github.com/mirantis/virtlet@v1.5.2-0.20191204181327-1659b8a48e9b/pkg/image/virtualsize.go (about)

     1  /*
     2  Copyright 2018 Mirantis
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package image
    18  
    19  import (
    20  	"encoding/json"
    21  	"fmt"
    22  	"os/exec"
    23  )
    24  
    25  func extractImageSizeFromInfo(out []byte) (uint64, error) {
    26  	var parsed struct {
    27  		VirtualSize uint64 `json:"virtual-size"`
    28  	}
    29  	if err := json.Unmarshal(out, &parsed); err != nil {
    30  		return 0, fmt.Errorf("can't parse image info: %v\ninfo:\n%s", err, out)
    31  	}
    32  	return parsed.VirtualSize, nil
    33  }
    34  
    35  // GetImageVirtualSize returns the virtual size of the specified QCOW2 image
    36  func GetImageVirtualSize(imagePath string) (uint64, error) {
    37  	cmd := exec.Command("qemu-img", "info", "--output", "json", imagePath)
    38  	out, err := cmd.Output()
    39  	if err == nil {
    40  		return extractImageSizeFromInfo(out)
    41  	}
    42  	if exitErr, ok := err.(*exec.ExitError); ok {
    43  		return 0, fmt.Errorf("qemu-img failed: %v\noutput:\n%s", err, exitErr.Stderr)
    44  	}
    45  	return 0, fmt.Errorf("qemu-img failed: %v", err)
    46  }