Golang的strings.Split()踩坑记录

type Info struct{
   Ids string // Ids: 123,456
}

func test3(info Info){
   ids := info.Ids
   idList := strings.Split(ids , ",")
   if len(idList) < 1 {
      return
   }
   log.Println("ids-not-empty")
   // ***
}

type stringHeader struct {
   Data unsafe.Pointer
   Len  int
}

func test3(info Info){  
    ids := info.Ids
    idList := strings.Split(ids, ",")
    log.Printf("idList长度: [%d], idList: [%v]", len(idList), idList)
    for index, _ := range idList {
       log.Printf("idList[%d]:[%v]", index, idList[index])
    }    
   // ***
}

const (
  basePrintInfoV3 = "%s 字符串的指针地址:[%v]，字符串buf数组地址:[%v] ,Len字段的地址:[%p] ,Len字段值:[%v]"
  basePrintInfoV2 = "%s切片的指针地址:[%p]，切片数组地址:[%p], Len字段的地址:[%p], Len字段的值:[%v]"
)

func test3(info Info) {
  ids := info.Ids
  idList := strings.Split(ids, ",")
  getStringPtr("ids ", &ids)
  getStringSliceAllPtr("idList ", &idList)
  // ***
}
func getStringPtr(name string, str *string) {
   s2 := (*reflect.StringHeader)(unsafe.Pointer(str))
   log.Printf(basePrintInfoV3, name, unsafe.Pointer(str), unsafe.Pointer(s2.Data), unsafe.Pointer(&s2.Len), s2.Len)
}

func getStringSliceAllPtr(name string, s1 *[]string) {
   s2 := (*reflect.StringHeader)(unsafe.Pointer(s1))
   log.Printf(basePrintInfoV2, name, unsafe.Pointer(&s1), unsafe.Pointer(s2.Data), unsafe.Pointer(&s2.Len), s2.Len)
}

func Split(s, sep string) []string { return genSplit(s, sep, 0, -1) }

func genSplit(s, sep string, sepSave, n int) []string {
   if n == 0 {
      return nil
   }
   if sep == "" {
      return explode(s, n)
   }
   if n < 0 {
      // 计算 s 按照 seq 能被切成多少份
      n = Count(s, sep) + 1
   }

   a := make([]string, n)
   n--
   i := 0
   for i < n {
      // 定位 s里的第一个 sep 所在的位置
      m := Index(s, sep)
      if m < 0 {
         break
      }
      // 放入返回的数组
      a[i] = s[:m+sepSave]
      // 切割s
      s = s[m+len(sep):]
      i++
   }
   a[i] = s
   return a[:i+1]
}

func Count(s, substr string) int {
   // special case
   if len(substr) == 0 {
      return utf8.RuneCountInString(s) + 1
   }
   if len(substr) == 1 {
      return bytealg.CountString(s, substr[0])
   }
   n := 0
   for {
      i := Index(s, substr)
      if i == -1 {
         return n
      }
      n++
      s = s[i+len(substr):]
   }
}

s := strings.Split("", "")
fmt.Println(s, len(s)) // [] 0 //返回空数组

s = strings.Split("abc,abc", "")
fmt.Println(s, len(s)) // [a b c , a b c] 7 //返回7个数组元素

s = strings.Split("", ",")
fmt.Println(s, len(s)) // [] 1 

s = strings.Split("abc,abc", ",")
fmt.Println(s, len(s)) // [abc abc] 2

s = strings.Split("abc,abc", "|")
fmt.Println(s, len(s)) // [abc,abc] 1

fmt.Println(len("")) // 0
fmt.Println(len([]string{""})) // 1 

str := ""
fmt.Println(str[0]) // panic