/* This file is part of limb                           https://lila.oss/limb
 * Copyright (C) 2023 Olivier Brunel                          jjk@jjacky.com */
/* SPDX-License-Identifier: GPL-2.0-only */
#include <limb/u64.h>

int
u64_unpack_trim(u64 *val, const char *sce_, size_t slen)
{
    const u8 *sce = (const u8 *) sce_;
    unsigned int b = 0;

    *val = 0;
    for (;;) {
        /* is there a(nother) byte to read? */
        if (b >= slen) return -1;

        u8 byte = sce[b];
        /* if we're on the last byte, add the last 8 bits and be done */
        if (b == 8) {
            *val |= (u64) byte << (7 * 8);
            break;
        }
        /* extract the last 7 bits from byte and add them into our val */
        *val |= (u64) (byte & 127) << (7 * b);
        /* are we done? */
        if (!(byte & 128))
            break;
        ++b;
    }

    return b + 1;
}