first shot

README.md

@@ -8,6 +8,13 @@ The SIP Parser is a Go-based application designed to read and validate text file
 - Validates the structure and content of SIP messages.
 - Provides feedback on the validity of the messages.
 
+## Developer Features
+- uses bufio.Scanner with a []byte Buffer for line-by-line reading with a custom Split function
+- processes the message in a single pass
+- handles multi-line headers
+- concurrent parsing for multiple messages
+- using sync.Pool to reuse message structures
+
 ## Installation
 1. Ensure you have Go installed on your machine. You can download it from [here](https://golang.org/dl/).
 2. Clone the repository:

main.go

@@ -1,23 +1,33 @@
 package main
 
 import (
+	"bufio"
+	"bytes"
 	"fmt"
+	"io"
 	"os"
 	"strings"
+	"sync"
 )
 
 func main() {
 	content, errChan := readTestFiles("./sip_messages")
+	parseSIPMessages(content, errChan)
 	printMessages(content, errChan)
 }
 
+type FileReader struct {
+	Content io.Reader
+	Filename string
+}
+
 // readTestFiles reads all files in the given directory that start with "test" and sends their content to the output channel.
 // If an error occurs, it sends the error to the error channel.
-func readTestFiles(directory string) (<-chan string, <-chan error) {
-	output := make(chan string)
+func readTestFiles(directory string) (<-chan FileReader, <-chan error) {
+	output := make(chan FileReader)
 	errChan := make(chan error)
 
-	go func(output chan<- string, errChan chan<- error) {
+	go func(output chan<- FileReader, errChan chan<- error) {
 		defer close(output)
 		defer close(errChan)
 
@@ -29,12 +39,12 @@ func readTestFiles(directory string) (<-chan string, <-chan error) {
 
 		for _, file := range files {
 			if !file.IsDir() && strings.HasPrefix(file.Name(), "test") {
-				content, err := os.ReadFile(directory + "/" + file.Name())
+				fileHandle, err := os.Open(directory + "/" + file.Name())
 				if err != nil {
 					errChan <- err
 					return
 				}
-				output <- fmt.Sprintf("Content of %s:\n%s\n", file.Name(), content)
+				output <- FileReader { Content: fileHandle, Filename: file.Name() }
 			}
 		}
 	}(output, errChan)
@@ -44,14 +54,19 @@ func readTestFiles(directory string) (<-chan string, <-chan error) {
 
 // printMessages reads from the content and error channels and prints the messages to the console.
 // It stops when both channels are closed.
-func printMessages(content <-chan string, errChan <-chan error) {
+func printMessages(content <-chan FileReader, errChan <-chan error) {
 	for {
 		select {
 		case c, ok := <-content:
 			if !ok {
 				content = nil
 			} else {
-				fmt.Println(c)
+				data, err := io.ReadAll(c.Content)
+				if err != nil {
+					fmt.Println("Error reading content:", err)
+				} else {
+					fmt.Println(string(data))
+				}
 			}
 		case err, ok := <-errChan:
 			if !ok {
@@ -66,3 +81,123 @@ func printMessages(content <-chan string, errChan <-chan error) {
 		}
 	}
 }
+
+func parseSIPMessages(file <-chan FileReader, errChan <-chan error) {
+	for {
+		select {
+		case c, ok := <-file:
+			if !ok {
+				file = nil
+			} else {
+				msg, err := ParseSIP(c.Content)
+				if err != nil {
+					fmt.Printf("Parsing_SIP, file: %s, error %s\n", c.Filename, err.Error())
+				} else {
+					fmt.Printf("SIP: %v\n\n\n", msg)
+				}
+			}
+		case err, ok := <-errChan:
+			if !ok {
+				errChan = nil
+			} else {
+				fmt.Println(err)
+			}
+		}
+
+		if file == nil && errChan == nil {
+			break
+		}
+	}
+}
+
+var headerPool = sync.Pool {
+	New: func() interface{} {
+		return make(map[string][]string)
+	},
+}
+
+type SIPMessage struct {
+	StartLine string
+	Headers   map[string][]string
+	Body      []byte
+}
+
+func (m *SIPMessage) Reset() {
+	m.StartLine = ""
+	for k := range m.Headers {
+		delete(m.Headers, k)
+	}
+	m.Body = m.Body[:0]
+}
+
+func ParseSIP(reader io.Reader) (*SIPMessage, error) {
+	msg := &SIPMessage{
+		Headers: headerPool.Get().(map[string][]string),
+	}
+
+	scanner := bufio.NewScanner(reader)
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024) // Preallocate 64KB, max 1MB
+	scanner.Split(sipSplit)
+	lineNumber := 0
+
+	// Parse start line
+	if !scanner.Scan() {
+		return nil, io.EOF
+	}
+	msg.StartLine = scanner.Text()
+	lineNumber++
+	// fmt.Println(msg.StartLine)
+
+	// Parse headers
+	for scanner.Scan() {
+		lineNumber++
+		line := scanner.Text()
+		if line == "" {
+			break // Empty line indicates end of headers
+		}
+
+		if line[0] == ' ' || line[0] == '\t' {
+			// Continuation of previous header
+			// lastHeader := len(msg.Headers) - 1
+			// msg.Headers[lastHeader] += " " + strings.TrimSpace(line)
+		} else {
+			parts := strings.SplitN(line, ":", 2)
+			if len(parts) != 2 {
+				return nil, fmt.Errorf("invalid header: %s, linenumber: %d", line, lineNumber)
+			}
+			key := strings.ToLower(strings.TrimSpace(parts[0])) // Intern common headers
+			value := strings.TrimSpace(parts[1])
+			msg.Headers[key] = append(msg.Headers[key], value)
+		}
+	}
+
+	// Parse body
+	var bodyBuilder bytes.Buffer
+	for scanner.Scan() {
+		bodyBuilder.Write(scanner.Bytes())
+		bodyBuilder.WriteByte('\n')
+	}
+	msg.Body = bodyBuilder.Bytes()
+
+	return msg, nil
+}
+
+func sipSplit(data []byte, atEOF bool) (advance int, token []byte, err error) {
+	if atEOF && len(data) == 0 {
+		return 0, nil, nil
+	}
+	if i := bytes.IndexByte(data, '\n'); i >= 0 {
+		if i > 0 && data[i-1] == '\r' {
+			// We have a CRLF-terminated line.
+			return i + 1, data[0:i-1], nil
+		}
+		// We have a full newline-terminated line.
+		return i + 1, data[0:i], nil
+	}
+	// If we're at EOF, we have a final, non-terminated line. Return it.
+	if atEOF {
+		return len(data), data, nil
+	}
+	// Request more data.
+	return 0, nil, nil
+}