From: Eric Hodel <drbrain@...7.net>
Date: 2005-03-18T15:15:59+09:00
Subject: Ruby/DL and libc's localtime

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I'm trying to wrap localtime from libc, and am having no luck.

Here's what I've got:

require "dl"
require "dl/import"
require "dl/struct"

module LIBC

   extend DL::Importable

   begin
     dlload "libc.so"
   rescue
     dlload "libc.dylib" # Mac
   end

   typealias "const time_t *clock", "long ref" # teach DL about const 
time_t * clock

   ##
   # I know this isn't necessary, but just so you can see it in 
c_localtime below

   StructTm = struct [
     "int tm_sec",     # seconds (0 - 60)
     "int tm_min",     # minutes (0 - 59)
     "int tm_hour",    # hours (0 - 23)
     "int tm_mday",    # day of month (1 - 31)
     "int tm_mon",     # month of year (0 - 11)
     "int tm_year",    # year - 1900
     "int tm_wday",    # day of week (Sunday = 0)
     "int tm_yday",    # day of year (0 - 365)
     "int tm_isdst",   # is summer time in effect?
     "long tm_gmtoff", # offset from UTC in seconds
     "char *tm_zone",  # abbreviation of timezone name
   ]

   extern "struct tm * localtime(const time_t *clock)"

   def self.c_localtime(clock)
     tm = LIBC.localtime(clock)
     return tm.to_a('IIIIIIIIILc') # should match StructTm above
   end

end

p LIBC.c_localtime(Time.now.to_i) # => []

If I add p tm before calling to_a, I see that its a pointer of size 0, 
which makes me think I've got something wrong.

-- 
Eric Hodel - drbrain@segment7.net - http://segment7.net
FEC2 57F1 D465 EB15 5D6E  7C11 332A 551C 796C 9F04

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