[PATCH what 1/3] what: add bits.b() for binary number "literals"

[Jakub Slepecki <jakub.slepecki@intel.com>]

Good chunk of documentation uses the "1001b" notation.  Lua does not
support it, but we can leverage function calls syntax sugar to be somewhat
similar to it.

Signed-off-by: Jakub Slepecki <jakub.slepecki@intel.com>
---
 spec/bits_spec.lua | 25 +++++++++++++++++++++++++
 what/bits.lua      | 20 ++++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 spec/bits_spec.lua

diff --git a/spec/bits_spec.lua b/spec/bits_spec.lua
new file mode 100644
index 000000000000..931ce32048d7
--- /dev/null
+++ b/spec/bits_spec.lua
@@ -0,0 +1,25 @@
+local bits = require"what.bits"
+local b = bits.b
+
+
+describe("bits.b()", function()
+	describe("builds integers from", function()
+		it("some examples", function()
+			assert.are.equal(1, b"1")
+			assert.are.equal(3, b"11")
+			assert.are.equal(5, b"101")
+			assert.are.equal(15, b"1111")
+			assert.are.equal(0, b"0000")
+			assert.are.equal(37, b"100101")
+		end)
+	end)
+
+	it("allows an empty string", function()
+		assert.are.equal(0, b"")
+	end)
+
+	it("rejects malformed strings", function()
+		assert.is_nil(b"abc")
+		assert.is_nil(b"10a1")
+	end)
+end)
diff --git a/what/bits.lua b/what/bits.lua
index c11571a725bd..440d5bacd36a 100644
--- a/what/bits.lua
+++ b/what/bits.lua
@@ -131,4 +131,24 @@ function bits.bit (nth)
 end
 
 
+--- Build an integer based on a string containing a [[binary]]
+--- representation of it, for example:
+---
+---     bits.b"011"  --> 3
+---     bits.b"101"  --> 5
+function bits.b (binary)
+	if not binary:match"^[01]*$" then
+		return nil
+	end
+	local len = #binary
+	local val = 0
+	local pos = binary:find"1"
+	while pos do
+		val = val + 2 ^ (len - pos)
+		pos = binary:find("1", pos + 1)
+	end
+	return math.tointeger(val)
+end
+
+
 return bits
-- 
2.43.0