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Tiwei Bie
d9eea0a42b
This patch adds the block based dirent lookup support to pkg/erofs, which will do the dirent lookup by doing binary search on disk data directly. This is helpful for searching files in large directories and also reduces the memory overhead. Signed-off-by: Tiwei Bie <[email protected]>
38 lines
1.4 KiB
Go
38 lines
1.4 KiB
Go
// Copyright 2023 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package erofs
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import "unsafe"
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// pointerAt returns a pointer to offset off within the memory backed by image.
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//
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// Precondition: Callers are responsible for the range check.
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func (i *Image) pointerAt(off uint64) unsafe.Pointer {
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// Although callers will always do the range check, there is no need to
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// bother with the slice's builtin range check below. Because this function
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// will be inlined into callers, and there are no redundant checks and
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// unnecessary out-of-range panic calls in the code generated by the compiler.
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return unsafe.Pointer(&i.bytes[off])
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}
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// direntAfter returns a pointer to the next adjacent dirent after dirent d.
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//
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// Preconditions:
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// - d is a pointer to the memory backed by image.
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// - d is not the last dirent in its block.
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func direntAfter(d *Dirent) *Dirent {
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return (*Dirent)(unsafe.Pointer(uintptr(unsafe.Pointer(d)) + DirentSize))
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}
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