New upstream release

[bcachefs-tools-debian] / libbcachefs / varint.c

diff --git a/libbcachefs/varint.c b/libbcachefs/varint.c
index a3d252c741c88cc0b9632b13be38735924220db2..e6a041541792676d8936fdbc44dfac95314de076 100644 (file)
--- a/libbcachefs/varint.c
+++ b/libbcachefs/varint.c
@@ -1,10 +1,18 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <linux/bitops.h>
+#include <linux/string.h>
 #include <asm/unaligned.h>
 
 #include "varint.h"
 
+/**
+ * bch2_varint_encode - encode a variable length integer
+ * @out - destination to encode to
+ * @v  - unsigned integer to encode
+ *
+ * Returns the size in bytes of the encoded integer - at most 9 bytes
+ */
 int bch2_varint_encode(u8 *out, u64 v)
 {
        unsigned bits = fls64(v|1);
@@ -13,16 +21,79 @@ int bch2_varint_encode(u8 *out, u64 v)
        if (likely(bytes < 9)) {
                v <<= bytes;
                v |= ~(~0 << (bytes - 1));
+               v = cpu_to_le64(v);
+               memcpy(out, &v, bytes);
        } else {
                *out++ = 255;
                bytes = 9;
+               put_unaligned_le64(v, out);
        }
 
-       put_unaligned_le64(v, out);
        return bytes;
 }
 
+/**
+ * bch2_varint_decode - encode a variable length integer
+ * @in - varint to decode
+ * @end        - end of buffer to decode from
+ * @out        - on success, decoded integer
+ *
+ * Returns the size in bytes of the decoded integer - or -1 on failure (would
+ * have read past the end of the buffer)
+ */
 int bch2_varint_decode(const u8 *in, const u8 *end, u64 *out)
+{
+       unsigned bytes = likely(in < end)
+               ? ffz(*in & 255) + 1
+               : 1;
+       u64 v;
+
+       if (unlikely(in + bytes > end))
+               return -1;
+
+       if (likely(bytes < 9)) {
+               v = 0;
+               memcpy(&v, in, bytes);
+               v = le64_to_cpu(v);
+               v >>= bytes;
+       } else {
+               v = get_unaligned_le64(++in);
+       }
+
+       *out = v;
+       return bytes;
+}
+
+/**
+ * bch2_varint_encode_fast - fast version of bch2_varint_encode
+ *
+ * This version assumes it's always safe to write 8 bytes to @out, even if the
+ * encoded integer would be smaller.
+ */
+int bch2_varint_encode_fast(u8 *out, u64 v)
+{
+       unsigned bits = fls64(v|1);
+       unsigned bytes = DIV_ROUND_UP(bits, 7);
+
+       if (likely(bytes < 9)) {
+               v <<= bytes;
+               v |= ~(~0 << (bytes - 1));
+       } else {
+               *out++ = 255;
+               bytes = 9;
+       }
+
+       put_unaligned_le64(v, out);
+       return bytes;
+}
+
+/**
+ * bch2_varint_decode_fast - fast version of bch2_varint_decode
+ *
+ * This version assumes that it is safe to read at most 8 bytes past the end of
+ * @end (we still return an error if the varint extends past @end).
+ */
+int bch2_varint_decode_fast(const u8 *in, const u8 *end, u64 *out)
 {
        u64 v = get_unaligned_le64(in);
        unsigned bytes = ffz(v & 255) + 1;