github.com/bytedance/gopkg@v0.0.0-20240514070511-01b2cbcf35e1/lang/dirtmake/bytes.go (about)

     1  // Copyright 2024 ByteDance Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package dirtmake
    16  
    17  import (
    18  	"unsafe"
    19  )
    20  
    21  type slice struct {
    22  	data unsafe.Pointer
    23  	len  int
    24  	cap  int
    25  }
    26  
    27  //go:linkname mallocgc runtime.mallocgc
    28  func mallocgc(size uintptr, typ unsafe.Pointer, needzero bool) unsafe.Pointer
    29  
    30  // Bytes allocates a byte slice but does not clean up the memory it references.
    31  // Throw a fatal error instead of panic if cap is greater than runtime.maxAlloc.
    32  // NOTE: MUST set any byte element before it's read.
    33  func Bytes(len, cap int) (b []byte) {
    34  	if len < 0 || len > cap {
    35  		panic("dirtmake.Bytes: len out of range")
    36  	}
    37  	p := mallocgc(uintptr(cap), nil, false)
    38  	sh := (*slice)(unsafe.Pointer(&b))
    39  	sh.data = p
    40  	sh.len = len
    41  	sh.cap = cap
    42  	return
    43  }