github.com/MerlinKodo/gvisor@v0.0.0-20231110090155-957f62ecf90e/pkg/sentry/kernel/auth/id_map_functions.go (about)

     1  // Copyright 2018 The gVisor Authors.
     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 auth
    16  
    17  // idMapFunctions "implements" generic interface segment.Functions for
    18  // idMapSet. An idMapSet maps non-overlapping ranges of contiguous IDs in one
    19  // user namespace to non-overlapping ranges of contiguous IDs in another user
    20  // namespace. Each such ID mapping is implemented as a range-to-value mapping
    21  // in the set such that [range.Start(), range.End()) => [value, value +
    22  // range.Length()).
    23  type idMapFunctions struct{}
    24  
    25  func (idMapFunctions) MinKey() uint32 {
    26  	return 0
    27  }
    28  
    29  func (idMapFunctions) MaxKey() uint32 {
    30  	return NoID
    31  }
    32  
    33  func (idMapFunctions) ClearValue(*uint32) {}
    34  
    35  func (idMapFunctions) Merge(r1 idMapRange, val1 uint32, r2 idMapRange, val2 uint32) (uint32, bool) {
    36  	// Mapped ranges have to be contiguous.
    37  	if val1+r1.Length() != val2 {
    38  		return 0, false
    39  	}
    40  	return val1, true
    41  }
    42  
    43  func (idMapFunctions) Split(r idMapRange, val uint32, split uint32) (uint32, uint32) {
    44  	return val, val + (split - r.Start)
    45  }