github.com/grailbio/base@v0.0.11/file/fsnode/parent.go (about)

     1  package fsnode
     2  
     3  import (
     4  	"context"
     5  	"os"
     6  
     7  	"github.com/grailbio/base/log"
     8  )
     9  
    10  // NewParent returns a Parent whose children are defined by gen. gen.GenerateChildren is called on
    11  // every Parent query (including Child, which returns one result). Implementers should cache
    12  // internally if necessary.
    13  func NewParent(info FileInfo, gen ChildrenGenerator) Parent {
    14  	if !info.IsDir() {
    15  		log.Panicf("FileInfo has file mode, require directory: %#v", info)
    16  	}
    17  	return parentImpl{FileInfo: info, gen: gen}
    18  }
    19  
    20  type (
    21  	// ChildrenGenerator generates child nodes.
    22  	ChildrenGenerator interface {
    23  		GenerateChildren(context.Context) ([]T, error)
    24  	}
    25  	childrenGenFunc  func(context.Context) ([]T, error)
    26  	childrenGenConst []T
    27  )
    28  
    29  // FuncChildren constructs a ChildrenGenerator that simply invokes fn, for convenience.
    30  func FuncChildren(fn func(context.Context) ([]T, error)) ChildrenGenerator {
    31  	return childrenGenFunc(fn)
    32  }
    33  
    34  func (fn childrenGenFunc) GenerateChildren(ctx context.Context) ([]T, error) { return fn(ctx) }
    35  
    36  // ConstChildren constructs a ChildrenGenerator that always returns the given children.
    37  func ConstChildren(children ...T) ChildrenGenerator {
    38  	children = append([]T{}, children...)
    39  	return childrenGenConst(children)
    40  }
    41  
    42  func (c childrenGenConst) GenerateChildren(ctx context.Context) ([]T, error) { return c, nil }
    43  
    44  type parentImpl struct {
    45  	ParentReadOnly
    46  	FileInfo
    47  	gen ChildrenGenerator
    48  }
    49  
    50  func (n parentImpl) Child(ctx context.Context, name string) (T, error) {
    51  	children, err := n.gen.GenerateChildren(ctx)
    52  	if err != nil {
    53  		return nil, err
    54  	}
    55  	for _, child := range children {
    56  		if child.Info().Name() == name {
    57  			return child, nil
    58  		}
    59  	}
    60  	return nil, os.ErrNotExist
    61  }
    62  
    63  func (n parentImpl) Children() Iterator {
    64  	return NewLazyIterator(n.gen.GenerateChildren)
    65  }
    66  
    67  func (n parentImpl) FSNodeT() {}