github.com/hasnat/dolt/go@v0.0.0-20210628190320-9eb5d843fbb7/store/blobstore/inmem.go (about)

     1  // Copyright 2019 Dolthub, Inc.
     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 blobstore
    16  
    17  import (
    18  	"bytes"
    19  	"context"
    20  	"io"
    21  	"io/ioutil"
    22  	"sync"
    23  
    24  	"github.com/google/uuid"
    25  )
    26  
    27  type byteSliceReadCloser struct {
    28  	io.Reader
    29  	io.Closer
    30  }
    31  
    32  func newByteSliceReadCloser(data []byte) *byteSliceReadCloser {
    33  	reader := bytes.NewReader(data)
    34  	return &byteSliceReadCloser{reader, ioutil.NopCloser(reader)}
    35  }
    36  
    37  // InMemoryBlobstore provides an in memory implementation of the Blobstore interface
    38  type InMemoryBlobstore struct {
    39  	mutex    sync.Mutex
    40  	blobs    map[string][]byte
    41  	versions map[string]string
    42  }
    43  
    44  // NewInMemoryBlobstore creates an instance of an InMemoryBlobstore
    45  func NewInMemoryBlobstore() *InMemoryBlobstore {
    46  	return &InMemoryBlobstore{blobs: make(map[string][]byte), versions: make(map[string]string)}
    47  }
    48  
    49  // Get retrieves an io.reader for the portion of a blob specified by br along with
    50  // its version
    51  func (bs *InMemoryBlobstore) Get(ctx context.Context, key string, br BlobRange) (io.ReadCloser, string, error) {
    52  	bs.mutex.Lock()
    53  	defer bs.mutex.Unlock()
    54  
    55  	if val, ok := bs.blobs[key]; ok {
    56  		if ver, ok := bs.versions[key]; ok && ver != "" {
    57  			var byteRange []byte
    58  			if br.isAllRange() {
    59  				byteRange = val
    60  			} else {
    61  				posBR := br.positiveRange(int64(len(val)))
    62  				if posBR.length == 0 {
    63  					byteRange = val[posBR.offset:]
    64  				} else {
    65  					byteRange = val[posBR.offset : posBR.offset+posBR.length]
    66  				}
    67  			}
    68  
    69  			return newByteSliceReadCloser(byteRange), ver, nil
    70  		}
    71  
    72  		panic("Blob without version, or with invalid version, should no be possible.")
    73  	}
    74  
    75  	return nil, "", NotFound{key}
    76  }
    77  
    78  // Put sets the blob and the version for a key
    79  func (bs *InMemoryBlobstore) Put(ctx context.Context, key string, reader io.Reader) (string, error) {
    80  	bs.mutex.Lock()
    81  	defer bs.mutex.Unlock()
    82  
    83  	ver := uuid.New().String()
    84  	data, err := ioutil.ReadAll(reader)
    85  
    86  	if err != nil {
    87  		return "", err
    88  	}
    89  
    90  	bs.blobs[key] = data
    91  	bs.versions[key] = ver
    92  
    93  	return ver, nil
    94  }
    95  
    96  // CheckAndPut will check the current version of a blob against an expectedVersion, and if the
    97  // versions match it will update the data and version associated with the key
    98  func (bs *InMemoryBlobstore) CheckAndPut(ctx context.Context, expectedVersion, key string, reader io.Reader) (string, error) {
    99  	bs.mutex.Lock()
   100  	defer bs.mutex.Unlock()
   101  
   102  	ver, ok := bs.versions[key]
   103  	check := !ok && expectedVersion == "" || ok && expectedVersion == ver
   104  
   105  	if !check {
   106  		return "", CheckAndPutError{key, expectedVersion, ver}
   107  	}
   108  
   109  	newVer := uuid.New().String()
   110  	data, err := ioutil.ReadAll(reader)
   111  
   112  	if err != nil {
   113  		return "", err
   114  	}
   115  
   116  	bs.blobs[key] = data
   117  	bs.versions[key] = newVer
   118  
   119  	return newVer, nil
   120  }
   121  
   122  // Exists returns true if a blob exists for the given key, and false if it does not.
   123  // For InMemoryBlobstore instances error should never be returned (though other
   124  // implementations of this interface can)
   125  func (bs *InMemoryBlobstore) Exists(ctx context.Context, key string) (bool, error) {
   126  	_, ok := bs.blobs[key]
   127  
   128  	return ok, nil
   129  }