Add api to parse string with specified length

include/rapidjson/document.h

@@ -1972,6 +1972,37 @@ class GenericDocument : public GenericValue<Encoding, Allocator> {
     GenericDocument& Parse(const Ch* str) {
         return Parse<kParseDefaultFlags>(str);
     }
+
+    //! Parse JSON text from a read-only string (with Encoding conversion)
+    /*! \tparam parseFlags Combination of \ref ParseFlag (must not contain \ref kParseInsituFlag).
+        \tparam SourceEncoding Transcoding from input Encoding
+        \param str Read-only string to be parsed.
+        \param len The length of the string.
+    */
+    template <unsigned parseFlags, typename SourceEncoding>
+    GenericDocument& Parse(const Ch* str, size_t len) {
+        RAPIDJSON_ASSERT(!(parseFlags & kParseInsituFlag));
+        GenericBufferStream<SourceEncoding> s(str, len);
+        return ParseStream<parseFlags, SourceEncoding>(s);
+    }
+
+    //! Parse JSON text from a read-only string with length
+    /*! \tparam parseFlags Combination of \ref ParseFlag (must not contain \ref kParseInsituFlag).
+        \param str Read-only string to be parsed.
+        \param len The length of the string.
+    */
+    template <unsigned parseFlags>
+    GenericDocument& Parse(const Ch* str, size_t len) {
+        return Parse<parseFlags, Encoding>(str, len);
+    }
+
+    //! Parse JSON text from a read-only string with length (with \ref kParseDefaultFlags)
+    /*! \param str Read-only string to be parsed.
+        \param len The length of the string.
+    */
+    GenericDocument& Parse(const Ch* str, size_t len) {
+        return Parse<kParseDefaultFlags>(str, len);
+    }
     //!@}
 
     //!@name Handling parse errors

include/rapidjson/rapidjson.h

@@ -594,6 +594,45 @@ struct StreamTraits<GenericStringStream<Encoding> > {
 //! String stream with UTF8 encoding.
 typedef GenericStringStream<UTF8<> > StringStream;
 
+///////////////////////////////////////////////////////////////////////////////
+// BufferStream
+
+//! Read-only buffer stream.
+/*! \note implements Stream concept
+*/
+template <typename Encoding>
+struct GenericBufferStream {
+    typedef typename Encoding::Ch Ch;
+
+    GenericBufferStream(const Ch *src, size_t len) : 
+        src_(src), length_(len), idx_(0) {}
+
+    Ch Peek() const { return src_[idx_]; }
+    Ch Take() {
+        if (idx_ != length_) return src_[idx_++];
+        else return '\0';
+    }
+    size_t Tell() const { return idx_; }
+
+    Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
+    void Put(Ch) { RAPIDJSON_ASSERT(false); }
+    void Flush() { RAPIDJSON_ASSERT(false); }
+    size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
+
+    const Ch* src_;     //!< Original buffer pointer.
+    size_t length_;     //!< The length of buffer.
+    size_t idx_;        //!< Current read position.
+};
+
+template <typename Encoding>
+struct StreamTraits<GenericBufferStream<Encoding> > {
+    enum { copyOptimization = 1 };
+};
+
+//! Buffer stream with UTF8 encoding.
+typedef GenericBufferStream<UTF8<> > BufferStream;
+
+
 ///////////////////////////////////////////////////////////////////////////////
 // InsituStringStream