Re: [PATCH v2 6/6] gzip: drop huffman code table tracking

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 17/04/2024 3:37 pm, Daniel P. Smith wrote:
> The "tracking" bits does not appear to be used, so dropping from the code.
>
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> ---
>  xen/common/gzip/inflate.c | 6 ------
>  1 file changed, 6 deletions(-)
>
> diff --git a/xen/common/gzip/inflate.c b/xen/common/gzip/inflate.c
> index c18ce20210b0..15bc187c2bbe 100644
> --- a/xen/common/gzip/inflate.c
> +++ b/xen/common/gzip/inflate.c
> @@ -264,8 +264,6 @@ static const int dbits = 6;          /* bits in base 
> distance lookup table */
>  #define BMAX 16         /* maximum bit length of any code (16 for explode) */
>  #define N_MAX 288       /* maximum number of codes in any set */
>  
> -static unsigned __initdata hufts;      /* track memory usage */
> -
>  /*
>   * Given a list of code lengths and a maximum table size, make a set of
>   * tables to decode that set of codes.  Return zero on success, one if
> @@ -445,7 +443,6 @@ static int __init huft_build(
>                      goto out;
>                  }
>                  DEBG1("4 ");
> -                hufts += z + 1;         /* track memory usage */
>                  *t = q + 1;             /* link to list for huft_free() */
>                  *(t = &(q->v.t)) = (struct huft *)NULL;
>                  u[h] = ++q;             /* table starts after link */
> @@ -1028,15 +1025,12 @@ static int __init inflate(struct gzip_state *s)
>      /* decompress until the last block */
>      h = 0;
>      do {
> -        hufts = 0;
>  #ifdef ARCH_HAS_DECOMP_WDOG
>          arch_decomp_wdog();
>  #endif
>          r = inflate_block(s, &e);
>          if (r)
>              return r;
> -        if (hufts > h)
> -            h = hufts;
>      } while (!e);

With 'hufts' removed, the local variable 'h' is now dead too.  It gets
read inside an #ifdef DEBUG, but as it's rendering a unqualified number
to stderr, it can also be deleted.

Specifically, I recommend this additional delta:

diff --git a/xen/common/gzip/inflate.c b/xen/common/gzip/inflate.c
index 15bc187c2bbe..13015bb45f4a 100644
--- a/xen/common/gzip/inflate.c
+++ b/xen/common/gzip/inflate.c
@@ -1015,7 +1015,6 @@ static int __init inflate(struct gzip_state *s)
 {
     int e;                /* last block flag */
     int r;                /* result code */
-    unsigned h;           /* maximum struct huft's malloc'ed */
 
     /* initialize window, bit buffer */
     wp = 0;
@@ -1023,7 +1022,6 @@ static int __init inflate(struct gzip_state *s)
     s->bb = 0;
 
     /* decompress until the last block */
-    h = 0;
     do {
 #ifdef ARCH_HAS_DECOMP_WDOG
         arch_decomp_wdog();
@@ -1045,9 +1043,6 @@ static int __init inflate(struct gzip_state *s)
     flush_output(s, wp);
 
     /* return success */
-#ifdef DEBUG
-    fprintf(stderr, "<%u> ", h);
-#endif /* DEBUG */
     return 0;
 }
 

which I'm happy to fold on commit.

~Andrew