Tool to extract a WARC record (or its headers or payload)

src/org/netpreserve/jwarc/IOUtils.java

@@ -99,6 +99,12 @@ public static void copy(InputStream inputStream, OutputStream outputStream) thro
         }
     }
 
+    public static ReadableByteChannel gunzipChannel(ReadableByteChannel gzipped) throws IOException {
+        ByteBuffer buffer = ByteBuffer.allocate(8192);
+        buffer.flip();
+        return new GunzipChannel(gzipped, buffer);
+    }
+
     static Socket connect(String scheme, String host, int port) throws IOException {
         Objects.requireNonNull(host);
         if ("http".equalsIgnoreCase(scheme)) {

src/org/netpreserve/jwarc/tools/ExtractTool.java

@@ -0,0 +1,156 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright (C) 2020 National Library of Australia and the jwarc contributors
+ */
+
+package org.netpreserve.jwarc.tools;
+
+import org.netpreserve.jwarc.*;
+
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.channels.Channels;
+import java.nio.channels.FileChannel;
+import java.nio.channels.ReadableByteChannel;
+import java.nio.channels.WritableByteChannel;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+public class ExtractTool {
+
+    private static enum ExtractAction { RECORD, HEADERS, PAYLOAD; };
+
+    private static void writeWarcHeaders(WritableByteChannel out, WarcRecord record) throws IOException {
+        StringBuilder sb = new StringBuilder();
+        sb.append(record.version().toString()).append("\r\n");
+        record.headers().appendTo(sb);
+        sb.append("\r\n");
+        out.write(ByteBuffer.wrap(sb.toString().getBytes(UTF_8)));
+    }
+
+    private static void writeHttpHeaders(WritableByteChannel out, WarcRecord record) throws IOException {
+        if (record instanceof WarcResponse) {
+            HttpResponse response = ((WarcResponse) record).http();
+            out.write(ByteBuffer.wrap(response.serializeHeader()));
+        } else if (record instanceof WarcRequest) {
+            HttpRequest request = ((WarcRequest) record).http();
+            out.write(ByteBuffer.wrap(request.serializeHeader()));
+        }
+    }
+
+    private static void writePayload(WritableByteChannel out, WarcRecord record) throws IOException {
+        MessageBody payload;
+        List<String> contentEncodings = Collections.emptyList();
+        if (record instanceof WarcResponse) {
+            HttpResponse response = ((WarcResponse) record).http();
+            payload = response.body();
+            contentEncodings = response.headers().all("Content-Encoding");
+        } else if (record instanceof WarcRequest) {
+            HttpRequest request = ((WarcRequest) record).http();
+            payload = request.body();
+            contentEncodings = request.headers().all("Content-Encoding");
+        } else {
+            payload = record.body();
+        }
+        if (contentEncodings.isEmpty()) {
+            writeBody(out, payload);
+        } else {
+            if (contentEncodings.size() > 1) {
+                System.err.println("Multiple Content-Encodings not supported: " + contentEncodings);
+            } else if (contentEncodings.get(0).equalsIgnoreCase("gzip")
+                    || contentEncodings.get(0).equalsIgnoreCase("x-gzip")) {
+                writeBody(out, IOUtils.gunzipChannel(payload));
+            } else {
+                System.err.println("Content-Encoding not supported: " + contentEncodings.get(0));
+            }
+        }
+    }
+
+    private static void writeBody(WritableByteChannel out, ReadableByteChannel body) throws IOException {
+        ByteBuffer buffer = ByteBuffer.allocate(8192);
+        while (body.read(buffer) > -1) {
+            buffer.flip();
+            out.write(buffer);
+            buffer.compact();
+        }
+    }
+
+    private static void usage(int exitValue) {
+        System.err.println("");
+        System.err.println("ExtractTool [-h] [--payload | --headers] filename offset");
+        System.err.println("");
+        System.err.println("Options:");
+        System.err.println("");
+        System.err.println(" --headers\toutput only record (and HTTP) headers");
+        System.err.println(" --payload\toutput only record payload, if necessary");
+        System.err.println("          \tdecode transfer and/or content encoding");
+        System.exit(exitValue);
+    }
+
+    public static void main(String[] args) throws IOException {
+        ExtractAction action = ExtractAction.RECORD;
+        Path warcFile = null;
+        long offset = -1;
+        for (String arg : args) {
+            switch (arg) {
+            case "-h":
+            case "--help":
+                usage(0);
+            case "--headers":
+                action = ExtractAction.HEADERS;
+                break;
+            case "--payload":
+                action = ExtractAction.PAYLOAD;
+                break;
+            default:
+                if (warcFile == null) {
+                    warcFile = Paths.get(arg);
+                    if (!warcFile.toFile().canRead()) {
+                        System.err.println("Cannot read WARC file: " + warcFile);
+                        usage(1);
+                    }
+                } else if (offset == -1) {
+                    try {
+                        offset = Long.parseLong(arg);
+                    } catch (NumberFormatException e) {
+                        System.err.println(e.getMessage());
+                        usage(1);
+                    }
+                } else {
+                    System.err.println("Unknown argument: " + arg);
+                    usage(1);
+                }
+            }
+        }
+        if (warcFile == null || offset == -1) {
+            usage(1);
+        }
+        try (FileChannel channel = FileChannel.open(warcFile);
+                WarcReader reader = new WarcReader(channel.position(offset))) {
+            Optional<WarcRecord> record = reader.next();
+            if (!record.isPresent()) {
+                System.err.println("No record found at position " + offset);
+                System.exit(1);
+            }
+            WritableByteChannel out = Channels.newChannel(System.out);
+            switch (action) {
+            case RECORD:
+                writeWarcHeaders(out, record.get());
+                writeBody(out, record.get().body());
+                break;
+            case HEADERS:
+                writeWarcHeaders(out, record.get());
+                writeHttpHeaders(out, record.get());
+                break;
+            case PAYLOAD:
+                writePayload(out, record.get());
+                break;
+            }
+        }
+    }
+}

src/org/netpreserve/jwarc/tools/WarcTool.java

@@ -17,6 +17,9 @@ public static void main(String[] args) throws Exception {
             case "cdx":
                 CdxTool.main(rest);
                 break;
+            case "extract":
+                ExtractTool.main(rest);
+                break;
             case "fetch":
                 FetchTool.main(rest);
                 break;
@@ -59,6 +62,7 @@ private static void usage() {
         System.out.println("Commands:");
         System.out.println("");
         System.out.println("  cdx         List records in CDX format");
+        System.out.println("  extract     Extract record by offset");
         System.out.println("  fetch       Download a URL recording the request and response");
         System.out.println("  filter      Copy records that match a given filter expression");
         System.out.println("  ls          List records in WARC file(s)");