VLQ

#include <stdio.h>
#include <stdint.h>

void to_seq(uint64_t x, uint8_t *out)
{
    int i, j;
    for (i = 9; i > 0; i--) {
        if (x & 127ULL << i * 7) break;
    }
    for (j = 0; j <= i; j++)
        out[j] = ((x >> ((i - j) * 7)) & 127) | 128;

    out[i] ^= 128;
}

uint64_t from_seq(uint8_t *in)
{
    uint64_t r = 0;

    do {
        r = (r << 7) | (uint64_t)(*in & 127);
    } while (*in++ & 128);

    return r;
}

int main()
{
    uint8_t s[10];
    uint64_t x[] = { 8192};

    int i, j;
    for (j = 0; j < sizeof(x)/8; j++) {
        to_seq(x[j], s);
        printf("seq from %llx: [ ", x[j]);

        i = 0;
        do { printf("%02x ", s[i]); } while ((s[i++] & 128));
        printf("] back: %llx\n", from_seq(s));
    }

    return 0;
}