refactor(httpheader): extract header parsing into dedicated package

Moved HTTP header parsing and building logic from server package to internal/httpheader

internal/httpheader/parser.go

@@ -0,0 +1,148 @@
+package httpheader
+
+import (
+	"bufio"
+	"bytes"
+	"fmt"
+)
+
+func setRemainingHeaders(remaining []byte, header interface {
+	Set(key string, value string)
+}) {
+	for len(remaining) > 0 {
+		lineEnd := bytes.Index(remaining, []byte("\r\n"))
+		if lineEnd == -1 {
+			lineEnd = len(remaining)
+		}
+
+		line := remaining[:lineEnd]
+
+		if len(line) == 0 {
+			break
+		}
+
+		colonIdx := bytes.IndexByte(line, ':')
+		if colonIdx != -1 {
+			key := bytes.TrimSpace(line[:colonIdx])
+			value := bytes.TrimSpace(line[colonIdx+1:])
+			header.Set(string(key), string(value))
+		}
+
+		if lineEnd == len(remaining) {
+			break
+		}
+
+		remaining = remaining[lineEnd+2:]
+	}
+}
+
+func parseHeadersFromBytes(headerData []byte) (RequestHeader, error) {
+	header := &requestHeader{
+		headers: make(map[string]string, 16),
+	}
+
+	lineEnd := bytes.Index(headerData, []byte("\r\n"))
+	if lineEnd == -1 {
+		return nil, fmt.Errorf("invalid request: no CRLF found in start line")
+	}
+
+	startLine := headerData[:lineEnd]
+	header.startLine = startLine
+	var err error
+	header.method, header.path, header.version, err = parseStartLine(startLine)
+	if err != nil {
+		return nil, err
+	}
+
+	remaining := headerData[lineEnd+2:]
+
+	setRemainingHeaders(remaining, header)
+
+	return header, nil
+}
+
+func parseStartLine(startLine []byte) (method, path, version string, err error) {
+	firstSpace := bytes.IndexByte(startLine, ' ')
+	if firstSpace == -1 {
+		return "", "", "", fmt.Errorf("invalid start line: missing method")
+	}
+
+	secondSpace := bytes.IndexByte(startLine[firstSpace+1:], ' ')
+	if secondSpace == -1 {
+		return "", "", "", fmt.Errorf("invalid start line: missing version")
+	}
+	secondSpace += firstSpace + 1
+
+	method = string(startLine[:firstSpace])
+	path = string(startLine[firstSpace+1 : secondSpace])
+	version = string(startLine[secondSpace+1:])
+
+	return method, path, version, nil
+}
+
+func parseHeadersFromReader(br *bufio.Reader) (RequestHeader, error) {
+	header := &requestHeader{
+		headers: make(map[string]string, 16),
+	}
+
+	startLineBytes, err := br.ReadSlice('\n')
+	if err != nil {
+		return nil, err
+	}
+
+	startLineBytes = bytes.TrimRight(startLineBytes, "\r\n")
+	header.startLine = make([]byte, len(startLineBytes))
+	copy(header.startLine, startLineBytes)
+
+	header.method, header.path, header.version, err = parseStartLine(header.startLine)
+	if err != nil {
+		return nil, err
+	}
+
+	for {
+		lineBytes, err := br.ReadSlice('\n')
+		if err != nil {
+			return nil, err
+		}
+
+		lineBytes = bytes.TrimRight(lineBytes, "\r\n")
+
+		if len(lineBytes) == 0 {
+			break
+		}
+
+		colonIdx := bytes.IndexByte(lineBytes, ':')
+		if colonIdx == -1 {
+			continue
+		}
+
+		key := bytes.TrimSpace(lineBytes[:colonIdx])
+		value := bytes.TrimSpace(lineBytes[colonIdx+1:])
+
+		header.headers[string(key)] = string(value)
+	}
+
+	return header, nil
+}
+
+func finalize(startLine []byte, headers map[string]string) []byte {
+	size := len(startLine) + 2
+	for key, val := range headers {
+		size += len(key) + 2 + len(val) + 2
+	}
+	size += 2
+
+	buf := make([]byte, 0, size)
+	buf = append(buf, startLine...)
+	buf = append(buf, '\r', '\n')
+
+	for key, val := range headers {
+		buf = append(buf, key...)
+		buf = append(buf, ':', ' ')
+		buf = append(buf, val...)
+		buf = append(buf, '\r', '\n')
+	}
+
+	buf = append(buf, '\r', '\n')
+	return buf
+}