Add support for an owned buffer

When passing a data buffer back from a function, it is not always clear
who owns the buffer, i.e. who is responsible for freeing the memory used.
An example of this is where multiple files are decompressed from the
firmware image, using a temporary buffer for reading (since the
compressed data has to live somewhere) and producing a temporary or
permanent buffer with the resuilts.

Where the firmware image can be memory-mapped, as on x86, the compressed
data does not need to be buffered, but the complexity of having a buffer
which is either allocated or not, makes the code hard to understand.

Introduce a new 'abuf' which supports simple buffer operations:

- encapsulating a buffer and its size
- either allocated with malloc() or not
- able to be reliably freed if necessary
- able to be converted to an allocated buffer if needed

This simple API makes it easier to deal with allocated and memory-mapped
buffers.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 109 insertions, 0 deletions

diff --git a/lib/abuf.c b/lib/abuf.c
new file mode 100644
index 0000000000..4b17e0b8c0
--- /dev/null
+++ b/lib/abuf.c
@@ -0,0 +1,109 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Handles a buffer that can be allocated and freed
+ *
+ * Copyright 2021 Google LLC
+ * Written by Simon Glass <sjg@chromium.org>
+ */
+
+#include <common.h>
+#include <abuf.h>
+#include <malloc.h>
+#include <mapmem.h>
+#include <string.h>
+
+void abuf_set(struct abuf *abuf, void *data, size_t size)
+{
+	abuf_uninit(abuf);
+	abuf->data = data;
+	abuf->size = size;
+}
+
+void abuf_map_sysmem(struct abuf *abuf, ulong addr, size_t size)
+{
+	abuf_set(abuf, map_sysmem(addr, size), size);
+}
+
+bool abuf_realloc(struct abuf *abuf, size_t new_size)
+{
+	void *ptr;
+
+	if (!new_size) {
+		/* easy case, just need to uninit, freeing any allocation */
+		abuf_uninit(abuf);
+		return true;
+	} else if (abuf->alloced) {
+		/* currently allocated, so need to reallocate */
+		ptr = realloc(abuf->data, new_size);
+		if (!ptr)
+			return false;
+		abuf->data = ptr;
+		abuf->size = new_size;
+		return true;
+	} else if (new_size <= abuf->size) {
+		/*
+		 * not currently alloced and new size is no larger. Just update
+		 * it. Data is lost off the end if new_size < abuf->size
+		 */
+		abuf->size = new_size;
+		return true;
+	} else {
+		/* not currently allocated and new size is larger. Alloc and
+		 * copy in data. The new space is not inited.
+		 */
+		ptr = memdup(abuf->data, new_size);
+		if (!ptr)
+			return false;
+		abuf->data = ptr;
+		abuf->size = new_size;
+		abuf->alloced = true;
+		return true;
+	}
+}
+
+void *abuf_uninit_move(struct abuf *abuf, size_t *sizep)
+{
+	void *ptr;
+
+	if (sizep)
+		*sizep = abuf->size;
+	if (!abuf->size)
+		return NULL;
+	if (abuf->alloced) {
+		ptr = abuf->data;
+	} else {
+		ptr = memdup(abuf->data, abuf->size);
+		if (!ptr)
+			return NULL;
+	}
+	/* Clear everything out so there is no record of the data */
+	abuf_init(abuf);
+
+	return ptr;
+}
+
+void abuf_init_set(struct abuf *abuf, void *data, size_t size)
+{
+	abuf_init(abuf);
+	abuf_set(abuf, data, size);
+}
+
+void abuf_init_move(struct abuf *abuf, void *data, size_t size)
+{
+	abuf_init_set(abuf, data, size);
+	abuf->alloced = true;
+}
+
+void abuf_uninit(struct abuf *abuf)
+{
+	if (abuf->alloced)
+		free(abuf->data);
+	abuf_init(abuf);
+}
+
+void abuf_init(struct abuf *abuf)
+{
+	abuf->data = NULL;
+	abuf->size = 0;
+	abuf->alloced = false;
+}