mirror of
https://github.com/Mrs4s/go-cqhttp.git
synced 2025-05-05 03:23:49 +08:00
129 lines
3.1 KiB
Go
129 lines
3.1 KiB
Go
package btree
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import (
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"math/rand"
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"unsafe"
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)
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type chunk struct {
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offset int64
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len int
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}
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const freeQueueLen = 64
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// todo(wdvxdr): move this to btree?
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var (
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fqueue [freeQueueLen]chunk
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fqueueLen = 0
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)
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func freeQueued(bt *Btree) {
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for i := 0; i < fqueueLen; i++ {
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chunk := &fqueue[i]
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bt.freeChunk(chunk.offset, chunk.len)
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}
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fqueueLen = 0
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}
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func (bt *Btree) allocChunk(size int) int64 {
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assert(size > 0)
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size = power2(size)
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var offset int64
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if bt.inAllocator {
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const i32s = unsafe.Sizeof(int32(0))
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/* create fake size SHA-1 */
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var sha1 [sha1Size]byte
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p := unsafe.Pointer(&sha1[0])
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*(*int32)(p) = -1 // *(uint32_t *) sha1 = -1;
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*(*uint32)(unsafe.Add(p, i32s)) = uint32(size) // ((__be32 *) sha1)[1] = to_be32(size);
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/* find free chunk with the larger or the same size/SHA-1 */
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bt.inAllocator = true
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bt.deleteLarger = true
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offset = bt.delete(bt.freeTop, &sha1[0])
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bt.deleteLarger = false
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if offset != 0 {
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assert(*(*int32)(p) == -1) // assert(*(uint32_t *) sha1 == (uint32_t) -1)
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flen := int(*(*uint32)(unsafe.Add(p, i32s))) // size_t free_len = from_be32(((__be32 *) sha1)[1])
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assert(power2(flen) == flen)
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assert(flen >= size)
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/* delete buddy information */
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resetsha1(&sha1[0])
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*(*int64)(p) = offset
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buddyLen := bt.delete(bt.freeTop, &sha1[0])
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assert(buddyLen == int64(size))
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bt.freeTop = collapse(bt, bt.freeTop)
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bt.inAllocator = false
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/* free extra space at the end of the chunk */
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for flen > size {
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flen >>= 1
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bt.freeChunk(offset+int64(flen), flen)
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}
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} else {
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bt.inAllocator = false
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}
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}
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if offset == 0 {
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/* not found, allocate from the end of the file */
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offset = bt.alloc
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/* TODO: this wastes memory.. */
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if offset&int64(size-1) != 0 {
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offset += int64(size) - (offset & (int64(size) - 1))
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}
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bt.alloc = offset + int64(size)
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}
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bt.flushSuper()
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// make sure the allocation tree is up-to-date before using the chunk
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_ = bt.fd.Sync()
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return offset
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}
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/* Mark a chunk as unused in the database file */
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func (bt *Btree) freeChunk(offset int64, size int) {
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assert(size > 0)
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assert(offset != 0)
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size = power2(size)
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assert(offset&int64(size-1) == 0)
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if bt.inAllocator {
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chunk := &fqueue[fqueueLen]
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fqueueLen++
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chunk.offset = offset
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chunk.len = size
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return
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}
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/* create fake offset SHA-1 for buddy allocation */
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var sha1 [sha1Size]byte
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p := unsafe.Pointer(&sha1[0])
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bt.inAllocator = true
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const i32s = unsafe.Sizeof(int32(0))
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/* add buddy information */
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resetsha1(&sha1[0])
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*(*int32)(p) = -1 // *(uint32_t *) sha1 = -1;
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*(*uint32)(unsafe.Add(p, i32s)) = uint32(size) // ((__be32 *) sha1)[1] = to_be32(size);
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*(*uint32)(unsafe.Add(p, i32s*2)) = rand.Uint32() /* to make SHA-1 unique */
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*(*uint32)(unsafe.Add(p, i32s*3)) = rand.Uint32()
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// insert_toplevel(btree, &btree->free_top, sha1, NULL, offset);
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_ = bt.insertTopLevel(&bt.freeTop, &sha1[0], nil, int(offset))
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bt.inAllocator = false
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bt.flushSuper()
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// make sure the allocation tree is up-to-date before removing
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// references to the chunk
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_ = bt.fd.Sync()
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}
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