createMap

pub fn createMap(env: Environ, allocator: Allocator) CreateMapError!Map {
    var map = Map.init(allocator);
    errdefer map.deinit();
    if (native_os == .windows) empty: {
        if (!env.block.use_global) break :empty;

        const peb = std.os.windows.peb();
        assert(std.os.windows.ntdll.RtlEnterCriticalSection(peb.FastPebLock) == .SUCCESS);
        defer assert(std.os.windows.ntdll.RtlLeaveCriticalSection(peb.FastPebLock) == .SUCCESS);
        try map.putWindowsBlock(.{ .ptr = peb.ProcessParameters.Environment });
    } else if (native_os == .wasi and !builtin.link_libc) empty: {
        if (!env.block.use_global) break :empty;

        var environ_count: usize = undefined;
        var environ_buf_size: usize = undefined;

        const environ_sizes_get_ret = std.os.wasi.environ_sizes_get(&environ_count, &environ_buf_size);
        if (environ_sizes_get_ret != .SUCCESS) {
            return posix.unexpectedErrno(environ_sizes_get_ret);
        }

        if (environ_count == 0) {
            return map;
        }

        const environ = try allocator.alloc([*:0]u8, environ_count);
        defer allocator.free(environ);
        const environ_buf = try allocator.alloc(u8, environ_buf_size);
        defer allocator.free(environ_buf);

        const environ_get_ret = std.os.wasi.environ_get(environ.ptr, environ_buf.ptr);
        if (environ_get_ret != .SUCCESS) {
            return posix.unexpectedErrno(environ_get_ret);
        }

        try map.putPosixBlock(.{ .slice = environ });
    } else try map.putPosixBlock(env.block.view());
    return map;
}