Restart (once again)

src/archive.zig

@@ -0,0 +1,53 @@
+//! A squashfs archive read from a file.
+//! Can be used to directly access File's contents or extract to the filesystem.
+
+const std = @import("std");
+const File = std.fs.File;
+
+const Superblock = @import("super.zig").Superblock;
+const OffsetFile = @import("util/offset_file.zig");
+
+const Archive = @This();
+
+// 4 Gigs
+const MIN_MEM_SIZE = 4 * 1024 * 1024 * 1024;
+
+parent_alloc: std.mem.Allocator,
+alloc: std.heap.FixedBufferAllocator,
+fixed_buf: []u8,
+fil: OffsetFile,
+
+super: Superblock,
+
+/// Default settings using std.Thread.getCpuCount() threads and the minimum of 4gb or half of system memory for memory usage.
+pub fn init(alloc: std.mem.Allocator, fil: File) !Archive {
+    return initAdvanced(
+        alloc,
+        fil,
+        0,
+        try std.Thread.getCpuCount(),
+        @min(MIN_MEM_SIZE, std.process.totalSystemMemory() / 2),
+    );
+}
+/// Create the Archive dictating the amount of threads & memory used.
+/// If trying to extract a full archive, a large memory size & thread count could help.
+/// If you're planning on only interacting with a small number of files, it should be fine to use few threads and a small memory size.
+pub fn initAdvanced(alloc: std.mem.Allocator, fil: File, offset: u64, threads: usize, mem: usize) !Archive {
+    _ = threads;
+    var super: Superblock = undefined;
+    const red = try fil.pread(@ptrCast(&super), offset);
+    std.debug.assert(red == @sizeOf(Superblock));
+    const fixed_buf = alloc.alloc(u8, mem);
+    return .{
+        .parent_alloc = alloc,
+        .alloc = .init(fixed_buf),
+        .fixed_buf = fixed_buf,
+        .fil = .init(fil, offset),
+
+        .super = super,
+    };
+}
+
+pub fn deinit(self: *Archive) void {
+    self.parent_alloc.free(self.fixed_buf);
+}