func (mFile *mmapFileImpl) Seek(pos int, from fs.FileOffset) {
switch from {
case fs.Beginning:
mFile.pos = pos
case fs.Current:
mFile.pos = pos + pos
case fs.End:
mFile.pos = mFile.mapSize - pos
}
mFile.pos = math.MaxInt(0, math.MinInt(mFile.pos, mFile.mapSize-1))
}
// used for building graphs from scratch
func (g *graph) addVertex(id int) int {
v := &vertex{
id: id,
excess: 0,
height: 0,
g: g,
mappings: make(map[int]wrapper),
}
g.mapping[v.id] = wrapper{value: v, idx: g.NumVertices()}
g.vertices = append(g.vertices, v)
g.id = math.MaxInt(g.id, id+1)
return id
}
// NewFile creates a new memory mapped file
func NewFile(fName string) (File, error) {
var err error
result := new(mmapFileImpl)
result.name = fName
// Create/Open file
result.file, err = os.OpenFile(fName, os.O_CREATE|os.O_RDWR, 0644)
if err != nil {
return nil, errors.New("Could not open file for reading")
}
// Check to see if new
info, _ := os.Stat(fName)
result.mapSize = math.MaxInt(_InitialSize, int(info.Size()))
if info.Size() == 0 {
result.newFile = true
result.file.Truncate(int64(result.mapSize))
} else {
result.newFile = false
}
// Map file to memory
result.memmap, err = mmap.Map(result.file, mmap.RDWR, 0)
// Validate
if err != nil {
return nil, err
}
result.lock = &sync.Mutex{}
if !result.newFile {
head := result.readHeader()
assert.Assert(bytes.Equal(head.sanity, _Sanity), "Sanity check failed '"+string(head.sanity)+"'")
assert.Assert(head.ver == _Version, "Versions do not match: ", head.ver, " vs. ", _Version)
assert.Assert(int(head.mSize) == result.mapSize, fName+": Sizes do not match: ", head.mSize, result.mapSize)
} else {
result.writeHeader()
}
return result, nil
}