luci-go/common/dirwalk: Code for walking a directory tree efficiently

common/dirwalk/tests/tools/gendir/generate.go

+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package main
+
+import (
+        "fmt"
+        "io"
+        "log"
+        "math/rand"
+        "os"
+        "path"
+
+        "github.com/dustin/go-humanize"
+)
+
+const (
+        blockSize uint64 = 1 * 1024 * 1024 // 1 Megabyte
+)
+
+func writeFile(fileName string, fileContent io.Reader, fileSize uint64) {
+        f, err := os.Create(fileName)
+        if err != nil {
+                log.Fatal(err)
+        }
+        defer f.Close()
+
+        var written uint64
+        for written < fileSize {

[mcgreevy_g, 2017/06/27 03:29:17]

I'm pretty sure that you can achieve this by just wrapping fileContent in an
io.LimitedReader, and then using io.Copy to f from the wrapped reader.

+                content := make([]byte, min(fileSize-written, blockSize))
+
+                // Generate a block of content
+                read, err := fileContent.Read(content)
+                if err != nil {
+                        log.Fatal(err)
+                }
+
+                // Write the block of content
+                write, err := f.Write(content[0:read])
+                if err != nil {
+                        log.Fatal(err)
+                }
+
+                written += uint64(write)
+        }
+}
+
+const (
+        fileNameMinSize uint64 = 4
+        fileNameMaxSize uint64 = 20
+)
+
+type fileType int
+
+const (
+        fileTypeBinaryRandom   fileType = iota // Truly random binary data (totally uncompressible)
+        fileTypeTextRandom                     // Truly random text data (mostly uncompressible)
+        fileTypeBinaryRepeated                 // Repeated binary data (compressible)
+        fileTypeTextRepeated                   // Repeated text data (very compressible)
+        fileTypeTextLorem                      // Lorem Ipsum txt data (very compressible)
+
+        fileTypeMax
+)
+
+var fileTypeName = []string{
+        "Random Binary",
+        "Random Text",
+        "Repeated Binary",
+        "Repeated Text",
+        "Lorem Text",
+}
+
+func (f fileType) String() string {
+        return fileTypeName[int(f)]
+}
+
+// Generate num files between (min, max) size
+func generateFiles(r *rand.Rand, dir string, num uint64, fileSizeMin uint64, fileSizeMax uint64) {
+        for i := uint64(0); i < num; i++ {
+                var fileName string
+                var filePath string
+                for true {

[mcgreevy_g, 2017/06/27 03:29:17]

This can be expressed as:

for {

Note: this pattern also occurs elsewhere in this file.

+                        fileName = fileNameRandom(r, randBetween(r, fileNameMinSize, fileNameMaxSize))
+                        filePath = path.Join(dir, fileName)
+                        if _, err := os.Stat(filePath); os.IsNotExist(err) {
+                                break
+                        }
+                }
+                fileSize := randBetween(r, fileSizeMin, fileSizeMax)
+                filetype := fileType(r.Intn(int(fileTypeMax)))
+
+                var fileContent io.Reader
+                switch filetype {
+                case fileTypeBinaryRandom:
+                        fileContent = RandomBinaryGenerator(r)
+                case fileTypeTextRandom:
+                        fileContent = RandomTextGenerator(r)
+                case fileTypeBinaryRepeated:
+                        fileContent = RepeatedBinaryGenerator(r)
+                case fileTypeTextRepeated:
+                        fileContent = RepeatedTextGenerator(r)
+                case fileTypeTextLorem:
+                        fileContent = LoremTextGenerator()
+                }
+
+                if num < 1000 {
+                        fmt.Printf("File: %-40s %-20s (%s)\n", fileName, filetype.String(), humanize.Bytes(fileSize))
+                }
+                writeFile(filePath, fileContent, fileSize)
+        }
+}
+
+// Generate num directories
+func generateDirs(r *rand.Rand, dir string, num uint64) []string {
+        var result []string
+
+        for i := uint64(0); i < num; i++ {
+                var dirname string
+                var dirpath string
+                for true {
+                        dirname = fileNameRandom(r, randBetween(r, fileNameMinSize, fileNameMaxSize))
+                        dirpath = path.Join(dir, dirname)
+                        if _, err := os.Stat(dirpath); os.IsNotExist(err) {
+                                break
+                        }
+                }
+
+                if err := os.MkdirAll(dirpath, 0755); err != nil {
+                        log.Fatal(err)
+                }
+                result = append(result, dirpath)
+        }
+        return result
+}
+
+type fileSettings struct {
+        MinNumber uint64
+        MaxNumber uint64
+        MinSize   uint64
+        MaxSize   uint64
+}
+
+type dirSettings struct {
+        Number       []uint64
+        MinFileDepth uint64
+}
+
+type treeSettings struct {
+        Files []fileSettings
+        Dir   dirSettings
+}
+
+func generateTreeInternal(r *rand.Rand, dir string, depth uint64, settings *treeSettings) {
+        fmt.Printf("%04d:%s -->\n", depth, dir)
+        // Generate the files in this directory
+        if depth >= settings.Dir.MinFileDepth {
+                for _, files := range settings.Files {
+                        numfiles := randBetween(r, files.MinNumber, files.MaxNumber)
+                        fmt.Printf("%04d:%s: Generating %d files (between %s and %s)\n", depth, dir, numfiles, humanize.Bytes(files.MinSize), humanize.Bytes(files.MaxSize))
+                        generateFiles(r, dir, numfiles, files.MinSize, files.MaxSize)
+                }
+        }
+
+        // Generate another depth of directories
+        if depth < uint64(len(settings.Dir.Number)) {
+                numdirs := settings.Dir.Number[depth]
+                fmt.Printf("%04d:%s: Generating %d directories\n", depth, dir, numdirs)
+                for _, childpath := range generateDirs(r, dir, numdirs) {
+                        generateTreeInternal(r, childpath, depth+1, settings)
+                }
+        }
+        fmt.Printf("%04d:%s <--\n", depth, dir)
+}
+
+func generateTree(r *rand.Rand, rootdir string, settings *treeSettings) {
+        generateTreeInternal(r, rootdir, 0, settings)
+        return
+}