Add structured output formatter for JSON and plain text (but don't use them yet).

Using the new structured printer support in sprinter.h, implement
sprinter_json_create, which returns a new JSON structured output
formatter. The formatter prints output similar to the existing JSON, but
with differences in whitespace (mostly newlines, --output=summary prints
the entire message summary on one line, not split across multiple lines).

Also implement a "structured" formatter for plain text that prints
prefixed strings, to be used with notmuch-search.c plain text output.

1 files changed, 187 insertions, 0 deletions

diff --git a/sprinter-json.c b/sprinter-json.c
new file mode 100644
index 00000000..46496551
--- /dev/null
+++ b/sprinter-json.c
@@ -0,0 +1,187 @@
+#include <stdbool.h>
+#include <stdio.h>
+#include <talloc.h>
+#include "sprinter.h"
+
+struct sprinter_json {
+    struct sprinter vtable;
+    FILE *stream;
+    /* Top of the state stack, or NULL if the printer is not currently
+     * inside any aggregate types. */
+    struct json_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 json_state {
+    struct json_state *parent;
+    /* True if nothing has been printed in this aggregate yet.
+     * Suppresses the comma before a value. */
+    notmuch_bool_t first;
+    /* 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 comma. */
+static struct sprinter_json *
+json_begin_value (struct sprinter *sp)
+{
+    struct sprinter_json *spj = (struct sprinter_json *) sp;
+
+    if (spj->state) {
+	if (! spj->state->first) {
+	    fputc (',', spj->stream);
+	    if (spj->insert_separator) {
+		fputc ('\n', spj->stream);
+		spj->insert_separator = FALSE;
+	    } else {
+		fputc (' ', spj->stream);
+	    }
+	} else {
+	    spj->state->first = FALSE;
+	}
+    }
+    return spj;
+}
+
+/* Helper function to begin an aggregate type.  Prints the open
+ * character and pushes a new state frame. */
+static void
+json_begin_aggregate (struct sprinter *sp, char open, char close)
+{
+    struct sprinter_json *spj = json_begin_value (sp);
+    struct json_state *state = talloc (spj, struct json_state);
+
+    fputc (open, spj->stream);
+    state->parent = spj->state;
+    state->first = TRUE;
+    state->close = close;
+    spj->state = state;
+}
+
+static void
+json_begin_map (struct sprinter *sp)
+{
+    json_begin_aggregate (sp, '{', '}');
+}
+
+static void
+json_begin_list (struct sprinter *sp)
+{
+    json_begin_aggregate (sp, '[', ']');
+}
+
+static void
+json_end (struct sprinter *sp)
+{
+    struct sprinter_json *spj = (struct sprinter_json *) sp;
+    struct json_state *state = spj->state;
+
+    fputc (spj->state->close, spj->stream);
+    spj->state = state->parent;
+    talloc_free (state);
+    if (spj->state == NULL)
+	fputc ('\n', spj->stream);
+}
+
+static void
+json_string (struct sprinter *sp, const char *val)
+{
+    static const char *const escapes[] = {
+	['\"'] = "\\\"", ['\\'] = "\\\\", ['\b'] = "\\b",
+	['\f'] = "\\f",  ['\n'] = "\\n",  ['\t'] = "\\t"
+    };
+    struct sprinter_json *spj = json_begin_value (sp);
+
+    fputc ('"', spj->stream);
+    for (; *val; ++val) {
+	unsigned char ch = *val;
+	if (ch < ARRAY_SIZE (escapes) && escapes[ch])
+	    fputs (escapes[ch], spj->stream);
+	else if (ch >= 32)
+	    fputc (ch, spj->stream);
+	else
+	    fprintf (spj->stream, "\\u%04x", ch);
+    }
+    fputc ('"', spj->stream);
+}
+
+static void
+json_integer (struct sprinter *sp, int val)
+{
+    struct sprinter_json *spj = json_begin_value (sp);
+
+    fprintf (spj->stream, "%d", val);
+}
+
+static void
+json_boolean (struct sprinter *sp, notmuch_bool_t val)
+{
+    struct sprinter_json *spj = json_begin_value (sp);
+
+    fputs (val ? "true" : "false", spj->stream);
+}
+
+static void
+json_null (struct sprinter *sp)
+{
+    struct sprinter_json *spj = json_begin_value (sp);
+
+    fputs ("null", spj->stream);
+}
+
+static void
+json_map_key (struct sprinter *sp, const char *key)
+{
+    struct sprinter_json *spj = (struct sprinter_json *) sp;
+
+    json_string (sp, key);
+    fputs (": ", spj->stream);
+    spj->state->first = TRUE;
+}
+
+static void
+json_set_prefix (unused (struct sprinter *sp), unused (const char *name))
+{
+}
+
+static void
+json_separator (struct sprinter *sp)
+{
+    struct sprinter_json *spj = (struct sprinter_json *) sp;
+
+    spj->insert_separator = TRUE;
+}
+
+struct sprinter *
+sprinter_json_create (const void *ctx, FILE *stream)
+{
+    static const struct sprinter_json template = {
+	.vtable = {
+	    .begin_map = json_begin_map,
+	    .begin_list = json_begin_list,
+	    .end = json_end,
+	    .string = json_string,
+	    .integer = json_integer,
+	    .boolean = json_boolean,
+	    .null = json_null,
+	    .map_key = json_map_key,
+	    .separator = json_separator,
+	    .set_prefix = json_set_prefix,
+	    .is_text_printer = FALSE,
+	}
+    };
+    struct sprinter_json *res;
+
+    res = talloc (ctx, struct sprinter_json);
+    if (! res)
+	return NULL;
+
+    *res = template;
+    res->stream = stream;
+    return &res->vtable;
+}