Added genzip1.py helper script for generating uncompressed deflate blocks in a zip file for unzip unit tests.

Author: Lethja

meta/test/unzip/genzip1.py

@@ -0,0 +1,94 @@
+#!/usr/bin/env python3
+
+import struct
+import sys
+import zlib
+
+def create_zip():
+    filename = sys.argv[1].encode() if len(sys.argv) > 1 else b"test.txt"
+    content = sys.stdin.buffer.read()
+    if len(content) <= 0:
+        content = b"Test"
+
+    # --- 1. Create the Raw Deflate Stream (Stored Block) ---
+    # We are faking "compression" by creating a valid Deflate stream
+    # that just wraps raw bytes.
+    # Header Byte: 0x01
+    #   Bit 0 = 1 (BFINAL, this is the last block)
+    #   Bits 1-2 = 00 (BTYPE, stored/uncompressed)
+    # LEN: 2 bytes, Little Endian length of data
+    # NLEN: 2 bytes, Little Endian one's complement of length
+
+    length = len(content)
+    nlen = (~length) & 0xFFFF
+
+    # Construct the payload
+    # <HH means two unsigned short integers (2 bytes) in Little Endian
+    deflate_header = b'\x01' + struct.pack('<HH', length, nlen)
+    compressed_data = deflate_header + content
+
+    # Calculate Metadata
+    crc = zlib.crc32(content)
+    compressed_size = len(compressed_data)
+    uncompressed_size = length
+
+    # --- 2. Construct ZIP Headers ---
+
+    # Common Values
+    # Version needed: 2.0 (20)
+    # Flags: 0
+    # Compression Method: 8 (Deflate)
+    # Time/Date: 0 (for simplicity)
+    ver = 20
+    flags = 0
+    method = 8
+
+    # A. Local File Header
+    # Signature (4s) = PK\x03\x04
+    lfh_fmt = '<4sHHHHHIIIHH'
+    lfh = struct.pack(
+        lfh_fmt,
+        b'\x50\x4b\x03\x04', # Signature
+        ver, flags, method, 0, 0, # Ver, Flags, Method, Time, Date
+        crc, compressed_size, uncompressed_size, # CRC, Sizes
+        len(filename), 0 # Filename len, Extra len
+    )
+
+    # B. Central Directory Header
+    # Signature (4s) = PK\x01\x02
+    cdh_fmt = '<4sHHHHHHIIIHHHHHII'
+    cdh = struct.pack(
+        cdh_fmt,
+        b'\x50\x4b\x01\x02', # Signature
+        ver, ver, flags, method, 0, 0, # MadeBy, Needed, Flags, Method, Time, Date
+        crc, compressed_size, uncompressed_size, # CRC, Sizes
+        len(filename), 0, 0, # Name len, Extra len, Comment len
+        0, 0, 0x81a40000, # Disk Start, Int Attr, Ext Attr (Permissions)
+        0 # Relative Offset of Local Header (0 because it's the first file)
+    )
+
+    # C. End of Central Directory Record
+    # Signature (4s) = PK\x05\x06
+    # We need to calculate where the Central Directory starts and how big it is
+    offset_of_cd = len(lfh) + len(filename) + compressed_size
+    size_of_cd = len(cdh) + len(filename)
+
+    eocd_fmt = '<4sHHHHIIH'
+    eocd = struct.pack(
+        eocd_fmt,
+        b'\x50\x4b\x05\x06', # Signature
+        0, 0, 1, 1, # Disk nums, Recs on disk, Total recs
+        size_of_cd, offset_of_cd, 0 # CD Size, CD Offset, Comment len
+    )
+
+    # --- 3. Write the File ---
+    with sys.stdout.buffer as f:
+        f.write(lfh)
+        f.write(filename)
+        f.write(compressed_data)
+        f.write(cdh)
+        f.write(filename)
+        f.write(eocd)
+
+if __name__ == "__main__":
+    create_zip()