// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Simple file i/o and string manipulation, to avoid
// depending on strconv and bufio.

package net

import (
	"io";
	"os";
)

type file struct {
	fd *os.FD;
	data []byte;
}

func (f *file) close() {
	f.fd.Close()
}

func (f *file) getLineFromData() (s string, ok bool) {
	data := f.data;
	for i := 0; i < len(data); i++ {
		if data[i] == '\n' {
			s = string(data[0:i]);
			ok = true;
			// move data
			i++;
			n := len(data) - i;
			for j := 0; j < n; j++ {
				data[j] = data[i+j];
			}
			f.data = data[0:n];
			return
		}
	}
	return
}

func (f *file) readLine() (s string, ok bool) {
	if s, ok = f.getLineFromData(); ok {
		return
	}
	if len(f.data) < cap(f.data) {
		ln := len(f.data);
		n, err := io.Readn(f.fd, f.data[ln:cap(f.data)]);
		if n >= 0 {
			f.data = f.data[0:ln+n];
		}
	}
	s, ok = f.getLineFromData();
	return
}

func open(name string) *file {
	fd, err := os.Open(name, os.O_RDONLY, 0);
	if err != nil {
		return nil
	}
	return &file{fd, make([]byte, 1024)[0:0]};
}

func byteIndex(s string, c byte) int {
	for i := 0; i < len(s); i++ {
		if s[i] == c {
			return i
		}
	}
	return -1
}

// Count occurrences in s of any bytes in t.
func countAnyByte(s string, t string) int {
	n := 0;
	for i := 0; i < len(s); i++ {
		if byteIndex(t, s[i]) >= 0 {
			n++;
		}
	}
	return n
}

// Split s at any bytes in t.
func splitAtBytes(s string, t string) []string {
	a := make([]string, 1+countAnyByte(s, t));
	n := 0;
	last := 0;
	for i := 0; i < len(s); i++ {
		if byteIndex(t, s[i]) >= 0 {
			if last < i {
				a[n] = string(s[last:i]);
				n++;
			}
			last = i+1;
		}
	}
	if last < len(s) {
		a[n] = string(s[last:len(s)]);
		n++;
	}
	return a[0:n];
}

func getFields(s string) []string {
	return splitAtBytes(s, " \r\t\n");
}

// Bigger than we need, not too big to worry about overflow
const big = 0xFFFFFF

// Decimal to integer starting at &s[i0].
// Returns number, new offset, success.
func dtoi(s string, i0 int) (n int, i int, ok bool) {
	n = 0;
	for i = i0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
		n = n*10 + int(s[i] - '0');
		if n >= big {
			return 0, i, false
		}
	}
	if i == i0 {
		return 0, i, false
	}
	return n, i, true
}

// Hexadecimal to integer starting at &s[i0].
// Returns number, new offset, success.
func xtoi(s string, i0 int) (n int, i int, ok bool) {
	n = 0;
	for i = i0; i < len(s); i++ {
		if '0' <= s[i] && s[i] <= '9' {
			n *= 16;
			n += int(s[i] - '0')
		} else if 'a' <= s[i] && s[i] <= 'f' {
			n *= 16;
			n += int(s[i] - 'a') + 10
		} else if 'A' <= s[i] && s[i] <= 'F' {
			n *= 16;
			n += int(s[i] -'A') + 10
		} else {
			break
		}
		if n >= big {
			return 0, i, false
		}
	}
	if i == i0 {
		return 0, i, false
	}
	return n, i, true
}