func newFile(f *os.File, maxSize int64, pgBits uint) (*file, error) {
if maxSize < 0 {
panic("internal error")
}
pgSize := 1 << pgBits
switch {
case sysPage > pgSize:
pgBits = uint(mathutil.Log2Uint64(uint64(sysPage)))
default:
pgBits = uint(mathutil.Log2Uint64(uint64(pgSize / sysPage * sysPage)))
}
pgSize = 1 << pgBits
fi := &file{
f: f,
m: fileMap{},
maxPages: int(mathutil.MinInt64(
1024,
mathutil.MaxInt64(maxSize/int64(pgSize), 1)),
),
pgBits: pgBits,
pgMask: pgSize - 1,
pgSize: pgSize,
}
info, err := f.Stat()
if err != nil {
return nil, err
}
if err = fi.Truncate(info.Size()); err != nil {
return nil, err
}
return fi, nil
}
// Put puts a *[]T into a pool for possible later reuse by CGet or Get. Put
// panics is its argument is not of type *[]T.
//
// Put is safe for concurrent use by multiple goroutines.
func (p *Pool) Put(b interface{}) {
size := p.cap(b)
if size == 0 {
return
}
p.m[mathutil.Log2Uint64(uint64(size))].Put(b)
}
// Get returns a *[]T of len size. The pointed to slice is not zeroed. Get
// panics for size < 0.
//
// Get is safe for concurrent use by multiple goroutines.
func (p *Pool) Get(size int) interface{} {
var index int
switch {
case size < 0:
panic("Pool.Get: negative size")
case size == 0:
return p.null
case size > 1:
index = mathutil.Log2Uint64(uint64(size-1)) + 1
}
s := p.m[index].Get()
p.setSize(s, size)
return s
}