Golang source Read OS. File

This is a creation in Article, where the information may have evolved or changed.

The recent writing process feels Golang reading and writing files is slow. So decided to read the source code.

Src/os/file.go

Http://www.ieyebrain.com:8080/golang/src/os/file.go

The function for file is defined in:

Name, Read,write,seek,close, and so on.

For example, the Read function

Func (f *file) Read (b []byte) (n int, err error) {
if f = = nil {
return 0, Errinvalid
}
N, E: = F.read (b)
if n = = 0 && len (b) > 0 && E = = Nil {
return 0, Io. Eof
}
If E! = Nil {
Err = &patherror{"read", F.name, E}
}
return N, err
}

This implements the interface technique for delegate invocation. is to delegate the read operation to the F.read function. F is a pointer to the file type, and a circle is found, only to find that it is defined in the implementation-specific file. For example: in File_windows.go,

Http://www.ieyebrain.com:8080/golang/src/os/file_windows.go

Type File struct {
*file
}
Type file struct {
FD Syscall. Handle
Name string
Dirinfo *dirinfo//nil unless directory being read
L Sync. Mutex//used to implement Windows Pread/pwrite

Only for console IO
isconsole BOOL
lastbits []byte//first few bytes of the last incomplete rune in last write
READBUF []rune//Input Console buffer
}

The following is the read main, Syscall. Read (f.fd,b). WindowsAPI, Syscall, file, file---

Three more calls, file---file is implemented across platforms. File This layer adds a lock. This could be a big drain. This lock is for unified operation semantics and does not have this lock on UNIX platforms.

Func (f *file) read (b []byte) (n int, err error) {
F.l.lock ()
Defer F.l.unlock ()
If F.isconsole {
return F.readconsole (b)
}
Return Fixcount (Syscall. Read (F.FD, B))
}

Call Procedure:

1 http://www.ieyebrain.com:8080/golang/src/syscall/syscall_windows.go

Func Read (FD Handle, P []byte) (n int, err error), ReadFile

2 Http://www.ieyebrain.com:8080/golang/src/syscall/zsyscall_windows.go

Func ReadFile (handle handle, buf []byte, Done *uint32, overlapped *overlapped) (err Error)

3 Http://www.ieyebrain.com:8080/golang/src/runtime/syscall_windows.go

Func syscall_syscall6 (FN, Nargs, A1, A2, A3, A4, A5, A6 uintptr) (R1, R2, err UIntPtr) {
c: = &GETG (). M.syscall
C.Fn = fn
C.N = Nargs
C.args = UIntPtr (Noescape (unsafe. Pointer (&A1)))
Cgocall (asmstdcalladdr, unsafe. Pointer (c))
Return C.R1, C.R2, C.err
}