From 2770d6f8813b6bfef89e80dfaf091287c8c0eb4d Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Fri, 28 Jan 2011 20:14:38 -0500
Subject: Introduce LLSDArray, LLSDMap, LLSDParam. LLSDArray is a helper to
construct an LLSD::Array value inline. LLSDMap is a helper to construct an
LLSD::Map value inline. LLSDParam is a customization point, a way for generic
code to support unforseen parameter types as conversion targets for LLSD
values.
---
indra/llcommon/llsdutil.h | 188 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 188 insertions(+)
(limited to 'indra')
diff --git a/indra/llcommon/llsdutil.h b/indra/llcommon/llsdutil.h
index bb8c0690b1..58ccc59f5e 100644
--- a/indra/llcommon/llsdutil.h
+++ b/indra/llcommon/llsdutil.h
@@ -138,4 +138,192 @@ template<typename Input> LLSD llsd_copy_array(Input iter, Input end)
return dest;
}
+/*****************************************************************************
+* LLSDArray
+*****************************************************************************/
+/**
+ * Construct an LLSD::Array inline, with implicit conversion to LLSD. Usage:
+ *
+ * @code
+ * void somefunc(const LLSD&);
+ * ...
+ * somefunc(LLSDArray("text")(17)(3.14));
+ * @endcode
+ *
+ * For completeness, LLSDArray() with no args constructs an empty array, so
+ * <tt>LLSDArray()("text")(17)(3.14)</tt> produces an array equivalent to the
+ * above. But for most purposes, LLSD() is already equivalent to an empty
+ * array, and if you explicitly want an empty isArray(), there's
+ * LLSD::emptyArray(). However, supporting a no-args LLSDArray() constructor
+ * follows the principle of least astonishment.
+ */
+class LLSDArray
+{
+public:
+ LLSDArray():
+ _data(LLSD::emptyArray())
+ {}
+ LLSDArray(const LLSD& value):
+ _data(LLSD::emptyArray())
+ {
+ _data.append(value);
+ }
+
+ LLSDArray& operator()(const LLSD& value)
+ {
+ _data.append(value);
+ return *this;
+ }
+
+ operator LLSD() const { return _data; }
+ LLSD get() const { return _data; }
+
+private:
+ LLSD _data;
+};
+
+/*****************************************************************************
+* LLSDMap
+*****************************************************************************/
+/**
+ * Construct an LLSD::Map inline, with implicit conversion to LLSD. Usage:
+ *
+ * @code
+ * void somefunc(const LLSD&);
+ * ...
+ * somefunc(LLSDMap("alpha", "abc")("number", 17)("pi", 3.14));
+ * @endcode
+ *
+ * For completeness, LLSDMap() with no args constructs an empty map, so
+ * <tt>LLSDMap()("alpha", "abc")("number", 17)("pi", 3.14)</tt> produces a map
+ * equivalent to the above. But for most purposes, LLSD() is already
+ * equivalent to an empty map, and if you explicitly want an empty isMap(),
+ * there's LLSD::emptyMap(). However, supporting a no-args LLSDMap()
+ * constructor follows the principle of least astonishment.
+ */
+class LLSDMap
+{
+public:
+ LLSDMap():
+ _data(LLSD::emptyMap())
+ {}
+ LLSDMap(const LLSD::String& key, const LLSD& value):
+ _data(LLSD::emptyMap())
+ {
+ _data[key] = value;
+ }
+
+ LLSDMap& operator()(const LLSD::String& key, const LLSD& value)
+ {
+ _data[key] = value;
+ return *this;
+ }
+
+ operator LLSD() const { return _data; }
+ LLSD get() const { return _data; }
+
+private:
+ LLSD _data;
+};
+
+/*****************************************************************************
+* LLSDParam
+*****************************************************************************/
+/**
+ * LLSDParam is a customization point for passing LLSD values to function
+ * parameters of more or less arbitrary type. LLSD provides a small set of
+ * native conversions; but if a generic algorithm explicitly constructs an
+ * LLSDParam object in the function's argument list, a consumer can provide
+ * LLSDParam specializations to support more different parameter types than
+ * LLSD's native conversions.
+ *
+ * Usage:
+ *
+ * @code
+ * void somefunc(const paramtype&);
+ * ...
+ * somefunc(..., LLSDParam<paramtype>(someLLSD), ...);
+ * @endcode
+ */
+template <typename T>
+class LLSDParam
+{
+public:
+ /**
+ * Default implementation converts to T on construction, saves converted
+ * value for later retrieval
+ */
+ LLSDParam(const LLSD& value):
+ _value(value)
+ {}
+
+ operator T() const { return _value; }
+
+private:
+ T _value;
+};
+
+/**
+ * LLSDParam<const char*> is an example of the kind of conversion you can
+ * support with LLSDParam beyond native LLSD conversions. Normally you can't
+ * pass an LLSD object to a function accepting const char* -- but you can
+ * safely pass an LLSDParam<const char*>(yourLLSD).
+ */
+template <>
+class LLSDParam<const char*>
+{
+private:
+ // The difference here is that we store a std::string rather than a const
+ // char*. It's important that the LLSDParam object own the std::string.
+ std::string _value;
+ // We don't bother storing the incoming LLSD object, but we do have to
+ // distinguish whether _value is an empty string because the LLSD object
+ // contains an empty string or because it's isUndefined().
+ bool _undefined;
+
+public:
+ LLSDParam(const LLSD& value):
+ _value(value),
+ _undefined(value.isUndefined())
+ {}
+
+ // The const char* we retrieve is for storage owned by our _value member.
+ // That's how we guarantee that the const char* is valid for the lifetime
+ // of this LLSDParam object. Constructing your LLSDParam in the argument
+ // list should ensure that the LLSDParam object will persist for the
+ // duration of the function call.
+ operator const char*() const
+ {
+ if (_undefined)
+ {
+ // By default, an isUndefined() LLSD object's asString() method
+ // will produce an empty string. But for a function accepting
+ // const char*, it's often important to be able to pass NULL, and
+ // isUndefined() seems like the best way. If you want to pass an
+ // empty string, you can still pass LLSD(""). Without this special
+ // case, though, no LLSD value could pass NULL.
+ return NULL;
+ }
+ return _value.c_str();
+ }
+};
+
+/**
+ * LLSDParam<float> resolves conversion ambiguity. g++ considers F64, S32 and
+ * bool equivalent candidates for implicit conversion to float. (/me rolls eyes)
+ */
+template <>
+class LLSDParam<float>
+{
+private:
+ float _value;
+
+public:
+ LLSDParam(const LLSD& value):
+ _value(value.asReal())
+ {}
+
+ operator float() const { return _value; }
+};
+
#endif // LL_LLSDUTIL_H
--
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