Added BCJ filter decoders.
diff --git a/README b/README
index 252f39d..fad17b8 100644
--- a/README
+++ b/README
@@ -17,13 +17,30 @@
Compiling the Linux kernel module
- cd linux/lib/xz
- make -C /path/to/kernel/source \
- CONFIG_XZ_DEC=m KCPPFLAGS=-I"$(pwd)/../../include" M="$(pwd)"
-
The xz_dec module depends on crc32 module, so make sure that you have
it enabled (CONFIG_CRC32).
+ Building the xz_dec module without support for BCJ filters:
+
+ cd linux/lib/xz
+ make -C /path/to/kernel/source \
+ KCPPFLAGS=-I"$(pwd)/../../include" M="$(pwd)" \
+ CONFIG_XZ_DEC=m
+
+ Building the xz_dec module with support for BCJ filters:
+
+ cd linux/lib/xz
+ make -C /path/to/kernel/source \
+ KCPPFLAGS=-I"$(pwd)/../../include" M="$(pwd)" \
+ CONFIG_XZ_DEC=m CONFIG_XZ_DEC_BCJ=y \
+ CONFIG_XZ_DEC_X86=y CONFIG_XZ_DEC_POWERPC=y \
+ CONFIG_XZ_DEC_IA64=y CONFIG_XZ_DEC_ARM=y \
+ CONFIG_XZ_DEC_ARMTHUMB=y CONFIG_XZ_DEC_SPARC=y
+
+ If you want only one or a few of the BCJ filters, omit the appropriate
+ variables. CONFIG_XZ_DEC_BCJ=y is always required to build the support
+ code shared between all BCJ filters.
+
Compiler requirements
XZ Embedded should compile as either GNU-C89 (used in the Linux
@@ -57,6 +74,34 @@
Your code should use only the functions declared in xz.h. The rest of
the .h files are meant only for internal use in XZ Embedded.
+BCJ filter support
+
+ If you want support for one or more BCJ filters, you need to copy also
+ linux/lib/xz/xz_dec_bcj.c into your application, and use appropriate
+ #defines when compiling XZ Embedded. You don't need these #defines in
+ the code that just uses XZ Embedded via xz.h, but having them always
+ #defined doesn't hurt either.
+
+ #define Instruction set BCJ filter endianness
+ XZ_DEC_X86 x86 or x86-64 Little endian only
+ XZ_DEC_POWERPC PowerPC Big endian only
+ XZ_DEC_IA64 Itanium (IA-64) Big or little endian
+ XZ_DEC_ARM ARM Little endian only
+ XZ_DEC_ARMTHUMB ARM-Thumb Little endian only
+ XZ_DEC_SPARC SPARC Big or little endian
+
+ While some architectures are (partially) bi-endian, the endianness
+ setting doesn't change the endianness of the instructions on all
+ architectures. That's why Itanium and SPARC filters work for both big
+ and little endian executables (Itanium has little endian instructions
+ and SPARC has big endian instructions).
+
+ There currently is no filter for little endian PowerPC or big endian
+ ARM or ARM-Thumb. Implementing filters for them can be considered if
+ there is a need for such filters in real-world applications.
+
+Notes about shared libraries
+
If you are including XZ Embedded into a shared library, you very
probably should rename the xz_* functions to prevent symbol
conflicts in case your library is linked against some other library
@@ -64,11 +109,11 @@
a different version of XZ Embedded). TODO: Provide an easy way
to do this.
- NOTE: Please don't create a shared library of XZ Embedded itself
- unless it is fine to rebuild everything depending on that shared
- library everytime you upgrade to a newer version of XZ Embedded.
- There are no API or ABI stability guarantees between different
- versions of XZ Embedded.
+ Please don't create a shared library of XZ Embedded itself unless
+ it is fine to rebuild everything depending on that shared library
+ everytime you upgrade to a newer version of XZ Embedded. There are
+ no API or ABI stability guarantees between different versions of
+ XZ Embedded.
Specifying the calling convention