examples/compareCentralAndLocalHeaders.js

README.md

@@ -452,11 +452,10 @@ These fields are of type `Number`:
 These fields are of type `Buffer`, and represent variable-length bytes before being processed:
  * `fileNameRaw`
  * `extraFieldRaw`
- * `commentRaw`
+ * `fileCommentRaw`
 
-There are additional fields described below: `fileName`, `extraFields`, `comment`.
-These are the `*Raw` fields above after going through some processing, such as UTF-8 decoding.
-See their own sections below.
+There are additional fields described below: `fileName`, `extraFields`, `fileComment`.
+These are the processed versions of the `*Raw` fields listed above. See their own sections below.
 (Note the inconsistency in pluralization of "field" vs "fields" in `extraField`, `extraFields`, and `extraFieldRaw`.
 Sorry about that.)
 
@@ -761,7 +760,8 @@ This library makes no attempt to interpret the Language Encoding Flag.
    * Added `readLocalFileHeader()` and `Class: LocalFileHeader`.
    * Added `openReadStreamLowLevel()`.
    * Added `getFileNameLowLevel()` and `parseExtraFields()`.
-     Added fields to `Class: Entry`: `fileNameRaw`, `extraFieldRaw`, `commentRaw`.
+     Added fields to `Class: Entry`: `fileNameRaw`, `extraFieldRaw`, `fileCommentRaw`.
+   * Added `examples/compareCentralAndLocalHeaders.js` that demonstrate many of these low level APIs.
    * Noted dropped support of node versions before 12 in the `"engines"` field of `package.json`.
  * 3.0.0
    * BREAKING CHANGE: implementations of [RandomAccessReader](#class-randomaccessreader) that implement a `destroy` method must instead implement `_destroy` in accordance with the node standard https://nodejs.org/api/stream.html#writable_destroyerr-callback (note the error and callback parameters). If you continue to override `destory` instead, some error handling may be subtly broken. Additionally, this is required for async iterators to work correctly in some versions of node. [issue #110](https://github.com/thejoshwolfe/yauzl/issues/110)

examples/compareCentralAndLocalHeaders.js

@@ -0,0 +1,142 @@
+
+var yauzl = require("../"); // replace with: var yauzl = require("yauzl");
+
+function usage() {
+  console.log(
+    "usage: node compareCentralAndLocalHeaders.js path/to/file.zip\n" +
+    "\n" +
+    "Shows a table comparing the central directory metadata and local\n" +
+    "file headers for each item in a zipfile.\n" +
+    "");
+  process.exit(1);
+}
+
+var zipfilePath = null;
+var detailedExtraFieldBreakdown = true;
+process.argv.slice(2).forEach(function(arg) {
+  if (/^-/.test(arg)) usage();
+  if (zipfilePath != null) usage();
+  zipfilePath = arg;
+});
+if (zipfilePath == null) usage();
+
+yauzl.open(zipfilePath, {lazyEntries: true, decodeStrings: false}, function(err, zipfile) {
+  if (err) throw err;
+  zipfile.on("error", function(err) {
+    throw err;
+  });
+  zipfile.readEntry();
+  zipfile.on("entry", function(entry) {
+    zipfile.readLocalFileHeader(entry, function(err, localFileHeader) {
+      if (err) throw err;
+      compare(entry, localFileHeader);
+      zipfile.readEntry();
+    });
+  });
+})
+
+function compare(entry, localFileHeader) {
+  console.log(yauzl.getFileNameLowLevel(entry.generalPurposeBitFlag, entry.fileNameRaw, entry.extraFields, false));
+
+  // Compare integers
+  var integerFields = [
+    "versionMadeBy",
+    "versionNeededToExtract",
+    "generalPurposeBitFlag",
+    "compressionMethod",
+    "lastModFileTime",
+    "lastModFileDate",
+    "crc32",
+    "compressedSize",
+    "uncompressedSize",
+    "fileNameLength",
+    "extraFieldLength",
+    "fileCommentLength",
+    "internalFileAttributes",
+    "externalFileAttributes",
+    "relativeOffsetOfLocalHeader",
+  ];
+  function formatNumber(numberOrNull) {
+    if (numberOrNull == null) return "-";
+    return "0x" + numberOrNull.toString(16);
+  }
+
+  var rows = [["field", "central", "local", "diff"]];
+  rows.push(...integerFields.map(function(name) {
+    var a = entry[name];
+    var b = localFileHeader[name];
+    var diff = a == null || b == null ? "" :
+      a === b ? "" : "x";
+    return [name, formatNumber(a), formatNumber(b), diff]
+  }));
+
+  var columnWidths = [0, 1, 2, 3].map(function(i) {
+    return Math.max(...rows.map(row => row[i].length));
+  });
+  var formatFunctions = ["padEnd", "padStart", "padStart", "padEnd"];
+
+  console.log("┌" + columnWidths.map(w => "─".repeat(w)).join("┬") + "┐");
+  for (var i = 0; i < rows.length; i++) {
+    console.log("│" + rows[i].map((x, j) => x[formatFunctions[j]](columnWidths[j])).join("│") + "│");
+    if (i === 0) {
+      console.log("├" + columnWidths.map(w => "─".repeat(w)).join("┼") + "┤");
+    }
+  }
+  console.log("└" + columnWidths.map(w => "─".repeat(w)).join("┴") + "┘");
+
+  // Compare variable length data.
+  console.log("central.fileName:", entry.fileNameRaw.toString("hex"));
+  if (entry.fileNameRaw.equals(localFileHeader.fileName)) {
+    console.log("(local matches)");
+  } else {
+    console.log("  local.fileName:", localFileHeader.fileName.toString("hex"));
+  }
+  console.log("central.extraField:", entry.extraFieldRaw.toString("hex"));
+  if (entry.extraFieldRaw.equals(localFileHeader.extraField)) {
+    console.log("(local matches)");
+  } else {
+    console.log("  local.extraField:", localFileHeader.extraField.toString("hex"));
+  }
+
+  if (detailedExtraFieldBreakdown) {
+    var centralExtraFieldMap = extraFieldsToMap(entry.extraFields);
+    var localExtraFieldMap = extraFieldsToMap(yauzl.parseExtraFields(localFileHeader.extraField));
+    for (var key in centralExtraFieldMap) {
+      var centralData = centralExtraFieldMap[key];
+      var localData = localExtraFieldMap[key];
+      delete localExtraFieldMap[key]; // to isolate unhandled keys.
+      console.log("    [" + key + "]central:", centralData.toString("hex"));
+      if (localData != null && centralData.equals(localData)) {
+        console.log("    [" + key + "](local matches)");
+      } else if (localData != null) {
+        console.log("    [" + key + "]  local:", localData.toString("hex"));
+      } else {
+        console.log("    [" + key + "]  local: <missing>");
+      }
+    }
+    // Any keys left here don't match anything.
+    for (var key in localExtraFieldMap) {
+      var localData = localExtraFieldMap[key];
+      console.log("    [" + key + "]central: <missing>");
+      console.log("    [" + key + "]  local:", localData.toString("hex"));
+    }
+  }
+  console.log("central.comment:", entry.fileCommentRaw.toString("hex"));
+
+  console.log("");
+}
+
+function extraFieldsToMap(extraFields) {
+  var map = {};
+  extraFields.forEach(({id, data}) => {
+    var key = "0x" + id.toString(16).padStart(4, "0");
+    var baseKey = key;
+    var i = 1;
+    while (key in map) {
+      key = baseKey + "." + i;
+      i++;
+    }
+    map[key] = data;
+  });
+  return map;
+}

index.js

@@ -685,8 +685,7 @@ function parseExtraFields(extraFieldBuffer) {
     var dataStart = i + 4;
     var dataEnd = dataStart + dataSize;
     if (dataEnd > extraFieldBuffer.length) throw new Error("extra field length exceeds extra field buffer size");
-    var dataBuffer = newBuffer(dataSize);
-    extraFieldBuffer.copy(dataBuffer, 0, dataStart, dataEnd);
+    var dataBuffer = extraFieldBuffer.subarray(dataStart, dataEnd);
     extraFields.push({
       id: headerId,
       data: dataBuffer,