From e3f4b3bdd01f828a32bac28b3541a1980d3f8b6b Mon Sep 17 00:00:00 2001
From: Andre Henriques <andr3h3nriqu3s@gmail.com>
Date: Tue, 23 May 2023 22:04:00 +0100
Subject: [PATCH] started working on decompressing

---
 src/main.zig | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/src/main.zig b/src/main.zig
index 32c881e..1b8a024 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -36,6 +36,8 @@ const ZipFileHeader = struct {
     file_name: []u8,
     extra_field: []u8,
     compressed_content: []u8,
+    uncompressed_content: []u8,
+    decompressed: bool,
 
     allocator: std.mem.Allocator,
 
@@ -61,6 +63,8 @@ const ZipFileHeader = struct {
             .file_name = undefined,
             .extra_field = undefined,
             .compressed_content = undefined,
+            .uncompressed_content = undefined,
+            .decompressed = false,
         };
 
         self.file_name = try allocator.alloc(u8, self.file_name_length);
@@ -74,10 +78,48 @@ const ZipFileHeader = struct {
         return self;
     }
 
+    fn extract(self: *Self) !void {
+        if (self.decompressed) {
+            return error.AlreadyDecompressed;
+        }
+
+        if (self.compression_method == 0) {
+            return error.uncompressed_file;
+        }
+
+        if (self.compression_method != 8) {
+            return error.unsuported_compression_method;
+        }
+
+        self.uncompressed_content = try self.allocator.alloc(u8, self.uncompressed_size);
+        errdefer self.allocator.free(self.uncompressed_size);
+
+        var byte = self.compressed_content[0];
+        var lastBlock = byte & 0b1000_0000 == 0b1000_0000;
+        var blockType = @shrExact(byte & 0b0110_0000, 5);
+
+        if (lastBlock) {
+            print("last block", .{});
+        } else {
+            print("not last block", .{});
+        }
+
+        print("blockType: {}", .{blockType});
+
+        if (blockType != 2) {
+            return error.unsuported_block_type;
+        }
+
+        self.decompressed = true;
+    }
+
     fn deinit(self: *Self) void {
         self.allocator.free(self.file_name);
         self.allocator.free(self.extra_field);
         self.allocator.free(self.compressed_content);
+        if (self.decompressed) {
+            self.allocator.free(self.uncompressed_content);
+        }
     }
 };
 
@@ -140,6 +182,8 @@ pub fn main() !void {
     var second_file = try ZipFileHeader.init(allocator, reader);
     defer second_file.deinit();
 
+    try second_file.extract();
+
     print("G: {s}", .{second_file.file_name});
     print("GI: {}", .{second_file.compression_method});
     print("xml stuff:\n{s}", .{second_file.compressed_content});