path: root/src/engine/SCons/Sig/__init__.py

"""SCons.Sig

The Signature package for the scons software construction utility.

"""

#
# Copyright (c) 2001, 2002 Steven Knight
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY
# KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
# WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#

__revision__ = "__FILE__ __REVISION__ __DATE__ __DEVELOPER__"

import os
import os.path
import string
import SCons.Node
import time

#XXX Get rid of the global array so this becomes re-entrant.
sig_files = []

def write():
    global sig_files
    for sig_file in sig_files:
        sig_file.write()

class SConsignEntry:
    def __init__(self, module, entry=None):

        self.timestamp = self.csig = self.bsig = self.implicit = None

        if not entry is None:
            arr = map(string.strip, string.split(entry, " ", 3))

            try:
                if arr[0] == '-': self.timestamp = None
                else:             self.timestamp = int(arr[0])

                if arr[1] == '-': self.bsig = None
                else:             self.bsig = module.from_string(arr[1])

                if arr[2] == '-': self.csig = None
                else:             self.csig = module.from_string(arr[2])

                if len(arr) < 4:        self.implicit = None # pre-0.07 format
                elif arr[3] == '':      self.implicit = '' # pre-0.08 format
                elif arr[3] == '-':     self.implicit = None
                else:                   self.implicit = string.replace(arr[3], '\0\0', '')
            except IndexError:
                pass

    def render(self, module):
        if self.timestamp is None: timestamp = '-'
        else:                      timestamp = "%d"%self.timestamp

        if self.bsig is None: bsig = '-'
        else:                 bsig = module.to_string(self.bsig)

        if self.csig is None: csig = '-'
        else:                 csig = module.to_string(self.csig)

        if self.implicit is None: implicit = '-'
        else:                     implicit = '\0\0%s\0\0'%self.implicit

        return '%s %s %s %s' % (timestamp, bsig, csig, implicit)

    def get_implicit(self):
        if self.implicit is None:
            return None
        elif self.implicit == '':
            return []
        else:
            return string.split(self.implicit, '\0')

    def set_implicit(self, implicit):
        if implicit is None:
            self.implicit = None
        else:
            if SCons.Util.is_String(implicit):
                implicit = [implicit]
            self.implicit = string.join(map(str, implicit), '\0')


class SConsignFile:
    """
    Encapsulates reading and writing a .sconsign file.
    """

    def __init__(self, dir, module=None):
        """
        dir - the directory for the file
        module - the signature module being used
        """

        self.dir = dir

        if module is None:
            self.module = default_calc.module
        else:
            self.module = module
        self.sconsign = os.path.join(dir.path, '.sconsign')
        self.entries = {}
        self.dirty = None

        try:
            file = open(self.sconsign, 'rt')
        except:
            pass
        else:
            for line in file.readlines():
                filename, rest = map(string.strip, string.split(line, ":", 1))
                self.entries[filename] = SConsignEntry(self.module, rest)

        global sig_files
        sig_files.append(self)

    def get(self, filename):
        """
        Get the .sconsign entry for a file

        filename - the filename whose signature will be returned
        returns - (timestamp, bsig, csig)
        """
        try:
            entry = self.entries[filename]
            return (entry.timestamp, entry.bsig, entry.csig)
        except KeyError:
            return (None, None, None)
    
    def create_entry(self, filename):
        """
        Create an entry for the filename and return it, or if one already exists,
        then return it.
        """
        try:
            entry = self.entries[filename]
        except KeyError:
            entry = SConsignEntry(self.module)
            self.entries[filename] = entry
            
        return entry

    def set_csig(self, filename, csig):
        """
        Set the csig .sconsign entry for a file

        filename - the filename whose signature will be set
        csig - the file's content signature
        """

        entry = self.create_entry(filename)
        entry.csig = csig
        self.dirty = 1

    def set_bsig(self, filename, bsig):
        """
        Set the csig .sconsign entry for a file

        filename - the filename whose signature will be set
        bsig - the file's built signature
        """

        entry = self.create_entry(filename)
        entry.bsig = bsig
        self.dirty = 1

    def set_timestamp(self, filename, timestamp):
        """
        Set the csig .sconsign entry for a file

        filename - the filename whose signature will be set
        timestamp - the file's timestamp
        """

        entry = self.create_entry(filename)
        entry.timestamp = timestamp
        self.dirty = 1

    def get_implicit(self, filename):
        """Fetch the cached implicit dependencies for 'filename'"""
        try:
            entry = self.entries[filename]
            return entry.get_implicit()
        except KeyError:
            return None

    def set_implicit(self, filename, implicit):
        """Cache the implicit dependencies for 'filename'."""
        entry = self.create_entry(filename)
        entry.set_implicit(implicit)
        self.dirty = 1

    def write(self):
        """
        Write the .sconsign file to disk.

        Try to write to a temporary file first, and rename it if we
        succeed.  If we can't write to the temporary file, it's
        probably because the directory isn't writable (and if so,
        how did we build anything in this directory, anyway?), so
        try to write directly to the .sconsign file as a backup.
        If we can't rename, try to copy the temporary contents back
        to the .sconsign file.  Either way, always try to remove
        the temporary file at the end.
        """
        if self.dirty:
            temp = os.path.join(self.dir.path, '.scons%d' % os.getpid())
            try:
                file = open(temp, 'wt')
                fname = temp
            except:
                try:
                    file = open(self.sconsign, 'wt')
                    fname = self.sconsign
                except:
                    return
            keys = self.entries.keys()
            keys.sort()
            for name in keys:
                file.write("%s: %s\n" % (name, self.entries[name].render(self.module)))
            file.close()
            if fname != self.sconsign:
                try:
                    mode = os.stat(self.sconsign)[0]
                    os.chmod(self.sconsign, 0666)
                    os.unlink(self.sconsign)
                except:
                    pass
                try:
                    os.rename(fname, self.sconsign)
                except:
                    open(self.sconsign, 'wb').write(open(fname, 'rb').read())
                    os.chmod(self.sconsign, mode)
            try:
                os.unlink(temp)
            except:
                pass


class Calculator:
    """
    Encapsulates signature calculations and .sconsign file generating
    for the build engine.
    """

    def __init__(self, module=None, max_drift=2*24*60*60):
        """
        Initialize the calculator.

        module - the signature module to use for signature calculations
        max_drift - the maximum system clock drift used to determine when to
          cache content signatures. A negative value means to never cache
          content signatures. (defaults to 2 days)
        """
        if module is None:
            try:
                import MD5
                self.module = MD5
            except ImportError:
                # fallback on timestamp signatures if MD5 is not available
                # XXX add a warning message here
                import TimeStamp
                self.module = TimeStamp
        else:
            self.module = module
        self.max_drift = max_drift

    def bsig(self, node):
        """
        Generate a node's build signature, the digested signatures
        of its dependency files and build information.

        node - the node whose sources will be collected
        returns - the build signature

        This no longer handles the recursive descent of the
        node's children's signatures.  We expect that they're
        already built and updated by someone else, if that's
        what's wanted.
        """
        if not node.use_signature:
            return None

        bsig = node.get_bsig()
        if not bsig is None:
            return bsig

        sigs = map(self.get_signature, node.children())
        if node.builder:
            sigs.append(self.module.signature(node.builder_sig_adapter()))

        bsig = self.module.collect(filter(lambda x: not x is None, sigs))

        node.set_bsig(bsig)

        # don't store the bsig here, because it isn't accurate until
        # the node is actually built.

        return bsig

    def csig(self, node):
        """
        Generate a node's content signature, the digested signature
        of its content.

        node - the node
        returns - the content signature
        """
        if not node.use_signature:
            return None

        csig = node.get_csig()
        if not csig is None:
            return csig

        if self.max_drift >= 0:
            info = node.get_prevsiginfo()
        else:
            info = None

        mtime = node.get_timestamp()

        if (info and info[0] and info[2] and info[0] == mtime):
            # use the signature stored in the .sconsign file
            csig = info[2]
            # Set the csig here so it doesn't get recalculated unnecessarily
            # and so it's set when the .sconsign file gets written
            node.set_csig(csig)
        else:
            csig = self.module.signature(node)
            # Set the csig here so it doesn't get recalculated unnecessarily
            # and so it's set when the .sconsign file gets written
            node.set_csig(csig)

            if self.max_drift >= 0 and (time.time() - mtime) > self.max_drift:
                node.store_csig()
                node.store_timestamp()

        return csig

    def get_signature(self, node):
        """
        Get the appropriate signature for a node.

        node - the node
        returns - the signature or None if the signature could not
        be computed.

        This method does not store the signature in the node and
        in the .sconsign file.
        """

        if not node.use_signature:
            # This node type doesn't use a signature (e.g. a
            # directory) so bail right away.
            return None
        elif node.builder:
            return self.bsig(node)
        elif not node.exists():
            return None
        else:
            return self.csig(node)

    def current(self, node, newsig):
        """
        Check if a signature is up to date with respect to a node.

        node - the node whose signature will be checked
        newsig - the (presumably current) signature of the file

        returns - 1 if the file is current with the specified signature,
        0 if it isn't
        """

        c = node.current()
        if not c is None:
            # The node itself has told us whether or not it's
            # current without checking the signature.  The
            # canonical uses here are a "0" return for a file
            # that doesn't exist, or a directory.
            return c

        oldtime, oldbsig, oldcsig = node.get_prevsiginfo()

        if not node.builder and node.get_timestamp() == oldtime:
            return 1

        return self.module.current(newsig, oldbsig)


default_calc = Calculator()