/**
* DAP Message Parser
*
* Parses Debug Adapter Protocol messages which use the format:
* Content-Length: <length>\r\n
* \r\n
* <JSON payload>
*/
export class DapMessageParser {
buffer = Buffer.alloc(0);
/**
* Add data to the internal buffer
*/
append(data) {
const chunk = Buffer.isBuffer(data) ? data : Buffer.from(data, 'utf8');
this.buffer = Buffer.concat([this.buffer, chunk]);
}
/**
* Try to parse the next complete message from the buffer.
* Returns null if no complete message is available.
*/
tryParse() {
// Convert to string for header parsing (headers are always ASCII)
const bufferStr = this.buffer.toString('utf8');
// Look for the header/body separator
const headerEnd = bufferStr.indexOf('\r\n\r\n');
if (headerEnd === -1) {
return null;
}
// Parse headers
const headerSection = bufferStr.substring(0, headerEnd);
const headers = this.parseHeaders(headerSection);
const contentLength = headers.get('content-length');
if (contentLength === undefined) {
// Invalid message - skip to next potential message
// Calculate byte position of header end
const headerBytes = Buffer.byteLength(headerSection, 'utf8') + 4;
this.buffer = this.buffer.subarray(headerBytes);
return null;
}
const length = parseInt(contentLength, 10);
if (isNaN(length) || length < 0) {
const headerBytes = Buffer.byteLength(headerSection, 'utf8') + 4;
this.buffer = this.buffer.subarray(headerBytes);
return null;
}
// Calculate byte positions (Content-Length is in bytes, not characters)
const headerBytes = Buffer.byteLength(headerSection, 'utf8') + 4; // +4 for \r\n\r\n
const totalBytes = headerBytes + length;
if (this.buffer.length < totalBytes) {
// Not enough data yet
return null;
}
// Extract the JSON body as bytes, then convert to string
const jsonBody = this.buffer.subarray(headerBytes, totalBytes).toString('utf8');
// Remove the processed message from buffer
this.buffer = this.buffer.subarray(totalBytes);
try {
const message = JSON.parse(jsonBody);
return {
message,
bytesConsumed: totalBytes
};
}
catch (error) {
// Invalid JSON - message is malformed
throw new Error(`Failed to parse DAP message JSON: ${error}`);
}
}
/**
* Parse all complete messages from the buffer
*/
parseAll() {
const messages = [];
let parsed;
while ((parsed = this.tryParse()) !== null) {
messages.push(parsed.message);
}
return messages;
}
/**
* Check if there's buffered data
*/
hasBufferedData() {
return this.buffer.length > 0;
}
/**
* Clear the buffer
*/
clear() {
this.buffer = Buffer.alloc(0);
}
/**
* Parse header lines into a map
*/
parseHeaders(headerSection) {
const headers = new Map();
const lines = headerSection.split('\r\n');
for (const line of lines) {
const colonIndex = line.indexOf(':');
if (colonIndex !== -1) {
const key = line.substring(0, colonIndex).trim().toLowerCase();
const value = line.substring(colonIndex + 1).trim();
headers.set(key, value);
}
}
return headers;
}
}
/**
* Encode a DAP message for sending
*/
export function encodeMessage(message) {
const json = JSON.stringify(message);
const contentLength = Buffer.byteLength(json, 'utf8');
return `Content-Length: ${contentLength}\r\n\r\n${json}`;
}
/**
* Encode a DAP message to a Buffer
*/
export function encodeMessageToBuffer(message) {
return Buffer.from(encodeMessage(message), 'utf8');
}
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