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3eab3173ac
There is no hardware control for DFLTCC window size, and because of that supporting small windows for deflate is not trivial: one has to make sure that DFLTCC does not emit large distances, which most likely entails somehow trimming the window and/or input in order to make sure that whave + avail_in <= wsize. But inflate is much easier: one only has to allocate enough space. Do that in dfltcc_alloc_window(), and also introduce ZCOPY_WINDOW() in order to copy everything, not just what the software implementation cares about. After this change, software and hardware window formats no longer match: the software will use wbits and wsize, and the hardware will use HB_BITS and HB_SIZE. Unlike deflate, inflate does not switch between software and hardware implementations mid-stream, which leaves only inflateSetDictionary() and inflateGetDictionary() interesting.
41 lines
1.3 KiB
C
41 lines
1.3 KiB
C
/* dfltcc_deflate.c - IBM Z DEFLATE CONVERSION CALL general support. */
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#include "zbuild.h"
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#include "dfltcc_common.h"
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#include "dfltcc_detail.h"
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/*
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Memory management.
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DFLTCC requires parameter blocks and window to be aligned. zlib-ng allows
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users to specify their own allocation functions, so using e.g.
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`posix_memalign' is not an option. Thus, we overallocate and take the
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aligned portion of the buffer.
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*/
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static const int PAGE_ALIGN = 0x1000;
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void Z_INTERNAL *PREFIX(dfltcc_alloc_window)(PREFIX3(streamp) strm, uInt items, uInt size) {
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void *p;
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void *w;
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/* To simplify freeing, we store the pointer to the allocated buffer right
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* before the window. Note that DFLTCC always uses HB_SIZE bytes.
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*/
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p = ZALLOC(strm, sizeof(void *) + MAX(items * size, HB_SIZE) + PAGE_ALIGN, sizeof(unsigned char));
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if (p == NULL)
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return NULL;
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w = ALIGN_UP((char *)p + sizeof(void *), PAGE_ALIGN);
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*(void **)((char *)w - sizeof(void *)) = p;
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return w;
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}
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void Z_INTERNAL PREFIX(dfltcc_copy_window)(void *dest, const void *src, size_t n) {
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memcpy(dest, src, MAX(n, HB_SIZE));
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}
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void Z_INTERNAL PREFIX(dfltcc_free_window)(PREFIX3(streamp) strm, void *w) {
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if (w)
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ZFREE(strm, *(void **)((unsigned char *)w - sizeof(void *)));
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}
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