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Add comment about not using windowBits of 8 for deflate().

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Mark Adler 2015-07-28 21:06:06 -07:00
parent e7ebb399d7
commit b56d1c62ee
1 changed files with 8 additions and 0 deletions
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zlib.h
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@ -544,6 +544,14 @@ ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
compression at the expense of memory usage. The default value is 15 if compression at the expense of memory usage. The default value is 15 if
deflateInit is used instead. deflateInit is used instead.
For the current implementation of deflate(), a windowBits value of 8 (a
window size of 256 bytes) is not supported. As a result, a request for 8
will result in 9 (a 512-byte window). In that case, providing 8 to
inflateInit2() will result in an error when the zlib header with 9 is
checked against the initialization of inflate(). The remedy is to not use 8
with deflateInit2() with this initialization, or at least in that case use 9
with inflateInit2().
windowBits can also be -8..-15 for raw deflate. In this case, -windowBits windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
determines the window size. deflate() will then generate raw deflate data determines the window size. deflate() will then generate raw deflate data
with no zlib header or trailer, and will not compute an adler32 check value. with no zlib header or trailer, and will not compute an adler32 check value.