scan using os package

c1-m4-activity/names.txt

@@ -1,10 +1,8 @@
-hoang le
-minh tran
-nghia nguyen
-tuan dang
-hung tran
 khanh tran
-tam do
 huu dao
 van ly
-nam ho
+nam ho
+hng le
+nghia nguyen
+tuan dang
+hung tran

c1-m4-activity/read.go

@@ -3,12 +3,16 @@ package main
 import (
 	"bufio"
 	"fmt"
+	"io"
 	"log"
 	"os"
+	"strings"
 )
 
 const (
-	maxLength = 20
+	maxLength         = 20
+	defaultScanRange  = 2
+	defaultReadOffset = 2
 )
 
 // Name represents data in each line from text
@@ -19,8 +23,8 @@ type Name struct {
 
 // InitMe init property for Name
 func (n *Name) InitMe(fname, lname string) {
-	n.fname = fname
-	n.lname = lname
+	n.fname = strings.Trim(fname, "\n")
+	n.lname = strings.Trim(lname, "\n")
 	var maxRunes []rune
 	if len(fname) > maxLength {
 		maxRunes = []rune(fname)
@@ -40,9 +44,18 @@ func (n *Name) InitMe(fname, lname string) {
 */
 
 func main() {
-	var fileName string
-	fmt.Println("Enter name of the file:")
-	fmt.Scan(&fileName)
+	// var fileName string
+	// fmt.Println("Enter name of the file:")
+	// fmt.Scan(&fileName)
+
+	names := readUsingOs("names.txt")
+	fmt.Printf("--------")
+	fmt.Printf("names value: %v\n", names)
+	// fmt.Printf("names value 12: %v\n", names[12])
+	// fmt.Printf("length: %d,capacity: %d \n", len(names), cap(names))
+}
+
+func readUsingBuf(fileName string) []Name {
 	file, err := os.Open(fileName)
 	if err != nil {
 		log.Fatal(err)
@@ -68,6 +81,75 @@ func main() {
 	if err := scanner.Err(); err != nil {
 		log.Fatal(err)
 	}
-	fmt.Printf("names value: %v\n", names)
-	fmt.Printf("length: %d,capacity: %d \n", len(names), cap(names))
+	return names
+}
+
+func readUsingOs(fileName string) []Name {
+	file, err := os.Open(fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+	names := make([]Name, 0, 20)
+
+	var scanRange int = 4
+	var readOffset int64 = 0
+	var foundNewLine bool = false
+	var meetEOF bool = false
+
+	text := make([]byte, scanRange)
+	count, err := file.Read(text)
+	var cycle int = 0
+	for count != 0 {
+		cycle++
+		// fmt.Printf("~~~~~~~~readOffset: %v~~~~scanRange: %v \n", readOffset, scanRange)
+		// fmt.Printf("text before check newline and whitespace:%v-with len:%v\n", string(text), len(text))
+		foundNewLine = false
+		for pos, char := range text {
+			// fmt.Printf("------POS: %v char: %c", pos, char)
+			if (char == '\n' || meetEOF) && pos != 0 {
+				foundNewLine = true
+				scanRange = defaultScanRange
+				// fmt.Printf("found '\\n' readOffset %v add pos %v in text have '\\n'\n", readOffset, pos)
+				line := text[:pos]
+				if meetEOF {
+					fmt.Printf("Count %v\n", count)
+					line = text[:count]
+					readOffset += int64(count)
+				} else {
+					readOffset += int64(pos)
+				}
+				fmt.Printf("found '\\n' line: %v and pos: %v\n", string(line), pos)
+				for pos, char := range line {
+					if char == ' ' {
+						tempName := &Name{}
+						fmt.Printf("ADDING fname %v \n", string(line[:pos]))
+						fmt.Printf("ADDING lname %v \n", string(line[pos+1:]))
+						tempName.InitMe(string(line[:pos]), string(line[pos+1:]))
+						names = append(names, *tempName)
+						// only check first new line
+						break
+					}
+				}
+				break
+			}
+		}
+		fmt.Println("ReadAtReadAtReadAtReadAtReadAtReadAt")
+		if !foundNewLine {
+			scanRange *= 2
+			// fmt.Printf("NF scanRange %v count: %v readOffset %v\n", scanRange, count, readOffset)
+		}
+		text = make([]byte, scanRange)
+		count, err = file.ReadAt(text, readOffset)
+		// fmt.Printf("Error:%v-Count:%v\n", err, count)
+		if err == io.EOF && meetEOF {
+			break
+		}
+		if err == io.EOF {
+			meetEOF = true
+			text = make([]byte, count)
+			count, err = file.ReadAt(text, readOffset)
+		}
+	}
+	return names
 }