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author | Mark Adler <madler@alumni.caltech.edu> | 2011-09-09 23:24:33 -0700 |
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committer | Mark Adler <madler@alumni.caltech.edu> | 2011-09-09 23:24:33 -0700 |
commit | 0484693e1723bbab791c56f95597bd7dbe867d03 (patch) | |
tree | 8f31dbed98b4390da74a90b484f2accf8f8a3a8e /FAQ | |
parent | 9811b53dd9e8f67015c7199fff12b5bfc6965330 (diff) | |
download | zlib-0484693e1723bbab791c56f95597bd7dbe867d03.tar.gz zlib-0484693e1723bbab791c56f95597bd7dbe867d03.tar.bz2 zlib-0484693e1723bbab791c56f95597bd7dbe867d03.zip |
zlib 1.2.2.2v1.2.2.2
Diffstat (limited to 'FAQ')
-rw-r--r-- | FAQ | 26 |
1 files changed, 14 insertions, 12 deletions
@@ -148,13 +148,6 @@ The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html | |||
148 | format using deflateInit2(). You can also request that inflate decode | 148 | format using deflateInit2(). You can also request that inflate decode |
149 | the gzip format using inflateInit2(). Read zlib.h for more details. | 149 | the gzip format using inflateInit2(). Read zlib.h for more details. |
150 | 150 | ||
151 | Note that you cannot specify special gzip header contents (e.g. a file | ||
152 | name or modification date), nor will inflate tell you what was in the | ||
153 | gzip header. If you need to customize the header or see what's in it, | ||
154 | you can use the raw deflate and inflate operations and the crc32() | ||
155 | function and roll your own gzip encoding and decoding. Read the gzip | ||
156 | RFC 1952 for details of the header and trailer format. | ||
157 | |||
158 | 21. Is zlib thread-safe? | 151 | 21. Is zlib thread-safe? |
159 | 152 | ||
160 | Yes. However any library routines that zlib uses and any application- | 153 | Yes. However any library routines that zlib uses and any application- |
@@ -295,20 +288,29 @@ The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html | |||
295 | were downright silly. So now, we simply make sure that the code always | 288 | were downright silly. So now, we simply make sure that the code always |
296 | works. | 289 | works. |
297 | 290 | ||
298 | 36. Will zlib read the (insert any ancient or arcane format here) compressed | 291 | 36. Valgrind (or some similar memory access checker) says that deflate is |
292 | performing a conditional jump that depends on an uninitialized value. | ||
293 | Isn't that a bug? | ||
294 | |||
295 | No. That is intentional for performance reasons, and the output of | ||
296 | deflate is not affected. This only started showing up recently since | ||
297 | zlib 1.2.x uses malloc() by default for allocations, whereas earlier | ||
298 | versions used calloc(), which zeros out the allocated memory. | ||
299 | |||
300 | 37. Will zlib read the (insert any ancient or arcane format here) compressed | ||
299 | data format? | 301 | data format? |
300 | 302 | ||
301 | Probably not. Look in the comp.compression FAQ for pointers to various | 303 | Probably not. Look in the comp.compression FAQ for pointers to various |
302 | formats and associated software. | 304 | formats and associated software. |
303 | 305 | ||
304 | 37. How can I encrypt/decrypt zip files with zlib? | 306 | 38. How can I encrypt/decrypt zip files with zlib? |
305 | 307 | ||
306 | zlib doesn't support encryption. The original PKZIP encryption is very weak | 308 | zlib doesn't support encryption. The original PKZIP encryption is very weak |
307 | and can be broken with freely available programs. To get strong encryption, | 309 | and can be broken with freely available programs. To get strong encryption, |
308 | use GnuPG, http://www.gnupg.org/ , which already includes zlib compression. | 310 | use GnuPG, http://www.gnupg.org/ , which already includes zlib compression. |
309 | For PKZIP compatible "encryption", look at http://www.info-zip.org/ | 311 | For PKZIP compatible "encryption", look at http://www.info-zip.org/ |
310 | 312 | ||
311 | 38. What's the difference between the "gzip" and "deflate" HTTP 1.1 encodings? | 313 | 39. What's the difference between the "gzip" and "deflate" HTTP 1.1 encodings? |
312 | 314 | ||
313 | "gzip" is the gzip format, and "deflate" is the zlib format. They should | 315 | "gzip" is the gzip format, and "deflate" is the zlib format. They should |
314 | probably have called the second one "zlib" instead to avoid confusion | 316 | probably have called the second one "zlib" instead to avoid confusion |
@@ -324,14 +326,14 @@ The lastest zlib FAQ is at http://www.gzip.org/zlib/zlib_faq.html | |||
324 | 326 | ||
325 | Bottom line: use the gzip format for HTTP 1.1 encoding. | 327 | Bottom line: use the gzip format for HTTP 1.1 encoding. |
326 | 328 | ||
327 | 39. Does zlib support the new "Deflate64" format introduced by PKWare? | 329 | 40. Does zlib support the new "Deflate64" format introduced by PKWare? |
328 | 330 | ||
329 | No. PKWare has apparently decided to keep that format proprietary, since | 331 | No. PKWare has apparently decided to keep that format proprietary, since |
330 | they have not documented it as they have previous compression formats. | 332 | they have not documented it as they have previous compression formats. |
331 | In any case, the compression improvements are so modest compared to other | 333 | In any case, the compression improvements are so modest compared to other |
332 | more modern approaches, that it's not worth the effort to implement. | 334 | more modern approaches, that it's not worth the effort to implement. |
333 | 335 | ||
334 | 40. Can you please sign these lengthy legal documents and fax them back to us | 336 | 41. Can you please sign these lengthy legal documents and fax them back to us |
335 | so that we can use your software in our product? | 337 | so that we can use your software in our product? |
336 | 338 | ||
337 | No. Go away. Shoo. | 339 | No. Go away. Shoo. |