import sys, os

# find_library(name) returns the pathname of a library, or None.
if os.name == "nt":
    def find_library(name):
        # See MSDN for the REAL search order.
        for directory in os.environ['PATH'].split(os.pathsep):
            fname = os.path.join(directory, name)
            if os.path.exists(fname):
                return fname
            if fname.lower().endswith(".dll"):
                continue
            fname = fname + ".dll"
            if os.path.exists(fname):
                return fname
        return None

if os.name == "ce":
    # search path according to MSDN:
    # - absolute path specified by filename
    # - The .exe launch directory
    # - the Windows directory
    # - ROM dll files (where are they?)
    # - OEM specified search path: HKLM\Loader\SystemPath
    def find_library(name):
        return name

if os.name == "posix" and sys.platform == "darwin":
    from ctypes.macholib.dyld import dyld_find as _dyld_find
    def find_library(name):
        possible = ['lib%s.dylib' % name,
                    '%s.dylib' % name,
                    '%s.framework/%s' % (name, name)]
        for name in possible:
            try:
                return _dyld_find(name)
            except ValueError:
                continue
        return None

elif os.name == "posix":
    # Andreas Degert's find functions, using gcc, /sbin/ldconfig, objdump
    import re, tempfile, errno

    def _findLib_gcc(name):
        expr = r'[^\(\)\s]*lib%s\.[^\(\)\s]*' % re.escape(name)
        fdout, ccout = tempfile.mkstemp()
        os.close(fdout)
        cmd = 'if type gcc >/dev/null 2>&1; then CC=gcc; else CC=cc; fi;' \
              '$CC -Wl,-t -o ' + ccout + ' 2>&1 -l' + name
        try:
            f = os.popen(cmd)
            try:
                trace = f.read()
            finally:
                f.close()
        finally:
            try:
                os.unlink(ccout)
            except OSError as e:
                if e.errno != errno.ENOENT:
                    raise
        res = re.search(expr, trace)
        if not res:
            return None
        return res.group(0)


    if sys.platform == "sunos5":
        # use /usr/ccs/bin/dump on solaris
        def _get_soname(f):
            if not f:
                return None
            cmd = "/usr/ccs/bin/dump -Lpv 2>/dev/null " + f
            f = os.popen(cmd)
            try:
                data = f.read()
            finally:
                f.close()
            res = re.search(r'\[.*\]\sSONAME\s+([^\s]+)', data)
            if not res:
                return None
            return res.group(1)
    else:
        def _get_soname(f):
            # assuming GNU binutils / ELF
            if not f:
                return None
            cmd = "objdump -p -j .dynamic 2>/dev/null " + f
            f = os.popen(cmd)
            try:
                data = f.read()
            finally:
                f.close()
            res = re.search(r'\sSONAME\s+([^\s]+)', data)
            if not res:
                return None
            return res.group(1)

    if (sys.platform.startswith("freebsd")
        or sys.platform.startswith("openbsd")
        or sys.platform.startswith("dragonfly")):

        def _num_version(libname):
            # "libxyz.so.MAJOR.MINOR" => [ MAJOR, MINOR ]
            parts = libname.split(".")
            nums = []
            try:
                while parts:
                    nums.insert(0, int(parts.pop()))
            except ValueError:
                pass
            return nums or [ sys.maxsize ]

        def find_library(name):
            ename = re.escape(name)
            expr = r':-l%s\.\S+ => \S*/(lib%s\.\S+)' % (ename, ename)
            f = os.popen('/sbin/ldconfig -r 2>/dev/null')
            try:
                data = f.read()
            finally:
                f.close()
            res = re.findall(expr, data)
            if not res:
                return _get_soname(_findLib_gcc(name))
            res.sort(key=_num_version)
            return res[-1]

    else:

        def _findLib_ldconfig(name):
            # XXX assuming GLIBC's ldconfig (with option -p)
            expr = r'/[^\(\)\s]*lib%s\.[^\(\)\s]*' % re.escape(name)
            f = os.popen('/sbin/ldconfig -p 2>/dev/null')
            try:
                data = f.read()
            finally:
                f.close()
            res = re.search(expr, data)
            if not res:
                # Hm, this works only for libs needed by the python executable.
                cmd = 'ldd %s 2>/dev/null' % sys.executable
                f = os.popen(cmd)
                try:
                    data = f.read()
                finally:
                    f.close()
                res = re.search(expr, data)
                if not res:
                    return None
            return res.group(0)

        def find_library(name):
            return _get_soname(_findLib_ldconfig(name) or _findLib_gcc(name))

################################################################
# test code

def test():
    from ctypes import cdll
    if os.name == "nt":
        print(cdll.msvcrt)
        print(cdll.load("msvcrt"))
        print(find_library("msvcrt"))

    if os.name == "posix":
        # find and load_version
        print(find_library("m"))
        print(find_library("c"))
        print(find_library("bz2"))

        # getattr
##        print cdll.m
##        print cdll.bz2

        # load
        if sys.platform == "darwin":
            print(cdll.LoadLibrary("libm.dylib"))
            print(cdll.LoadLibrary("libcrypto.dylib"))
            print(cdll.LoadLibrary("libSystem.dylib"))
            print(cdll.LoadLibrary("System.framework/System"))
        else:
            print(cdll.LoadLibrary("libm.so"))
            print(cdll.LoadLibrary("libcrypt.so"))
            print(find_library("crypt"))

if __name__ == "__main__":
    test()