Eratostene Sieve in Ruby

axsaxs (Alessio Saltarin) — Thu, 02 Aug 2007 15:22:12 GMT

A simple Eratostene Sieve implementation
for the computing of prime numbers



#!/usr/bin/env ruby



#

# Compute prime numbers

# with the good old Eratostene Sieve method

# Author: Alessio Saltarin

#





# Eratostene Sieve computer class

class Sieve

    # Constructor

    # maxprime: max upper limit

    def initialize(maxprime)

            puts "Initializing sieve."

            @max = maxprime

            @sieve = Array.new

            @sieve[0] = 0

            @sieve[1] = 0

            for i in 2 ... @max

                    @sieve[i] = 1

            end

    end

    

    # Return a list of prime numbers

    def primes

            printf("Computing primes to %d ...\n", @max)

            crivello()

            puts "Done."

            retprimes = Array.new

            for k in 0..@max

                    if @sieve[k] == 1

                            retprimes.push(k)

                    end

            end

            return retprimes

    end

    

    # Sieve (Crivello) algorithm

    def crivello

            currprime = nextprime(0)

            while (currprime * currprime < @max)

                    i = currprime * currprime

                    while (i < @max)

                            @sieve[i] = 0

                            i += currprime

                    end

                    currprime = nextprime(currprime)

            end

    end



    # Return next prime

    # lastprime: the last computer prime number

    def nextprime(lastprime)

        

            for i in lastprime+1...@max

                    return i if @sieve[i] == 1

            end

    end

	

	

end



# Print a list of prime numbers

def printPrimes(primes)

    primes.each { |nr| printf("Prime: %d\n", nr) }

end



# Print the sum of prime numbers

def printSumPrimes(primes)

    sum = 0

    puts("Computing...")

    primes.each { |nr|  sum += nr }

    puts("Done.")

    printf("Prime Sum: %d\n", sum)

end



# Main

crivello = Sieve.new(1000000) # Compute primes for the first 1000000 natural numbers

printSumPrimes(crivello.primes)

MD5 and SHA1 in Ruby

axsaxs (Alessio Saltarin) — Tue, 23 Jan 2007 20:53:03 GMT

// A Simple MD5/SHA1 calculator in Ruby



#!/usr/bin/ruby1.8 -w



#

# A Simple Hash Code Calculator

# Returns SHA1 and MD5 hash for any given file

# Author: Alessio Saltarin

#



require 'digest/md5'

require 'digest/sha1'



$BUFLEN = 1024



class Hasher

	# Constructor

	# method = "SHA1" or "MD5"

	# filepath = Full filepath

	def initialize(method, filepath)

		if (method.upcase == "-SHA1")

			@hashfunc = Digest::SHA1.new

			@hashname = "SHA1"

		else

			@hashfunc = Digest::MD5.new

			@hashname = "MD5"

		end

		@fullfilename = filepath

	end



	def hashname

		@hashname

	end



	# Compute hash code

	def hashsum

		open(@fullfilename, "r") do |io|

			puts "Reading "+@fullfilename

			counter = 0

			while (!io.eof)

				readBuf = io.readpartial($BUFLEN)

				putc '.' if ((counter+=1) % 3 == 0)

				@hashfunc.update(readBuf)

			end

		end

		return @hashfunc.hexdigest

	end

end



def usage

	puts "Usage: Hasher.rb [-SHA1|-MD5] filename"

end



def printresult(filename, method, sum)

	puts "\n" + filename + " ==> "+ method + ": " + sum	

end



#Program starts

if (ARGV.length == 2)

	hashcomp = Hasher.new(ARGV[0], ARGV[1])

	printresult(ARGV[1], hashcomp.hashname, hashcomp.hashsum)

	

elsif (ARGV.length == 1)

	hashcomp = Hasher.new("-MD5", ARGV[0])

	printresult(ARGV[0], hashcomp.hashname, hashcomp.hashsum)

else

	usage

end

DZone Snippets: Axsaxs's Code Snippets

Eratostene Sieve in Ruby

MD5 and SHA1 in Ruby