Re: [PATCH v5] json_writer: new routines to create data in JSON format

[Wink Saville]

On Tue, Mar 27, 2018 at 2:02 PM  wrote:
>
> From: Jeff Hostetler 
>
> Add a series of jw_ routines and "struct json_writer" structure to compose
> JSON data.  The resulting string data can then be output by commands wanting
> to support a JSON output format.



>
>
>
>  void jw_object_intmax(struct json_writer *jw, const char *key, intmax_t 
> value)
> +{
> +   object_common(jw, key);
> +   strbuf_addf(>json, "%"PRIdMAX, (intmax_t)value);

Cast is not necessary.

> +}
> +



>
> +void jw_array_intmax(struct json_writer *jw, intmax_t value)
> +{
> +   array_common(jw);
> +   strbuf_addf(>json, "%"PRIdMAX, (intmax_t)value);

Cast is not necessary

>
> +}
> +



-- Wink

[PATCH v5] json_writer: new routines to create data in JSON format

[git]

From: Jeff Hostetler 

Add a series of jw_ routines and "struct json_writer" structure to compose
JSON data.  The resulting string data can then be output by commands wanting
to support a JSON output format.

The json-writer routines can be used to generate structured data in a
JSON-like format.  We say "JSON-like" because we do not enforce the Unicode
(usually UTF-8) requirement on string fields.  Internally, Git does not
necessarily have Unicode/UTF-8 data for most fields, so it is currently
unclear the best way to enforce that requirement.  For example, on Linx
pathnames can contain arbitrary 8-bit character data, so a command like
"status" would not know how to encode the reported pathnames.  We may want
to revisit this (or double encode such strings) in the future.

The initial use for the json-writer routines is for generating telemetry
data for executed Git commands.  Later, we may want to use them in other
commands, such as status.

Helped-by: René Scharfe 
Helped-by: Wink Saville 
Helped-by: Ramsay Jones 
Signed-off-by: Jeff Hostetler 
---
 Makefile|   2 +
 json-writer.c   | 394 ++
 json-writer.h   |  91 +++
 t/helper/test-json-writer.c | 572 
 t/t0019-json-writer.sh  | 253 
 5 files changed, 1312 insertions(+)
 create mode 100644 json-writer.c
 create mode 100644 json-writer.h
 create mode 100644 t/helper/test-json-writer.c
 create mode 100755 t/t0019-json-writer.sh

diff --git a/Makefile b/Makefile
index 1a9b23b..57f58e6 100644
--- a/Makefile
+++ b/Makefile
@@ -662,6 +662,7 @@ TEST_PROGRAMS_NEED_X += test-fake-ssh
 TEST_PROGRAMS_NEED_X += test-genrandom
 TEST_PROGRAMS_NEED_X += test-hashmap
 TEST_PROGRAMS_NEED_X += test-index-version
+TEST_PROGRAMS_NEED_X += test-json-writer
 TEST_PROGRAMS_NEED_X += test-lazy-init-name-hash
 TEST_PROGRAMS_NEED_X += test-line-buffer
 TEST_PROGRAMS_NEED_X += test-match-trees
@@ -815,6 +816,7 @@ LIB_OBJS += hashmap.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
 LIB_OBJS += ident.o
+LIB_OBJS += json-writer.o
 LIB_OBJS += kwset.o
 LIB_OBJS += levenshtein.o
 LIB_OBJS += line-log.o
diff --git a/json-writer.c b/json-writer.c
new file mode 100644
index 000..1b49158
--- /dev/null
+++ b/json-writer.c
@@ -0,0 +1,394 @@
+#include "cache.h"
+#include "json-writer.h"
+
+void jw_init(struct json_writer *jw)
+{
+   strbuf_reset(>json);
+   strbuf_reset(>open_stack);
+   jw->first = 0;
+   jw->pretty = 0;
+}
+
+void jw_release(struct json_writer *jw)
+{
+   strbuf_release(>json);
+   strbuf_release(>open_stack);
+}
+
+/*
+ * Append JSON-quoted version of the given string to 'out'.
+ */
+static void append_quoted_string(struct strbuf *out, const char *in)
+{
+   unsigned char c;
+
+   strbuf_addch(out, '"');
+   while ((c = *in++) != '\0') {
+   if (c == '"')
+   strbuf_addstr(out, "\\\"");
+   else if (c == '\\')
+   strbuf_addstr(out, "");
+   else if (c == '\n')
+   strbuf_addstr(out, "\\n");
+   else if (c == '\r')
+   strbuf_addstr(out, "\\r");
+   else if (c == '\t')
+   strbuf_addstr(out, "\\t");
+   else if (c == '\f')
+   strbuf_addstr(out, "\\f");
+   else if (c == '\b')
+   strbuf_addstr(out, "\\b");
+   else if (c < 0x20)
+   strbuf_addf(out, "\\u%04x", c);
+   else
+   strbuf_addch(out, c);
+   }
+   strbuf_addch(out, '"');
+}
+
+static inline void indent_pretty(struct json_writer *jw)
+{
+   int k;
+
+   if (!jw->pretty)
+   return;
+
+   for (k = 0; k < jw->open_stack.len; k++)
+   strbuf_addstr(>json, "  ");
+}
+
+static inline void begin(struct json_writer *jw, char ch_open, int pretty)
+{
+   jw->pretty = pretty;
+   jw->first = 1;
+
+   strbuf_addch(>json, ch_open);
+
+   strbuf_addch(>open_stack, ch_open);
+}
+
+/*
+ * Assert that the top of the open-stack is an object.
+ */
+static inline void assert_in_object(const struct json_writer *jw, const char 
*key)
+{
+   if (!jw->open_stack.len)
+   die("json-writer: object: missing jw_object_begin(): '%s'", 
key);
+   if (jw->open_stack.buf[jw->open_stack.len - 1] != '{')
+   die("json-writer: object: not in object: '%s'", key);
+}
+
+/*
+ * Assert that the top of the open-stack is an array.
+ */
+static inline void assert_in_array(const struct json_writer *jw)
+{
+   if (!jw->open_stack.len)
+   die("json-writer: array: missing jw_array_begin()");
+   if (jw->open_stack.buf[jw->open_stack.len - 1] != '[')
+