src/lib/numpack.c

/* Copyright (c) 2013-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "buffer.h"
#include "numpack.h"

void numpack_encode(buffer_t *buf, uint64_t num)
{
    /* number continues as long as the highest bit is set */
    while (num >= 0x80) {
        buffer_append_c(buf, (num & 0x7f) | 0x80);
        num >>= 7;
    }

    buffer_append_c(buf, num);
}

int numpack_decode(const uint8_t **p, const uint8_t *end, uint64_t *num_r)
{
    const uint8_t *c = *p;
    uint64_t value = 0;
    unsigned int bits = 0;

    while (bits < 64) {
        if (c == end)
            return -1;

        value |= (uint64_t)(*c & 0x7f) << bits;
        if (*c < 0x80)
            break;

        bits += 7;
        c++;
    }

    bits += bits_required8(*c);
    if (bits > 64) /* overflow */
        return -1;

    *p = c + 1;
    *num_r = value;
    return 0;
}

int numpack_decode32(const uint8_t **p, const uint8_t *end, uint32_t *num_r)
{
    uint64_t num;

    if (numpack_decode(p, end, &num) < 0)
        return -1;
    if (num > 4294967295U)
        return -1;

    *num_r = (uint32_t)num;
    return 0;
}