[PATCH 1/2] libfile: copy_fd: add size argument

[Sascha Hauer <s.hauer@pengutronix.de>]

Add a size argument to copy_fd() to allow copying a specified number of
bytes. While at it add some function documentation.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 common/firmware.c |  2 +-
 include/libfile.h |  2 +-
 lib/libfile.c     | 37 +++++++++++++++++++++++++++++++++----
 3 files changed, 35 insertions(+), 6 deletions(-)

diff --git a/common/firmware.c b/common/firmware.c
index 264fc9d66d..cdc55467cd 100644
--- a/common/firmware.c
+++ b/common/firmware.c
@@ -292,7 +292,7 @@ int firmwaremgr_load_file(struct firmware_mgr *mgr, const char *firmware)
 		ret = uncompress_fd_to_fd(firmwarefd, devicefd,
 					  uncompress_err_stdout);
 	else
-		ret = copy_fd(firmwarefd, devicefd);
+		ret = copy_fd(firmwarefd, devicefd, 0);
 
 out:
 	free(dst);
diff --git a/include/libfile.h b/include/libfile.h
index dc292e422e..370f8b9725 100644
--- a/include/libfile.h
+++ b/include/libfile.h
@@ -11,7 +11,7 @@ int pread_full(int fd, void *buf, size_t size, loff_t offset);
 int pwrite_full(int fd, const void *buf, size_t size, loff_t offset);
 int write_full(int fd, const void *buf, size_t size);
 int read_full(int fd, void *buf, size_t size);
-int copy_fd(int in, int out);
+int copy_fd(int in, int out, size_t size);
 
 ssize_t read_file_into_buf(const char *filename, void *buf, size_t size);
 
diff --git a/lib/libfile.c b/lib/libfile.c
index 01189773b7..32b0c27eba 100644
--- a/lib/libfile.c
+++ b/lib/libfile.c
@@ -124,25 +124,54 @@ int read_full(int fd, void *buf, size_t size)
 }
 EXPORT_SYMBOL(read_full);
 
-int copy_fd(int in, int out)
+/*
+ * copy_fd - copy one file descriptor to another
+ * @in: input file descriptor
+ * @out: output file descriptor
+ * @size: size to copy
+ *
+ * This copies at @size bytes from @in file descriptor to @out
+ * file descriptor. If @size is zero then all data is copied until
+ * EOF is reached.
+ *
+ * @return: 0 for success and negatibe error code otherwise. If @size
+ * is non zero and not all data could be read from @in then -ENODATA
+ * is returned.
+ */
+int copy_fd(int in, int out, size_t size)
 {
-	int bs = 4096, ret;
+	size_t copied = 0, bs = 4096;
 	void *buf = malloc(bs);
+	int ret;
 
 	if (!buf)
 		return -ENOMEM;
 
 	while (1) {
-		ret = read(in, buf, bs);
+		size_t now = min(bs, size - copied);
+
+		if (!now) {
+			ret = 0;
+			break;
+		}
+
+		ret = read(in, buf, now);
 		if (ret <= 0)
 			break;
 
+		now = ret;
+
 		ret = write_full(out, buf, ret);
 		if (ret < 0)
 			break;
+
+		copied += now;
 	}
 
-        free(buf);
+	free(buf);
+
+	if (size && copied < size)
+		ret = -ENODATA;
 
 	return ret;
 }

-- 
2.47.3