In order to understand memory layout consider the declaration of the
following structs. The first one is a part of our API:
struct vpx_codec_ctx {
// ...
struct vpx_codec_priv *priv;
};
The second one is defined in vpx_codec_internal.h:
struct vpx_codec_priv {
// ...
};
The following struct is defined 4 times for encoder/decoder VP8/VP9:
struct vpx_codec_alg_priv {
struct vpx_codec_priv base;
// ...
};
Private data allocation for the given ctx:
struct vpx_codec_ctx *ctx = <get>
struct vpx_codec_alg_priv *alg_priv = <allocate>
ctx->priv = (struct vpx_codec_priv *)alg_priv;
The cast works because vpx_codec_alg_priv has a
vpx_codec_priv instance as a first member 'base'.
Change-Id: I10d1afc8c9a7dfda50baade8c7b0296678bdb0d0
73edeb03ea