6

sync/sync.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
 	"regexp"
@@ -111,7 +112,7 @@ func sync(frompath, topath string) (err error) {
 				return true
 			}
 			fmt.Println(fromfile, " ==> ", tofile)
-			frombs, e := os.ReadFile(fromfile)
+			frombs, e := ReadFile(fromfile)
 			if e != nil {
 				err = fmt.Errorf("from file %v", e)
 				return false
@@ -141,3 +142,54 @@ func sync(frompath, topath string) (err error) {
 	}
 	return
 }
+
+func ReadFile(name string) (data []byte, err error) {
+	data = make([]byte, 0, 512)
+	for {
+		data, err = ReadFileContinue(name, data)
+		if err == io.EOF {
+			err = nil
+			return
+		}
+	}
+}
+
+func ReadFileContinue(name string, data []byte) ([]byte, error) {
+	f, err := os.Open(name)
+	if err != nil {
+		return data, err
+	}
+	defer f.Close()
+
+	var size int
+	if info, err := f.Stat(); err == nil {
+		size64 := info.Size()
+		if int64(int(size64)) == size64 {
+			size = int(size64)
+		}
+	}
+	size++ // one byte for final read at EOF
+
+	// If a file claims a small size, read at least 512 bytes.
+	// In particular, files in Linux's /proc claim size 0 but
+	// then do not work right if read in small pieces,
+	// so an initial read of 1 byte would not work correctly.
+	offset := len(data)
+	if size > cap(data) {
+		ndata := make([]byte, len(data), size)
+		copy(ndata, data)
+		data = ndata
+	}
+
+	for {
+		n, err := f.ReadAt(data[offset:cap(data)], int64(offset))
+		offset += n
+		if err != nil {
+			return data[:offset], err
+		}
+		if offset >= cap(data) {
+			d := append(data[:cap(data)], 0)
+			data = d[:offset]
+		}
+	}
+}