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Re: [libvirt] [PATCH 3/5] util: virbuffer: introduce virBufferEscapeN



On Thu, Feb 23, 2017 at 04:26:58PM +0100, Pavel Hrdina wrote:
> Signed-off-by: Pavel Hrdina <phrdina redhat com>
> ---
>  src/libvirt_private.syms |   1 +
>  src/util/virbuffer.c     | 104 +++++++++++++++++++++++++++++++++++++++++++++++
>  src/util/virbuffer.h     |   2 +
>  tests/virbuftest.c       |  41 +++++++++++++++++++
>  4 files changed, 148 insertions(+)
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index e9c4d73779..6ce32f1101 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1286,6 +1286,7 @@ virBufferContentAndReset;
>  virBufferCurrentContent;
>  virBufferError;
>  virBufferEscape;
> +virBufferEscapeN;
>  virBufferEscapeSexpr;
>  virBufferEscapeShell;
>  virBufferEscapeString;
> diff --git a/src/util/virbuffer.c b/src/util/virbuffer.c
> index d582e7dbec..ad6b29951e 100644
> --- a/src/util/virbuffer.c
> +++ b/src/util/virbuffer.c
> @@ -33,6 +33,7 @@
>  #include "virbuffer.h"
>  #include "viralloc.h"
>  #include "virerror.h"
> +#include "virstring.h"
>  
>  
>  /* If adding more fields, ensure to edit buf.h to match
> @@ -588,6 +589,109 @@ virBufferEscape(virBufferPtr buf, char escape, const char *toescape,
>      VIR_FREE(escaped);
>  }
>  
> +
> +struct _virBufferEscapePair {
> +    char escape;
> +    char *toescape;
> +};
> +
> +
> +/**
> + * virBufferEscapeN:
> + * @buf: the buffer to append to
> + * @format: a printf like format string but with only one %s parameter
> + * @str: the string argument which needs to be escaped
> + * @...: the variable list of arguments composed
> + *
> + * The variable list of arguments @... must be composed of
> + * 'char escape, char *toescape' pairs followed by NULL.

So most of the complexity you have here is to deal with the ability
to turn a single character into a string of escaped characters. Unless
I'm missing something, you don't actually use that ability in practice.
If we make it more restrictive so you just have a 1-1 mapping we can
simplify the API & implementation. eg

  virBufferEscapeN(virBufferPtr buf,
                   const char *format,
                   const char *str,
                   const char *forbidden,
                   const char *replacements)

with strlen(forbidden) == strlen(replacements);


> + *
> + * This has the same functionality as virBufferEscape with the extension
> + * that allows to specify multiple pairs of chars that needs to be escaped.
> + */
> +void
> +virBufferEscapeN(virBufferPtr buf,
> +                 const char *format,
> +                 const char *str,
> +                 ...)
> +{
> +    int len;
> +    size_t i;
> +    char escape;
> +    char *toescape;
> +    char *toescapeall = NULL;
> +    char *escaped = NULL;
> +    char *out;
> +    const char *cur;
> +    struct _virBufferEscapePair escapeItem;
> +    struct _virBufferEscapePair *escapeList = NULL;
> +    size_t nescapeList = 0;
> +    va_list ap;
> +
> +    if ((format == NULL) || (buf == NULL) || (str == NULL))
> +        return;
> +
> +    if (buf->error)
> +        return;
> +
> +    va_start(ap, str);
> +
> +    while ((escape = va_arg(ap, int))) {
> +        if (!(toescape = va_arg(ap, char *))) {
> +            virBufferSetError(buf, errno);
> +            goto cleanup;
> +        }
> +
> +        escapeItem.escape = escape;
> +        escapeItem.toescape = toescape;
> +
> +        if (VIR_STRCAT_QUIET(toescapeall, toescape) < 0) {
> +            virBufferSetError(buf, errno);
> +            goto cleanup;
> +        }
> +
> +        if (VIR_APPEND_ELEMENT_QUIET(escapeList, nescapeList, escapeItem) < 0) {
> +            virBufferSetError(buf, errno);
> +            goto cleanup;
> +        }
> +    }

This whole loop would go away with the simpler API contract, which
nicely avoids doing allocations in the loop body.


> +    len = strlen(str);
> +    if (strcspn(str, toescapeall) == len) {
> +        virBufferAsprintf(buf, format, str);
> +        goto cleanup;
> +    }
> +
> +    if (xalloc_oversized(2, len) ||
> +        VIR_ALLOC_N_QUIET(escaped, 2 * len + 1) < 0) {
> +        virBufferSetError(buf, errno);
> +        goto cleanup;
> +    }
> +
> +    cur = str;
> +    out = escaped;
> +    while (*cur != 0) {
> +        for (i = 0; i < nescapeList; i++) {
> +            if (strchr(escapeList[i].toescape, *cur)) {
> +                *out++ = escapeList[i].escape;
> +                break;
> +            }
> +        }
> +        *out++ = *cur;
> +        cur++;
> +    }
> +    *out = 0;
> +
> +    virBufferAsprintf(buf, format, escaped);
> +
> + cleanup:
> +    va_end(ap);
> +    VIR_FREE(toescapeall);
> +    VIR_FREE(escapeList);
> +    VIR_FREE(escaped);
> +}

Regards,
Daniel
-- 
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