Quoting Diego Biurrun (2015-03-31 16:31:33)
> +unsigned ff_els_decode_unsigned(ElsDecCtx *ctx, ElsUnsignedRung *ur)
> +{
> + int i, n, r, bit;
> + ElsRungNode *rung_node;
> +
> + if (ctx->err)
> + return 0;
> +
> + /* decode unary prefix */
> + for (n = 0; n < ELS_EXPGOLOMB_LEN + 1; n++)
> + if (ff_els_decode_bit(ctx, &ur->prefix_rung[n]))
> + break;
> +
> + /* handle the error/overflow case */
> + if (ctx->err || n >= ELS_EXPGOLOMB_LEN) {
> + ctx->err = AVERROR(EOVERFLOW);
> + return 0;
> + }
> +
> + /* handle the zero case */
> + if (!n)
> + return 0;
> +
> + /* initialize probability tree */
> + if (!ur->rem_rung_list) {
> + ur->rem_rung_list = av_mallocz(RUNG_SPACE);
> + if (!ur->rem_rung_list) {
> + ctx->err = AVERROR(ENOMEM); // Probability tree initialization
> failed
> + return 0;
> + }
> + ur->rung_list_size = RUNG_SPACE;
> + ur->avail_index = ELS_EXPGOLOMB_LEN;
> + }
> +
> + /* decode the remainder */
> + for (i = 0, r = 0, bit = 0; i < n; i++) {
> + if (!i)
> + rung_node = &ur->rem_rung_list[n];
> + else {
> + if (!rung_node->next_index) {
> + if (ur->rung_list_size <= (ur->avail_index + 2) *
> sizeof(ElsRungNode)) {
> + // remember rung_node position
> + ptrdiff_t pos = rung_node - ur->rem_rung_list;
> + ur->rem_rung_list = av_realloc(ur->rem_rung_list,
> + ur->rung_list_size +
> + RUNG_SPACE);
> + if (!ur->rem_rung_list) {
memleak on failure
> +#define LOAD_NEIGHBOURS(x) \
> + W = curr_row[(x) - 1]; \
> + N = above_row[(x)]; \
> + WW = curr_row[(x) - 2]; \
> + NW = above_row[(x) - 1]; \
> + NE = above_row[(x) + 1]; \
> + NN = above2_row[(x)]; \
> + NNW = above2_row[(x) - 1]; \
> + NWW = above_row[(x) - 2]; \
> + NNE = above2_row[(x) + 1]
> +
> +#define UPDATE_NEIGHBOURS(x) \
> + NNW = NN; \
> + NN = NNE; \
> + NWW = NW; \
> + NW = N; \
> + N = NE; \
> + NE = above_row[(x) + 1]; \
> + NNE = above2_row[(x) + 1]
> +
> +#define R_shift 16
> +#define G_shift 8
> +#define B_shift 0
> +
> +static inline int log2_ceil(uint32_t x)
> +{
> + int c = 0;
> +
> + for (--x; x > 0; x >>= 1, c++)
> + ;
Nit: I think this would look better with c++ in the loop body. But maybe
that's just me.
> +static int epic_jb_decode_tile(G2MContext *c, int tile_x, int tile_y,
> + const uint8_t *src, size_t src_size,
> + AVCodecContext *avctx)
> +{
> + uint8_t prefix, mask;
> + int extrabytes, tile_width, tile_height, awidth, aheight;
> + size_t els_dsize;
> + uint8_t *dst;
> +
> + if (!src_size)
> + return 0;
> +
> + /* get data size of the ELS partition as unsigned variable-length
> integer */
> + prefix = *src++;
> + for (extrabytes = 0, mask = 0x80; (prefix & mask) && (extrabytes < 7);
> + mask >>= 1, extrabytes++)
> + ;
Again, I think mask >>= 1 would look better in the loop body.
> + if (extrabytes > 3 || --src_size < extrabytes) {
I think it'd be cleaner to decrement src_size immediately after we read
from src above.
--
Anton Khirnov
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