| // Copyright 2018 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| //go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd |
| // +build darwin dragonfly freebsd linux netbsd openbsd |
| |
| package typecheck |
| |
| import ( |
| "os" |
| "reflect" |
| "syscall" |
| "unsafe" |
| ) |
| |
| // TODO(mdempsky): Is there a higher-level abstraction that still |
| // works well for iimport? |
| |
| // mapFile returns length bytes from the file starting at the |
| // specified offset as a string. |
| func mapFile(f *os.File, offset, length int64) (string, error) { |
| // POSIX mmap: "The implementation may require that off is a |
| // multiple of the page size." |
| x := offset & int64(os.Getpagesize()-1) |
| offset -= x |
| length += x |
| |
| buf, err := syscall.Mmap(int(f.Fd()), offset, int(length), syscall.PROT_READ, syscall.MAP_SHARED) |
| keepAlive(f) |
| if err != nil { |
| return "", err |
| } |
| |
| buf = buf[x:] |
| pSlice := (*reflect.SliceHeader)(unsafe.Pointer(&buf)) |
| |
| var res string |
| pString := (*reflect.StringHeader)(unsafe.Pointer(&res)) |
| |
| pString.Data = pSlice.Data |
| pString.Len = pSlice.Len |
| |
| return res, nil |
| } |
| |
| // keepAlive is a reimplementation of runtime.KeepAlive, which wasn't |
| // added until Go 1.7, whereas we need to compile with Go 1.4. |
| var keepAlive = func(interface{}) {} |