av/codec/h264/h264dec/helpers.go

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2022-05-31 08:17:06 +03:00
/*
DESCRIPTION
helpers.go provides general helper utilities.
AUTHORS
Saxon Nelson-Milton <saxon@ausocean.org>, The Australian Ocean Laboratory (AusOcean)
LICENSE
rtp.go is Copyright (C) 2018 the Australian Ocean Lab (AusOcean)
It is free software: you can redistribute it and/or modify them
under the terms of the GNU General Public License as published by the
Free Software Foundation, either version 3 of the License, or (at your
option) any later version.
It is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
for more details.
You should have received a copy of the GNU General Public License
along with revid in gpl.txt. If not, see [GNU licenses](http://www.gnu.org/licenses).
*/
package h264dec
import (
"errors"
"math"
)
// binToSlice is a helper function to convert a string of binary into a
// corresponding byte slice, e.g. "0100 0001 1000 1100" => {0x41,0x8c}.
// Spaces in the string are ignored.
func binToSlice(s string) ([]byte, error) {
var (
a byte = 0x80
cur byte
bytes []byte
)
for i, c := range s {
switch c {
case ' ':
continue
case '1':
cur |= a
case '0':
default:
return nil, errors.New("invalid binary string")
}
a >>= 1
if a == 0 || i == (len(s)-1) {
bytes = append(bytes, cur)
cur = 0
a = 0x80
}
}
return bytes, nil
}
// binToInt converts a binary string provided as a string and returns as an int.
// White spaces are ignored.
func binToInt(s string) (int, error) {
var sum int
var nSpace int
for i := len(s) - 1; i >= 0; i-- {
if s[i] == ' ' {
nSpace++
continue
}
sum += int(math.Pow(2, float64(len(s)-1-i-nSpace))) * int(s[i]-'0')
}
return sum, nil
}
func maxi(a, b int) int {
if a > b {
return a
}
return b
}
func mini(a, b int) int {
if a < b {
return a
}
return b
}
func absi(a int) int {
if a < 0 {
return -a
}
return a
}