You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mmap_unix.go
    path of file: ./repos/sliver/vendor/modernc.org/memory
    
    the code of the file until where you have to start completion: // Copyright 2011 Evan Shaw. All rights reserved.
// Use of this source code i
    
func mmap(size int) (uintptr, int, error) {
	size = roundup(size, osPageSize)
	// The actual mmap syscall varies by architecture. mmapSyscall provides same
	// functionality as the unexported funtion syscall.mmap and is declared in
	// mmap_*_*.go and mmap_fallback.go. To add support for a new architecture,
	// check function mmap in src/syscall/syscall_*_*.go or
	// src/syscall/zsyscall_*_*.go in Go's source code.
	p, err := mmapSyscall(0, uintptr(size+pageSize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_PRIVATE|syscall.MAP_ANON, -1, 0)
	if err != nil {
		return 0, 0, err
	}

	n := size + pageSize
	if p&uintptr(osPageMask) != 0 {
		panic("internal error")
	}

	mod := int(p) & pageMask
	if mod != 0 {
		m := pageSize - mod
		if err := unmap(p, m); err != nil {
			return 0, 0, err
		}

		n -= m
		p += uintptr(m)
	}

	if p&uintptr(pageMask) != 0 {
		panic("internal error")
	}

	if n-size != 0 {
		if err := unmap(p+uintptr(size), n-size); err != nil {
			return 0, 0, err
		}
	}

	return p, size, nil
}