diff mbox

[3/16] crypto: scatterwalk - Add scatterwalk_ffwd helper

Message ID E1YvKd9-0005dN-WD@gondolin.me.apana.org.au (mailing list archive)
State Accepted
Delegated to: Herbert Xu
Headers show

Commit Message

Herbert Xu May 21, 2015, 7:10 a.m. UTC 
This patch adds the scatterwalk_ffwd helper which can create an
SG list that starts in the middle of an existing SG list.  The
new list may either be part of the existing list or be a chain
that latches onto part of the existing list.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---

 crypto/scatterwalk.c         |   22 ++++++++++++++++++++++
 include/crypto/scatterwalk.h |    4 ++++
 2 files changed, 26 insertions(+)

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diff mbox

Patch

diff --git a/crypto/scatterwalk.c b/crypto/scatterwalk.c
index 3bd749c..db920b5 100644
--- a/crypto/scatterwalk.c
+++ b/crypto/scatterwalk.c
@@ -146,3 +146,25 @@  int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes)
 	return n;
 }
 EXPORT_SYMBOL_GPL(scatterwalk_bytes_sglen);
+
+struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
+				     struct scatterlist *src,
+				     unsigned int len)
+{
+	for (;;) {
+		if (!len)
+			return src;
+
+		if (src->length > len)
+			break;
+
+		len -= src->length;
+		src = sg_next(src);
+	}
+
+	sg_set_page(dst, sg_page(src), src->length - len, src->offset + len);
+	scatterwalk_crypto_chain(dst, sg_next(src), 0, 2);
+
+	return dst;
+}
+EXPORT_SYMBOL_GPL(scatterwalk_ffwd);
diff --git a/include/crypto/scatterwalk.h b/include/crypto/scatterwalk.h
index 20e4226..96670e7 100644
--- a/include/crypto/scatterwalk.h
+++ b/include/crypto/scatterwalk.h
@@ -102,4 +102,8 @@  void scatterwalk_map_and_copy(void *buf, struct scatterlist *sg,
 
 int scatterwalk_bytes_sglen(struct scatterlist *sg, int num_bytes);
 
+struct scatterlist *scatterwalk_ffwd(struct scatterlist dst[2],
+				     struct scatterlist *src,
+				     unsigned int len);
+
 #endif  /* _CRYPTO_SCATTERWALK_H */