[PATCH v4 1/5] Adding an S-expression structured output printer.

[Peter Feigl <craven@gmx.net>]

This commit adds a structured output printer for Lisp
S-Expressions. Later commits will use this printer in notmuch search,
show and reply.

The structure is the same as json, but:
- arrays are written as lists: ("foo" "bar" "baaz" 1 2 3)
- maps are written as p-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 | 238 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 sprinter.h      |   4 +
 3 files changed, 243 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..8f84eed
--- /dev/null
+++ b/sprinter-sexp.c
@@ -0,0 +1,238 @@
+/* notmuch - Not much of an email program, (just index and search)
+ *
+ * Copyright © 2012 Peter Feigl
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Author: Peter Feigl <peter.feigl@gmx.at>
+ */
+
+#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;
+};
+
+/* 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 {
+		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)
+{
+    struct sprinter_sexp *sps = sexp_begin_value (sp);
+    struct sexp_state *state = talloc (sps, struct sexp_state);
+    fputc ('(', sps->stream);
+    state->parent = sps->state;
+    state->first = TRUE;
+    sps->state = state;
+}
+
+static void
+sexp_begin_map (struct sprinter *sp)
+{
+    sexp_begin_aggregate (sp);
+}
+
+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;
+
+    fputc (')', sps->stream);
+    sps->state = state->parent;
+    talloc_free (state);
+    if (sps->state == NULL)
+	fputc ('\n', sps->stream);
+}
+
+static void
+sexp_string_len (struct sprinter *sp, const char *val, size_t len)
+{
+    /* Some characters need escaping. " and \ work fine in all Lisps,
+     * \n is not supported in CL, but all others work fine.
+     * Characters below 32 are printed as \123o (three-digit 
+     * octals), which work fine in most Schemes and Emacs. */
+    static const char *const escapes[] = {
+	['\"'] = "\\\"", ['\\'] = "\\\\",  ['\n'] = "\\n"
+    };
+    struct sprinter_sexp *sps = sexp_begin_value (sp);
+
+    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, "\\%03oo", ch);
+    }
+    fputc ('"', sps->stream);
+}
+
+static void
+sexp_string (struct sprinter *sp, const char *val)
+{
+    if (val == NULL)
+	val = "";
+    sexp_string_len (sp, val, strlen (val));
+}
+
+/* Prints a symbol, i.e. the name preceded by a colon. This should work
+ * in all Lisps, at least as a symbol, if not as a proper keyword */
+static void
+sexp_symbol (struct sprinter *sp, const char *val)
+{
+    static const char illegal_characters[] = {
+	' ', '\t', '\n'
+    };
+    unsigned int i = 0;
+    struct sprinter_sexp *sps = (struct sprinter_sexp *) sp;
+
+    if (val == NULL)
+	INTERNAL_ERROR ("illegal symbol NULL");
+
+    for(i = 0; i < ARRAY_SIZE (illegal_characters); i++) {
+	if(strchr(val, illegal_characters[i]) != NULL) {
+	    INTERNAL_ERROR ("illegal character in symbol %s", val);
+	}
+    }
+    fputc (':', sps->stream);
+    fputs (val, sps->stream);
+}
+
+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 && ! sps->state->first)
+	fputc (' ', sps->stream);
+
+    sps->state->first = FALSE;
+    sexp_symbol (sp, key);
+}
+
+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;
+}
diff --git a/sprinter.h b/sprinter.h
index 912a526..59776a9 100644
--- a/sprinter.h
+++ b/sprinter.h
@@ -70,4 +70,8 @@ sprinter_text_create (const void *ctx, FILE *stream);
 struct sprinter *
 sprinter_json_create (const void *ctx, FILE *stream);
 
+/* Create a new structure printer that emits S-Expressions. */
+struct sprinter *
+sprinter_sexp_create (const void *ctx, FILE *stream);
+
 #endif // NOTMUCH_SPRINTER_H
-- 
1.8.0