func main() {
 m := make(map[int]string)
 for i := 0; i < 9; i++ {
  m[i] = "xiaoming"
 }
 
}

0x0092 00146 (F:\github\awesomeProject\main.go:10)      CALL    runtime.mapassign_fast64(SB)

func mapassign_fast64(t *maptype, h *hmap, key uint64) unsafe.Pointer {
 // ......

again:
 bucket := hash & bucketMask(h.B)
 if h.growing() {
  growWork_fast64(t, h, bucket)
 }
 b := (*bmap)(add(h.buckets, bucket*uintptr(t.bucketsize)))

 var insertb *bmap
 var inserti uintptr
 var insertk unsafe.Pointer

 // ......

 //如果map未進(jìn)行擴(kuò)容，且當(dāng)前map負(fù)載超過(guò)最大值(默認(rèn)6.5)或者溢出桶數(shù)量超過(guò)了bucket數(shù)量則進(jìn)行擴(kuò)容
 if !h.growing() && (overLoadFactor(h.count+1, h.B) || tooManyOverflowBuckets(h.noverflow, h.B)) {
  hashGrow(t, h)
  goto again // Growing the table invalidates everything, so try again
 }

 // ......
}

func hashGrow(t *maptype, h *hmap) {
 //默認(rèn)B的值是+1
 bigger := uint8(1)
 
 //oldbuckets 記錄現(xiàn)在的bucket
 oldbuckets := h.buckets
 //創(chuàng)建一個(gè)新的bucket和溢出桶
 newbuckets, nextOverflow := makeBucketArray(t, h.B+bigger, nil)

 //更新b、oldbuckets 指針指向原有bucket、buckets 指向新創(chuàng)建的bucket
 h.B += bigger
 h.flags = flags
 h.oldbuckets = oldbuckets
 h.buckets = newbuckets
 h.nevacuate = 0
 h.noverflow = 0
 
 //如果原有的bucket還有空閑溢出桶，則記錄到h.extra.oldoverflow指針上
 if h.extra != nil && h.extra.overflow != nil {
  // Promote current overflow buckets to the old generation.
  if h.extra.oldoverflow != nil {
   throw("oldoverflow is not nil")
  }
  h.extra.oldoverflow = h.extra.overflow
  h.extra.overflow = nil
 }
 //如果剛剛有新創(chuàng)建的溢出桶，則用h.extra.nextOverflow指針進(jìn)行管理
 if nextOverflow != nil {
  if h.extra == nil {
   h.extra = new(mapextra)
  }
  h.extra.nextOverflow = nextOverflow
 }

 
}

func growWork_fast64(t *maptype, h *hmap, bucket uintptr) {
 //將對(duì)應(yīng)哈希的oldbucket的元素驅(qū)逐到新bucket上
 evacuate_fast64(t, h, bucket&h.oldbucketmask())

 //......
}



func evacuate_fast64(t *maptype, h *hmap, oldbucket uintptr) {
 //獲取舊的bucket的指針
 b := (*bmap)(add(h.oldbuckets, oldbucket*uintptr(t.bucketsize)))
 //......

 //通過(guò)[2]evacDst數(shù)組的0索引記錄oldbucket的bucket、keys、values指針，1記錄new buckets的bucket、keys、values指針
 if !evacuated(b) {
  
  var xy [2]evacDst
  x := &xy[0]
  //記錄oldbucket的bucket、keys、values指針
  x.b = (*bmap)(add(h.buckets, oldbucket*uintptr(t.bucketsize)))
  x.k = add(unsafe.Pointer(x.b), dataOffset)
  x.e = add(x.k, bucketCnt*8)

  //new buckets的bucket、keys、values指針
  if !h.sameSizeGrow() {
   // Only calculate y pointers if we're growing bigger.
   // Otherwise GC can see bad pointers.
   y := &xy[1]
   y.b = (*bmap)(add(h.buckets, (oldbucket+newbit)*uintptr(t.bucketsize)))
   y.k = add(unsafe.Pointer(y.b), dataOffset)
   y.e = add(y.k, bucketCnt*8)
  }
  //循環(huán)遍歷非空的tophash進(jìn)行驅(qū)逐操作
  for ; b != nil; b = b.overflow(t) {
   //獲取在old bucket上的地址
   k := add(unsafe.Pointer(b), dataOffset)
   e := add(k, bucketCnt*8)
   
   for i := 0; i < bucketCnt; i, k, e = i+1, add(k, 8), add(e, uintptr(t.elemsize)) {
    //計(jì)算在舊的bucket的tophash以定位鍵值對(duì)
    top := b.tophash[i]
    if isEmpty(top) {
     b.tophash[i] = evacuatedEmpty
     continue
    }
    if top < minTopHash {
     throw("bad map state")
    }
    //計(jì)算在新的bucket上的hash值
    var useY uint8
    if !h.sameSizeGrow() {
     // Compute hash to make our evacuation decision (whether we need
     // to send this key/elem to bucket x or bucket y).
     hash := t.hasher(k, uintptr(h.hash0))
     if hash&newbit != 0 {
      useY = 1
     }
    }

    b.tophash[i] = evacuatedX + useY // evacuatedX + 1 == evacuatedY, enforced in makemap
    //獲取新的bucket的指針地址
    dst := &xy[useY]                 // evacuation destination

   //到新bucke的tophash數(shù)組上的位置記錄這個(gè)tophash
    dst.b.tophash[dst.i&(bucketCnt-1)] = top // mask dst.i as an optimization, to avoid a bounds check

    //將舊的bucket的key復(fù)制到新bucket上
    if t.key.ptrdata != 0 && writeBarrier.enabled {
     if goarch.PtrSize == 8 {
      // 通過(guò)指針操作，將舊的key復(fù)制到新的bucket的key上
      *(*unsafe.Pointer)(dst.k) = *(*unsafe.Pointer)(k)
     } else {
      // There are three ways to squeeze at least one 32 bit pointer into 64 bits.
      // Give up and call typedmemmove.
      typedmemmove(t.key, dst.k, k)
     }
    } else {
     *(*uint64)(dst.k) = *(*uint64)(k)
    }
    //復(fù)制value到新bucket的位置上
    typedmemmove(t.elem, dst.e, e)
    //....
   }
  }
  // 完成后刪除舊的bucket的鍵值對(duì)，輔助GC
  if h.flags&oldIterator == 0 && t.bucket.ptrdata != 0 {
   b := add(h.oldbuckets, oldbucket*uintptr(t.bucketsize))
   // Preserve b.tophash because the evacuation
   // state is maintained there.
   ptr := add(b, dataOffset)
   n := uintptr(t.bucketsize) - dataOffset
   memclrHasPointers(ptr, n)
  }
 }

 if oldbucket == h.nevacuate {
  advanceEvacuationMark(h, t, newbit)
 }
}

func mapassign_fast64(t *maptype, h *hmap, key uint64) unsafe.Pointer {

//......

//定位到key的指針
bucketloop:
 for {
  for i := uintptr(0); i < bucketCnt; i++ {
   //若定位到的bucket為nil,則說(shuō)明這個(gè)位置沒(méi)有被使用過(guò)，則進(jìn)入該分支定位指針
   if isEmpty(b.tophash[i]) {
    if insertb == nil {
     insertb = b
     inserti = i
    }
    //如果找到當(dāng)前tophash為0值，說(shuō)明這個(gè)位置沒(méi)有被用過(guò)，直接退出循環(huán)，到外部直接賦值
    if b.tophash[i] == emptyRest {
     break bucketloop
    }
    continue
   }
   //獲取k判斷和當(dāng)前key值是否一致，若不一致的continue，反之記錄直接到done代碼段，直接設(shè)置value的值
   k := *((*uint64)(add(unsafe.Pointer(b), dataOffset+i*8)))
   if k != key {
    continue
   }
   insertb = b
   inserti = i
   goto done
  }
  //.....
 }

 
 //定位到key位置設(shè)置key
 insertk = add(unsafe.Pointer(insertb), dataOffset+inserti*8)
 // store new key at insert position
 *(*uint64)(insertk) = key
 
 //元素?cái)?shù)量+1
 h.count++

done:
 //設(shè)置value
 elem := add(unsafe.Pointer(insertb), dataOffset+bucketCnt*8+inserti*uintptr(t.elemsize))
 if h.flags&hashWriting == 0 {
  fatal("concurrent map writes")
 }
 h.flags &^= hashWriting
 return elem

}

func mapaccess1(t *maptype, h *hmap, key unsafe.Pointer) unsafe.Pointer {
 //......
 //定位hash值
 hash := t.hasher(key, uintptr(h.hash0))
 //先定位到bucket指針
 m := bucketMask(h.B)
 b := (*bmap)(add(h.buckets, (hash&m)*uintptr(t.bucketsize)))
 
 //在基于hash到oldbucket定位舊的bucket指針，若未發(fā)生驅(qū)逐則上b指針指向oldbucket
 if c := h.oldbuckets; c != nil {
  if !h.sameSizeGrow() {
   // There used to be half as many buckets; mask down one more power of two.
   m >>= 1
  }
  oldb := (*bmap)(add(c, (hash&m)*uintptr(t.bucketsize)))
  //若未發(fā)生驅(qū)逐則上b指針指向oldbucket
  if !evacuated(oldb) {
   b = oldb
  }
 }
 top := tophash(hash)
bucketloop:
 //循環(huán)定位鍵值對(duì)
 for ; b != nil; b = b.overflow(t) {
  for i := uintptr(0); i < bucketCnt; i++ {
   //......
   
   //如果找到的key和我們要查詢的key相等則直接返回
   if t.key.equal(key, k) {
    e := add(unsafe.Pointer(b), dataOffset+bucketCnt*uintptr(t.keysize)+i*uintptr(t.elemsize))
    if t.indirectelem() {
     e = *((*unsafe.Pointer)(e))
    }
    return e
   }
  }
 }
 return unsafe.Pointer(&zeroVal[0])
}