From 212d2f72f9297a092b3a1955f737cbf33fe94cf3 Mon Sep 17 00:00:00 2001
From: Alex Aizman <alex.aizman@gmail.com>
Date: Tue, 3 Sep 2024 15:05:09 -0400
Subject: [PATCH] micro-optimize obj props to http headers conversion

* target obj-head handler: use pre-mapped headers, avoid repetitive churn
* api/apc: fuse textproto logic; optimize and simplify
* part two, prev. commit: 530288d44fa5fe26

Signed-off-by: Alex Aizman <alex.aizman@gmail.com>
---
 ais/target.go      |  6 +-----
 api/apc/headers.go | 36 ++++++++++++++++++++++++++++++++----
 api/object.go      |  6 ++----
 cmn/objattrs.go    |  7 ++-----
 4 files changed, 37 insertions(+), 18 deletions(-)

diff --git a/ais/target.go b/ais/target.go
index ff8455af2b..5d51b8e609 100644
--- a/ais/target.go
+++ b/ais/target.go
@@ -1157,11 +1157,7 @@ func (t *target) objHead(r *http.Request, whdr http.Header, q url.Values, bck *m
 		if v == "" {
 			return nil, false
 		}
-		name := apc.PropToHeader(tag)
-		debug.Func(func() {
-			vv := whdr.Get(name)
-			debug.Assertf(vv == "", "not expecting duplications: %s=(%q, %q)", name, v, vv)
-		})
+		name := cmn.PropToHeader(tag)
 		whdr.Set(name, v)
 		return nil, false
 	})
diff --git a/api/apc/headers.go b/api/apc/headers.go
index 5174881b06..676dc541f2 100644
--- a/api/apc/headers.go
+++ b/api/apc/headers.go
@@ -6,7 +6,9 @@ package apc
 
 import (
 	"strings"
+	"unicode"
 
+	"github.com/NVIDIA/aistore/cmn/cos"
 	"github.com/NVIDIA/aistore/cmn/debug"
 )
 
@@ -101,13 +103,39 @@ const (
 	HdrPromoteNamesNum  = aisPrefix + "Promote-Names-Num"
 )
 
-// (compare with cmn.PropToHeader)
+const lais = len(aisPrefix)
+
+// internal (json) obj prop => canonical http header
+// usage:
+// - target InitObjProps2Hdr
+// - api/object
 func PropToHeader(prop string) string {
 	debug.Assert(!strings.HasPrefix(prop, aisPrefix), "already converted: ", prop)
 	if prop[0] == '.' || prop[0] == '_' {
 		prop = prop[1:]
 	}
-	prop = strings.ReplaceAll(prop, ".", "-")
-	prop = strings.ReplaceAll(prop, "_", "-")
-	return aisPrefix + prop
+
+	var (
+		l   = len(prop)
+		out = make([]byte, l+lais)
+		o   = out[lais:]
+		up  = true
+	)
+	copy(out, aisPrefix)
+	for i := range l {
+		c := prop[i]
+		if c == '.' || c == '_' {
+			c = '-'
+		}
+		switch {
+		case up && 'a' <= c && c <= 'z':
+			o[i] = byte(unicode.ToUpper(rune(c)))
+		case !up && 'A' <= c && c <= 'Z':
+			o[i] = byte(unicode.ToLower(rune(c)))
+		default:
+			o[i] = c
+		}
+		up = c == '-'
+	}
+	return cos.UnsafeS(out)
 }
diff --git a/api/object.go b/api/object.go
index 84b9fe23be..11c598342c 100644
--- a/api/object.go
+++ b/api/object.go
@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"io"
 	"net/http"
-	"net/textproto"
 	"net/url"
 	"strconv"
 	"time"
@@ -353,9 +352,8 @@ func HeadObject(bp BaseParams, bck cmn.Bck, objName string, args HeadArgs) (*cmn
 
 	// second, all the rest
 	err = cmn.IterFields(op, func(tag string, field cmn.IterField) (error, bool) {
-		h1 := apc.PropToHeader(tag)
-		h2 := textproto.CanonicalMIMEHeaderKey(h1)
-		v, ok := hdr[h2]
+		name := apc.PropToHeader(tag) // internal (json) obj prop => canonical http header
+		v, ok := hdr[name]
 		if !ok {
 			return nil, false // skip missing
 		}
diff --git a/cmn/objattrs.go b/cmn/objattrs.go
index 235fb0cdb2..6a8ee3faf1 100644
--- a/cmn/objattrs.go
+++ b/cmn/objattrs.go
@@ -8,7 +8,6 @@ package cmn
 import (
 	"fmt"
 	"net/http"
-	"net/textproto"
 	"strconv"
 	"strings"
 
@@ -78,15 +77,13 @@ var (
 	props2hdr cos.StrKVs
 )
 
-// (compare with api.HeadObject)
 func InitObjProps2Hdr() {
 	props2hdr = make(cos.StrKVs, 18)
 
 	op := &ObjectProps{}
 	err := IterFields(op, func(tag string, _ IterField) (error, bool) {
-		h1 := apc.PropToHeader(tag)
-		h2 := textproto.CanonicalMIMEHeaderKey(h1)
-		props2hdr[tag] = h2
+		name := apc.PropToHeader(tag)
+		props2hdr[tag] = name // internal (json) obj prop => canonical http header
 		return nil, false
 	}, IterOpts{OnlyRead: false})