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(Working title) libctr9

Copyright 2016 Gabriel Marcano
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Licensing
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This project is licensed under the GPL 2 or later licenses, at your choice.
Refer to COPYING for more licensing information and for the licensing for the
code borrowed from other sources.


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About
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This library is meant to be a collection of useful routines for ARM9 3DS
development. The plan is for it to eventually grow to something like libnds.
Currently the main contribution to this library is a generic disk IO framework
that has been designed for ease of use and extensibility.

The library was meant to be linked with LTO, but due to technical limitations of
devKitARM with GCC 5.3, it is not. Instead, it is compiled with
-ffunction-section, so if the final executable uses the gc-section option for
the linker, the linker when linking the final executable will be able to throw
out parts of the library that are not in use, reducing executable size.

Note this library is still in active development and the API is not considered
stable. Breaking changes will be mentioned in commits at the very least.


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Dependencies
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 - https://github.com/b1l1s/ctr - Used for unit tests
    Make sure it is installed somewhere that the compiler can pick it up, or
	use -L and -I to instruct the compiler where to find it.

 - Autotools in general. These are used to create the build scripts.

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Compiling
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The Autotools setup assumes that devkitarm is already in the PATH.

 # this following line is if the 3ds compiler isn't in the path
 export PATH=${PATH}:${DEVKITPRO}/bin:${DEVKITARM}/bin
 autoreconf -if
 ./configure --host arm-none-eabi --prefix=[lib install path]
 make

Example:
  export PATH=${PATH}:${DEVKITPRO}/bin:${DEVKITARM}/bin
  autoreconf -if
  ./configure --host arm-none-eabi --prefix="$HOME/.local/usr/arm-none-eabi-9/"
  make -j10


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Installation
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TBD. This library is built using Autotools, so it supports the 'make install'
and 'make uninstall' targets. Be sure to set --prefix when calling configure
if either of the preceeding targets will be used, else by default the generated
Makefile will install to /usr/local/ (most likely)) !

Example (after having compiled):
  #this will install to the directory specified in prefix, or /usr/local/ if
  #prefix isn't defined (most likely)!
  make install


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Usage
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Depending on where the library is installed, one may need to use -L in one's
projects to point the compiler to find the library, then use -lctr9 to cause
the linker to link in the static library.

Example:
  arm-none-eabi-gcc -I$HOME/.local/usr/arm-none-eabi-9/include \
    -L$HOME/.local/usr/arm-none-eabi-9/lib -Os -Wall -Wextra -Wpedantic hello.c

One setup that is recommended is to export a variable such as, CTRARM9, to point
to the root of the prefix where libctr9 is installed. This way, it is easier to
point to the lib and include directories (such as by using $CTRARM9/include and
$CTRARM9/lib).


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Documentation
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This project uses Doxygen markup in order to facilitate the generation of
documentation, which should be found when generated in the doc/ folder. Each
header in the include/ directory should also be well documented and can be used
as reference for programming.

In addition, some documentation is hosted in GitHub pages:
	https://gemarcano.github.io/libctr9/


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Design: IO subsystem/framework
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The IO framework is based on the idea of IO interfaces that can be layered. The
implementation of each IO interface layer depends on a function table that is
embedded into the IO interface context object. It is via this function table
that the generic IO interface functions determine what function to call, acting
as a virtual table for the IO interface functionality. Refer to
ctr_io_interface.h for the definition of this function table.

One of the advantages of the framework is that it lends itself well to layering
IO interfaces. For example, after implementing a NAND IO interface, it is
possible to develop an IO interface layer that takes as an input at
initialization a NAND IO interface and transforms the input/output of the NAND
IO interface layer as necessary. An example of this is the crypto IO interface
layer included in this library, which takes as an input any IO interface layer
(most likely NAND) and then applies crypto to the input/output to/from the
NAND IO layer, based on the initialization parameters of the crypto layer. This
allows for the encrypted NAND to be read and written transparently, for example.

The IO subsystem was designed with extensibility in mind. In order to create a
new IO interface layer, all one needs to do is implement six functions and
load a function table at the beginning of the new IO interface object with those
functions. Instead of calling the function pointers directly, use the ctr_io_*
functions supplied by the framework. These will make sure to call the right
functions.

For examples of how IO interfaces are implemented refer to the source code for
this library. Some example IO interfaces are ctr_nand_interface (the actual
implementation for this one was abstracted to ctr_sdmmc_implementation),
ctr_nand_crypto_interface, and ctr_fatfs_interface. It is feasible to make a
ctr_xorpad_interface to generate xorpads, for example, taking two IO interface
layers, one providing the raw encrypted ouput and another the plaintext.


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Testing
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This project does include a homegrown unit testing framework and some unit tests
for this library. See the test/ directory for more information. Note that the
unit testing payload WILL write to NAND (in theory writes to areas that are
unused) as a part of unit testing.

To compile it, change directory to test/, then execute `make test`. The
generated test.bin is an A9LH compatible binary.


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Issues/Bugs
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Please report these to the issue tracker at the repository, and these will be
addressed as soon as possible, if not at least acknowledged. The more detailed
the reports, the more likely they are to be addressed quickly. In particular,
the following information can be quite useful when debugging bugs:

 - Type of 2/3DS system
 - Operating system being used to compile
 - Release/commit of library in use
 - Steps to reproduce issue
 - Expected behavior
 - Actual behavior
 - ARM9 entry point
 - Any modifications to the library, or extensions


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Contributing
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Pull requests are welcome. All requests will be looked at in detail, and must be
documented in a similar fashion as the rest of the code for this project. In
particular, it is unlikely (but not impossible) that code that emmits warnings
with the warnings in use by this library would be merged without first fixing/
addressing what is causing the warnings to be emitted.


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Credits
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 - #3dshacks @ Rizon for starting me on my path to 3DS homebrew development
 - #Cakey @ Freenode for the continued development support
 - #3dsdev @ EFNet for the occasional help answering questions
 - d0k3 for some code use in this library and for suggestions
 - dark_samus for helping to develop A9LH stuff in Cakey, which drove for the
    development of this library
 - Delebile for publishing the public arm9loaderhax implementation, making using
    and testing this library possible (or less of a pain)
 - Aurora, et. al (you know who you are, I hope) for for general development
    help and brainstorming
 - Normmatt for yelling at me for screwing up his sdmmc code :) Also a lot of
    other general 3DS development stuff

 - See COPYING for details about code usage from other sources