1 files changed, 60 insertions, 0 deletions
diff --git a/iredis/data/commands/bitpos.md b/iredis/data/commands/bitpos.md
new file mode 100644
index 0000000..56dc588
--- /dev/null
+++ b/iredis/data/commands/bitpos.md
@@ -0,0 +1,60 @@
+Return the position of the first bit set to 1 or 0 in a string.
+
+The position is returned, thinking of the string as an array of bits from left
+to right, where the first byte's most significant bit is at position 0, the
+second byte's most significant bit is at position 8, and so forth.
+
+The same bit position convention is followed by `GETBIT` and `SETBIT`.
+
+By default, all the bytes contained in the string are examined. It is possible
+to look for bits only in a specified interval passing the additional arguments
+_start_ and _end_ (it is possible to just pass _start_, the operation will
+assume that the end is the last byte of the string. However there are semantic
+differences as explained later). The range is interpreted as a range of bytes
+and not a range of bits, so `start=0` and `end=2` means to look at the first
+three bytes.
+
+Note that bit positions are returned always as absolute values starting from bit
+zero even when _start_ and _end_ are used to specify a range.
+
+Like for the `GETRANGE` command start and end can contain negative values in
+order to index bytes starting from the end of the string, where -1 is the last
+byte, -2 is the penultimate, and so forth.
+
+Non-existent keys are treated as empty strings.
+
+@return
+
+@integer-reply
+
+The command returns the position of the first bit set to 1 or 0 according to the
+request.
+
+If we look for set bits (the bit argument is 1) and the string is empty or
+composed of just zero bytes, -1 is returned.
+
+If we look for clear bits (the bit argument is 0) and the string only contains
+bit set to 1, the function returns the first bit not part of the string on the
+right. So if the string is three bytes set to the value `0xff` the command
+`BITPOS key 0` will return 24, since up to bit 23 all the bits are 1.
+
+Basically, the function considers the right of the string as padded with zeros
+if you look for clear bits and specify no range or the _start_ argument
+**only**.
+
+However, this behavior changes if you are looking for clear bits and specify a
+range with both **start** and **end**. If no clear bit is found in the specified
+range, the function returns -1 as the user specified a clear range and there are
+no 0 bits in that range.
+
+@examples
+
+```cli
+SET mykey "\xff\xf0\x00"
+BITPOS mykey 0
+SET mykey "\x00\xff\xf0"
+BITPOS mykey 1 0
+BITPOS mykey 1 2
+set mykey "\x00\x00\x00"
+BITPOS mykey 1
+```