dlib C++ Library - Miscellaneous

Miscellaneous

This page documents library components that don't really fit in anywhere else. They all follow the same conventions as the rest of the library.

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# bit_stream

This object represents a middle man between a user and the iostream classes that allows single bits to be read/written easily from/to the iostream classes
More Details...
#include <dlib/bit_stream.h>
Implementations:

> bit_stream_kernel_1:
> This implementation is done by buffering single bits in the obvious way.

> kernel_1a | is a typedef for bit_stream_kernel_1
> kernel_1a_c | is a typedef for kernel_1a that checks its preconditions.

# Extensions to bit_stream

bit_stream_multi
This extension gives a bit_stream object the ability to read/write multiple bits at a time.
More Details...
Implementations:

> bit_stream_multi_1:
> This implementation is done by calling the read/write functions in the bit_stream kernel.

> multi_1a | is a typedef for bit_stream_kernel_1 extended by bit_stream_multi_1
> multi_1a_c | is a typedef for multi_1a that checks its preconditions.

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# bound_function_pointer

This object represents a function with all its arguments bound to specific objects.

This implementation is done using type erasure and placement new. This means that it never allocates memory on the heap and instead stores everything on the stack.

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#include <dlib/bound_function_pointer.h>
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# byte_orderer

This object provides a simple type safe mechanism to convert data to and from network and host byte orders. I.e. to convert things between big and little endian byte ordering.
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#include <dlib/byte_orderer.h>
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# check_serialized_version

This function deserializes a string and checks if it matches a user supplied string (the version). If they don't match then dlib::serialization_error is thrown. The point of this function is to make checking version strings in serialized files a little more convenient.
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#include <dlib/serialize.h>
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# console_progress_indicator

This object is a tool for reporting how long a task will take to complete.
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#include <dlib/console_progress_indicator.h>
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# copy_functor

This is a templated function object that makes copies of something.
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#include <dlib/algs.h>
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# database

This object is a C++ wrapper around a SQLite database connection handle and therefore represents a SQLite database file.

Note that this wrapper is targeted at SQLite Version 3. To use it you must make sure you link your application with SQLite. However, if you use CMake and dlib's default CMakeLists.txt file then it will get setup automatically. This is assuming sqlite3 is properly installed on your system. On ubuntu you can get it by installing the libsqlite3-dev package. Or you can always download the SQLite source and compile it straight into your application (download the amalgamation).

C++ Example Programs: sqlite_ex.cpp
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#include <dlib/sqlite.h>
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# decoder

This class is a libavcodec wrapper which decodes video or audio from raw memory. Note, if you are reading raw memory from file, it is easier to use demuxer as it also works with raw codec files like .h264 files. This class is suitable for example when reading raw encoded data from a socket, or interfacing with another library that provides encoded data.
C++ Example Programs: ffmpeg_video_decoding2_ex.cpp, ffmpeg_video_decoding_ex.cpp
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#include <dlib/media.h>
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# default_memory_manager

This is a memory manager object which simply calls new and delete directly (i.e. it doesn't really do anything). It is the default memory manager used by most of the objects in dlib.
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#include <dlib/algs.h>
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# demuxer

This class is a libavformat wrapper which demuxes video and/or audio streams from file and decodes them. It is analogous to OpenCV's cv::VideoCapture class but is more configurable, supports audio, devices (X11, webcam, microphone, ...) and network streams such as RTSP, HTTP, and more. Note that a video file, e.g. MP4, can contain multiple streams: video, audio, subtitles, etc. This class can decode both video and audio at the same time. For audio files, e.g. MP3, FLAG, it only decodes audio.
C++ Example Programs: ffmpeg_file_to_speaker_ex.cpp, ffmpeg_info_ex.cpp, ffmpeg_microphone_to_file_ex.cpp, ffmpeg_rtsp_ex.cpp, ffmpeg_screen_grab_ex.cpp, ffmpeg_video_decoding_ex.cpp, ffmpeg_video_demuxing2_ex.cpp, ffmpeg_video_demuxing_ex.cpp, ffmpeg_video_encoding_ex.cpp, ffmpeg_video_muxing_ex.cpp, ffmpeg_webcam_face_pose_ex.cpp
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#include <dlib/media.h>
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# deserialize

This is actually a set of overloaded functions which provide the ability to restore an object's state from an input stream. Currently all dlib container classes, non pointer C++ intrinsics, std::string, std::vector, std::map, std::set, std::complex, dlib::bigint, dlib::uint64, dlib::int64, C style arrays, and dlib::vector objects are serializable.

You can also use serialize() and deserialize() to read/write Google protocol buffer objects. However, note that dlib::serialize() writes additional delimiting bytes at the start of each protocol buffer message. We do this because Google protocol buffers are not self-delimiting on their own. This means that you can't write more than one protocol buffer object to an output stream unless you include some kind of delimiter between the messages. So dlib takes care of this for you by prefixing each message with its length in bytes. In particular, the number of bytes is encoded as a 32bit little endian integer.

More Details...
#include <dlib/serialize.h>
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# dlib_testing_suite

This library comes with a command line driven regression test suite. All the testing code is located in the dlib/test folder. If you want to build it and test the library on your system you can use the makefile at dlib/test/makefile (you may have to edit it to make it work on your system) or use the CMake CMakeLists.txt file at dlib/test/CMakeLists.txt to build it.

What you may find more useful however is the testing framework itself. It uses a fairly simple and modular design. Each test is contained in its own cpp file and when compiled into the program it automatically shows up in the list of tests to run. If you want to use the testing framework all you need to do is add the files dlib/test/tester.h, dlib/test/tester.cpp, and dlib/test/main.cpp to your project and then add cpp files that contain your tests (see dlib/test/example.cpp and dlib/test/example_args.cpp for some examples).

From the command line you can choose to run all the installed tests, enable or disable the loggers, set various logging levels, specify how many times to run the tests, or pick just one or two tests to run at a time rather than the entire suite. The output of the program, that is, its return value from main() is the number of failed tests. So if every test succeeds then it returns 0.

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# encoder

This class is a libavcodec wrapper which encodes video or audio to raw memory. Note, if you are creating a media file, it is easier to use the muxer object as it also works with raw codec files like .h264 files. This class is suitable for example if you need to send raw packets over a socket or interface with another library that requires encoded data, not raw images or raw audio samples.
C++ Example Programs: ffmpeg_video_encoding_ex.cpp
More Details...
#include <dlib/media.h>
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# error

This is the base exception class from which all exceptions in this library inherit.
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#include <dlib/error.h>
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# frame

This class wraps ffmpeg's AVFrame* into a cleaner RAII C++ class.
C++ Example Programs: ffmpeg_file_to_speaker_ex.cpp, ffmpeg_microphone_to_file_ex.cpp, ffmpeg_rtsp_ex.cpp, ffmpeg_screen_grab_ex.cpp, ffmpeg_video_decoding2_ex.cpp, ffmpeg_video_decoding_ex.cpp, ffmpeg_video_demuxing2_ex.cpp, ffmpeg_video_demuxing_ex.cpp, ffmpeg_video_encoding_ex.cpp, ffmpeg_video_muxing_ex.cpp, ffmpeg_webcam_face_pose_ex.cpp
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#include <dlib/media.h>
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# int16

This is just a typedef for a 16 bit integer.
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#include <dlib/uintn.h>
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# int32

This is just a typedef for a 32 bit integer.
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#include <dlib/uintn.h>
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# int64

This is just a typedef for a 64 bit integer.
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#include <dlib/uintn.h>
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# int8

This is just a typedef for an 8 bit integer.
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#include <dlib/uintn.h>
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# Java

dlib contains some CMake scripts and related tools that make calling C++ code from Java easy. If you look in the dlib/java folder you can find a CMake project that uses SWIG to build some C++ code and then call it from Java. In particular, if you run the run_test.sh script it will build and run the code, calling it from java.

The dlib/java folder also contains some SWIG aware C++ classes that make interacting with java arrays (e.g. double[]) from C++ efficient and easy. See the documentation at the top of the java_array.h file for details.

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# logger

This component is a logging output stream in the style of the log4j logger available for Java.
C++ Example Programs: logger_ex.cpp, logger_ex_2.cpp, logger_custom_output_ex.cpp, pipe_ex.cpp
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#include <dlib/logger.h>

# Extensions to logger

config_file
This extension provides the configure_loggers_from_file() function which reads a configuration file from disk that sets up all your loggers.
More Details...
extra_logger_headers
This extension contains additional logger headers you may chose to use instead of the default one.
More Details...
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# make_mfp

This function is a simple factory for creating member_function_pointer objects without needing to know the necessary template arguments for the member_function_pointer.
More Details...
#include <dlib/member_function_pointer.h>
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# MATLAB

dlib contains a tool that makes it easy to call C++ code from MATLAB. It's documented in the examples in the dlib/matlab folder. In particular, the dlib/matlab/example_mex_function.cpp, dlib/matlab/example_mex_callback.cpp, and dlib/matlab/example_mex_struct.cpp examples. You can also easily compile these files using CMake. See the instructions in the README file in the dlib/matlab folder for further details.
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# member_function_pointer

This object represents a member function pointer. It is useful because instances of this object can be created without needing to know the type of object whose member function we will be calling.

The implementation of this object is done using type erasure and placement new. This means that it never allocates memory on the heap and instead stores everything on the stack.

C++ Example Programs: member_function_pointer_ex.cpp
More Details...
#include <dlib/member_function_pointer.h>
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# memory_manager

This object represents a memory pool.
More Details...
#include <dlib/memory_manager.h>
Implementations:

> memory_manager_kernel_1:
> This memory manager implementation allocates objects one at a time when there are allocation requests. Then when there is a deallocate request the returning object is placed into a list of free blocks if that list has less than max_pool_size blocks in it. Subsequent allocation requests will be serviced by drawing from the free list whenever it isn't empty. Array allocations, on the other hand, are not managed at all but are passed directly on to new and delete.

> When this object's max_pool_size template parameter is set to 0 it simply calls new and delete directly and doesn't function as a memory pool.

> kernel_1a | is a typedef for memory_manager_kernel_1 with a max_pool_size of 0
> kernel_1b | is a typedef for memory_manager_kernel_1 with a max_pool_size of 10
> kernel_1c | is a typedef for memory_manager_kernel_1 with a max_pool_size of 100
> kernel_1d | is a typedef for memory_manager_kernel_1 with a max_pool_size of 1000
> kernel_1e | is a typedef for memory_manager_kernel_1 with a max_pool_size of 10000
> kernel_1f | is a typedef for memory_manager_kernel_1 with a max_pool_size of 100000

> memory_manager_kernel_2:
> This memory manager implementation allocates memory in blocks of chunk_size*sizeof(T) bytes. All the sizeof(T) sub-blocks are kept in a linked list of free memory blocks and are given out whenever an allocation request occurs. Also, memory is not freed until this object is destructed. Also note that array allocations are not managed at all but are passed directly on to new and delete.

> kernel_2a | is a typedef for memory_manager_kernel_2 with a chunk_size of 10
> kernel_2b | is a typedef for memory_manager_kernel_2 with a chunk_size of 100
> kernel_2c | is a typedef for memory_manager_kernel_2 with a chunk_size of 1000
> kernel_2d | is a typedef for memory_manager_kernel_2 with a chunk_size of 10000
> kernel_2e | is a typedef for memory_manager_kernel_2 with a chunk_size of 100000

> memory_manager_kernel_3:
> This memory manager implementation allocates memory in blocks of chunk_size*sizeof(T) bytes. All the sizeof(T) sub-blocks are kept in a linked list of free memory blocks and are given out whenever an allocation request occurs. Note that array allocations are managed. So this object is just like kernel_2 but it also pools memory from array allocations (chunk_size has no effect with respect to array allocations, each array is allocated one at a time). Also, memory is not freed until this object is destructed.

> kernel_3a | is a typedef for memory_manager_kernel_3 with a chunk_size of 10
> kernel_3b | is a typedef for memory_manager_kernel_3 with a chunk_size of 100
> kernel_3c | is a typedef for memory_manager_kernel_3 with a chunk_size of 1000
> kernel_3d | is a typedef for memory_manager_kernel_3 with a chunk_size of 10000
> kernel_3e | is a typedef for memory_manager_kernel_3 with a chunk_size of 100000

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# memory_manager_global

This object represents some kind of global memory manager or memory pool.
More Details...
#include <dlib/memory_manager_global.h>
Implementations:

> memory_manager_global_kernel_1:
> This is implemented in the obvious way. See the code for details.

> kernel_1a | is a typedef for memory_manager_global_kernel_1

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# memory_manager_stateless

This object represents some kind of stateless memory manager or memory pool. Stateless means that all instances (instances of the same type that is) of this object are identical and can be used interchangeably. Note that implementations are allowed to have some shared global state such as a global memory pool. This object is also thread safe.
More Details...
#include <dlib/memory_manager_stateless.h>
Implementations:

> memory_manager_stateless_kernel_1:
> This implementation just calls new and delete. So it doesn't do anything special.

> kernel_1a | is a typedef for memory_manager_stateless_kernel_1

> memory_manager_stateless_kernel_2:
> This implementation uses a global instance of a memory_manager object guarded by a mutex as its implementation.

> kernel_2_1a | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1a
> kernel_2_1b | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1b
> kernel_2_1c | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1c
> kernel_2_1d | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1d
> kernel_2_1e | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1e
> kernel_2_1f | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_1f
> kernel_2_2a | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_2a
> kernel_2_2b | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_2b
> kernel_2_2c | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_2c
> kernel_2_2d | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_2d
> kernel_2_2e | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_2e
> kernel_2_3a | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_3a
> kernel_2_3b | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_3b
> kernel_2_3c | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_3c
> kernel_2_3d | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_3d
> kernel_2_3e | is a typedef for memory_manager_stateless_kernel_2 that uses memory_manager_3e

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# muxer

This class is a libavformat wrapper which muxes video and/or audio streams to file. It is analogous to OpenCV's cv::VideoWriter class but is more configurable, supports audio, devices (X11, speaker, ...) and network streams such as RTSP, HTTP, and more. Note that a video file, e.g. MP4, can contain multiple streams: video, audio, subtitles, etc. This class can encode both video and audio at the same time.
C++ Example Programs: ffmpeg_file_to_speaker_ex.cpp, ffmpeg_info_ex.cpp, ffmpeg_microphone_to_file_ex.cpp, ffmpeg_rtsp_ex.cpp, ffmpeg_screen_grab_ex.cpp, ffmpeg_video_decoding_ex.cpp, ffmpeg_video_demuxing2_ex.cpp, ffmpeg_video_demuxing_ex.cpp, ffmpeg_video_encoding_ex.cpp, ffmpeg_video_muxing_ex.cpp, ffmpeg_webcam_face_pose_ex.cpp
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#include <dlib/media.h>
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# pipe

This is a first in first out queue with a fixed maximum size. It is suitable for passing objects between threads.

This object is optimized for speed, therefore, it uses global `swap()` to create a zero-copy method for moving objects around. For example, on a computer running Ubuntu 12.04 with a 2.67GHz Intel i7 920 CPU it is possible to pass over 4.4 million `std::vector<int>` objects a second between two threads. This is regardless of the number of ints in the `std::vector` objects. In particular, this test was done with 100,000 ints in each `std::vector`.

Finally, note that you can use the pipe as an efficient method to pass messages between two networked computers by using the bridge.

C++ Example Programs: pipe_ex.cpp, pipe_ex_2.cpp, bridge_ex.cpp
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#include <dlib/pipe.h>
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# ramdump

This is a type decoration used to indicate that serialization should be done by simply dumping the memory of some object to disk as fast as possible without any sort of conversions. This means that the data written will be "non-portable" in the sense that the format output by a RAM dump may depend on things like the endianness of your CPU or settings of certain compiler switches.

You use this object like this:

    serialize("yourfile.dat") << ramdump(yourobject);
    deserialize("yourfile.dat") >> ramdump(yourobject);

or

    serialize(ramdump(yourobject), out);
    deserialize(ramdump(yourobject), in);

Also, not all objects have a ramdump mode. If you try to use ramdump on an object that does not define a serialization dump for ramdump you will get a compiler error.
More Details...
#include <dlib/serialize.h>
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# serialize

This is actually a set of overloaded functions which provide the ability to save an object's state to an output stream. Currently all dlib container classes, non pointer C++ intrinsics, std::string, std::vector, std::map, std::set, std::complex, dlib::bigint, dlib::uint64, dlib::int64, C style arrays, and dlib::vector objects are serializable.

You can also use serialize() and deserialize() to read/write Google protocol buffer objects. However, note that dlib::serialize() writes additional delimiting bytes at the start of each protocol buffer message. We do this because Google protocol buffers are not self-delimiting on their own. This means that you can't write more than one protocol buffer object to an output stream unless you include some kind of delimiter between the messages. So dlib takes care of this for you by prefixing each message with its length in bytes. In particular, the number of bytes is encoded as a 32bit little endian integer.

More Details...
#include <dlib/serialize.h>
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# statement

This object represents a SQL statement which can be executed against a database object. In particular, this object is a C++ wrapper around a SQLite prepared statement.

Note that this wrapper is targeted at SQLite Version 3. To use it you must make sure you link your application with SQLite.

C++ Example Programs: sqlite_ex.cpp
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#include <dlib/sqlite.h>
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# std_allocator

This object is an implementation of an allocator that conforms to the C++ standard requirements for allocator objects. The M template argument is one of the dlib memory manager objects and this allocator implementation will do all of its memory allocations using whatever dlib memory manager you supply.

Thus, using this allocator object you can use any of the dlib memory manager objects with the containers in the STL or with any other object that requires an STL style allocator object.

C++ Example Programs: std_allocator_ex.cpp
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#include <dlib/std_allocator.h>
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# sync_extension

This object represents a general extension to any object. This object gives any object which it extends an integrated rmutex and rsignaler object. The extended object will then be able to be treated as if it was also a rmutex and rsignaler.
More Details...
#include <dlib/sync_extension.h>
Implementations:

> sync_extension_kernel_1:
> This is implemented using a rmutex and rsignaler in the obvious way.

> kernel_1a | is a typedef for sync_extension_kernel_1

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# timeout

This object provides a simple way to implement a timeout.
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#include <dlib/timeout.h>
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# timer

This object represents a timer that will call a given member function repeatedly at regular intervals.

The implementation of this object has a single master thread that does all the waiting. This master thread creates and dispatches threads to specific timer objects when they need to run their action functions. When a timer object isn't executing its action function then it doesn't have any thread allocated to it at all. So it is fairly efficient.

C++ Example Programs: timer_ex.cpp
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#include <dlib/timer.h>
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# TIME_THIS

This is a macro function for timing blocks of code. Its form is `TIME_THIS(whatever you want to time)` It's pretty straight forward. It just prints the time it took to std::cout.

There is another version of this function called TIME_THIS_TO which takes as a parameter an ostream object to write its output to. Its form is `TIME_THIS_TO(what you want to time, the output stream)`;

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#include <dlib/time_this.h>
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# timing code blocks

This is a set of set of functions for timing blocks of code. Unlike TIME_THIS, it can be used to find the cumulative time spent on a block which is executed multiple times.
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#include <dlib/timing.h>
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# transaction

This object is a tool for creating exception safe database transactions.
C++ Example Programs: sqlite_ex.cpp
More Details...
#include <dlib/sqlite.h>
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# uint16

This is just a typedef for a 16 bit unsigned integer.
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#include <dlib/uintn.h>
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# uint32

This is just a typedef for a 32 bit unsigned integer.
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#include <dlib/uintn.h>
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# uint64

This is just a typedef for a 64 bit unsigned integer.
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#include <dlib/uintn.h>
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# uint8

This is just a typedef for an 8 bit unsigned integer.
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#include <dlib/uintn.h>
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# unserialize

This object effectively allows you to peek at the next serialized object in an istream. It does this by allowing you to read an object and then put it back.
More Details...
#include <dlib/vectorstream.h>
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# vectorstream

This is an iostream object that reads and writes from an in-memory buffer. It functions very much the same way as the std::stringstream object. However, while the std::stringstream holds its buffer internally and it can only be accessed by copying it out, the vectorstream uses an external std::vector<char> as its buffer. That is, it holds a reference to an external vector and does not contain any internal buffers of its own.

This object is useful as a slightly more efficient alternative to the std::stringstream since you can avoid the overhead of copying buffer contents to and from the stream. This is particularly useful when used as a source or target for serialization routines.

More Details...
#include <dlib/vectorstream.h>
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# wrap_function

This is a template that allows you to turn a global function into a function object. See the specs for more details.
More Details...
#include <dlib/algs.h>
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# zero_extend_cast

This is a global function that performs a zero extending cast from one integral type to another integral type.
More Details...
#include <dlib/uintn.h>