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https://github.com/git/git
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b130a72b27
Add USE_WIN32_MMAP which triggers the use of windows' native file memory mapping functionality in git_mmap()/git_munmap() functions. As git functions currently use mmap with MAP_PRIVATE set only, this implementation supports only that mode for now. On Windows, offsets for memory mapped files need to match the allocation granularity. Take this into account when calculating the packed git- windowsize and file offsets. At the moment, the only function which makes use of offsets in conjunction with mmap is use_pack() in sha1-file.c. Git fast-import's code path tries to map a portion of the temporary packfile that exceeds the current filesize, i.e. offset+length is greater than the filesize. The NO_MMAP code worked with that since pread() just reads the file content until EOF and returns gracefully, while MapViewOfFile() aborts the mapping and returns 'Access Denied'. Working around that by determining the filesize and adjusting the length parameter. Signed-off-by: Janos Laube <janos.dev@gmail.com> Signed-off-by: Johannes Sixt <j6t@kdbg.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
53 lines
1.2 KiB
C
53 lines
1.2 KiB
C
#include "../git-compat-util.h"
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/*
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* Note that this doesn't return the actual pagesize, but
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* the allocation granularity. If future Windows specific git code
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* needs the real getpagesize function, we need to find another solution.
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*/
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int mingw_getpagesize(void)
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{
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SYSTEM_INFO si;
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GetSystemInfo(&si);
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return si.dwAllocationGranularity;
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}
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void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
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{
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HANDLE hmap;
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void *temp;
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size_t len;
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struct stat st;
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uint64_t o = offset;
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uint32_t l = o & 0xFFFFFFFF;
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uint32_t h = (o >> 32) & 0xFFFFFFFF;
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if (!fstat(fd, &st))
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len = xsize_t(st.st_size);
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else
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die("mmap: could not determine filesize");
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if ((length + offset) > len)
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length = len - offset;
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if (!(flags & MAP_PRIVATE))
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die("Invalid usage of mmap when built with USE_WIN32_MMAP");
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hmap = CreateFileMapping((HANDLE)_get_osfhandle(fd), 0, PAGE_WRITECOPY,
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0, 0, 0);
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if (!hmap)
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return MAP_FAILED;
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temp = MapViewOfFileEx(hmap, FILE_MAP_COPY, h, l, length, start);
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if (!CloseHandle(hmap))
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warning("unable to close file mapping handle\n");
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return temp ? temp : MAP_FAILED;
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}
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int git_munmap(void *start, size_t length)
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{
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return !UnmapViewOfFile(start);
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}
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