github.com/peterbourgon/diskv@v2.0.1+incompatible/examples/content-addressable-store/cas.go (about)

     1  package main
     2  
     3  import (
     4  	"crypto/md5"
     5  	"fmt"
     6  	"io"
     7  
     8  	"github.com/peterbourgon/diskv"
     9  )
    10  
    11  const transformBlockSize = 2 // grouping of chars per directory depth
    12  
    13  func blockTransform(s string) []string {
    14  	var (
    15  		sliceSize = len(s) / transformBlockSize
    16  		pathSlice = make([]string, sliceSize)
    17  	)
    18  	for i := 0; i < sliceSize; i++ {
    19  		from, to := i*transformBlockSize, (i*transformBlockSize)+transformBlockSize
    20  		pathSlice[i] = s[from:to]
    21  	}
    22  	return pathSlice
    23  }
    24  
    25  func main() {
    26  	d := diskv.New(diskv.Options{
    27  		BasePath:     "data",
    28  		Transform:    blockTransform,
    29  		CacheSizeMax: 1024 * 1024, // 1MB
    30  	})
    31  
    32  	for _, valueStr := range []string{
    33  		"I am the very model of a modern Major-General",
    34  		"I've information vegetable, animal, and mineral",
    35  		"I know the kings of England, and I quote the fights historical",
    36  		"From Marathon to Waterloo, in order categorical",
    37  		"I'm very well acquainted, too, with matters mathematical",
    38  		"I understand equations, both the simple and quadratical",
    39  		"About binomial theorem I'm teeming with a lot o' news",
    40  		"With many cheerful facts about the square of the hypotenuse",
    41  	} {
    42  		d.Write(md5sum(valueStr), []byte(valueStr))
    43  	}
    44  
    45  	var keyCount int
    46  	for key := range d.Keys(nil) {
    47  		val, err := d.Read(key)
    48  		if err != nil {
    49  			panic(fmt.Sprintf("key %s had no value", key))
    50  		}
    51  		fmt.Printf("%s: %s\n", key, val)
    52  		keyCount++
    53  	}
    54  	fmt.Printf("%d total keys\n", keyCount)
    55  
    56  	// d.EraseAll() // leave it commented out to see how data is kept on disk
    57  }
    58  
    59  func md5sum(s string) string {
    60  	h := md5.New()
    61  	io.WriteString(h, s)
    62  	return fmt.Sprintf("%x", h.Sum(nil))
    63  }