[PATCH v3 2/5] util: Function to parse boolean term queries

[Austin Clements]

On Sat, 29 Dec 2012, Tomi Ollila <tomi.ollila at iki.fi> wrote:
> On Fri, Dec 28 2012, Austin Clements <amdragon at MIT.EDU> wrote:
>
>> This parses the subset of Xapian's boolean term quoting rules that are
>> used by make_boolean_term.  This is provided as a generic string
>> utility, but will be used shortly in notmuch restore to parse and
>> optimize for ID queries.
>> ---
>>  util/string-util.c |   55 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  util/string-util.h |   11 +++++++++++
>>  2 files changed, 66 insertions(+)
>>
>> diff --git a/util/string-util.c b/util/string-util.c
>> index e4bea21..83b4953 100644
>> --- a/util/string-util.c
>> +++ b/util/string-util.c
>> @@ -96,3 +96,58 @@ make_boolean_term (void *ctx, const char *prefix, const char *term,
>>  
>>      return 0;
>>  }
>> +
>> +int
>> +parse_boolean_term (void *ctx, const char *str,
>> +		    char **prefix_out, char **term_out)
>> +{
>> +    *prefix_out = *term_out = NULL;
>> +
>> +    /* Parse prefix */
>> +    const char *pos = strchr (str, ':');
>> +    if (! pos)
>> +	goto FAIL;
>> +    *prefix_out = talloc_strndup (ctx, str, pos - str);
>> +    ++pos;
>> +
>> +    /* Implement de-quoting compatible with make_boolean_term. */
>> +    if (*pos == '"') {
>> +	char *out = talloc_array (ctx, char, strlen (pos));
>> +	int closed = 0;
>> +	*term_out = out;
>> +	/* Skip the opening quote, find the closing quote, and
>> +	 * un-double doubled internal quotes. */
>> +	for (++pos; *pos; ) {
>> +	    if (*pos == '"') {
>> +		++pos;
>> +		if (*pos != '"') {
>> +		    /* Found the closing quote. */
>> +		    closed = 1;
>> +		    break;
>> +		}
>> +	    }
>> +	    *out++ = *pos++;
>> +	}
>> +	/* Did the term terminate without a closing quote or is there
>> +	 * trailing text after the closing quote? */
>> +	if (!closed || *pos)
>> +	    goto FAIL;
>> +	*out = '\0';
>> +    } else {
>> +	const char *start = pos;
>> +	/* Check for text after the boolean term. */
>> +	while (*pos > ' ' && *pos != ')')
>> +	    ++pos;
>> +	if (*pos)
>> +	    goto FAIL;
>
> Mark pointed out a good case about trailing whitespace -- It would be nice
> if the core were lenient for such cases. I personally remember once wasting
> hours of work by just failing to notice trailing whitespace in one system
> so this subject is sensitive to me...

Will do.

> Another thing I saw earlyer today: make_boolean_term() checks
>
>    if (*in <= ' ' || *in == ')' || *in == '"' || (unsigned char)*in > 127)
>
> but here the check is only
>
>    while (*pos > ' ' && *pos != ')')
>
> I wonder whether it matters...

This is correct in a conservative way.  We quote things that we don't
strictly need to quote (for example, a double quote in the middle of a
term doesn't actually require the term to be quoted, but we do anyway),
but we look for the end of an unquoted term in exactly the same way
Xapian does.

> Everyting else looks good to me.
>
>
> Tomi
>
>> +	/* No trailing text; dup the string so the caller can free
>> +	 * it. */
>> +	*term_out = talloc_strdup (ctx, start);
>> +    }
>> +    return 0;
>> +
>> + FAIL:
>> +    talloc_free (*prefix_out);
>> +    talloc_free (*term_out);
>> +    return 1;
>> +}
>> diff --git a/util/string-util.h b/util/string-util.h
>> index b8844a3..43d49d0 100644
>> --- a/util/string-util.h
>> +++ b/util/string-util.h
>> @@ -33,4 +33,15 @@ char *strtok_len (char *s, const char *delim, size_t *len);
>>  int make_boolean_term (void *talloc_ctx, const char *prefix, const char *term,
>>  		       char **buf, size_t *len);
>>  
>> +/* Parse a boolean term query produced by make_boolean_term, returning
>> + * the prefix in *prefix_out and the term in *term_out.  *prefix_out
>> + * and *term_out will be talloc'd with context ctx.
>> + *
>> + * Return: 0 on success, non-zero on parse error (including trailing
>> + * data in str).
>> + */
>> +int
>> +parse_boolean_term (void *ctx, const char *str,
>> +		    char **prefix_out, char **term_out);
>> +
>>  #endif
>> -- 
>> 1.7.10.4
>>
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