test/internal/mountinfo: move from sandbox

This also improves its API.

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

1 files changed, 177 insertions, 0 deletions

diff --git a/test/internal/mountinfo/mountinfo.go b/test/internal/mountinfo/mountinfo.go
new file mode 100644
index 00000000..19892cd2
--- /dev/null
+++ b/test/internal/mountinfo/mountinfo.go
@@ -0,0 +1,177 @@
+// Package mountinfo provides util-linux bindings for parsing
+// proc_pid_mountinfo(5).
+//
+// This package must never be used outside integration tests, a much better
+// implementation can be found in package vfs.
+//
+// Attempting to import this package outside testing causes the resulting
+// program to panic.
+package mountinfo
+
+/*
+#cgo linux pkg-config: --static mount
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <libmount.h>
+
+const char *HAKUREI_MOUNTINFO_PATH = "/proc/self/mountinfo";
+*/
+import "C"
+
+import (
+	"errors"
+	"fmt"
+	"runtime"
+	"unsafe"
+)
+
+var (
+	// ErrParse is returned by [Open] when encountering a bad record.
+	ErrParse = errors.New("invalid mountinfo record")
+	// ErrIter is returned by [Open] if an iterator cannot be allocated.
+	ErrIter = errors.New("cannot allocate iterator")
+	// ErrIterAdvance is stored when the iterator is unable to advance.
+	ErrIterAdvance = errors.New("unable to advance iterator")
+)
+
+type (
+	// Iter refers to libmnt iterator state.
+	Iter struct {
+		// Last stored error.
+		err error
+		// Whether iteration has concluded.
+		ok bool
+		// Whether Close had already been called.
+		closed bool
+
+		tb  *C.struct_libmnt_table
+		itr *C.struct_libmnt_iter
+
+		fs *C.struct_libmnt_fs
+	}
+
+	// Entry represents deterministic mountinfo parts of a libmnt_fs entry.
+	Entry struct {
+		// mount ID: a unique ID for the mount (may be reused after umount(2)).
+		ID int `json:"id"`
+		// parent ID: the ID of the parent mount (or of self for the root of
+		// this mount namespace's mount tree).
+		Parent int `json:"parent"`
+		// root: the pathname of the directory in the filesystem which forms the
+		// root of this mount.
+		Root string `json:"root"`
+		// mount point: the pathname of the mount point relative to the
+		// process's root directory.
+		Target string `json:"target"`
+		// mount options: per-mount options (see mount(2)).
+		VfsOptstr string `json:"vfs_optstr"`
+		// filesystem type: the filesystem type in the form "type[.subtype]".
+		FsType string `json:"fstype"`
+		// mount source: filesystem-specific information or "none".
+		Source string `json:"source"`
+		// super options: per-superblock options (see mount(2)).
+		FsOptstr string `json:"fs_optstr"`
+	}
+)
+
+// Copy populates v with the current record.
+func (m *Iter) Copy(v *Entry) {
+	if m.fs == nil {
+		panic("invalid entry")
+	}
+	v.ID = int(C.mnt_fs_get_id(m.fs))
+	v.Parent = int(C.mnt_fs_get_parent_id(m.fs))
+	v.Root = C.GoString(C.mnt_fs_get_root(m.fs))
+	v.Target = C.GoString(C.mnt_fs_get_target(m.fs))
+	v.VfsOptstr = C.GoString(C.mnt_fs_get_vfs_options(m.fs))
+	v.FsType = C.GoString(C.mnt_fs_get_fstype(m.fs))
+	v.Source = C.GoString(C.mnt_fs_get_source(m.fs))
+	v.FsOptstr = C.GoString(C.mnt_fs_get_fs_options(m.fs))
+}
+
+// Err returns the saved iterator error.
+func (m *Iter) Err() error { return m.err }
+
+// Open opens a mountinfo document. If name is an empty string, the mountinfo
+// document of the current process is opened instead.
+func Open(name string) (*Iter, error) {
+	var m Iter
+	if name == "" {
+		m.tb = C.mnt_new_table_from_file(C.HAKUREI_MOUNTINFO_PATH)
+	} else {
+		_name := C.CString(name)
+		m.tb = C.mnt_new_table_from_file(_name)
+		C.free(unsafe.Pointer(_name))
+	}
+	if m.tb == nil {
+		return nil, ErrParse
+	}
+	m.itr = C.mnt_new_iter(C.MNT_ITER_FORWARD)
+	if m.itr == nil {
+		C.mnt_unref_table(m.tb)
+		return nil, ErrIter
+	}
+	m.ok = true
+
+	runtime.SetFinalizer(&m, (*Iter).Close)
+	return &m, nil
+}
+
+// Close frees the iterator.
+func (m *Iter) Close() {
+	if m.closed {
+		return
+	}
+	if m.tb == nil {
+		panic("unref called before open")
+	}
+
+	C.mnt_unref_table(m.tb)
+	C.mnt_free_iter(m.itr)
+	m.closed = true
+	runtime.SetFinalizer(m, nil)
+}
+
+// Reset resets the iterator to the first record for reuse.
+func (m *Iter) Reset() {
+	if m.err != nil {
+		panic("attempting to reset a faulted iterator")
+	}
+	m.ok = true
+	C.mnt_reset_iter(m.itr, -1)
+}
+
+// Next advances the iterator to the next record. The record may be copied if
+// Next returns true.
+func (m *Iter) Next() bool {
+	if !m.ok || m.err != nil {
+		return false
+	}
+
+	r := C.mnt_table_next_fs(m.tb, m.itr, &m.fs)
+	if r < 0 {
+		m.err = ErrIterAdvance
+	}
+	m.ok = r == 0
+	return m.ok
+}
+
+// EqualWithIgnore compares e with want, ignoring fields with the specified
+// ignore value.
+func (e *Entry) EqualWithIgnore(want *Entry, ignore string) bool {
+	return (e.ID == want.ID || want.ID == -1) &&
+		(e.Parent == want.Parent || want.Parent == -1) &&
+		(e.Root == want.Root || want.Root == ignore) &&
+		(e.Target == want.Target || want.Target == ignore) &&
+		(e.VfsOptstr == want.VfsOptstr || want.VfsOptstr == ignore) &&
+		(e.FsType == want.FsType || want.FsType == ignore) &&
+		(e.Source == want.Source || want.Source == ignore) &&
+		(e.FsOptstr == want.FsOptstr || want.FsOptstr == ignore)
+}
+
+// String returns a text representation of e loosely following the kernel format.
+func (e *Entry) String() string {
+	return fmt.Sprintf("%d %d %s %s %s %s %s %s",
+		e.ID, e.Parent, e.Root, e.Target, e.VfsOptstr, e.FsType, e.Source, e.FsOptstr)
+}