gogrep.go

package main

import (
  "fmt"
  "os"
  "bufio"
  "regexp"
  "io"
)  

func main() {
  restr := os.Args[1]
  re, _ := regexp.Compile(restr)
  fmt.Println(re)
  n := 4
  iobuf := make([]byte, n)
  buf := make([]byte, n*2)
  in := bufio.NewReader(os.Stdin)
  chunk := -1
  lastFound := make(map[int]string)
  curFound := make(map[int]string)
  for {
    b, e := in.Read(iobuf)
    if e != nil && e != io.EOF { panic(e) }
    if b == 0 { break }

    copy(buf[0:n],buf[n:n*2])
    copy(buf[n:n*2],iobuf)

    if chunk == -1 { 
      chunk++
      continue 
    }

    fmt.Println(buf)    

    matches := re.FindAllIndex(buf[0:n+b],-1)
    for _,m := range matches {
      fmt.Println(m)
      rel := m[0]+chunk*n
      _,ok := lastFound[rel]
      if ! ok {
        str := string(buf[m[0]:m[1]])
        curFound[rel] = str
        fmt.Println(rel,`:`,str)
      }

    }
    chunk += 1
    lastFound = curFound
    curFound = make(map[int]string) // reset map
  }
}