Expose ability for LocalFileHeader to pull values from CEN

Can be done by extending the zip-reader strategies and calling the method in the post-process protected method.

Author: Col-E

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>software.coley</groupId>
     <artifactId>lljzip</artifactId>
-    <version>1.1.9</version>
+    <version>1.2.0</version>
 
     <name>LL Java ZIP</name>
     <description>Lower level ZIP support for Java</description>

src/main/java/software/coley/llzip/part/LocalFileHeader.java

@@ -7,7 +7,7 @@
 
 import java.io.IOException;
 
-import static software.coley.llzip.ZipCompressions.*;
+import static software.coley.llzip.ZipCompressions.STORED;
 
 /**
  * ZIP LocalFileHeader structure.
@@ -35,8 +35,11 @@ public class LocalFileHeader implements ZipPart, ZipRead {
 
 	private transient String fileNameCache;
 
+	private ByteData data;
+
 	@Override
 	public void read(ByteData data, long offset) {
+		this.data = data;
 		this.offset = offset;
 		versionNeededToExtract = ByteDataUtil.readWord(data, offset + 4);
 		generalPurposeBitFlag = ByteDataUtil.readWord(data, offset + 6);
@@ -59,6 +62,43 @@ public void read(ByteData data, long offset) {
 		fileData = data.sliceOf(offset + 30 + fileNameLength + extraFieldLength, fileDataLength);
 	}
 
+	/**
+	 * When called before being {@link #freeze() frozen} values can be adopted from the linked
+	 * {@link #getLinkedDirectoryFileHeader() CentralDirectoryFileHeader}.
+	 * <br>
+	 * In some cases the {@link LocalFileHeader} file size may be 0, but the authoritative CEN states a non-0 value,
+	 * which you may want to adopt.
+	 */
+	public void adoptLinkedCentralDirectoryValues() {
+		if (data != null && linkedDirectoryFileHeader != null) {
+			versionNeededToExtract = linkedDirectoryFileHeader.getVersionNeededToExtract();
+			generalPurposeBitFlag = linkedDirectoryFileHeader.getGeneralPurposeBitFlag();
+			setCompressionMethod(linkedDirectoryFileHeader.getCompressionMethod());
+			lastModFileTime = linkedDirectoryFileHeader.getLastModFileTime();
+			lastModFileDate = linkedDirectoryFileHeader.getLastModFileDate();
+			setCrc32(linkedDirectoryFileHeader.getCrc32());
+			setCompressedSize(linkedDirectoryFileHeader.getCompressedSize());
+			setUncompressedSize(linkedDirectoryFileHeader.getUncompressedSize());
+			setFileNameLength(linkedDirectoryFileHeader.getFileNameLength());
+			setFileName(data.sliceOf(offset + 30, fileNameLength));
+			extraField = data.sliceOf(offset + 30 + fileNameLength, extraFieldLength);
+			long fileDataLength;
+			if (compressionMethod == STORED) {
+				fileDataLength = uncompressedSize;
+			} else {
+				fileDataLength = compressedSize;
+			}
+			fileData = data.sliceOf(offset + 30 + fileNameLength + extraFieldLength, fileDataLength);
+		}
+	}
+
+	/**
+	 * Clears the reference to the source {@link ByteData}, preventing further modification.
+	 */
+	public void freeze() {
+		data = null;
+	}
+
 	@Override
 	public long length() {
 		return MIN_FIXED_SIZE + fileName.length() + extraField.length() + fileData.length();

src/main/java/software/coley/llzip/strategy/DefaultZipReaderStrategy.java

@@ -53,6 +53,8 @@ public void read(ZipArchive zip, ByteData data) throws IOException {
 				zip.getParts().add(file);
 				directory.link(file);
 				file.link(directory);
+				postProcessLocalFileHeader(file);
+				file.freeze();
 				offsets.add(offset);
 			} else {
 				logger.warn("Central-Directory-File-Header's offset[{}] to Local-File-Header does not match the Local-File-Header magic!", offset);
@@ -61,4 +63,8 @@ public void read(ZipArchive zip, ByteData data) throws IOException {
 		// Sort based on order
 		zip.getParts().sort(new OffsetComparator());
 	}
+
+	protected void postProcessLocalFileHeader(LocalFileHeader file) {
+		// no-op
+	}
 }

src/main/java/software/coley/llzip/strategy/JvmZipReaderStrategy.java

@@ -120,6 +120,8 @@ else if (ByteDataUtil.startsWith(data, jvmBaseFileOffset, ZipPatterns.CENTRAL_DI
 					zip.getParts().add(file);
 					directory.link(file);
 					file.link(directory);
+					postProcessLocalFileHeader(file);
+					file.freeze();
 					offsets.add(offset);
 				} catch (Exception ex) {
 					logger.warn("Failed to read 'local file header' at offset[{}]", offset, ex);
@@ -131,4 +133,8 @@ else if (ByteDataUtil.startsWith(data, jvmBaseFileOffset, ZipPatterns.CENTRAL_DI
 		// Sort based on order
 		zip.getParts().sort(new OffsetComparator());
 	}
+
+	protected void postProcessLocalFileHeader(LocalFileHeader file) {
+		// no-op
+	}
 }