// license that can be found in the LICENSE file.

// This package is a lightly modified version of the mmap code
// in github.com/google/codesearch/index.

// The mmap package provides an abstraction for memory mapping files
// on different platforms.
package mmap

import (
	"os"
)

// The backing file is never closed, so Data
// remains valid for the lifetime of the process.

	if length < threshold {
		return nil, false
	}

	// Have we reached the mmap limit?
	if atomic.AddInt32(&mmapLimit, -1) < 0 {
		atomic.AddInt32(&mmapLimit, 1)
		return nil, false
	}

	// Page-align the offset.
	off := r.Offset()
	align := syscall.Getpagesize()
	aoff := off &^ int64(align-1)

	// for which we have computed the size and offset, in a
	// mmap'd region. The second part writes more content, for
	// which we don't know the size.
	if ctxt.Arch.Family != sys.Wasm {
		// Don't mmap if we're building for Wasm. Wasm file
		// layout is very different so filesize is meaningless.
		if err := ctxt.Out.Mmap(filesize); err != nil {
			Exitf("mapping output file failed: %v", err)
		}
	}

//go:build unix && (!solaris || go1.20)

package mmap

import (
	"fmt"
	"io/fs"
	"os"
	"syscall"
)

func mmapFile(f *os.File, _ *Data) (Data, error) {
	st, err := f.Stat()
	if err != nil {
		return Data{}, err
	}
	size := st.Size()
	pagesize := int64(os.Getpagesize())
	if int64(int(size+(pagesize-1))) != size+(pagesize-1) {
		return Data{}, fmt.Errorf("%s: too large for mmap", f.Name())
	}
	n := int(size)

// license that can be found in the LICENSE file.

//go:build unix

package ld

import (
	"syscall"
)

// Mmap maps the output file with the given size. It unmaps the old mapping
// if it is already mapped. It also flushes any in-heap data to the new
// mapping.
func (out *OutBuf) Mmap(filesize uint64) (err error) {
	oldlen := len(out.buf)
	if oldlen != 0 {
		out.munmap()
	}

	for {

// prevents us from allocating more stack.
//
//go:nosplit
func sysAllocOS(n uintptr) unsafe.Pointer {
	p, err := mmap(nil, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
	if err != 0 {
		if err == _EACCES {
			print("runtime: mmap: access denied\n")
			exit(2)
		}
		if err == _EAGAIN {
			print("runtime: mmap: too much locked memory (check 'ulimit -l').\n")
			exit(2)
		}
		return nil
	}
	return p
}

//go:build !unix && !windows

package ld

// Mmap allocates an in-heap output buffer with the given size. It copies
// any old data (if any) to the new buffer.
func (out *OutBuf) Mmap(filesize uint64) error {
	// We need space to put all the symbols before we apply relocations.
	oldheap := out.heap
	if filesize < uint64(len(oldheap)) {
		panic("mmap size too small")
	}
	out.heap = make([]byte, filesize)

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

//go:build (js && wasm) || wasip1 || plan9 || (solaris && !go1.20)

package mmap

import (
	"io"
	"os"
)

// mmapFile on other systems doesn't mmap the file. It just reads everything.
func mmapFile(f *os.File, _ *Data) (Data, error) {
	b, err := io.ReadAll(f)
	if err != nil {
		return Data{}, err
	}

//go:build unix

package syscall

import _ "unsafe" // for linkname

// mmap should be an internal detail,
// but widely used packages access it using linkname.
// Notable members of the hall of shame include:
//   - modernc.org/memory
//   - github.com/ncruces/go-sqlite3
//
// Do not remove or change the type signature.
// See go.dev/issue/67401.
//

// license that can be found in the LICENSE file.

//go:build aix || darwin || dragonfly || freebsd || openbsd || solaris || zos

package unix

var mapper = &mmapper{
	active: make(map[*byte][]byte),
	mmap:   mmap,
	munmap: munmap,