components/jansson/doc/html/_sources/conformance.txt
changeset 2190 0e3f360be1b9
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/components/jansson/doc/html/_sources/conformance.txt	Wed Oct 29 17:55:16 2014 +0100
@@ -0,0 +1,110 @@
+.. _rfc-conformance:
+
+***************
+RFC Conformance
+***************
+
+JSON is specified in :rfc:`4627`, *"The application/json Media Type
+for JavaScript Object Notation (JSON)"*.
+
+Character Encoding
+==================
+
+Jansson only supports UTF-8 encoded JSON texts. It does not support or
+auto-detect any of the other encodings mentioned in the RFC, namely
+UTF-16LE, UTF-16BE, UTF-32LE or UTF-32BE. Pure ASCII is supported, as
+it's a subset of UTF-8.
+
+Strings
+=======
+
+JSON strings are mapped to C-style null-terminated character arrays,
+and UTF-8 encoding is used internally.
+
+All Unicode codepoints U+0000 through U+10FFFF are allowed in string
+values. However, U+0000 is not allowed in object keys because of API
+restrictions.
+
+Unicode normalization or any other transformation is never performed
+on any strings (string values or object keys). When checking for
+equivalence of strings or object keys, the comparison is performed
+byte by byte between the original UTF-8 representations of the
+strings.
+
+Numbers
+=======
+
+.. _real-vs-integer:
+
+Real vs. Integer
+----------------
+
+JSON makes no distinction between real and integer numbers; Jansson
+does. Real numbers are mapped to the ``double`` type and integers to
+the ``json_int_t`` type, which is a typedef of ``long long`` or
+``long``, depending on whether ``long long`` is supported by your
+compiler or not.
+
+A JSON number is considered to be a real number if its lexical
+representation includes one of ``e``, ``E``, or ``.``; regardless if
+its actual numeric value is a true integer (e.g., all of ``1E6``,
+``3.0``, ``400E-2``, and ``3.14E3`` are mathematical integers, but
+will be treated as real values). With the ``JSON_DECODE_INT_AS_REAL``
+decoder flag set all numbers are interpreted as real.
+
+All other JSON numbers are considered integers.
+
+When encoding to JSON, real values are always represented
+with a fractional part; e.g., the ``double`` value 3.0 will be
+represented in JSON as ``3.0``, not ``3``.
+
+Overflow, Underflow & Precision
+-------------------------------
+
+Real numbers whose absolute values are too small to be represented in
+a C ``double`` will be silently estimated with 0.0. Thus, depending on
+platform, JSON numbers very close to zero such as 1E-999 may result in
+0.0.
+
+Real numbers whose absolute values are too large to be represented in
+a C ``double`` will result in an overflow error (a JSON decoding
+error). Thus, depending on platform, JSON numbers like 1E+999 or
+-1E+999 may result in a parsing error.
+
+Likewise, integer numbers whose absolute values are too large to be
+represented in the ``json_int_t`` type (see above) will result in an
+overflow error (a JSON decoding error). Thus, depending on platform,
+JSON numbers like 1000000000000000 may result in parsing error.
+
+Parsing JSON real numbers may result in a loss of precision. As long
+as overflow does not occur (i.e. a total loss of precision), the
+rounded approximate value is silently used. Thus the JSON number
+1.000000000000000005 may, depending on platform, result in the
+``double`` value 1.0.
+
+Signed zeros
+------------
+
+JSON makes no statement about what a number means; however Javascript
+(ECMAscript) does state that +0.0 and -0.0 must be treated as being
+distinct values, i.e. -0.0 |not-equal| 0.0. Jansson relies on the
+underlying floating point library in the C environment in which it is
+compiled. Therefore it is platform-dependent whether 0.0 and -0.0 will
+be distinct values. Most platforms that use the IEEE 754
+floating-point standard will support signed zeros.
+
+Note that this only applies to floating-point; neither JSON, C, or
+IEEE support the concept of signed integer zeros.
+
+.. |not-equal| unicode:: U+2260
+
+Types
+-----
+
+No support is provided in Jansson for any C numeric types other than
+``json_int_t`` and ``double``. This excludes things such as unsigned
+types, ``long double``, etc. Obviously, shorter types like ``short``,
+``int``, ``long`` (if ``json_int_t`` is ``long long``) and ``float``
+are implicitly handled via the ordinary C type coercion rules (subject
+to overflow semantics). Also, no support or hooks are provided for any
+supplemental "bignum" type add-on packages.