[FFmpeg-devel] [PATCH] avutil/hash: Avoid relocations for hash names

[Andreas Rheinhardt]

Andreas Rheinhardt:
> These strings are so short (longest takes 11B) that using
> pointers is wasteful. Avoiding them also moves hashdesc
> into .rodata (from .data.rel.ro).
> 
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
> ---
>  libavutil/hash.c | 71 +++++++++++++++++++++++++++---------------------
>  1 file changed, 40 insertions(+), 31 deletions(-)
> 
> diff --git a/libavutil/hash.c b/libavutil/hash.c
> index 12333982fb..43f77852da 100644
> --- a/libavutil/hash.c
> +++ b/libavutil/hash.c
> @@ -38,22 +38,27 @@
>  #include "intreadwrite.h"
>  #include "mem.h"
>  
> +// ENTRY(HASH_TYPE, HASH_NAME, HASH_SIZE)
> +#define HASHES(ENTRY)                   \
> +    ENTRY(MD5,        "MD5",        16) \
> +    ENTRY(MURMUR3,    "murmur3",    16) \
> +    ENTRY(RIPEMD128,  "RIPEMD128",  16) \
> +    ENTRY(RIPEMD160,  "RIPEMD160",  20) \
> +    ENTRY(RIPEMD256,  "RIPEMD256",  32) \
> +    ENTRY(RIPEMD320,  "RIPEMD320",  40) \
> +    ENTRY(SHA160,     "SHA160",     20) \
> +    ENTRY(SHA224,     "SHA224",     28) \
> +    ENTRY(SHA256,     "SHA256",     32) \
> +    ENTRY(SHA512_224, "SHA512/224", 28) \
> +    ENTRY(SHA512_256, "SHA512/256", 32) \
> +    ENTRY(SHA384,     "SHA384",     48) \
> +    ENTRY(SHA512,     "SHA512",     64) \
> +    ENTRY(CRC32,      "CRC32",       4) \
> +    ENTRY(ADLER32,    "adler32",     4) \
> +
>  enum hashtype {
> -    MD5,
> -    MURMUR3,
> -    RIPEMD128,
> -    RIPEMD160,
> -    RIPEMD256,
> -    RIPEMD320,
> -    SHA160,
> -    SHA224,
> -    SHA256,
> -    SHA512_224,
> -    SHA512_256,
> -    SHA384,
> -    SHA512,
> -    CRC32,
> -    ADLER32,
> +#define HASH_TYPE(TYPE, NAME, SIZE) TYPE,
> +    HASHES(HASH_TYPE)
>      NUM_HASHES
>  };
>  
> @@ -64,25 +69,29 @@ typedef struct AVHashContext {
>      uint32_t crc;
>  } AVHashContext;
>  
> +#define HASH_MAX_SIZE(TYPE, NAME, SIZE) \
> +    HASH_MAX_SIZE_BEFORE_ ## TYPE,      \
> +    HASH_MAX_SIZE_UNTIL_ ## TYPE ## _MINUS_ONE = FFMAX(SIZE, HASH_MAX_SIZE_BEFORE_ ## TYPE) - 1,
> +enum {
> +    HASHES(HASH_MAX_SIZE)
> +    MAX_HASH_SIZE
> +};
> +_Static_assert(AV_HASH_MAX_SIZE >= MAX_HASH_SIZE, "AV_HASH_MAX_SIZE needs to be updated!");
> +
> +#define HASH_MAX_NAME_SIZE(TYPE, NAME, SIZE) \
> +    HASH_MAX_NAME_SIZE_BEFORE_ ## TYPE,      \
> +    HASH_MAX_NAME_SIZE_UNTIL_ ## TYPE ## _MINUS_ONE = FFMAX(sizeof(NAME), HASH_MAX_NAME_SIZE_BEFORE_ ## TYPE) - 1,
> +enum {
> +    HASHES(HASH_MAX_NAME_SIZE)
> +    MAX_HASH_NAME_SIZE
> +};
> +
>  static const struct {
> -    const char *name;
> +    const char name[MAX_HASH_NAME_SIZE];
>      int size;
>  } hashdesc[] = {
> -    [MD5]     = {"MD5",     16},
> -    [MURMUR3] = {"murmur3", 16},
> -    [RIPEMD128] = {"RIPEMD128", 16},
> -    [RIPEMD160] = {"RIPEMD160", 20},
> -    [RIPEMD256] = {"RIPEMD256", 32},
> -    [RIPEMD320] = {"RIPEMD320", 40},
> -    [SHA160]  = {"SHA160",  20},
> -    [SHA224]  = {"SHA224",  28},
> -    [SHA256]  = {"SHA256",  32},
> -    [SHA512_224]  = {"SHA512/224",  28},
> -    [SHA512_256]  = {"SHA512/256",  32},
> -    [SHA384]  = {"SHA384",  48},
> -    [SHA512]  = {"SHA512",  64},
> -    [CRC32]   = {"CRC32",    4},
> -    [ADLER32] = {"adler32",  4},
> +#define HASH_DESC(TYPE, NAME, SIZE) [TYPE] = { NAME, SIZE },
> +    HASHES(HASH_DESC)
>  };
>  
>  const char *av_hash_names(int i)

Will apply tomorrow unless there are objections.

- Andreas