[ovs-dev] [eviction 01/12] util: Move bitwise_copy() here, add new bitwise functions.
Ben Pfaff
blp at nicira.com
Sat Jan 14 00:43:42 UTC 2012
bitwise_copy() is generally useful so make it a general utility function.
Also add a comment.
Upcoming commits will introduce users for the new functions.
---
lib/nx-match.c | 54 +----------------------------
lib/util.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
lib/util.h | 8 ++++
3 files changed, 115 insertions(+), 53 deletions(-)
diff --git a/lib/nx-match.c b/lib/nx-match.c
index 63e5e5b..ef166c7 100644
--- a/lib/nx-match.c
+++ b/lib/nx-match.c
@@ -29,6 +29,7 @@
#include "openflow/nicira-ext.h"
#include "packets.h"
#include "unaligned.h"
+#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(nx_match);
@@ -1044,59 +1045,6 @@ nxm_check_reg_load(const struct nx_action_reg_load *action,
/* nxm_execute_reg_move(), nxm_execute_reg_load(). */
-static void
-bitwise_copy(const void *src_, unsigned int src_len, unsigned int src_ofs,
- void *dst_, unsigned int dst_len, unsigned int dst_ofs,
- unsigned int n_bits)
-{
- const uint8_t *src = src_;
- uint8_t *dst = dst_;
-
- src += src_len - (src_ofs / 8 + 1);
- src_ofs %= 8;
-
- dst += dst_len - (dst_ofs / 8 + 1);
- dst_ofs %= 8;
-
- if (src_ofs == 0 && dst_ofs == 0) {
- unsigned int n_bytes = n_bits / 8;
- if (n_bytes) {
- dst -= n_bytes - 1;
- src -= n_bytes - 1;
- memcpy(dst, src, n_bytes);
-
- n_bits %= 8;
- src--;
- dst--;
- }
- if (n_bits) {
- uint8_t mask = (1 << n_bits) - 1;
- *dst = (*dst & ~mask) | (*src & mask);
- }
- } else {
- while (n_bits > 0) {
- unsigned int max_copy = 8 - MAX(src_ofs, dst_ofs);
- unsigned int chunk = MIN(n_bits, max_copy);
- uint8_t mask = ((1 << chunk) - 1) << dst_ofs;
-
- *dst &= ~mask;
- *dst |= ((*src >> src_ofs) << dst_ofs) & mask;
-
- src_ofs += chunk;
- if (src_ofs == 8) {
- src--;
- src_ofs = 0;
- }
- dst_ofs += chunk;
- if (dst_ofs == 8) {
- dst--;
- dst_ofs = 0;
- }
- n_bits -= chunk;
- }
- }
-}
-
/* Returns the value of the NXM field corresponding to 'header' at 'ofs_nbits'
* in 'flow'. */
uint64_t
diff --git a/lib/util.c b/lib/util.c
index 8379c9a..7114d9f 100644
--- a/lib/util.c
+++ b/lib/util.c
@@ -25,7 +25,9 @@
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
+#include "byte-order.h"
#include "coverage.h"
+#include "openvswitch/types.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(util);
@@ -733,3 +735,107 @@ is_all_ones(const uint8_t *p, size_t n)
return true;
}
+/* Copies 'n_bits' bits starting from bit 'src_ofs' in 'src' to the 'n_bits'
+ * starting from bit 'dst_ofs' in 'dst'. 'src' is 'src_len' bytes long and
+ * 'dst' is 'dst_len' bytes long. Bit 0 of 'src' is the bit with value 1 in
+ * src[src_len - 1], bit 1 is the bit with value 2, bit 8 is the bit with value
+ * 1 in src[src_len - 2], and so on, and similarly for 'dst'.
+ *
+ * Required invariants:
+ * src_ofs + n_bits <= src_len * 8
+ * dst_ofs + n_bits <= dst_len * 8
+ * 'src' and 'dst' must not overlap.
+ */
+void
+bitwise_copy(const void *src_, unsigned int src_len, unsigned int src_ofs,
+ void *dst_, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits)
+{
+ const uint8_t *src = src_;
+ uint8_t *dst = dst_;
+
+ src += src_len - (src_ofs / 8 + 1);
+ src_ofs %= 8;
+
+ dst += dst_len - (dst_ofs / 8 + 1);
+ dst_ofs %= 8;
+
+ if (src_ofs == 0 && dst_ofs == 0) {
+ unsigned int n_bytes = n_bits / 8;
+ if (n_bytes) {
+ dst -= n_bytes - 1;
+ src -= n_bytes - 1;
+ memcpy(dst, src, n_bytes);
+
+ n_bits %= 8;
+ src--;
+ dst--;
+ }
+ if (n_bits) {
+ uint8_t mask = (1 << n_bits) - 1;
+ *dst = (*dst & ~mask) | (*src & mask);
+ }
+ } else {
+ while (n_bits > 0) {
+ unsigned int max_copy = 8 - MAX(src_ofs, dst_ofs);
+ unsigned int chunk = MIN(n_bits, max_copy);
+ uint8_t mask = ((1 << chunk) - 1) << dst_ofs;
+
+ *dst &= ~mask;
+ *dst |= ((*src >> src_ofs) << dst_ofs) & mask;
+
+ src_ofs += chunk;
+ if (src_ofs == 8) {
+ src--;
+ src_ofs = 0;
+ }
+ dst_ofs += chunk;
+ if (dst_ofs == 8) {
+ dst--;
+ dst_ofs = 0;
+ }
+ n_bits -= chunk;
+ }
+ }
+}
+
+/* Copies the 'n_bits' low-order bits of 'value' into the 'n_bits' bits
+ * starting at bit 'dst_ofs' in 'dst', which is 'dst_len' bytes long. Bit 0 of
+ * 'dst' is the bit with value 1 in dst[dst_len - 1], bit 1 is the bit with
+ * value 2, bit 8 is the bit with value 1 in dst[dst_len - 2], and so on.
+ *
+ * Required invariants:
+ * dst_ofs + n_bits <= dst_len * 8
+ * n_bits <= 64
+ */
+void
+bitwise_put(uint64_t value,
+ void *dst, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits)
+{
+ ovs_be64 n_value = htonll(value);
+ bitwise_copy(&n_value, sizeof n_value, 0,
+ dst, dst_len, dst_ofs,
+ n_bits);
+}
+
+/* Returns the value of the 'n_bits' bits starting at bit 'src_ofs' in 'src',
+ * which is 'src_len' bytes long. Bit 0 of 'src' is the bit with value 1 in
+ * src[src_len - 1], bit 1 is the bit with value 2, bit 8 is the bit with value
+ * 1 in src[src_len - 2], and so on.
+ *
+ * Required invariants:
+ * src_ofs + n_bits <= src_len * 8
+ * n_bits <= 64
+ */
+uint64_t
+bitwise_get(const void *src, unsigned int src_len,
+ unsigned int src_ofs, unsigned int n_bits)
+{
+ ovs_be64 value = htonll(0);
+
+ bitwise_copy(src, src_len, src_ofs,
+ &value, sizeof value, 0,
+ n_bits);
+ return ntohll(value);
+}
diff --git a/lib/util.h b/lib/util.h
index b2052f3..c8eb004 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -208,6 +208,14 @@ int ctz(uint32_t);
bool is_all_zeros(const uint8_t *, size_t);
bool is_all_ones(const uint8_t *, size_t);
+void bitwise_copy(const void *src, unsigned int src_len, unsigned int src_ofs,
+ void *dst, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits);
+void bitwise_put(uint64_t value,
+ void *dst, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits);
+uint64_t bitwise_get(const void *src, unsigned int src_len,
+ unsigned int src_ofs, unsigned int n_bits);
#ifdef __cplusplus
}
--
1.7.2.5
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