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7ce7ee2d82
Often we are mmap()ing read-only. In those cases, it is wasteful to map in copy-on-write mode. Even worse: it can cause errors where we run out of space in the page file. So let's be extra careful to map files in read-only mode whenever possible. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
48 lines
1.1 KiB
C
48 lines
1.1 KiB
C
#include "../git-compat-util.h"
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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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off_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 = 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 = xsize_t(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), NULL,
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prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL);
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if (!hmap) {
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errno = EINVAL;
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return MAP_FAILED;
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}
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temp = MapViewOfFileEx(hmap, prot == PROT_READ ?
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FILE_MAP_READ : 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");
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if (temp)
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return temp;
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errno = GetLastError() == ERROR_COMMITMENT_LIMIT ? EFBIG : EINVAL;
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return 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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