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

[notmuch] / sprinter-json.c

diff --git a/sprinter-json.c b/sprinter-json.c
new file mode 100644 (file)
index 0000000..4649655
--- /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;
+}