Replace decimal numbers in string by hex equivalent - ruby

Question

I have a huge set of strings like:
// Register 10:
typedef struct RegAddr_10
{
uint8 something: 4;
uint8 something_else: 4;
} tRegAddr_10;
and want to convert all register addresses (given in decimal numbers) to hexadecimal. Other numbers can occur within each typedef; therefore I have to consider the Reg part as a kind of delimiter. The example should result in:
// Register 0x0A:
typedef struct RegAddr_0x0A
{
uint8 something: 4;
uint8 something_else: 4;
} tRegAddr_0x0A;
My solution is this:
class String
def convert_base(from, to)
self.to_i(from).to_s(to)
end
end
new = text.gsub(/Reg\D*\d*/) do |number|
number.gsub(/(\d+)/) {'0x'+$1.convert_base(10,16)}
end
It works, but:
(How) is it possible to do this with one gsub only?
How can I make the conversion generate 2-digit-hex numbers in upper case, e.g. 10 → 0x0A, not 0xa?

Answer 1

Code
R = /
(?: # begin non-capture group
^ # match beginning of line
\/{2}\s+Register\s+ # match string
| # or
\s+RegAddr_ # match string
| # or
\s+tRegAddr_ # match string
) # close non-capture group
\K # discard everything matched so far
\d+ # match >= 1 digits
/x # extended mode
def replace_with_hex(str)
str.gsub(R) { |s| "0x%02X" % s }
end
The part of the format string for String#% that follows the percent character is: 0, meaning pad left with zeros, 2 for field width and X to convert to hex with letters A-F in capitals (x for lower case).
Example
str = <<_
// Register 10:
typedef struct RegAddr_10
{
uint8 something: 4;
uint8 something_else: 4;
} tRegAddr_10;
_
puts replace_with_hex(str)
prints:
// Register 0x0A:
typedef struct RegAddr_0x0A
{
uint8 something: 4;
uint8 something_else: 4;
} tRegAddr_0x0A;
Alternatives
If you are less fussy:
R = /
[\s|t] # match whitespace or t
Reg\D+ # match string
\K # discard everything matched so far
\d+ # match >= 1 digits
/x # extended mode
works as well.
You could also change the operative line of replace_with_hex to:
str.gsub(R, "0x%02X" % $~[0])