[Ffmpeg-devel] [PATCH] simple internal lzo decoder

[Michael Niedermayer]

Hi

On Sat, Jan 14, 2006 at 02:07:30PM +0100, Reimar D?ffinger wrote:
[...]
>  static inline void copy(LZOContext *c, int cnt) {
> -    if (c->in + cnt > c->in_end) {
> -        cnt = c->in_end - c->in;
> +    register uint8_t *in_ptr = c->in;
> +    register uint8_t *out_ptr = c->out;
> +    if (in_ptr + cnt > c->in_end) {
> +        cnt = c->in_end - in_ptr;
>          c->error |= LZO_INPUT_DEPLETED;
>      }
> -    if (c->out + cnt > c->out_end) {
> -        cnt = c->out_end - c->out;
> +    if (out_ptr + cnt > c->out_end) {
> +        cnt = c->out_end - out_ptr;
>          c->error |= LZO_OUTPUT_FULL;
>      }
>      do {
> -        *c->out++ = *c->in++;
> +        *out_ptr++ = *in_ptr++;
>      } while (--cnt);
> +    c->in = in_ptr;
> +    c->out = out_ptr;

what about:

static inline void copy(LZOContext *c, int cnt) {
    register uint8_t *in_ptr = c->in;
    register uint8_t *out_ptr = c->out;
    out_ptr += cnt;
    in_ptr += cnt;
    if (in_ptr > c->in_end) {
        cnt     -= in_ptr - c->in_end;
        out_ptr -= in_ptr - c->in_end;
         in_ptr= c->in_end;
        c->error |= LZO_INPUT_DEPLETED;
    }
    if (out_ptr > c->out_end) {
        cnt     -= out_ptr - c->out_end;
         in_ptr -= out_ptr - c->out_end;
        out_ptr= c->out_end;
        c->error |= LZO_OUTPUT_FULL;
    }
    c->in = in_ptr;
    c->out = out_ptr;
    cnt= -cnt;
    do {
        out_ptr[cnt] = in_ptr[cnt];
    } while (++cnt);
}

or something like

c->in = in_ptr + cnt;
c->out = out_ptr + cnt;
cnt= (cnt+3)>>2;
do {
    out_ptr[0] = in_ptr[0];
    out_ptr[1] = in_ptr[1];
    out_ptr[2] = in_ptr[2];
    out_ptr[3] = in_ptr[3];
    out_ptr += 4;
    in_ptr += 4;
} while(cnt --)

note, the idea here is that a few more bytes wont matter as long as they dont
go over the end of th buffer

[...]

-- 
Michael