From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48715) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dk336-00021T-3q for qemu-devel@nongnu.org; Tue, 22 Aug 2017 02:52:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dk333-0007nZ-2O for qemu-devel@nongnu.org; Tue, 22 Aug 2017 02:52:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55486) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dk332-0007n7-S4 for qemu-devel@nongnu.org; Tue, 22 Aug 2017 02:52:24 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B95EF7EA80 for ; Tue, 22 Aug 2017 06:52:22 +0000 (UTC) From: Markus Armbruster Date: Tue, 22 Aug 2017 08:52:19 +0200 Message-Id: <1503384739-17207-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH] qobject: Explain how QNum works, and why List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: mreitz@redhat.com, marcandre.lureau@redhat.com Suggested-by: Max Reitz Signed-off-by: Markus Armbruster --- include/qapi/qmp/qnum.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/include/qapi/qmp/qnum.h b/include/qapi/qmp/qnum.h index 09d745c..9182129 100644 --- a/include/qapi/qmp/qnum.h +++ b/include/qapi/qmp/qnum.h @@ -23,6 +23,27 @@ typedef enum { QNUM_DOUBLE } QNumKind; +/* + * QNum encapsulates how our dialect of JSON fills in the blanks left + * by the JSON specification (RFC 7159) regarding numbers. + * + * Conceptually, we treat number as an abstract type with three + * concrete subtypes: floating-point, signed integer, unsigned + * integer. QNum implements this a discriminated union of double, + * int64_t, uint64_t. + * + * The JSON parser picks the subtype as follows. If the number has a + * decimal point or an exponent, it is floating-point. Else if it + * fits into int64_t, it's signed integer. Else if it first into + * uint64_t, it's unsigned integer. Else it's floating-point. + * + * Any number can serve as double: qnum_get_double() converts under + * the hood. + * + * An integer can serve as signed / unsigned integer as long as it is + * in range: qnum_get_try_int() / qnum_get_try_uint() check range and + * convert under the hood. + */ typedef struct QNum { QObject base; QNumKind kind; -- 2.7.5