const std = @import("std");
const os = std.os;

const DB = @import("DB.zig");
const InvalidHeader = @import("header.zig").Invalid;

const File = @This();

db: DB,
ptr: []align(4096) const u8,

pub const Error = os.OpenError || os.FStatError || os.MMapError || InvalidHeader;
pub fn open(fname: []const u8) Error!File {
    const fd = try os.open(fname, os.O.RDONLY, 0);
    var fd_open = true;
    errdefer {
        if (fd_open) os.close(fd);
    }

    const st = try os.fstat(fd);
    const size = @intCast(u64, st.size);
    const ptr = try os.mmap(null, size, os.PROT.READ, os.MAP.SHARED, fd, 0);
    errdefer os.munmap(ptr);

    os.close(fd);
    fd_open = false;

    const db = try DB.fromBytes(ptr);
    return File{ .db = db, .ptr = ptr };
}

pub fn close(self: *File) void {
    os.munmap(self.ptr);
    self.* = undefined;
}