cmd/swarm, swarm: cross-platform Content-Type detection (#17782)

- Mime types generator (Standard "mime" package rely on system-settings, see mime.osInitMime)
- Changed swarm/api.Upload:
    - simplify I/O throttling by semaphore primitive and use file name where possible
    - f.Close() must be called in Defer - otherwise panic or future added early return will cause leak of file descriptors
    - one error was suppressed

Makefile

@@ -57,6 +57,9 @@ devtools:
 	@type "solc" 2> /dev/null || echo 'Please install solc'
 	@type "protoc" 2> /dev/null || echo 'Please install protoc'
 
+swarm-devtools:
+	env GOBIN= go install ./cmd/swarm/mimegen
+
 # Cross Compilation Targets (xgo)
 
 geth-cross: geth-linux geth-darwin geth-windows geth-android geth-ios

cmd/swarm/mimegen/generator.go

@@ -0,0 +1,124 @@
+// Copyright 2018 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+package main
+
+// Standard "mime" package rely on system-settings, see mime.osInitMime
+// Swarm will run on many OS/Platform/Docker and must behave similar
+// This command generates code to add common mime types based on mime.types file
+//
+// mime.types file provided by mailcap, which follow https://www.iana.org/assignments/media-types/media-types.xhtml
+//
+// Get last version of mime.types file by:
+// docker run --rm -v $(pwd):/tmp alpine:edge /bin/sh -c "apk add -U mailcap; mv /etc/mime.types /tmp"
+
+import (
+	"bufio"
+	"bytes"
+	"flag"
+	"html/template"
+	"io/ioutil"
+	"strings"
+
+	"log"
+)
+
+var (
+	typesFlag   = flag.String("types", "", "Input mime.types file")
+	packageFlag = flag.String("package", "", "Golang package in output file")
+	outFlag     = flag.String("out", "", "Output file name for the generated mime types")
+)
+
+type mime struct {
+	Name string
+	Exts []string
+}
+
+type templateParams struct {
+	PackageName string
+	Mimes       []mime
+}
+
+func main() {
+	// Parse and ensure all needed inputs are specified
+	flag.Parse()
+	if *typesFlag == "" {
+		log.Fatalf("--types is required")
+	}
+	if *packageFlag == "" {
+		log.Fatalf("--types is required")
+	}
+	if *outFlag == "" {
+		log.Fatalf("--out is required")
+	}
+
+	params := templateParams{
+		PackageName: *packageFlag,
+	}
+
+	types, err := ioutil.ReadFile(*typesFlag)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	scanner := bufio.NewScanner(bytes.NewReader(types))
+	for scanner.Scan() {
+		txt := scanner.Text()
+		if strings.HasPrefix(txt, "#") || len(txt) == 0 {
+			continue
+		}
+		parts := strings.Fields(txt)
+		if len(parts) == 1 {
+			continue
+		}
+		params.Mimes = append(params.Mimes, mime{parts[0], parts[1:]})
+	}
+
+	if err = scanner.Err(); err != nil {
+		log.Fatal(err)
+	}
+
+	result := bytes.NewBuffer([]byte{})
+
+	if err := template.Must(template.New("_").Parse(tpl)).Execute(result, params); err != nil {
+		log.Fatal(err)
+	}
+
+	if err := ioutil.WriteFile(*outFlag, result.Bytes(), 0600); err != nil {
+		log.Fatal(err)
+	}
+}
+
+var tpl = `// Code generated by github.com/ethereum/go-ethereum/cmd/swarm/mimegen. DO NOT EDIT.
+
+package {{ .PackageName }}
+
+import "mime"
+func init() {
+	var mimeTypes = map[string]string{
+{{- range .Mimes -}}
+	{{ $name := .Name -}}
+	{{- range .Exts }}
+		".{{ . }}": "{{ $name | html }}",
+	{{- end }}
+{{- end }}
+	}
+	for ext, name := range mimeTypes {
+		if err := mime.AddExtensionType(ext, name); err != nil {
+			panic(err)
+		}
+	}
+}
+`