changed behavior of aliases header

arangodb · Nov 19, 2015 · 56d3f5f · 56d3f5f
1 parent d99a5e9
commit 56d3f5f
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Showing 3 changed files with 116 additions and 46 deletions.
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
@@ -6,9 +6,10 @@ message(STATUS "Building examples: ${BuildExamples}")
 # build examples
 if(BuildExamples)
   foreach (exampleName
-           exampleAttributeTranslation
+           exampleAliases
            exampleArrayHandling
            exampleArrayIterator
+           exampleAttributeTranslation
            exampleBuilder
            exampleBuilderFancy
            exampleCustom

diff --git a/examples/Embedding.md b/examples/Embedding.md
@@ -168,13 +168,27 @@ allocated. Client-code must not access the `Buffer` object's memory
 after that.
 
 
+Including the VPack headers
+---------------------------
+
+The easiest way of making the VPack library's classes available to a client
+program is to include the header `velocypack/vpack.h`. This will import all
+class declarations from the namespace `arangodb::velocypack`. It is also possible 
+to selectively include the headers for just the classes needed, e.g.
+
+```cpp
+// only need Builder and Slice in the following code
+// no need to include all VPack classes 
+#include <velocypack/Builder.h>
+#include <velocypack/Slice.h>
+```
+
+Because only the actually required headers will be included, this variant may 
+save some compilation time.
+
 Name clashes and class aliases
 ------------------------------
 
-The default way of making the VPack library's classes available to a client
-program is to include the header `velocypack/vpack.h`. This will load the
-classes definitions from namespace `arangodb::velocypack`.
-
 To avoid full name qualification in client programs, it may be convenient to
 make all classes from this namespace available without extra qualification.
 The following line will do that:
@@ -192,26 +206,31 @@ not an option, an alternative is to use the class name aliases that are
 defined in the header file `velocypack/velocypack-aliases.h`. 
 
 This header file makes the most common VPack classes available under alternative 
-(hopefully unambiguous) class names with the prefix *VPack*:
+(hopefully unambiguous) class names with the prefix *VPack*, for example:
 
 ```cpp
 using VPackArrayIterator      = arangodb::velocypack::ArrayIterator;
 using VPackBuilder            = arangodb::velocypack::Builder;
 using VPackCharBuffer         = arangodb::velocypack::CharBuffer;
 using VPackCharBufferSink     = arangodb::velocypack::CharBufferSink;
-using VPackCollection         = arangodb::velocypack::Collection;
-using VPackDumper             = arangodb::velocypack::Dumper;
-using VPackException          = arangodb::velocypack::Exception;
-using VPackHexDump            = arangodb::velocypack::HexDump;
-using VPackObjectIterator     = arangodb::velocypack::ObjectIterator;
-using VPackOptions            = arangodb::velocypack::Options;
-using VPackParser             = arangodb::velocypack::Parser;
-using VPackSink               = arangodb::velocypack::Sink;
-using VPackSlice              = arangodb::velocypack::Slice;
-using VPackStringSink         = arangodb::velocypack::StringSink;
-using VPackStringStreamSink   = arangodb::velocypack::StringStreamSink;
-using VPackValue              = arangodb::velocypack::Value;
-using VPackValueLength        = arangodb::velocypack::ValueLength;
-using VPackValueType          = arangodb::velocypack::ValueType;
-using VPackVersion            = arangodb::velocypack::Version;
+...
 ```
+
+Note that the `velocypack-aliases.h` header will only make those VPack classes
+available under alternative names that have been included already. When using
+this header, it should be included after the other VPack headers have been
+included:
+
+```cpp
+#include <velocypack/vpack.h>
+#include <velocypack/velocypack-aliases.h>
+```
+
+or, when using selective headers:
+
+```cpp
+#include <velocypack/Builder.h>
+#include <velocypack/Slice.h>
+#include <velocypack/velocypack-aliases.h>
+```
+
diff --git a/include/velocypack/velocypack-aliases.h b/include/velocypack/velocypack-aliases.h
@@ -27,30 +27,80 @@
 #ifndef VELOCYPACK_ALIASES_H
 #define VELOCYPACK_ALIASES_H 1
 
-#include "velocypack/vpack.h"
-
-using VPackArrayIterator           = arangodb::velocypack::ArrayIterator;
-using VPackAttributeExcludeHandler = arangodb::velocypack::AttributeExcludeHandler;
-using VPackAttributeTranslator     = arangodb::velocypack::AttributeTranslator;
-using VPackBuilder                 = arangodb::velocypack::Builder;
-using VPackCharBuffer              = arangodb::velocypack::CharBuffer;
-using VPackCharBufferSink          = arangodb::velocypack::CharBufferSink;
-using VPackCollection              = arangodb::velocypack::Collection;
-using VPackCustomTypeHandler       = arangodb::velocypack::CustomTypeHandler;
-using VPackDumper                  = arangodb::velocypack::Dumper;
-using VPackException               = arangodb::velocypack::Exception;
-using VPackHexDump                 = arangodb::velocypack::HexDump;
-using VPackObjectIterator          = arangodb::velocypack::ObjectIterator;
-using VPackOptions                 = arangodb::velocypack::Options;
-using VPackParser                  = arangodb::velocypack::Parser;
-using VPackSink                    = arangodb::velocypack::Sink;
-using VPackSlice                   = arangodb::velocypack::Slice;
-using VPackStringSink              = arangodb::velocypack::StringSink;
-using VPackStringStreamSink        = arangodb::velocypack::StringStreamSink;
-using VPackValue                   = arangodb::velocypack::Value;
-using VPackValueLength             = arangodb::velocypack::ValueLength;
-using VPackValuePair               = arangodb::velocypack::ValuePair;
-using VPackValueType               = arangodb::velocypack::ValueType;
-using VPackVersion                 = arangodb::velocypack::Version;
+#include "velocypack/velocypack-common.h"
+
+namespace {
+
+  // unconditional typedefs
+  using VPackValueLength             = arangodb::velocypack::ValueLength;
+
+  // conditional typedefs, only uses when the respective headers are already included
+#ifdef VELOCYPACK_ITERATOR_H
+  using VPackArrayIterator           = arangodb::velocypack::ArrayIterator;
+  using VPackObjectIterator          = arangodb::velocypack::ObjectIterator;
+#endif
+
+#ifdef VELOCYPACK_BUILDER_H
+  using VPackBuilder                 = arangodb::velocypack::Builder;
+#endif
+
+#ifdef VELOCYPACK_BUILDER_H
+  using VPackCharBuffer              = arangodb::velocypack::CharBuffer;
+#endif
+
+#ifdef VELOCYPACK_SINK_H
+  using VPackSink                    = arangodb::velocypack::Sink;
+  using VPackCharBufferSink          = arangodb::velocypack::CharBufferSink;
+  using VPackStringSink              = arangodb::velocypack::StringSink;
+  using VPackStringStreamSink        = arangodb::velocypack::StringStreamSink;
+#endif
+
+#ifdef VELOCYPACK_COLLECTION_H
+  using VPackCollection              = arangodb::velocypack::Collection;
+#endif
+
+#ifdef VELOCYPACK_ATTRIBUTETRANSLATOR_H
+  using VPackAttributeTranslator     = arangodb::velocypack::AttributeTranslator;
+#endif
+
+#ifdef VELOCYPACK_DUMPER_H
+  using VPackDumper                  = arangodb::velocypack::Dumper;
+#endif
+
+#ifdef VELOCYPACK_EXCEPTION_H
+  using VPackException               = arangodb::velocypack::Exception;
+#endif
+
+#ifdef VELOCYPACK_HEXDUMP_H
+  using VPackHexDump                 = arangodb::velocypack::HexDump;
+#endif
+
+#ifdef VELOCYPACK_OPTIONS_H
+  using VPackOptions                 = arangodb::velocypack::Options;
+  using VPackAttributeExcludeHandler = arangodb::velocypack::AttributeExcludeHandler;
+  using VPackCustomTypeHandler       = arangodb::velocypack::CustomTypeHandler;
+#endif
+
+#ifdef VELOCYPACK_PARSER_H
+  using VPackParser                  = arangodb::velocypack::Parser;
+#endif
+
+#ifdef VELOCYPACK_SLICE_H
+  using VPackSlice                   = arangodb::velocypack::Slice;
+#endif
+
+#ifdef VELOCYPACK_VALUE_H
+  using VPackValue                   = arangodb::velocypack::Value;
+  using VPackValuePair               = arangodb::velocypack::ValuePair;
+#endif
+
+#ifdef VELOCYPACK_VALUETYPE_H
+  using VPackValueType               = arangodb::velocypack::ValueType;
+#endif
+
+#ifdef VELOCYPACK_VERSION_H
+  using VPackVersion                 = arangodb::velocypack::Version;
+#endif
+}
 
 #endif