[PATCH 1/3] Adding an S-expression structured output printer.

[Tomi Ollila]

On Sat, Dec 01 2012, Mark Walters wrote:

> Hi
>
> Overall I like the series: I think I agree with all of Jani's
> comments. 
>
> My one extra comment is that I think we should decide on whether we also
> want a sexp plist version. I think we might want one for the emacs
> front-end as that currently uses plists for everything.
>
> If we do we might want to change the names a little, both for functions
> and options (eg sexp_a and sexp_p or something). Probably a lot of
> sprinter-sexp would be common to both versions.

This is an important question that needs to be addressed fast: options
are:

1) have options to spit both alist & plist formats
2) when converting emacs to use s-expressions, convert it to use alists
3) start using plists instead of alists in Peter's android client


In case (1) is chosen then we just need to support one more format.

How much work would it involve to convert emacs to receive content in
alists (and how feasible would that be)?

How much work would it require in Peter's client to use plists (and how
feasible would that be)?

>
> Best wishes
>
> Mark

Tomi


>
>
> On Fri, 30 Nov 2012, Peter Feigl <craven at gmx.net> wrote:
>> This commit adds an sprinter for Lisp S-Expressions. Later commits will
>> use this printer.
>>
>> The structure is the same as json, but:
>> - arrays are written as lists: ("foo" "bar" "baaz" 1 2 3)
>> - maps are written as a-lists: ((key "value") (other-key "other-value"))
>> - true is written as t
>> - false is written as nil
>> - null is written as nil
>> ---
>>  Makefile.local  |   1 +
>>  sprinter-sexp.c | 235 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 236 insertions(+)
>>  create mode 100644 sprinter-sexp.c
>>
>> diff --git a/Makefile.local b/Makefile.local
>> index 2b91946..0db1713 100644
>> --- a/Makefile.local
>> +++ b/Makefile.local
>> @@ -270,6 +270,7 @@ notmuch_client_srcs =		\
>>  	notmuch-tag.c		\
>>  	notmuch-time.c		\
>>  	sprinter-json.c		\
>> +	sprinter-sexp.c		\
>>  	sprinter-text.c		\
>>  	query-string.c		\
>>  	mime-node.c		\
>> diff --git a/sprinter-sexp.c b/sprinter-sexp.c
>> new file mode 100644
>> index 0000000..8401c52
>> --- /dev/null
>> +++ b/sprinter-sexp.c
>> @@ -0,0 +1,235 @@
>> +#include <stdbool.h>
>> +#include <stdio.h>
>> +#include <talloc.h>
>> +#include "sprinter.h"
>> +
>> +struct sprinter_sexp {
>> +    struct sprinter vtable;
>> +    FILE *stream;
>> +    /* Top of the state stack, or NULL if the printer is not currently
>> +     * inside any aggregate types. */
>> +    struct sexp_state *state;
>> +
>> +    /* A flag to signify that a separator should be inserted in the
>> +     * output as soon as possible.
>> +     */
>> +    notmuch_bool_t insert_separator;
>> +};
>> +
>> +struct sexp_state {
>> +    struct sexp_state *parent;
>> +
>> +    /* True if nothing has been printed in this aggregate yet.
>> +     * Suppresses the space before a value. */
>> +    notmuch_bool_t first;
>> +
>> +    /* True if the state is a map state.
>> +       Used to add a space between key/value pairs. */
>> +    notmuch_bool_t in_map;
>> +
>> +    /* The character that closes the current aggregate. */
>> +    char close;
>> +};
>> +
>> +/* Helper function to set up the stream to print a value.  If this
>> + * value follows another value, prints a space. */
>> +static struct sprinter_sexp *
>> +sexp_begin_value (struct sprinter *sp)
>> +{
>> +    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
>> +
>> +    if (sps->state) {
>> +        if (! sps->state->first) {
>> +            if (sps->insert_separator) {
>> +                fputc ('\n', sps->stream);
>> +                sps->insert_separator = FALSE;
>> +            } else {
>> +                if( ! sps->state->in_map)
>> +                    fputc (' ', sps->stream);
>> +            }
>> +        } else {
>> +            sps->state->first = FALSE;
>> +        }
>> +    }
>> +    return sps;
>> +}
>> +
>> +/* Helper function to begin an aggregate type.  Prints the open
>> + * character and pushes a new state frame. */
>> +static void
>> +sexp_begin_aggregate (struct sprinter *sp, char open, char close)
>> +{
>> +    struct sprinter_sexp *sps = sexp_begin_value (sp);
>> +    struct sexp_state *state = talloc (sps, struct sexp_state);
>> +    fputc (open, sps->stream);
>> +    state->parent = sps->state;
>> +    state->first = TRUE;
>> +    state->in_map = FALSE;
>> +    state->close = close;
>> +    sps->state = state;
>> +}
>> +
>> +static void
>> +sexp_begin_map (struct sprinter *sp)
>> +{
>> +    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
>> +    sexp_begin_aggregate (sp, '(', ')');
>> +    sps->state->in_map = TRUE;
>> +}
>> +
>> +static void
>> +sexp_begin_list (struct sprinter *sp)
>> +{
>> +    sexp_begin_aggregate (sp, '(', ')');
>> +}
>> +
>> +static void
>> +sexp_end (struct sprinter *sp)
>> +{
>> +    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
>> +    struct sexp_state *state = sps->state;
>> +
>> +    if (sps->state->in_map)
>> +        fputc (')', sps->stream);
>> +    fputc (sps->state->close, sps->stream);
>> +    sps->state = state->parent;
>> +    talloc_free (state);
>> +    if (sps->state == NULL)
>> +        fputc ('\n', sps->stream);
>> +}
>> +
>> +/* This implementation supports embedded NULs as allowed by the JSON
>> + * specification and Unicode.  Support for *parsing* embedded NULs
>> + * varies, but is generally not a problem outside of C-based parsers
>> + * (Python's json module and Emacs' json.el take embedded NULs in
>> + * stride). */
>> +static void
>> +sexp_string_len_internal (struct sprinter *sp, const char *val, size_t len, notmuch_bool_t quote)
>> +{
>> +    static const char *const escapes[] = {
>> +        ['\"'] = "\\\"", ['\\'] = "\\\\", ['\b'] = "\\b",
>> +        ['\f'] = "\\f",  ['\n'] = "\\n",  ['\t'] = "\\t"
>> +    };
>> +    struct sprinter_sexp *sps = sexp_begin_value (sp);
>> +
>> +    if(quote)
>> +        fputc ('"', sps->stream);
>> +    for (; len; ++val, --len) {
>> +        unsigned char ch = *val;
>> +        if (ch < ARRAY_SIZE (escapes) && escapes[ch])
>> +            fputs (escapes[ch], sps->stream);
>> +        else if (ch >= 32)
>> +            fputc (ch, sps->stream);
>> +        else
>> +            fprintf (sps->stream, "\\u%04x", ch);
>> +    }
>> +    if(quote)
>> +        fputc ('"', sps->stream);
>> +}
>> +
>> +static void
>> +sexp_string_len (struct sprinter *sp, const char *val, size_t len)
>> +{
>> +    sexp_string_len_internal (sp, val, len, TRUE); /* print quoted */
>> +}
>> +
>> +static void
>> +sexp_symbol_len (struct sprinter *sp, const char *val, size_t len)
>> +{
>> +    sexp_string_len_internal (sp, val, len, FALSE); /* print unquoted */
>> +}
>> +
>> +static void
>> +sexp_string (struct sprinter *sp, const char *val)
>> +{
>> +    if (val == NULL)
>> +        val = "";
>> +    sexp_string_len (sp, val, strlen (val));
>> +}
>> +
>> +static void
>> +sexp_symbol (struct sprinter *sp, const char *val)
>> +{
>> +    if (val == NULL)
>> +        val = "";
>> +    sexp_symbol_len (sp, val, strlen (val));
>> +}
>> +
>> +static void
>> +sexp_integer (struct sprinter *sp, int val)
>> +{
>> +    struct sprinter_sexp *sps = sexp_begin_value (sp);
>> +
>> +    fprintf (sps->stream, "%d", val);
>> +}
>> +
>> +static void
>> +sexp_boolean (struct sprinter *sp, notmuch_bool_t val)
>> +{
>> +    struct sprinter_sexp *sps = sexp_begin_value (sp);
>> +
>> +    fputs (val ? "t" : "nil", sps->stream);
>> +}
>> +
>> +static void
>> +sexp_null (struct sprinter *sp)
>> +{
>> +    struct sprinter_sexp *sps = sexp_begin_value (sp);
>> +
>> +    fputs ("nil", sps->stream);
>> +}
>> +
>> +static void
>> +sexp_map_key (struct sprinter *sp, const char *key)
>> +{
>> +    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
>> +
>> +    if( sps->state->in_map && ! sps->state->first)
>> +        fputs (") ", sps->stream);
>> +    fputc ('(', sps->stream);
>> +    sexp_symbol (sp, key);
>> +    fputc (' ', sps->stream);
>> +}
>> +
>> +static void
>> +sexp_set_prefix (unused (struct sprinter *sp), unused (const char *name))
>> +{
>> +}
>> +
>> +static void
>> +sexp_separator (struct sprinter *sp)
>> +{
>> +    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
>> +
>> +    sps->insert_separator = TRUE;
>> +}
>> +
>> +struct sprinter *
>> +sprinter_sexp_create (const void *ctx, FILE *stream)
>> +{
>> +    static const struct sprinter_sexp template = {
>> +        .vtable = {
>> +            .begin_map = sexp_begin_map,
>> +            .begin_list = sexp_begin_list,
>> +            .end = sexp_end,
>> +            .string = sexp_string,
>> +            .string_len = sexp_string_len,
>> +            .integer = sexp_integer,
>> +            .boolean = sexp_boolean,
>> +            .null = sexp_null,
>> +            .map_key = sexp_map_key,
>> +            .separator = sexp_separator,
>> +            .set_prefix = sexp_set_prefix,
>> +            .is_text_printer = FALSE,
>> +        }
>> +    };
>> +    struct sprinter_sexp *res;
>> +
>> +    res = talloc (ctx, struct sprinter_sexp);
>> +    if (! res)
>> +        return NULL;
>> +
>> +    *res = template;
>> +    res->stream = stream;
>> +    return &res->vtable;
>> +}
>> -- 
>> 1.8.0
>>
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