1 files changed, 40 insertions, 0 deletions
diff --git a/compat/mmap.c b/compat/mmap.c
new file mode 100644
index 0000000000..7f662fef7b
--- /dev/null
+++ b/compat/mmap.c
@@ -0,0 +1,40 @@
+#include "../git-compat-util.h"
+
+void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
+{
+	size_t n = 0;
+
+	if (start != NULL || !(flags & MAP_PRIVATE))
+		die("Invalid usage of mmap when built with NO_MMAP");
+
+	start = xmalloc(length);
+	if (start == NULL) {
+		errno = ENOMEM;
+		return MAP_FAILED;
+	}
+
+	while (n < length) {
+		ssize_t count = xpread(fd, (char *)start + n, length - n, offset + n);
+
+		if (count == 0) {
+			memset((char *)start+n, 0, length-n);
+			break;
+		}
+
+		if (count < 0) {
+			free(start);
+			errno = EACCES;
+			return MAP_FAILED;
+		}
+
+		n += count;
+	}
+
+	return start;
+}
+
+int git_munmap(void *start, size_t length)
+{
+	free(start);
+	return 0;
+}