1 files changed, 44 insertions, 0 deletions
diff --git a/compat/writev.c b/compat/writev.c
new file mode 100644
index 0000000000..3a94870a2f
--- /dev/null
+++ b/compat/writev.c
@@ -0,0 +1,44 @@
+#include "../git-compat-util.h"
+#include "../wrapper.h"
+
+ssize_t git_writev(int fd, const struct iovec *iov, int iovcnt)
+{
+	size_t total_written = 0;
+	size_t sum = 0;
+
+	/*
+	 * According to writev(3p), the syscall shall error with EINVAL in case
+	 * the sum of `iov_len` overflows `ssize_t`.
+	 */
+	 for (int i = 0; i < iovcnt; i++) {
+		if (iov[i].iov_len > maximum_signed_value_of_type(ssize_t) ||
+		    iov[i].iov_len + sum > maximum_signed_value_of_type(ssize_t)) {
+			errno = EINVAL;
+			return -1;
+		}
+
+		sum += iov[i].iov_len;
+	}
+
+	for (int i = 0; i < iovcnt; i++) {
+		const char *bytes = iov[i].iov_base;
+		size_t iovec_written = 0;
+
+		while (iovec_written < iov[i].iov_len) {
+			ssize_t bytes_written = xwrite(fd, bytes + iovec_written,
+						       iov[i].iov_len - iovec_written);
+			if (bytes_written < 0) {
+				if (total_written)
+					goto out;
+				return bytes_written;
+			}
+			if (!bytes_written)
+				goto out;
+			iovec_written += bytes_written;
+			total_written += bytes_written;
+		}
+	}
+
+out:
+	return (ssize_t) total_written;
+}