[CRYPTO] scatterwalk: Add scatterwalk_map_and_copy
This patch adds the function scatterwalk_map_and_copy which reads or
writes a chunk of data from a scatterlist at a given offset. It will
be used by authenc which would read/write the authentication data at
the end of the cipher/plain text.
Signed-off-by: Herbert Xu <[email protected]>
---
crypto/scatterwalk.c | 22 ++++++++++++++++++++++
crypto/scatterwalk.h | 3 +++
2 files changed, 25 insertions(+)
diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 81afd17..e93a8f6 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -107,3 +107,25 @@ void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
}
}
EXPORT_SYMBOL_GPL(scatterwalk_copychunks);
+
+void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
+ unsigned int start, unsigned int nbytes, int out)
+{
+ struct scatter_walk walk;
+ unsigned int offset = 0;
+
+ for (;;) {
+ scatterwalk_start(&walk, sg);
+
+ if (start < offset + sg->length)
+ break;
+
+ offset += sg->length;
+ sg = sg_next(sg);
+ }
+
+ scatterwalk_advance(&walk, start - offset);
+ scatterwalk_copychunks(buf, &walk, nbytes, out);
+ scatterwalk_done(&walk, out, 0);
+}
+EXPORT_SYMBOL_GPL(scatterwalk_map_and_copy);
diff --git a/crypto/scatterwalk.h b/crypto/scatterwalk.h
index f1592cc..500a220 100644
--- a/crypto/scatterwalk.h
+++ b/crypto/scatterwalk.h
@@ -74,4 +74,7 @@ void scatterwalk_copychunks(void *buf, struct scatter_walk *walk,
void *scatterwalk_map(struct scatter_walk *walk, int out);
void scatterwalk_done(struct scatter_walk *walk, int out, int more);
+void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
+ unsigned int start, unsigned int nbytes, int out);
+
#endif /* _CRYPTO_SCATTERWALK_H */