jsmin.py

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#http://www.crockford.com/javascript/jsmin.html
from StringIO import StringIO

def jsmin(js):
    ins = StringIO(js)
    outs = StringIO()
    JavascriptMinify().minify(ins, outs)
    str = outs.getvalue()
    if len(str) > 0 and str[0] == '\n':
        str = str[1:]
    return str

##
# return true if the character is a letter, digit, underscore,
#            dollar sign, or non-ASCII character.
#     
def isAlphanum(c):
    return ((c >= 'a' and c <= 'z') or (c >= '0' and c <= '9') or
            (c >= 'A' and c <= 'Z') or c == '_' or c == '$' or c == '\\' or (c is not None and ord(c) > 126));

class UnterminatedComment(Exception):
    pass

class UnterminatedStringLiteral(Exception):
    pass

class UnterminatedRegularExpression(Exception):
    pass

class JavascriptMinify(object):

    def _outA(self):
        self.outstream.write(self.theA)
    def _outB(self):
        self.outstream.write(self.theB)

    ##
    # return the next character from stdin. Watch out for lookahead. If
    #            the character is a control character, translate it to a space or
    #            linefeed.
    #         
    def _get(self):
        c = self.theLookahead
        self.theLookahead = None
        if c == None:
            c = self.instream.read(1)
        if c >= ' ' or c == '\n':
            return c
        if c == '': # EOF
            return '\000'
        if c == '\r':
            return '\n'
        return ' '

    def _peek(self):
        self.theLookahead = self._get()
        return self.theLookahead

    ##
    # get the next character, excluding comments. peek() is used to see
    #            if an unescaped '/' is followed by a '/' or '*'.
    #         
    def _next(self):
        c = self._get()
        if c == '/' and self.theA != '\\':
            p = self._peek()
            if p == '/':
                c = self._get()
                while c > '\n':
                    c = self._get()
                return c
            if p == '*':
                c = self._get()
                while 1:
                    c = self._get()
                    if c == '*':
                        if self._peek() == '/':
                            self._get()
                            return ' '
                    if c == '\000':
                        raise UnterminatedComment()

        return c

    ##
    # do something! What you do is determined by the argument:
    #            1   Output A. Copy B to A. Get the next B.
    #            2   Copy B to A. Get the next B. (Delete A).
    #            3   Get the next B. (Delete B).
    #            action treats a string as a single character. Wow!
    #            action recognizes a regular expression if it is preceded by ( or , or =.
    #         
    def _action(self, action):
        if action <= 1:
            self._outA()

        if action <= 2:
            self.theA = self.theB
            if self.theA == "'" or self.theA == '"':
                while 1:
                    self._outA()
                    self.theA = self._get()
                    if self.theA == self.theB:
                        break
                    if self.theA <= '\n':
                        raise UnterminatedStringLiteral()
                    if self.theA == '\\':
                        self._outA()
                        self.theA = self._get()


        if action <= 3:
            self.theB = self._next()
            if self.theB == '/' and (self.theA == '(' or self.theA == ',' or
                                     self.theA == '=' or self.theA == ':' or
                                     self.theA == '[' or self.theA == '?' or
                                     self.theA == '!' or self.theA == '&' or
                                     self.theA == '|' or self.theA == ';' or
                                     self.theA == '{' or self.theA == '}' or
                                     self.theA == '\n'):
                self._outA()
                self._outB()
                while 1:
                    self.theA = self._get()
                    if self.theA == '/':
                        break
                    elif self.theA == '\\':
                        self._outA()
                        self.theA = self._get()
                    elif self.theA <= '\n':
                        raise UnterminatedRegularExpression()
                    self._outA()
                self.theB = self._next()


    ##
    # Copy the input to the output, deleting the characters which are
    #            insignificant to JavaScript. Comments will be removed. Tabs will be
    #            replaced with spaces. Carriage returns will be replaced with linefeeds.
    #            Most spaces and linefeeds will be removed.
    #         
    def _jsmin(self):
        self.theA = '\n'
        self._action(3)

        while self.theA != '\000':
            if self.theA == ' ':
                if isAlphanum(self.theB):
                    self._action(1)
                else:
                    self._action(2)
            elif self.theA == '\n':
                if self.theB in ['{', '[', '(', '+', '-']:
                    self._action(1)
                elif self.theB == ' ':
                    self._action(3)
                else:
                    if isAlphanum(self.theB):
                        self._action(1)
                    else:
                        self._action(2)
            else:
                if self.theB == ' ':
                    if isAlphanum(self.theA):
                        self._action(1)
                    else:
                        self._action(3)
                elif self.theB == '\n':
                    if self.theA in ['}', ']', ')', '+', '-', '"', '\'']:
                        self._action(1)
                    else:
                        if isAlphanum(self.theA):
                            self._action(1)
                        else:
                            self._action(3)
                else:
                    self._action(1)

    def minify(self, instream, outstream):
        self.instream = instream
        self.outstream = outstream
        self.theA = '\n'
        self.theB = None
        self.theLookahead = None

        self._jsmin()
        self.instream.close()

if (__name__ == '__main__'):
    import sys
    jsm = JavascriptMinify()
    jsm.minify(sys.stdin, sys.stdout)