contentdb file.ext to content-type lookups

pkg/contentdb/Makefile

@@ -0,0 +1,26 @@
+# Generate db.go from db.json downloaded nodejs mime-db project.
+# NOTE: Autogenerated db.go needs to be vet proofed. \
+	Manually edit json -> JSON for all variable names
+all: checkdeps download build
+
+# go-bindata generates go source from any data file.
+checkdeps:
+	@go get -u github.com/jteeuwen/go-bindata/...
+
+# Download db.json from NodeJS's mime-db project. It is under MIT license.
+download: checkdeps
+	@mkdir db
+	@wget -nv https://cdn.rawgit.com/jshttp/mime-db/master/db.json -O db/db.json
+
+
+# After generating db.go, clean up downloaded db.json.
+build: download
+	@go-bindata -pkg contentdb -o db.go db
+	@rm -fv db/db.json
+	@rm -rfv db
+
+# Clean auto-generated files and backups.
+clean:
+	@rm -rf db.go
+	@rm -f *~
+

pkg/contentdb/contentdb.go

@@ -0,0 +1,109 @@
+/*
+ * mime-db: Mime Database, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package contentdb is a database of file extension to mime content-type.
+// Definitions are imported from NodeJS mime-db project under MIT license.
+package contentdb
+
+import (
+	"fmt"
+	"strings"
+
+	"encoding/json"
+)
+
+var (
+	// Make note of initialization.
+	isInitialized = false
+
+	// Database of extension:content-type.
+	extDB map[string]string
+)
+
+// Load JSON data from gobindata and parse them into extDB.
+func loadDB() error {
+	// Structure of JSON data from mime-db project.
+	type dbEntry struct {
+		Source       string   `json:"source"`
+		Compressible bool     `json:"compresible"`
+		Extensions   []string `json:"extensions"`
+	}
+
+	// Access embedded "db.json" inside go-bindata.
+	jsonDB, e := Asset("db/db.json")
+	if e != nil {
+		return e
+	}
+
+	// Convert db.json into go's typed structure.
+	db := make(map[string]dbEntry)
+	if e := json.Unmarshal(jsonDB, &db); e != nil {
+		return e
+	}
+
+	// Generate a new database from mime-db.
+	for key, val := range db {
+		if len(val.Extensions) > 0 {
+			/* Denormalize - each extension has its own
+			unique content-type now. Looks will be fast. */
+			for _, ext := range val.Extensions {
+				/* Single extension type may map to
+				multiple content-types. In that case,
+				simply prefer the longest content-type
+				to maintain some level of
+				consistency. Only guarantee is,
+				whatever content type is assigned, it
+				is appropriate and valid type. */
+				if strings.Compare(extDB[ext], key) < 0 {
+					extDB[ext] = key
+				}
+			}
+		}
+	}
+	return nil
+}
+
+// Init initializes contentdb for lookups. JSON structure is parsed into a simple map of extension and content-type.
+func Init() error {
+	var e error
+	extDB = make(map[string]string)
+
+	if !isInitialized {
+		e = loadDB()
+	}
+	isInitialized = true
+	return e
+}
+
+// Lookup returns matching content-type for known types of file extensions.
+func Lookup(extension string) (contentType string, e error) {
+	if !isInitialized {
+		e = Init()
+	}
+
+	return extDB[extension], e
+}
+
+// MustLookup returns matching content-type for known types of file extensions. In case of error, it panics.
+func MustLookup(extension string) (contentType string) {
+	if !isInitialized {
+		if e := Init(); e != nil {
+			panic(fmt.Sprintf("Error loading contentdb: %s\n", e))
+		}
+	}
+
+	return extDB[extension]
+}

pkg/contentdb/contentdb_test.go

@@ -0,0 +1,46 @@
+/*
+ * mime-db: Mime Database, (C) 2015 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package contentdb_test
+
+import (
+	"testing"
+
+	"github.com/minio/minio/pkg/contentdb"
+
+	. "gopkg.in/check.v1"
+)
+
+func Test(t *testing.T) { TestingT(t) }
+
+type MySuite struct{}
+
+var _ = Suite(&MySuite{})
+
+func (s *MySuite) TestLookup(c *C) {
+	// Test initializing.
+	e := contentdb.Init()
+	c.Assert(e, IsNil)
+
+	// Test MustLookup.
+	contentType, e := contentdb.Lookup("exe")
+	c.Assert(e, IsNil)
+	c.Assert(contentType, Not(Equals), "")
+
+	// Test MustLookup.
+	contentType = contentdb.MustLookup("exe")
+	c.Assert(contentType, Not(Equals), "")
+}