Line data    Source code

       1             : // Copyright 2024 The LevelDB-Go and Pebble Authors. All rights reserved. Use
       2             : // of this source code is governed by a BSD-style license that can be found in
       3             : // the LICENSE file.
       4             : 
       5             : package colblk
       6             : 
       7             : import (
       8             :         "unsafe"
       9             : 
      10             :         "golang.org/x/exp/constraints"
      11             : )
      12             : 
      13             : // align returns the next value greater than or equal to offset that's divisible
      14             : // by val.
      15           1 : func align[T constraints.Integer](offset, val T) T {
      16           1 :         return (offset + val - 1) & ^(val - 1)
      17           1 : }
      18             : 
      19             : // alignWithZeroes aligns the provided offset to val, and writing zeroes to any
      20             : // bytes in buf between the old offset and new aligned offset. This provides
      21             : // determinism when reusing memory that has not been zeroed.
      22           1 : func alignWithZeroes[T constraints.Integer](buf []byte, offset, val T) T {
      23           1 :         aligned := align[T](offset, val)
      24           1 :         for i := offset; i < aligned; i++ {
      25           1 :                 buf[i] = 0
      26           1 :         }
      27           1 :         return aligned
      28             : }
      29             : 
      30             : const (
      31             :         align16 = 2
      32             :         align32 = 4
      33             :         align64 = 8
      34             : )
      35             : 
      36             : // When multiplying or dividing by align{16,32,64} using signed integers, it's
      37             : // faster to shift to the left to multiply or shift to the right to divide. (The
      38             : // compiler optimization is limited to unsigned integers.) The below constants
      39             : // define the shift amounts corresponding to the above align constants.  (eg,
      40             : // alignNShift = log(alignN)).
      41             : //
      42             : // TODO(jackson): Consider updating usages to use uints? They can be less
      43             : // ergonomic.
      44             : const (
      45             :         align16Shift = 1
      46             :         align32Shift = 2
      47             :         align64Shift = 3
      48             : )
      49             : 
      50             : // TODO(jackson): A subsequent Go release will remove the ability to call these
      51             : // runtime functions. We should consider asm implementations that we maintain
      52             : // within the crlib repo.
      53             : //
      54             : // See https://github.com/golang/go/issues/67401
      55             : 
      56             : //go:linkname memmove runtime.memmove
      57             : func memmove(to, from unsafe.Pointer, n uintptr)
      58             : 
      59             : //go:linkname mallocgc runtime.mallocgc
      60             : func mallocgc(size uintptr, typ unsafe.Pointer, needzero bool) unsafe.Pointer