segments/segments.go

   1 package segments
   2
   3 type Int = int64
   4
   5 type Length = Int
   6
   7 func min(i Int, rest ...Int) Int {
   8         ret := i
   9         for _, i := range rest {
  10                 if i < ret {
  11                         ret = i
  12                 }
  13         }
  14         return ret
  15 }
  16
  17 type Extent struct {
  18         Start, Length Int
  19 }
  20
  21 func (e Extent) End() Int {
  22         return e.Start + e.Length
  23 }
  24
  25 type (
  26         Callback   = func(int, Extent) bool
  27         LengthIter = func() (Length, bool)
  28 )
  29
  30 func Scan(haystack LengthIter, needle Extent, callback Callback) bool {
  31         i := 0
  32         for needle.Length != 0 {
  33                 l, ok := haystack()
  34                 if !ok {
  35                         return false
  36                 }
  37                 if needle.Start < l || needle.Start == l && l == 0 {
  38                         e1 := Extent{
  39                                 Start:  needle.Start,
  40                                 Length: min(l, needle.End()) - needle.Start,
  41                         }
  42                         if e1.Length >= 0 {
  43                                 if !callback(i, e1) {
  44                                         return true
  45                                 }
  46                                 needle.Start = 0
  47                                 needle.Length -= e1.Length
  48                         }
  49                 } else {
  50                         needle.Start -= l
  51                 }
  52                 i++
  53         }
  54         return true
  55 }
  56
  57 func LocaterFromLengthIter(li LengthIter) Locater {
  58         return func(e Extent, c Callback) bool {
  59                 return Scan(li, e, c)
  60         }
  61 }
  62
  63 type Locater func(Extent, Callback) bool