go.chromium.org/luci@v0.0.0-20240309015107-7cdc2e660f33/client/cmd/cas/casimpl/scattergather.go (about)

     1  // Copyright 2017 The LUCI 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 casimpl
    16  
    17  import (
    18  	"fmt"
    19  	"path/filepath"
    20  	"strings"
    21  
    22  	"go.chromium.org/luci/common/errors"
    23  )
    24  
    25  // scatterGather represents a mapping of working directories to relative paths.
    26  //
    27  // The purpose is to represent some notion of "local" vs. "archived" paths.
    28  // All relative paths are relative to both their corresponding working
    29  // directories as well as the root of an archive.
    30  //
    31  // filepath.Join(working dir, relative path) == location of file or directory
    32  // on the system.
    33  //
    34  // relative path == location of file or directory in an archive.
    35  //
    36  // Notably, in such a design, we may not have more than one copy of a relative
    37  // path in the archive, because there is a conflict. In order to efficiently
    38  // check this case at the expense of extra memory, scatterGather actually
    39  // stores a mapping of relative paths to working directories.
    40  type scatterGather map[string]string
    41  
    42  // Add adds a (working directory, relative path) pair to the ScatterGather.
    43  //
    44  // Add returns an error if the relative path was already added.
    45  func (sc *scatterGather) Add(wd, rel string) error {
    46  	cleaned := filepath.Clean(rel)
    47  	if _, ok := (*sc)[cleaned]; ok {
    48  		return errors.Reason("name conflict %q", rel).Err()
    49  	}
    50  	(*sc)[cleaned] = wd
    51  	return nil
    52  }
    53  
    54  // Set implements the flags.Var interface.
    55  func (sc *scatterGather) Set(value string) error {
    56  	colon := strings.LastIndexByte(value, ':')
    57  	if colon == -1 {
    58  		return errors.Reason("malformed input %q", value).Err()
    59  	}
    60  	if *sc == nil {
    61  		*sc = scatterGather{}
    62  	}
    63  	return sc.Add(value[:colon], value[colon+1:])
    64  }
    65  
    66  // String implements the Stringer interface.
    67  func (sc *scatterGather) String() string {
    68  	mapping := make(map[string][]string, len(*sc))
    69  	for item, wd := range *sc {
    70  		mapping[wd] = append(mapping[wd], item)
    71  	}
    72  	return fmt.Sprintf("%v", mapping)
    73  }