test/sandbox: wrap libc getmntent

For checking mounts outcome.

Signed-off-by: Ophestra <cat@gensokyo.uk>

test/sandbox/mount.go

@@ -0,0 +1,134 @@
+package sandbox
+
+/*
+#include <stdlib.h>
+#include <stdio.h>
+#include <mntent.h>
+
+const char *F_PROC_MOUNTS = "";
+const char *F_SET_TYPE = "r";
+*/
+import "C"
+
+import (
+	"fmt"
+	"runtime"
+	"sync"
+	"unsafe"
+)
+
+type Mntent struct {
+	/* name of mounted filesystem */
+	FSName string `json:"fsname"`
+	/* filesystem path prefix */
+	Dir string `json:"dir"`
+	/* mount type (see mntent.h) */
+	Type string `json:"type"`
+	/* mount options (see mntent.h) */
+	Opts string `json:"opts"`
+	/* dump frequency in days */
+	Freq int `json:"freq"`
+	/* pass number on parallel fsck */
+	Passno int `json:"passno"`
+}
+
+func (e *Mntent) String() string {
+	return fmt.Sprintf("%s %s %s %s %d %d",
+		e.FSName, e.Dir, e.Type, e.Opts, e.Freq, e.Passno)
+}
+
+func IterMounts(name string, f func(e *Mntent)) error {
+	m := new(mounts)
+	m.p = name
+	if err := m.open(); err != nil {
+		return err
+	}
+
+	for m.scan() {
+		e := new(Mntent)
+		m.copy(e)
+		f(e)
+	}
+
+	m.close()
+	return m.Err()
+}
+
+type mounts struct {
+	p  string
+	f  *C.FILE
+	mu sync.RWMutex
+
+	ent *C.struct_mntent
+	err error
+}
+
+func (m *mounts) open() error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.f != nil {
+		panic("open called twice")
+	}
+
+	if m.p == "" {
+		m.p = "/proc/mounts"
+	}
+
+	name := C.CString(m.p)
+	f, err := C.setmntent(name, C.F_SET_TYPE)
+	C.free(unsafe.Pointer(name))
+
+	if f == nil {
+		return err
+	}
+	m.f = f
+	runtime.SetFinalizer(m, (*mounts).close)
+	return err
+}
+
+func (m *mounts) close() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.f == nil {
+		panic("close called before open")
+	}
+
+	C.endmntent(m.f)
+	runtime.SetFinalizer(m, nil)
+}
+
+func (m *mounts) scan() bool {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	if m.f == nil {
+		panic("invalid file")
+	}
+
+	m.ent, m.err = C.getmntent(m.f)
+	return m.ent != nil
+}
+
+func (m *mounts) Err() error {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	return m.err
+}
+
+func (m *mounts) copy(v *Mntent) {
+	m.mu.RLock()
+	defer m.mu.RUnlock()
+
+	if m.ent == nil {
+		panic("invalid entry")
+	}
+	v.FSName = C.GoString(m.ent.mnt_fsname)
+	v.Dir = C.GoString(m.ent.mnt_dir)
+	v.Type = C.GoString(m.ent.mnt_type)
+	v.Opts = C.GoString(m.ent.mnt_opts)
+	v.Freq = int(m.ent.mnt_freq)
+	v.Passno = int(m.ent.mnt_passno)
+}