From 6c9102f75fe4440f52dc908d61bce579a333b682 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E6=BA=90=E6=96=87=E9=9B=A8?=
 <41315874+fumiama@users.noreply.github.com>
Date: Mon, 26 Feb 2024 03:44:30 +0900
Subject: [PATCH] feat: add iterator

---
 reader.go      | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++
 reader_test.go | 42 +++++++++++++++++++++++++++++++
 spb.go         | 11 +++++----
 3 files changed, 115 insertions(+), 5 deletions(-)
 create mode 100644 reader.go
 create mode 100644 reader_test.go

diff --git a/reader.go b/reader.go
new file mode 100644
index 0000000..c8aa5db
--- /dev/null
+++ b/reader.go
@@ -0,0 +1,67 @@
+package spb
+
+import "io"
+
+type Iterator struct {
+	r                  io.Reader
+	structlen, reallen uint32
+	i                  uint32
+	v                  []byte
+}
+
+// NewReader 迭代器形式读取而非一次解析完
+func NewReader(r io.Reader) (it Iterator, err error) {
+	it.structlen, it.reallen, err = ReadNum(r)
+	if err != nil {
+		return
+	}
+	if it.structlen <= 1 || it.structlen >= uint32(1)<<20 {
+		err = ErrInvalidStructLen
+		return
+	}
+	it.r = r
+	return
+}
+
+// Next 是否有下一个
+func (it *Iterator) Next() bool {
+	if it.i >= it.structlen {
+		return false
+	}
+	var offset, datalen, n uint32
+	var err error
+	offset, n, err = ReadNum(it.r)
+	it.reallen += n
+	if err != nil {
+		return false
+	}
+	datalen, n, err = ReadNum(it.r)
+	it.reallen += n
+	if err != nil {
+		return false
+	}
+	if datalen == 0 {
+		return false
+	}
+	if datalen > offset {
+		return false
+	}
+	it.v = append(it.v[:0], make([]byte, datalen)...)
+	x, err := it.r.Read(it.v)
+	it.reallen += uint32(x)
+	if err != nil {
+		return false
+	}
+	it.i += offset
+	return true
+}
+
+// Bytes 本次迭代的原始值
+func (it *Iterator) Bytes() []byte {
+	return it.v
+}
+
+// String 将本次迭代的值解释为 string
+func (it *Iterator) String() string {
+	return string(it.v)
+}
diff --git a/reader_test.go b/reader_test.go
new file mode 100644
index 0000000..588df3c
--- /dev/null
+++ b/reader_test.go
@@ -0,0 +1,42 @@
+package spb
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"testing"
+)
+
+func TestReader(t *testing.T) {
+	f, err := os.Open("dict.sp")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	ft, err := os.Open("dict.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer ft.Close()
+	sc := bufio.NewScanner(ft)
+	var s Iterator
+	i := 1
+	for sc.Scan() {
+		s, err = NewReader(f)
+		if err != nil {
+			break
+		}
+		if !s.Next() {
+			t.Fatal("unexpected no next")
+		}
+		t0 := s.String()
+		if !s.Next() {
+			t.Fatal("unexpected no next")
+		}
+		t1 := s.String()
+		if fmt.Sprint(t0, "\t", t1) != sc.Text() {
+			t.Fatal("invalid text @ line", i)
+		}
+		i++
+	}
+}
diff --git a/spb.go b/spb.go
index 73e63ba..943feb3 100644
--- a/spb.go
+++ b/spb.go
@@ -2,7 +2,7 @@ package spb
 
 import "io"
 
-func ReadNum(r io.Reader) (n uint32, cnt int, err error) {
+func ReadNum(r io.Reader) (n uint32, cnt uint32, err error) {
 	var buf [1]byte
 	for cnt < 5 {
 		_, err = r.Read(buf[:])
@@ -43,7 +43,7 @@ type SimplePB struct {
 }
 
 func NewSimplePB(r io.Reader) (s SimplePB, err error) {
-	cnt := 0
+	cnt := uint32(0)
 	s.StructLen, cnt, err = ReadNum(r)
 	if err != nil {
 		s.RealLen = uint32(cnt)
@@ -55,7 +55,7 @@ func NewSimplePB(r io.Reader) (s SimplePB, err error) {
 		return
 	}
 	var offset, datalen uint32
-	n := 0
+	n := uint32(0)
 	for i := uint32(0); i < s.StructLen; i += offset {
 		offset, n, err = ReadNum(r)
 		cnt += n
@@ -75,8 +75,9 @@ func NewSimplePB(r io.Reader) (s SimplePB, err error) {
 			break
 		}
 		t := make([]byte, datalen)
-		n, err = r.Read(t)
-		cnt += n
+		x := 0
+		x, err = r.Read(t)
+		cnt += uint32(x)
 		if err != nil {
 			break
 		}