsed.RRAPtrs, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "RRAPtrs", err)
+	}
+	if err := decoder.Decode(&parsed.Values, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "Values", err)
+	}
+	if err := decoder.Decode(&rrdbinary.EOF{}, ""); err != nil {
+		return fmt.Errorf("field %s: %w", "EOF", err)
 	}
 
 	*rrd = RRD{
-- 
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