#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <openssl/objects.h>
#include <openssl/comp.h>

static int rle_compress_block(COMP_CTX *ctx, unsigned char *out,
                              unsigned int olen, unsigned char *in,
                              unsigned int ilen);
static int rle_expand_block(COMP_CTX *ctx, unsigned char *out,
                            unsigned int olen, unsigned char *in,
                            unsigned int ilen);

static COMP_METHOD rle_method = {
    NID_rle_compression,
    LN_rle_compression,
    NULL,
    NULL,
    rle_compress_block,
    rle_expand_block,
    NULL,
    NULL,
};

COMP_METHOD *COMP_rle(void)
{
    return (&rle_method);
}

static int rle_compress_block(COMP_CTX *ctx, unsigned char *out,
                              unsigned int olen, unsigned char *in,
                              unsigned int ilen)
{
    if (ilen == 0)
        return 0;

    if (olen <= ilen)
        return -1;

    *(out++) = 0;
    memcpy(out, in, ilen);
    return (ilen + 1);
}

static int rle_expand_block(COMP_CTX *ctx, unsigned char *out,
                            unsigned int olen, unsigned char *in,
                            unsigned int ilen)
{
    int i;

    if (ilen == 0)
        return 0;

    if (olen < (ilen - 1))
        return -1;

    i = *(in++);
    if (i != 0)
        return -1;

    memcpy(out, in, ilen - 1);
    return (ilen - 1);
}