=== Stones of Nvwa ===
The Name
Nvwa ("v" is pronounced like the French "u") is one of the most
ancient Chinese goddesses. She was said to have created human beings,
and, when the evil god Gong-gong crashed himself upon one of the
pillars that supported the sky and made a hole in it, she mended the
sky with five-coloured stones.
I thought of the name Nvwa by analogy with Loki. Since it is so small
a project and it contains utilities instead of a complete framework, I
think "stones" a good metaphor.
Code Organization
Nvwa versions prior to 1.0 did not use a namespace. It looked to me
overkill to use a namespace in this small project. However, having
had more project experience and seen more good examples, I changed my
mind. All nvwa functions and global variables were moved into the
namespace "nvwa".
This said, I did not want to break backward compatibility abruptly.
First, people are still able to disable the namespace by defining the
macro NVWA_USE_NAMESPACE to 0 (not really recommended, though).
Second, I still used the quotation mark (") to include header files
internally so that old users do not have to change the include
directory (again, not recommended and intended to help the transition
only). Third, I did not change most of the macro names -- that would
break existing code and could do more harm than good now. In
addition, I am not a fan of macro prefixes anyway.
The changes do not mean anything to new users. You just need to
follow the modern C++ way. You should add the root directory of this
project to your include directory (there should be a "nvwa" directory
inside it with the source files). To include the header file, use
"#include <nvwa/...>".
Contents
A brief introduction follows. Check the Doxygen documentation for
more (technical) details.
* boolarray.cpp
* boolarray.h
A replacement of std::vector<bool>. I wrote it before I knew of
vector<bool>, or I might not have written it at all. However, it is
faster than many vector<bool> implementations (your mileage may
vary), and it has members like at, set, reset, flip, and count. I
personally find "count" very useful.
* c++_features.h
Detection macros for certain modern C++ features that might be of
interest to code/library writers. I have used existing online
resources, and I have tested them on popular platforms and compilers
that I have access to (Windows, Linux, and macOS; MSVC, GCC, and
Clang), but of course not all versions or all combinations. Patches
are welcome for corrections and amendments.
* class_level_lock.h
The Loki ClassLevelLockable adapted to use the fast_mutex layer. One
minor divergence from Loki is that the template has an additional
template parameter _RealLock to boost the performance in non-locking
scenarios. Cf. object_level_lock.h.
* cont_ptr_utils.h
Utility functors for containers of pointers adapted from Scott Meyers'
Effective STL.
* debug_new.cpp
* debug_new.h
A cross-platform, thread-safe memory leak detector. It is a
light-weight one designed only to catch unmatched pairs of
new/delete. I know there are already many existing memory leak
detectors, but as far as I know, free solutions are generally slow,
memory-consuming, and quite complicated to use. This solution is
very easy to use, and has very low space/time overheads. Just link
in debug_new.cpp for leakage report, and include debug_new.h for
additional file/line information. It will automatically switch on
multi-threading when the appropriate option of a recognized compiler
is specified. Check fast_mutex.h for more threading details.
Special support for gcc/binutils has been added to debug_new lately.
Even if the header file debug_new.h is not included, or
_DEBUG_NEW_REDEFINE_NEW is defined to 0 when it is included,
file/line information can be displayed if debugging symbols are
present in the executable, since debug_new stores the caller
addresses of memory allocation/deallocation routines and they will be
converted with addr2line (or atos on a Mac) on the fly. This makes
memory tracing much easier.
NOTE for macOS users: Unless you were still using Snow Leopard or
earlier, you would need to add "-Wl,-no_pie" at the end of the
command line. By default macOS will now create position-independent
executables (PIE), and the OS will load a PIE at a random address
each time it is executed, making it difficult to convert the address
to symbols. (I Googled a while for a way to get the base address of
a process, but could not find working code. If you know how to do it
right, drop me a message.)
With an idea from Greg Herlihy's post in comp.lang.c++.moderated, the
implementation was much improved in 2007. The most significant
result is that placement new can be used with debug_new now! Full
support for new(std::nothrow) is provided, with its null-returning
error semantics (by default). Memory corruption will be checked on
freeing the pointers and checking the leaks, and a new function
check_mem_corruption is added for your on-demand use in debugging.
You may also want to define _DEBUG_NEW_TAILCHECK to something like 4
for past-end memory corruption check, which is off by default to
ensure performance is not affected.
An article on its design and implementation is available at
http://nvwa.sourceforge.net/article/debug_new.htm
* fast_mutex.h
The threading transparent layer simulating a non-recursive mutex. It
supports C++11 mutex, POSIX mutex, and Win32 critical section, as
well as a no-threads mode. Unlike Loki and some other libraries,
threading mode is not to be specified in code, but detected from the
environment. It will automatically switch on multi-threading mode
(inter-thread exclusion) when the "-MT"/"-MD" option of MSVC, the
"-mthreads" option of MinGW GCC, or the "-pthread" option of GCC
under POSIX environments, is used. One advantage of the current
implementation is that the construction and destruction of a static
object using a static fast_mutex not yet constructed or already
destroyed are allowed to work (with lock/unlock operations ignored),
and there are re-entry checks for lock/unlock operations when the
preprocessing symbol _DEBUG is defined.
* fc_queue.h
A queue that has a fixed capacity (maximum number of allowed items).
All memory is pre-allocated when the queue is initialized, so memory
consumption is well controlled. When the queue is full, inserting a
new item will discard the oldest item in the queue. Care is taken to
ensure this class template provides the strong exception safety
guarantee.
This class template is a good exercise for me to make a STL-type
container. Depending on your needs, you may find circular_buffer in
Boost more useful, which provides similar functionalities and a
richer API. However, the design philosophies behind the two
implementations are quite different. fc_queue is modelled closely on
std::queue, and I optimize mainly for a lockless producer-consumer
pattern -- when there is one producer and one consumer, and the
producer does not try to queue an element when the queue is already
full, no lock is needed for the queue operations.
I have recently also switched to using C++11 atomic variables in
fc_queue. Previously the code worked for me, but at least
theoretically it was not safe: compilers may optimize the code in
unexpected ways, and multiple processors may cause surprises too.
There is a problem after the change, though. Using the old interface
is not optimal now in the producer-consumer scenario, and two new
read/write functions are provided to make it work more efficiently.
* file_line_reader.cpp
* file_line_reader.h
This is one of the line reading classes I implemented modelling the
Python approach. They make reading lines from a file a simple loop.
This implementation allows reading from a traditional FILE*.
Cf. istream_line_reader.h, mmap_byte_reader.h, and mmap_line_reader.h.
See the following blog for the motivation and example code:
https://tinyurl.com/cpp-line-readers
* fixed_mem_pool.h
A memory pool implementation that requires initialization (allocates
a fixed-size chunk) prior to its use. It is simple and makes no
memory fragmentation, but the memory pool size cannot be changed
after initialization. Macros are provided to easily make a class use
pooled new/delete.
* functional.h
This is my test bed for functional programming. If you are into
functional programming, check it out. It includes functional
programming patterns like:
- map
- reduce
- compose
- fixed-point combinator
- curry
- optional
My blogs on functional programming may be helpful:
https://tinyurl.com/cpp-functional-notes
https://tinyurl.com/cpp-y-combinator
https://tinyurl.com/cpp-type-deduction
https://tinyurl.com/generic-lambdas-compose
* istream_line_reader.h
This is one of the line reading classes I implemented modelling the
Python approach. They make reading lines from a file a simple loop.
This implementation allows reading from an input stream.
Cf. file_line_reader.h and mmap_line_reader.h.
See the following blogs for the motivation and example code:
https://tinyurl.com/cpp-coroutines
https://tinyurl.com/cpp-line-readers
* mem_pool_base.cpp
* mem_pool_base.h
A class solely to be inherited by memory pool implementations. It is
used by static_mem_pool and fixed_mem_pool.
* mmap_byte_reader.h
This file contains the byte reading class template I implemented
modelling the Python approach. It makes reading characters from a
file a simple loop. This implementation uses memory-mapped file I/O.
Cf. mmap_line_reader.h.
* mmap_line_reader.h
This file contains the line reading class template I implemented
modelling the Python approach. It makes reading lines from a file a
simple loop. This implementation uses memory-mapped file I/O. Cf.
istream_line_reader.h, file_line_reader.h, and mmap_byte_reader.h.
See the following blogs for the motivation and example code:
https://tinyurl.com/cpp-line-readers
https://tinyurl.com/mmap-string-view
* mmap_line_view.h
A mmap_line_view is similar to mmap_line_reader_sv defined in
mmap_line_reader.h, but it has gone an extra mile to satisfy the View
concept (to be introduced in C++20). It can be trivially copied.
* mmap_reader_base.cpp
* mmap_reader_base.h
A class that wraps the difference of memory-mapped file I/O between
Unix and Windows. It is used by mmap_byte_reader and mmap_line_reader.
* object_level_lock.h
The Loki ObjectLevelLockable adapted to use the fast_mutex layer.
The member function get_locked_object does not exist in Loki, but is
also taken from Mr Alexandrescu's article. Cf. class_level_lock.h.
* pctimer.h
A function to get a high-resolution timer for Win32/Cygwin/Unix. It
is useful for measurement and optimization, and remains easier to use
than std::chrono::high_resolution_clock after the advent of C++11.
* set_assign.h
Utility routines to make up for the fact that STL only has set_union
(+) and set_difference (-) algorithms but no corresponding += and -=
operations available.
* split.h
Implementation of a split routine that allows efficient and lazy
split of a string (or string_view). It takes advantage of the C++17
string_view, and the split result can be either used on the fly or
returned as a vector.
While the ranges library provides a similar function, it does not yet
use string_view, and compiling with ranges is typically much slower
-- of course, it is much more powerful as well.
* static_mem_pool.cpp
* static_mem_pool.h
A memory pool implementation to pool memory blocks according to
compile-time block sizes. Macros are provided to easily make a class
use pooled new/delete.
An article on its design and implementation is available at
http://nvwa.sourceforge.net/article/static_mem_pool.htm
* tree.h
A generic tree class template along with traversal utilities.
Besides the usual template argument of value type, it has an
additional argument of storage policy, which can be either unique or
shared. Traversal utility classed are provided so that traversing a
tree can be simply done in a range-based for loop. The test code,
test/test_tree.cpp, shows its basic usage.
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