Re: [FFmpeg-devel] [PATCH v1 09/19] avcodec/h274: add ff_h274_hash functions

[Andreas Rheinhardt <andreas.rheinhardt@outlook.com>]

toqsxw@gmail.com:
> From: Wu Jianhua <toqsxw@outlook.com>
> 
> Signed-off-by: Wu Jianhua <toqsxw@outlook.com>
> ---
>  libavcodec/h274.c | 163 ++++++++++++++++++++++++++++++++++++++++++++++
>  libavcodec/h274.h |   7 ++
>  2 files changed, 170 insertions(+)
> 
> diff --git a/libavcodec/h274.c b/libavcodec/h274.c
> index 5709200322..9edc705042 100644
> --- a/libavcodec/h274.c
> +++ b/libavcodec/h274.c
> @@ -26,7 +26,11 @@
>   */
>  
>  #include "libavutil/avassert.h"
> +#include "libavutil/bswap.h"
> +#include "libavutil/crc.h"
>  #include "libavutil/imgutils.h"
> +#include "libavutil/md5.h"
> +#include "libavutil/mem.h"
>  
>  #include "h274.h"
>  
> @@ -790,3 +794,162 @@ static const int8_t R64T[64][64] = {
>           17, -16,  15, -14,  13, -12,  11, -10,   9,  -8,   7,  -6,   4,  -3,   2,  -1,
>      }
>  };
> +
> +static int verify_plane_md5(struct AVMD5 *ctx,
> +    const uint8_t *src, const int w, const int h, const int stride,
> +    const uint8_t *expected)
> +{
> +#define MD5_SIZE 16
> +    uint8_t md5[MD5_SIZE];
> +    av_md5_init(ctx);
> +    for (int j = 0; j < h; j++) {
> +        av_md5_update(ctx, src, w);
> +        src += stride;
> +    }
> +    av_md5_final(ctx, md5);
> +
> +    if (memcmp(md5, expected, MD5_SIZE))
> +        return AVERROR_INVALIDDATA;
> +
> +    return 0;
> +}
> +
> +static int verify_plane_crc(const uint8_t *src, const int w, const int h, const int stride,
> +    const uint8_t *expected)
> +{
> +    uint32_t crc = 0x0F1D;     // CRC-16-CCITT-AUG
> +    const AVCRC *ctx = av_crc_get_table(AV_CRC_16_CCITT);
> +
> +    for (int j = 0; j < h; j++) {
> +        crc = av_crc(ctx, crc, src, w);
> +        src += stride;
> +    }
> +    crc = av_bswap16(crc);
> +
> +    if (memcmp(&crc, expected, sizeof(uint16_t)))

This seems endian-dependent (as are the other checks). Why don't you
simply pass the proper CRC as uint16_t/uint32_t parameter?

> +        return AVERROR_INVALIDDATA;
> +
> +    return 0;
> +}
> +
> +#define CAL_CHECKSUM(pixel) (checksum + ((pixel) ^ xor_mask))
> +static int verify_plane_checksum(const uint8_t *src, const int w, const int h, const int stride, const int ps,
> +    const uint8_t *expected)
> +{
> +    uint32_t checksum = 0;
> +
> +    for (int y = 0; y < h; y++) {
> +        for (int x = 0; x < w; x++) {
> +            const int xor_mask = (x & 0xFF) ^ (y & 0xFF) ^ (x >> 8) ^ (y >> 8);
> +            checksum = CAL_CHECKSUM(src[x << ps]);
> +            if (ps)
> +                checksum = CAL_CHECKSUM(src[(x << ps) + 1]);

Why don't you use checksum += instead of using checksum in the
CAL_CHECKSUM macro in a hardcoded manner?

> +        }
> +        src += stride;
> +    }
> +
> +    if (checksum != *(uint32_t*)expected)
> +        return AVERROR_INVALIDDATA;
> +
> +    return 0;
> +}
> +
> +static const uint8_t *get_plane_hash(const H274SEIPictureHash *h, const int plane)
> +{
> +    if (!h->hash_type)
> +        return h->md5[plane];
> +    if (h->hash_type == 1)
> +        return (uint8_t*)&h->crc[plane];
> +    return (uint8_t*)&h->checksum[plane];
> +}

This function seems completely useless; you should better pass the
proper expected value to the functions directly (by value for non-md5).

> +
> +enum {
> +    HASH_MD5SUM,
> +    HASH_CRC,
> +    HASH_CHECKSUM,
> +    HASH_LAST = HASH_CHECKSUM,
> +};
> +
> +struct H274HashContext {
> +    int type;
> +    struct AVMD5 *ctx;
> +};
> +
> +int ff_h274_hash_freep(H274HashContext **ctx)
> +{
> +    if (ctx && *ctx) {

Don't check for ctx. Passing a NULL to a freep-function is insane.

> +        H274HashContext *c = *ctx;
> +        if (c->ctx)
> +            av_free(c->ctx);
> +        av_freep(ctx);
> +    }
> +    return 0;

Why is this function returning anything?

> +}
> +
> +int ff_h274_hash_init(H274HashContext **ctx, const int type)
> +{
> +    H274HashContext *c;
> +
> +    if (type > HASH_LAST || !ctx)
> +        return AVERROR(EINVAL);
> +
> +    c = *ctx;
> +    if (c) {
> +        if (c->type != type) {
> +            if (c->type == HASH_MD5SUM)
> +                av_freep(&c->ctx);
> +            c->type = type;
> +        }
> +    } else {
> +        *ctx = c = av_mallocz(sizeof(H274HashContext));

Why is this separately allocated?

> +        if (!c)
> +            return AVERROR(ENOMEM);
> +        c->type = type;
> +    }
> +
> +    if (type == HASH_MD5SUM && !c->ctx) {
> +        c->ctx = av_md5_alloc();
> +        if (!c->ctx)
> +            return AVERROR(ENOMEM);
> +    }
> +
> +    return 0;
> +}
> +
> +int ff_h274_hash_verify(H274HashContext *c, const H274SEIPictureHash *hash,
> +    const AVFrame *frame, const int coded_width, const int coded_height)
> +{
> +    const AVPixFmtDescriptor *desc;
> +    int err = 0;
> +
> +    if (!c || !hash || !frame)
> +        return AVERROR(EINVAL);
> +
> +    if (c->type != hash->hash_type)
> +        return AVERROR(EINVAL);
> +
> +    desc = av_pix_fmt_desc_get(frame->format);
> +    if (!desc)
> +        return AVERROR(EINVAL);
> +
> +    for (int i = 0; i < desc->nb_components; i++) {
> +        const int w             = i ? (coded_width  >> desc->log2_chroma_w) : coded_width;
> +        const int h             = i ? (coded_height >> desc->log2_chroma_h) : coded_height;
> +        const int ps            = desc->comp[i].step - 1;
> +        const uint8_t *expected = get_plane_hash(hash, i);
> +        const uint8_t *src      = frame->data[i];
> +        const int stride        = frame->linesize[i];
> +
> +        if (c->type == HASH_MD5SUM)
> +            err = verify_plane_md5(c->ctx, src, w << ps, h, stride, expected);
> +        else if (c->type == HASH_CRC)
> +            err = verify_plane_crc(src, w << ps, h, stride, expected);
> +        else if (c->type == HASH_CHECKSUM)
> +            err = verify_plane_checksum(src, w, h, stride, ps, expected);
> +        if (err < 0)
> +            goto fail;
> +    }
> +
> +fail:
> +    return err;
> +}
> diff --git a/libavcodec/h274.h b/libavcodec/h274.h
> index e1803edaf3..e2bb1aec55 100644
> --- a/libavcodec/h274.h
> +++ b/libavcodec/h274.h
> @@ -64,6 +64,8 @@ int ff_h274_apply_film_grain(AVFrame *out, const AVFrame *in,
>                               H274FilmGrainDatabase *db,
>                               const AVFilmGrainParams *params);
>  
> +typedef struct H274HashContext H274HashContext;
> +
>  typedef struct H274SEIPictureHash {
>      int present;
>      union {
> @@ -74,4 +76,9 @@ typedef struct H274SEIPictureHash {
>      uint8_t hash_type;
>  } H274SEIPictureHash;
>  
> +int ff_h274_hash_init(H274HashContext **c, int type);
> +int ff_h274_hash_verify(H274HashContext *c, const H274SEIPictureHash *hash,
> +    const AVFrame *frame, int coded_width, int coded_height);
> +int ff_h274_hash_freep(H274HashContext **c);
> +
>  #endif /* AVCODEC_H274_H */

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