1 files changed, 41 insertions, 0 deletions
diff --git a/compat/win32mmap.c b/compat/win32mmap.c
new file mode 100644
index 0000000000..b58aa69fa0
--- /dev/null
+++ b/compat/win32mmap.c
@@ -0,0 +1,41 @@
+#include "../git-compat-util.h"
+
+void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
+{
+	HANDLE hmap;
+	void *temp;
+	off_t len;
+	struct stat st;
+	uint64_t o = offset;
+	uint32_t l = o & 0xFFFFFFFF;
+	uint32_t h = (o >> 32) & 0xFFFFFFFF;
+
+	if (!fstat(fd, &st))
+		len = st.st_size;
+	else
+		die("mmap: could not determine filesize");
+
+	if ((length + offset) > len)
+		length = xsize_t(len - offset);
+
+	if (!(flags & MAP_PRIVATE))
+		die("Invalid usage of mmap when built with USE_WIN32_MMAP");
+
+	hmap = CreateFileMapping((HANDLE)_get_osfhandle(fd), 0, PAGE_WRITECOPY,
+		0, 0, 0);
+
+	if (!hmap)
+		return MAP_FAILED;
+
+	temp = MapViewOfFileEx(hmap, FILE_MAP_COPY, h, l, length, start);
+
+	if (!CloseHandle(hmap))
+		warning("unable to close file mapping handle\n");
+
+	return temp ? temp : MAP_FAILED;
+}
+
+int git_munmap(void *start, size_t length)
+{
+	return !UnmapViewOfFile(start);
+}