[Libguestfs] [PATCH v2 2/5] lib: qemu: Factor out common code for reading and writing cache files.

[Pino Toscano]

On Tuesday, 12 September 2017 14:29:13 CEST Richard W.M. Jones wrote:
> +/**
> + * Generic functions for reading and writing the cache files, used
> + * where we are just reading and writing plain text strings.
> + */
> +static int
> +generic_read_cache (guestfs_h *g, const char *filename, char **strp)
> +{
> +  if (access (filename, R_OK) == -1 && errno == ENOENT)
> +    return 0;                   /* no cache, run the test instead */

This will go ahead if access() failed for any other error though;
IMHO a better check could be:

  if (access (filename, R_OK) == -1) {
    if (errno == ENOENT)
      return 0;                   /* no cache, run the test instead */
    perrorf (g, "access: %s", filename);
    return -1;
  }

> +static int
> +generic_write_cache (guestfs_h *g, const char *filename, const char *str)
> +{
> +  CLEANUP_FCLOSE FILE *fp = fopen (filename, "w");
> +  if (fp == NULL) {
> +    perrorf (g, "%s", filename);
> +    return -1;
> +  }
> +
> +  if (fprintf (fp, "%s", str) == -1) {
> +    perrorf (g, "%s: write", filename);
> +    return -1;
> +  }
> +
> +  return 0;
> +}

While this is the same code already used, IMHO it would make more sense
to use open/write directly (since we have a buffer already, it will be
faster than using sprintf); there are snippets that call write() in a
loop until the whole buffer is written in different parts of the
library, so factorizing them could help.

Thanks,
-- 
Pino Toscano
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