Besides being nicer code this also has the advantage of not making assumptions about the internal implementation: While it is documented that the AVFilter.inputs and AVFilter.outputs arrays are terminated by a zeroed sentinel, one is not allowed to infer that one can just check avfilter_pad_get_name(padarray, i) to see whether one has reached the sentinel: It could be that the pointer to the string is contained in a different structure than AVFilterPad that needs to be accessed first: return pad->struct->string. It could be that for small strings an internal buffer in AVFilterPad is used (to avoid a relocation) whereas for longer strings an external string is used; this is useful to avoid relocations: return pad->string_ptr ? pad->string_ptr : pad->interal_string Or it could be that the name has a default value: return pad->name ? pad->name : "default" (This actually made sense for us because the name of most of our AVFilterPads is just "default"; doing so would save lots of relocations.) The only thing one is allowed to infer from the existence of the sentinel is that one is allowed to use avfilter_pad_count() to get the number of pads. Therefore it is used.
Unified · Split
| @@ -1707,12 +1707,14 @@ int show_filters(void *optctx, const char *opt, const char *arg) · 1706 unmodified lines | ||
| 1707 | 1707 | while ((filter = av_filter_iterate(&opaque))) { |
| 1708 | 1708 | descr_cur = descr; |
| 1709 | 1709 | for (i = 0; i < 2; i++) { |
| 1710 | + unsigned nb_pads; | |
| 1710 | 1711 | if (i) { |
| 1711 | 1712 | *(descr_cur++) = '-'; |
| 1712 | 1713 | *(descr_cur++) = '>'; |
| 1713 | 1714 | } |
| 1714 | 1715 | pad = i ? filter->outputs : filter->inputs; |
| 1715 | − for (j = 0; pad && avfilter_pad_get_name(pad, j); j++) { | |
| 1716 | + nb_pads = avfilter_pad_count(pad); | |
| 1717 | + for (j = 0; j < nb_pads; j++) { | |
| 1716 | 1718 | if (descr_cur >= descr + sizeof(descr) - 4) |
| 1717 | 1719 | break; |
| 1718 | 1720 | *(descr_cur++) = get_media_type_char(avfilter_pad_get_type(pad, j)); |