whatcanGOwrong

go/pkg/mod/github.com/google/go-dap@v0.12.0/io.go

@@ -0,0 +1,137 @@
+// Copyright 2020 Google LLC
+//
+// 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
+//
+//     https://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.
+
+// This file contains utilities for DAP Base protocol I/O.
+// For additional information, see "Base protocol" section in
+// https://microsoft.github.io/debug-adapter-protocol/overview.
+
+package dap
+
+import (
+	"bufio"
+	"encoding/json"
+	"fmt"
+	"io"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+// BaseProtocolError represents base protocol error, which occurs when the raw
+// message does not conform to the header+content format of the base protocol.
+type BaseProtocolError struct {
+	Err string
+}
+
+func (bpe *BaseProtocolError) Error() string { return bpe.Err }
+
+var (
+	// ErrHeaderDelimiterNotCrLfCrLf is returned when only partial header
+	// delimiter \r\n\r\n is encountered.
+	ErrHeaderDelimiterNotCrLfCrLf = &BaseProtocolError{fmt.Sprintf("header delimiter is not %q", crLfcrLf)}
+
+	// ErrHeaderNotContentLength is returned when the parsed header is
+	// not of valid Content-Length format.
+	ErrHeaderNotContentLength = &BaseProtocolError{fmt.Sprintf("header format is not %q", contentLengthHeaderRegex)}
+
+	// ErrHeaderContentTooLong is returned when the content length specified in
+	// the header is above contentMaxLength.
+	ErrHeaderContentTooLong = &BaseProtocolError{fmt.Sprintf("content length over %v bytes", contentMaxLength)}
+)
+
+const (
+	crLfcrLf               = "\r\n\r\n"
+	contentLengthHeaderFmt = "Content-Length: %d\r\n\r\n"
+	contentMaxLength       = 4 * 1024 * 1024
+)
+
+var (
+	contentLengthHeaderRegex = regexp.MustCompile("^Content-Length: ([0-9]+)$")
+)
+
+// WriteBaseMessage formats content with Content-Length header and delimiters
+// as per the base protocol and writes the resulting message to w.
+func WriteBaseMessage(w io.Writer, content []byte) error {
+	header := fmt.Sprintf(contentLengthHeaderFmt, len(content))
+	if _, err := w.Write([]byte(header)); err != nil {
+		return err
+	}
+	_, err := w.Write(content)
+	return err
+}
+
+// ReadBaseMessage reads one message from r consisting of a Content-Length
+// header and a content part. It parses the header to determine the size of
+// the content part and extracts and returns the actual content of the message.
+// Returns nil bytes on error, which can be one of the standard IO errors or
+// a BaseProtocolError defined in this package.
+func ReadBaseMessage(r *bufio.Reader) ([]byte, error) {
+	contentLength, err := readContentLengthHeader(r)
+	if err != nil {
+		return nil, err
+	}
+	if contentLength > contentMaxLength {
+		return nil, ErrHeaderContentTooLong
+	}
+	content := make([]byte, contentLength)
+	if _, err = io.ReadFull(r, content); err != nil {
+		return nil, err
+	}
+	return content, nil
+}
+
+// readContentLengthHeader looks for the only header field that is supported
+// and required:
+// 		Content-Length: [0-9]+\r\n\r\n
+// Extracts and returns the content length.
+func readContentLengthHeader(r *bufio.Reader) (contentLength int64, err error) {
+	// Look for <some header>\r\n\r\n
+	headerWithCr, err := r.ReadString('\r')
+	if err != nil {
+		return 0, err
+	}
+	nextThree := make([]byte, 3)
+	if _, err = io.ReadFull(r, nextThree); err != nil {
+		return 0, err
+	}
+	if string(nextThree) != "\n\r\n" {
+		return 0, ErrHeaderDelimiterNotCrLfCrLf
+	}
+
+	// If header is in the right format, get the length
+	header := strings.TrimSuffix(headerWithCr, "\r")
+	headerAndLength := contentLengthHeaderRegex.FindStringSubmatch(header)
+	if len(headerAndLength) < 2 {
+		return 0, ErrHeaderNotContentLength
+	}
+	return strconv.ParseInt(headerAndLength[1], 10, 64)
+}
+
+// WriteProtocolMessage encodes message and writes it to w.
+func WriteProtocolMessage(w io.Writer, message Message) error {
+	b, err := json.Marshal(message)
+	if err != nil {
+		return err
+	}
+	return WriteBaseMessage(w, b)
+}
+
+// ReadProtocolMessage reads a message from r, decodes and returns it.
+func ReadProtocolMessage(r *bufio.Reader) (Message, error) {
+	content, err := ReadBaseMessage(r)
+	if err != nil {
+		return nil, err
+	}
+	return DecodeProtocolMessage(content)
+}