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| author | Lasse Collin <lasse.collin@tukaani.org> | 2013-02-27 09:34:49 +0200 |
|---|---|---|
| committer | Lasse Collin <lasse.collin@tukaani.org> | 2013-02-27 09:34:49 +0200 |
| commit | 25a0224510ba143251e6df122b649b3b3b0b0257 (patch) | |
| tree | 4bee79003d367e539aff200b3c622d831f55524b | |
| parent | 0568cfabccc8a23b4d4a23266b39bf14134df434 (diff) | |
| download | xz-embedded-25a0224510ba143251e6df122b649b3b3b0b0257.tar.gz | |
Document integrity check #defines in README.
| -rw-r--r-- | README | 36 |
1 files changed, 36 insertions, 0 deletions
@@ -84,6 +84,42 @@ Embedding into userspace applications environment. Probably you should at least skim through it even if the default file works as is. +Integrity check support + + XZ Embedded always supports the integrity check types None and + CRC32. Support for CRC64 is optional. SHA-256 is currently not + supported in XZ Embedded although the .xz format does support it. + The xz tool from XZ Utils uses CRC64 by default, but CRC32 is usually + enough in embedded systems to keep the code size smaller. + + If you want support for CRC64, you need to copy linux/lib/xz/xz_crc64.c + into your application, and #define XZ_USE_CRC64 in xz_config.h or in + compiler flags. + + When using the internal CRC32 or CRC64, their lookup tables need to be + initialized with xz_crc32_init() and xz_crc64_init(), respectively. + See xz.h for details. + + To use external CRC32 or CRC64 code instead of the code from + xz_crc32.c or xz_crc64.c, the following #defines may be used + in xz_config.h or in compiler flags: + + #define XZ_INTERNAL_CRC32 0 + #define XZ_INTERNAL_CRC64 0 + + Then it is up to you to provide compatible xz_crc32() or xz_crc64() + functions. + + If the .xz file being decompressed uses an integrity check type that + isn't supported by XZ Embedded, it is treated as an error and the + file cannot be decompressed. For multi-call mode, this can be modified + by #defining XZ_DEC_ANY_CHECK. Then xz_dec_run() will return + XZ_UNSUPPORTED_CHECK when unsupported check type is detected. After + that decompression can be continued normally except that the + integrity check won't be verified. In single-call mode there's + no way to continue decoding, so XZ_DEC_ANY_CHECK is almost useless + in single-call mode. + BCJ filter support If you want support for one or more BCJ filters, you need to copy also |