Change empty string checks to be more idiomatic (valyala#1684)

.golangci.yml

@@ -68,6 +68,9 @@ linters-settings:
       "all",
       "-ST1000", # at least one file in a package should have a package comment
     ]
+  gocritic:
+    enabled-checks:
+      - emptyStringTest
 
 issues:
   # Show all issues from a linter.

client.go

@@ -1825,7 +1825,7 @@ func newClientTLSConfig(c *tls.Config, addr string) *tls.Config {
 		c = c.Clone()
 	}
 
-	if len(c.ServerName) == 0 {
+	if c.ServerName == "" {
 		serverName := tlsServerName(addr)
 		if serverName == "*" {
 			c.InsecureSkipVerify = true

expvarhandler/expvar.go

@@ -53,7 +53,7 @@ func ExpvarHandler(ctx *fasthttp.RequestCtx) {
 
 func getExpvarRegexp(ctx *fasthttp.RequestCtx) (*regexp.Regexp, error) {
 	r := string(ctx.QueryArgs().Peek("r"))
-	if len(r) == 0 {
+	if r == "" {
 		return defaultRE, nil
 	}
 	rr, err := regexp.Compile(r)

fs.go

@@ -16,6 +16,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/klauspost/compress/zstd"
 	"github.com/andybalholm/brotli"
 	"github.com/klauspost/compress/gzip"
 	"github.com/valyala/bytebufferpool"
@@ -370,6 +371,7 @@ const FSCompressedFileSuffix = ".fasthttp.gz"
 var FSCompressedFileSuffixes = map[string]string{
 	"gzip": ".fasthttp.gz",
 	"br":   ".fasthttp.br",
+	"zstd": ".fasthttp.zst",
 }
 
 // FSHandlerCacheDuration is the default expiration duration for inactive
@@ -459,8 +461,10 @@ func (fs *FS) initRequestHandler() {
 	}
 
 	compressedFileSuffixes := fs.CompressedFileSuffixes
-	if len(compressedFileSuffixes["br"]) == 0 || len(compressedFileSuffixes["gzip"]) == 0 ||
-		compressedFileSuffixes["br"] == compressedFileSuffixes["gzip"] {
+	if compressedFileSuffixes["br"] == "" || compressedFileSuffixes["gzip"] == "" ||
+		len(compressedFileSuffixes["zstd"]) == 0 || compressedFileSuffixes["br"] == compressedFileSuffixes["gzip"] ||
+		compressedFileSuffixes["br"] == compressedFileSuffixes["zstd"] ||
+		compressedFileSuffixes["gzip"] == compressedFileSuffixes["zstd"] {
 		// Copy global map
 		compressedFileSuffixes = make(map[string]string, len(FSCompressedFileSuffixes))
 		for k, v := range FSCompressedFileSuffixes {
@@ -471,6 +475,7 @@ func (fs *FS) initRequestHandler() {
 	if len(fs.CompressedFileSuffix) > 0 {
 		compressedFileSuffixes["gzip"] = fs.CompressedFileSuffix
 		compressedFileSuffixes["br"] = FSCompressedFileSuffixes["br"]
+		compressedFileSuffixes["zstd"] = FSCompressedFileSuffixes["zstd"]
 	}
 
 	h := &fsHandler{
@@ -794,6 +799,7 @@ const (
 	defaultCacheKind CacheKind = iota
 	brotliCacheKind
 	gzipCacheKind
+	zstdCacheKind
 )
 
 func newCacheManager(fs *FS) cacheManager {
@@ -1040,6 +1046,11 @@ func (h *fsHandler) handleRequest(ctx *RequestCtx) {
 			mustCompress = true
 			fileCacheKind = gzipCacheKind
 			fileEncoding = "gzip"
+		} else if ctx.Request.Header.HasAcceptEncodingBytes(strZstd) {
+			mustCompress = true
+			fileCacheKind = zstdCacheKind
+			fileEncoding = "zstd"
+
 		}
 	}
 
@@ -1101,6 +1112,8 @@ func (h *fsHandler) handleRequest(ctx *RequestCtx) {
 			hdr.SetContentEncodingBytes(strBr)
 		} else if fileEncoding == "gzip" {
 			hdr.SetContentEncodingBytes(strGzip)
+		} else if fileEncoding == "zstd" {
+			hdr.SetContentEncodingBytes(strZstd)
 		}
 	}
 
@@ -1308,6 +1321,8 @@ nestedContinue:
 			zbuf.B = AppendBrotliBytesLevel(zbuf.B, w.B, CompressDefaultCompression)
 		} else if fileEncoding == "gzip" {
 			zbuf.B = AppendGzipBytesLevel(zbuf.B, w.B, CompressDefaultCompression)
+		} else if fileEncoding == "zstd" {
+			zbuf.B = AppendZstdBytesLevel(zbuf.B, w.B, CompressZstdDefault)
 		}
 		w = &zbuf
 	}
@@ -1420,6 +1435,13 @@ func (h *fsHandler) compressFileNolock(
 			err = err1
 		}
 		releaseStacklessGzipWriter(zw, CompressDefaultCompression)
+	} else if fileEncoding == "zstd" {
+		zw := acquireStacklessZstdWriter(zf, CompressZstdDefault)
+		_, err = copyZeroAlloc(zw, f)
+		if err1 := zw.Flush(); err == nil {
+			err = err1
+		}
+		releaseStacklessZstdWriter(zw, CompressZstdDefault)
 	}
 	_ = zf.Close()
 	_ = f.Close()
@@ -1457,6 +1479,13 @@ func (h *fsHandler) newCompressedFSFileCache(f fs.File, fileInfo fs.FileInfo, fi
 			err = err1
 		}
 		releaseStacklessGzipWriter(zw, CompressDefaultCompression)
+	} else if fileEncoding == "zstd" {
+		zw := acquireStacklessZstdWriter(w, CompressZstdDefault)
+		_, err = copyZeroAlloc(zw, f)
+		if err1 := zw.Flush(); err == nil {
+			err = err1
+		}
+		releaseStacklessZstdWriter(zw, CompressZstdDefault)
 	}
 	defer func() { _ = f.Close() }()
 
@@ -1600,8 +1629,9 @@ func (h *fsHandler) newFSFile(f fs.File, fileInfo fs.FileInfo, compressed bool,
 func readFileHeader(f io.Reader, compressed bool, fileEncoding string) ([]byte, error) {
 	r := f
 	var (
-		br *brotli.Reader
-		zr *gzip.Reader
+		br  *brotli.Reader
+		zr  *gzip.Reader
+		zsr *zstd.Decoder
 	)
 	if compressed {
 		var err error
@@ -1615,6 +1645,11 @@ func readFileHeader(f io.Reader, compressed bool, fileEncoding string) ([]byte,
 				return nil, err
 			}
 			r = zr
+		} else if fileEncoding == "zstd" {
+			if zsr, err = acquireZstdReader(f); err != nil {
+				return nil, err
+			}
+			r = zsr
 		}
 	}
 
@@ -1639,6 +1674,10 @@ func readFileHeader(f io.Reader, compressed bool, fileEncoding string) ([]byte,
 		releaseGzipReader(zr)
 	}
 
+	if zsr != nil {
+		releaseZstdReader(zsr)
+	}
+
 	return data, err
 }
 

header_test.go

@@ -2355,7 +2355,7 @@ type bufioPeekReader struct {
 }
 
 func (r *bufioPeekReader) Read(b []byte) (int, error) {
-	if len(r.s) == 0 {
+	if r.s == "" {
 		return 0, io.EOF
 	}
 

http.go

@@ -958,7 +958,7 @@ func (req *Request) MultipartForm() (*multipart.Form, error) {
 	}
 
 	req.multipartFormBoundary = string(req.Header.MultipartFormBoundary())
-	if len(req.multipartFormBoundary) == 0 {
+	if req.multipartFormBoundary == "" {
 		return nil, ErrNoMultipartForm
 	}
 
@@ -1014,7 +1014,7 @@ func marshalMultipartForm(f *multipart.Form, boundary string) ([]byte, error) {
 func WriteMultipartForm(w io.Writer, f *multipart.Form, boundary string) error {
 	// Do not care about memory allocations here, since multipart
 	// form processing is slow.
-	if len(boundary) == 0 {
+	if boundary == "" {
 		return errors.New("form boundary cannot be empty")
 	}
 

http_test.go

@@ -2214,7 +2214,7 @@ func testRequestSuccess(t *testing.T, method, requestURI, host, userAgent, body,
 	if string(req1.Header.Method()) != expectedMethod {
 		t.Fatalf("Unexpected method: %q. Expected %q", req1.Header.Method(), expectedMethod)
 	}
-	if len(requestURI) == 0 {
+	if requestURI == "" {
 		requestURI = "/"
 	}
 	if string(req1.Header.RequestURI()) != requestURI {
@@ -2467,7 +2467,7 @@ func testRequestPostArgsError(t *testing.T, req *Request, s string) {
 		t.Fatalf("Unexpected error when reading %q: %v", s, err)
 	}
 	ss := req.PostArgs().String()
-	if len(ss) != 0 {
+	if ss != "" {
 		t.Fatalf("unexpected post args: %q. Expecting empty post args", ss)
 	}
 }

server.go

@@ -1736,7 +1736,7 @@ func (s *Server) ServeTLSEmbed(ln net.Listener, certData, keyData []byte) error
 // This function allows programmer to handle multiple domains
 // in one server structure. See examples/multidomain.
 func (s *Server) AppendCert(certFile, keyFile string) error {
-	if len(certFile) == 0 && len(keyFile) == 0 {
+	if certFile == "" && keyFile == "" {
 		return errNoCertOrKeyProvided
 	}