478 lines
14 KiB
Go
478 lines
14 KiB
Go
// Copyright 2017 The Memory Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package memory implements a memory allocator.
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//
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// # Build status
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//
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// available at https://modern-c.appspot.com/-/builder/?importpath=modernc.org%2fmemory
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//
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// # Changelog
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//
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// 2017-10-03 Added alternative, unsafe.Pointer-based API.
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//
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// Package memory implements a memory allocator.
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//
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// # Changelog
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//
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// 2017-10-03 Added alternative, unsafe.Pointer-based API.
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//
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// # Benchmarks
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//
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// jnml@3900x:~/src/modernc.org/memory$ date ; go version ; go test -run @ -bench . -benchmem |& tee log
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// Mon Sep 25 16:02:02 CEST 2023
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// go version go1.21.1 linux/amd64
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// goos: linux
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// goarch: amd64
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// pkg: modernc.org/memory
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// cpu: AMD Ryzen 9 3900X 12-Core Processor
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// BenchmarkFree16-24 123506772 9.802 ns/op 0 B/op 0 allocs/op
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// BenchmarkFree32-24 73853230 15.08 ns/op 0 B/op 0 allocs/op
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// BenchmarkFree64-24 43070334 25.15 ns/op 0 B/op 0 allocs/op
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// BenchmarkCalloc16-24 59353304 18.92 ns/op 0 B/op 0 allocs/op
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// BenchmarkCalloc32-24 39415004 29.00 ns/op 0 B/op 0 allocs/op
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// BenchmarkCalloc64-24 35825725 32.02 ns/op 0 B/op 0 allocs/op
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// BenchmarkGoCalloc16-24 38274313 26.99 ns/op 16 B/op 1 allocs/op
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// BenchmarkGoCalloc32-24 44590477 33.06 ns/op 32 B/op 1 allocs/op
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// BenchmarkGoCalloc64-24 44233016 37.20 ns/op 64 B/op 1 allocs/op
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// BenchmarkMalloc16-24 145736911 7.720 ns/op 0 B/op 0 allocs/op
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// BenchmarkMalloc32-24 128898334 7.887 ns/op 0 B/op 0 allocs/op
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// BenchmarkMalloc64-24 149569483 7.994 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrFree16-24 117043012 9.205 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrFree32-24 77399617 14.20 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrFree64-24 48770785 25.04 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrCalloc16-24 79257636 15.44 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrCalloc32-24 49644562 23.62 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrCalloc64-24 39854710 28.22 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrMalloc16-24 252987727 4.525 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrMalloc32-24 241423840 4.433 ns/op 0 B/op 0 allocs/op
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// BenchmarkUintptrMalloc64-24 256450324 4.669 ns/op 0 B/op 0 allocs/op
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// PASS
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// ok modernc.org/memory 93.178s
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// jnml@3900x:~/src/modernc.org/memory$
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package memory // import "modernc.org/memory"
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import (
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"fmt"
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"math/bits"
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"os"
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"reflect"
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"unsafe"
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)
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const (
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headerSize = unsafe.Sizeof(page{})
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mallocAllign = 2 * unsafe.Sizeof(uintptr(0))
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maxSlotSize = 1 << maxSlotSizeLog
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maxSlotSizeLog = pageSizeLog - 2
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pageAvail = pageSize - headerSize
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pageMask = pageSize - 1
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pageSize = 1 << pageSizeLog
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)
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func init() {
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if unsafe.Sizeof(page{})%mallocAllign != 0 {
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panic("internal error")
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}
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}
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// if n%m != 0 { n += m-n%m }. m must be a power of 2.
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func roundup(n, m int) int { return (n + m - 1) &^ (m - 1) }
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type node struct {
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prev, next uintptr // *node
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}
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type page struct {
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brk int
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log uint
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size int
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used int
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}
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// Allocator allocates and frees memory. Its zero value is ready for use. The
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// exported counters are updated only when build tag memory.counters is
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// present.
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type Allocator struct {
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Allocs int // # of allocs.
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Bytes int // Asked from OS.
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cap [64]int
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lists [64]uintptr // *node
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Mmaps int // Asked from OS.
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pages [64]uintptr // *page
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regs map[uintptr]struct{} // map[*page]struct{}
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}
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func (a *Allocator) mmap(size int) (uintptr /* *page */, error) {
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p, size, err := mmap(size)
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if err != nil {
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return 0, err
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}
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if counters {
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a.Mmaps++
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a.Bytes += size
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}
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if a.regs == nil {
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a.regs = map[uintptr]struct{}{}
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}
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(*page)(unsafe.Pointer(p)).size = size
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a.regs[p] = struct{}{}
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return p, nil
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}
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func (a *Allocator) newPage(size int) (uintptr /* *page */, error) {
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size += int(headerSize)
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p, err := a.mmap(size)
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if err != nil {
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return 0, err
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}
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(*page)(unsafe.Pointer(p)).log = 0
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return p, nil
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}
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func (a *Allocator) newSharedPage(log uint) (uintptr /* *page */, error) {
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if a.cap[log] == 0 {
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a.cap[log] = int(pageAvail) / (1 << log)
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}
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size := int(headerSize) + a.cap[log]<<log
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p, err := a.mmap(size)
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if err != nil {
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return 0, err
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}
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a.pages[log] = p
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(*page)(unsafe.Pointer(p)).log = log
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return p, nil
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}
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func (a *Allocator) unmap(p uintptr /* *page */) error {
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delete(a.regs, p)
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if counters {
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a.Mmaps--
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}
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return unmap(p, (*page)(unsafe.Pointer(p)).size)
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}
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// UintptrCalloc is like Calloc except it returns an uintptr.
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func (a *Allocator) UintptrCalloc(size int) (r uintptr, err error) {
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if trace {
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defer func() {
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fmt.Fprintf(os.Stderr, "Calloc(%#x) %#x, %v\n", size, r, err)
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}()
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}
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if r, err = a.UintptrMalloc(size); r == 0 || err != nil {
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return 0, err
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}
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b := ((*rawmem)(unsafe.Pointer(r)))[:size:size]
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for i := range b {
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b[i] = 0
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}
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return r, nil
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}
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// UintptrFree is like Free except its argument is an uintptr, which must have
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// been acquired from UintptrCalloc or UintptrMalloc or UintptrRealloc.
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func (a *Allocator) UintptrFree(p uintptr) (err error) {
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if trace {
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defer func() {
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fmt.Fprintf(os.Stderr, "Free(%#x) %v\n", p, err)
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}()
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}
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if p == 0 {
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return nil
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}
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if counters {
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a.Allocs--
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}
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pg := p &^ uintptr(pageMask)
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log := (*page)(unsafe.Pointer(pg)).log
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if log == 0 {
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if counters {
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a.Bytes -= (*page)(unsafe.Pointer(pg)).size
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}
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return a.unmap(pg)
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}
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(*node)(unsafe.Pointer(p)).prev = 0
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(*node)(unsafe.Pointer(p)).next = a.lists[log]
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if next := (*node)(unsafe.Pointer(p)).next; next != 0 {
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(*node)(unsafe.Pointer(next)).prev = p
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}
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a.lists[log] = p
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(*page)(unsafe.Pointer(pg)).used--
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if (*page)(unsafe.Pointer(pg)).used != 0 {
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return nil
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}
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for i := 0; i < (*page)(unsafe.Pointer(pg)).brk; i++ {
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n := pg + headerSize + uintptr(i)<<log
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next := (*node)(unsafe.Pointer(n)).next
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prev := (*node)(unsafe.Pointer(n)).prev
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switch {
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case prev == 0:
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a.lists[log] = next
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if next != 0 {
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(*node)(unsafe.Pointer(next)).prev = 0
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}
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case next == 0:
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(*node)(unsafe.Pointer(prev)).next = 0
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default:
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(*node)(unsafe.Pointer(prev)).next = next
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(*node)(unsafe.Pointer(next)).prev = prev
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}
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}
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if a.pages[log] == pg {
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a.pages[log] = 0
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}
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if counters {
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a.Bytes -= (*page)(unsafe.Pointer(pg)).size
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}
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return a.unmap(pg)
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}
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// UintptrMalloc is like Malloc except it returns an uinptr.
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func (a *Allocator) UintptrMalloc(size int) (r uintptr, err error) {
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if trace {
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defer func() {
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fmt.Fprintf(os.Stderr, "Malloc(%#x) %#x, %v\n", size, r, err)
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}()
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}
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if size < 0 {
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panic("invalid malloc size")
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}
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if size == 0 {
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return 0, nil
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}
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if counters {
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a.Allocs++
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}
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log := uint(bits.Len(uint((size+int(mallocAllign)-1)&^int(mallocAllign-1) - 1)))
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if log > maxSlotSizeLog {
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p, err := a.newPage(size)
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if err != nil {
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return 0, err
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}
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return p + headerSize, nil
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}
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if a.lists[log] == 0 && a.pages[log] == 0 {
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if _, err := a.newSharedPage(log); err != nil {
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return 0, err
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}
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}
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if p := a.pages[log]; p != 0 {
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(*page)(unsafe.Pointer(p)).used++
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(*page)(unsafe.Pointer(p)).brk++
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if (*page)(unsafe.Pointer(p)).brk == a.cap[log] {
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a.pages[log] = 0
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}
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return p + headerSize + uintptr((*page)(unsafe.Pointer(p)).brk-1)<<log, nil
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}
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n := a.lists[log]
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p := n &^ uintptr(pageMask)
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a.lists[log] = (*node)(unsafe.Pointer(n)).next
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if next := (*node)(unsafe.Pointer(n)).next; next != 0 {
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(*node)(unsafe.Pointer(next)).prev = 0
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}
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(*page)(unsafe.Pointer(p)).used++
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return n, nil
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}
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// UintptrRealloc is like Realloc except its first argument is an uintptr,
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// which must have been returned from UintptrCalloc, UintptrMalloc or
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// UintptrRealloc.
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func (a *Allocator) UintptrRealloc(p uintptr, size int) (r uintptr, err error) {
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if trace {
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defer func() {
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fmt.Fprintf(os.Stderr, "UnsafeRealloc(%#x, %#x) %#x, %v\n", p, size, r, err)
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}()
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}
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switch {
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case p == 0:
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return a.UintptrMalloc(size)
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case size == 0 && p != 0:
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return 0, a.UintptrFree(p)
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}
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us := UintptrUsableSize(p)
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if us >= size {
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return p, nil
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}
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if r, err = a.UintptrMalloc(size); err != nil {
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return 0, err
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}
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if us < size {
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size = us
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}
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copy((*rawmem)(unsafe.Pointer(r))[:size:size], (*rawmem)(unsafe.Pointer(p))[:size:size])
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return r, a.UintptrFree(p)
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}
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// UintptrUsableSize is like UsableSize except its argument is an uintptr,
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// which must have been returned from UintptrCalloc, UintptrMalloc or
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// UintptrRealloc.
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func UintptrUsableSize(p uintptr) (r int) {
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if trace {
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defer func() {
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fmt.Fprintf(os.Stderr, "UsableSize(%#x) %#x\n", p, r)
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}()
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}
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if p == 0 {
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return 0
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}
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return usableSize(p)
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}
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func usableSize(p uintptr) (r int) {
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pg := p &^ uintptr(pageMask)
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if log := (*page)(unsafe.Pointer(pg)).log; log != 0 {
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return 1 << log
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}
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return (*page)(unsafe.Pointer(pg)).size - int(headerSize)
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}
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// Calloc is like Malloc except the allocated memory is zeroed.
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func (a *Allocator) Calloc(size int) (r []byte, err error) {
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p, err := a.UintptrCalloc(size)
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if err != nil {
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return nil, err
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}
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var b []byte
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&b))
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sh.Cap = usableSize(p)
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sh.Data = p
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sh.Len = size
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return b, nil
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}
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// Close releases all OS resources used by a and sets it to its zero value.
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//
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// It's not necessary to Close the Allocator when exiting a process.
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func (a *Allocator) Close() (err error) {
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for p := range a.regs {
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if e := a.unmap(p); e != nil && err == nil {
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err = e
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}
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}
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*a = Allocator{}
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return err
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}
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// Free deallocates memory (as in C.free). The argument of Free must have been
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// acquired from Calloc or Malloc or Realloc.
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func (a *Allocator) Free(b []byte) (err error) {
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if b = b[:cap(b)]; len(b) == 0 {
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return nil
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}
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return a.UintptrFree(uintptr(unsafe.Pointer(&b[0])))
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}
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// Malloc allocates size bytes and returns a byte slice of the allocated
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// memory. The memory is not initialized. Malloc panics for size < 0 and
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// returns (nil, nil) for zero size.
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//
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// It's ok to reslice the returned slice but the result of appending to it
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// cannot be passed to Free or Realloc as it may refer to a different backing
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// array afterwards.
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func (a *Allocator) Malloc(size int) (r []byte, err error) {
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p, err := a.UintptrMalloc(size)
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if p == 0 || err != nil {
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return nil, err
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}
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&r))
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sh.Cap = usableSize(p)
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sh.Data = p
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sh.Len = size
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return r, nil
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}
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// Realloc changes the size of the backing array of b to size bytes or returns
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// an error, if any. The contents will be unchanged in the range from the
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// start of the region up to the minimum of the old and new sizes. If the
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// new size is larger than the old size, the added memory will not be
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// initialized. If b's backing array is of zero size, then the call is
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// equivalent to Malloc(size), for all values of size; if size is equal to
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// zero, and b's backing array is not of zero size, then the call is equivalent
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// to Free(b). Unless b's backing array is of zero size, it must have been
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// returned by an earlier call to Malloc, Calloc or Realloc. If the area
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// pointed to was moved, a Free(b) is done.
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func (a *Allocator) Realloc(b []byte, size int) (r []byte, err error) {
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var p uintptr
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if b = b[:cap(b)]; len(b) != 0 {
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p = uintptr(unsafe.Pointer(&b[0]))
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}
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if p, err = a.UintptrRealloc(p, size); p == 0 || err != nil {
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return nil, err
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}
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sh := (*reflect.SliceHeader)(unsafe.Pointer(&r))
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sh.Cap = usableSize(p)
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sh.Data = p
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sh.Len = size
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return r, nil
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}
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// UsableSize reports the size of the memory block allocated at p, which must
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// point to the first byte of a slice returned from Calloc, Malloc or Realloc.
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// The allocated memory block size can be larger than the size originally
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// requested from Calloc, Malloc or Realloc.
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func UsableSize(p *byte) (r int) { return UintptrUsableSize(uintptr(unsafe.Pointer(p))) }
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// UnsafeCalloc is like Calloc except it returns an unsafe.Pointer.
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func (a *Allocator) UnsafeCalloc(size int) (r unsafe.Pointer, err error) {
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p, err := a.UintptrCalloc(size)
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if err != nil {
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return nil, err
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}
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return unsafe.Pointer(p), nil
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}
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// UnsafeFree is like Free except its argument is an unsafe.Pointer, which must
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// have been acquired from UnsafeCalloc or UnsafeMalloc or UnsafeRealloc.
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func (a *Allocator) UnsafeFree(p unsafe.Pointer) (err error) { return a.UintptrFree(uintptr(p)) }
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// UnsafeMalloc is like Malloc except it returns an unsafe.Pointer.
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func (a *Allocator) UnsafeMalloc(size int) (r unsafe.Pointer, err error) {
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p, err := a.UintptrMalloc(size)
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if err != nil {
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return nil, err
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}
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return unsafe.Pointer(p), nil
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}
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// UnsafeRealloc is like Realloc except its first argument is an
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// unsafe.Pointer, which must have been returned from UnsafeCalloc,
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// UnsafeMalloc or UnsafeRealloc.
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func (a *Allocator) UnsafeRealloc(p unsafe.Pointer, size int) (r unsafe.Pointer, err error) {
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q, err := a.UintptrRealloc(uintptr(p), size)
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if err != nil {
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return nil, err
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}
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return unsafe.Pointer(q), nil
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}
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// UnsafeUsableSize is like UsableSize except its argument is an
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// unsafe.Pointer, which must have been returned from UnsafeCalloc,
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// UnsafeMalloc or UnsafeRealloc.
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func UnsafeUsableSize(p unsafe.Pointer) (r int) { return UintptrUsableSize(uintptr(p)) }
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