encint.h

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/*
 
  Copyright (C) 2010 Alex Andreotti <alex.andreotti@gmail.com>
 
  This file is part of chmc.
 
  chmc is free software: you can redistribute it and/or modify
  it 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.
 
  chmc 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 chmc.  If not, see <http://www.gnu.org/licenses/>.
 
*/
#ifndef CHMC_ENCINT_H
#define CHMC_ENCINT_H
 
// 0x7f 127
// 0x3fff 16383
// 0x1fffff 2097151
// 0xfffffff 268435455
static inline int chmc_encint_len ( const UInt32 val ) {
    int len;
 
    // FIXME should support 64 bit?
    if ( val > 0xfffffffUL )
        len = 0; // overflow
    else if ( val > 0x1fffffUL )
        len = 4;
    else if ( val > 0x3fffUL )
        len = 3;
    else if ( val > 0x7fUL )
        len = 2;
    else
        len = 1;
 
    return len;
}
 
static inline int chmc_encint ( const UInt32 val, UChar *out ) {
    int len;
    UInt32 a;
    UChar *p, *l;
 
    // FIXME should support 64 bit?
    if ( ! out || val > 0xfffffffUL )
        return 0; // FIXME can't handle, overflow
 
    if ( val > 0x1fffffUL )
        len = 4;
    else if ( val > 0x3fffUL )
        len = 3;
    else if ( val > 0x7fUL )
        len = 2;
    else
        len = 1;
 
    a = val;
    l = p = out + (len - 1);
 
    while ( p >= out ) {
        *p = (a & 0x7fUL);
        if ( p < l )
            *p |= 0x80UL;
        p--;
        a >>= 7;
    }
 
    return len;
}
 
static inline int chmc_decint ( const UChar *in, UInt32 *value ) {
    int len;
 
    len = 0;
    *value = 0;
 
    while ( (in[len] & 0x80) && (len < 3) ) {
        *value <<= 7;
        *value |= in[len] & 0x7f;
        len++;
    }
    *value <<= 7;
    *value |= in[len] & 0x7f;
    len++;
 
    return len;
}
 
#endif /* CHMC_ENCINT_H */