import os, sys

from Quartz import *
import Quartz

import objc

def createDataProviderFromPathName (path):
    # Create a CFURL for the supplied file system path.
    url = CFURLCreateWithFileSystemPath(None, path, kCFURLPOSIXPathStyle, False)
    if url is None:
        print >>sys.stderr, "Couldn't create url!"
        return None

    # Create a Quartz data provider for the URL.
    dataProvider = CGDataProviderCreateWithURL(url)
    if dataProvider is None:
        print >>sys.stderr, "Couldn't create data provider!"
        return None

    return dataProvider

def createRGBRampDataProvider():
    width = 256
    height = 256
    imageDataSize = width*height*3

    dataP = objc.allocateBuffer(imageDataSize)
    
    #    Build an image that is RGB 24 bits per sample. This is a ramp
    #    where the red component value increases in red from left to 
    #    right and the green component increases from top to bottom.
    #
    idx=0
    for g in xrange(height):
        for r in xrange(width):
            dataP[idx] = chr(r)
            dataP[idx+1] = chr(g)
            dataP[idx+2] = '\0'
            idx += 3

    # Once this data provider is created, the data associated 
    # with dataP MUST be available until Quartz calls the data 
    # releaser function 'rgbReleaseRampData'.
    dataProvider = CGDataProviderCreateWithData(
            None, dataP, imageDataSize, None)
    return dataProvider

class MyImageDataInfo (object):
    fp = None
    totalBytesRead = 0
    skippedBytes = 0
    numRewinds = 0

def getBytesSequentialAccessDP(data, buffer, count):
    buf = data.fp.read(count)
    buffer[:len(buf)] = buf
    data.totalBytesRead += len(buf)
    return len(buf), buffer

def skipBytesSequentialAccessDP(data, count):
    try:
        data.fp.seek(count, os.SEEK_CUR)
        data.skippedBytes += count

    except IOError, msg:
        print >>sys.stderr, "Couldn't seek %d bytes because of %s"%(count, msg)


def rewindSequentialAccessDP(data):
    # Rewind the beginning of the data.
    data.fp.seek(0, 0)
    data.numRewinds += 1

def releaseSequentialAccessDP(data):
    if data is not None:
        print >>sys.stderr, "read %d bytes, skipped %d bytes, rewind called %d times"%(
		    data.totalBytesRead, data.skippedBytes,
		    data.numRewinds)
        data.fp.close()

def createSequentialAccessDPForURL(url):
    success, pathString = CFURLGetFileSystemRepresentation(url, True, None, 1024)
    pathString = pathString.rstrip('\0')
    if not success:
        print >>sys.stderr, "Couldn't get the path name C string!"
        return None

    fp = open(pathString, "rb")
    if fp is None:
        print >>sys.stderr, "Couldn't open path to file %s!"%(pathString,)
        return None
    
    imageDataInfoP = MyImageDataInfo()
    imageDataInfoP.fp = fp

    provider = CGDataProviderCreate(imageDataInfoP, (
        getBytesSequentialAccessDP,
        skipBytesSequentialAccessDP,
        rewindSequentialAccessDP,
        releaseSequentialAccessDP))
    if provider is None:
        print >>sys.stderr, "Couldn't create data provider!"
        # Release the info data and cleanup.
        releaseSequentialAccessDP(imageDataInfoP)
        return None

    return provider


def getBytesGrayRampDirectAccess(info, buffer, offset, count):
	# This computes a linear gray ramp that is 256 samples wide and
	# 1 sample high. The ith byte in the image is the sample
	# value i. This produces a gray ramp that goes from 0 (black) to 
	# FF (white). 
	idx = 0

	# This data provider provides 256 bytes total. If Quartz
	# requests more data than is available, only return
	# the available data.
        if (offset + count) > 256:
		count = 256 - offset

        for i in range(offset, offset+count):
            buffer[idx] = chr(i)
            idx+=1

	return count, buffer

def  createGrayRampDirectAccessDP():
	provider = CGDataProviderCreateDirectAccess(None, 256, (
            None,
            None,
            getBytesGrayRampDirectAccess,
            None))
        if provider is None:
            print >>sys.stderr, "Couldn't create data provider!"
            return None

	return provider

# This only builds on Tiger and later.
def myCGDataProviderCreateWithCFData(data):
    # If the CFData object passed in is None, this code returns
    # a None data provider.
    if data is None:
        return None

    # Test to see if the Quartz version is available and if so, use it.
   
    #XXX: force the replacment code to be used
    #if hasattr(Quartz, 'CGDataProviderCreateWithCFData'):
    #    return CGDataProviderCreateWithCFData(data)

    dataSize = CFDataGetLength(data)
    provider = CGDataProviderCreateWithData(data, buffer(data), dataSize, None)
    return provider

def createDataConsumerFromPathName(path):
    # Create a CFURL for the supplied file system path.
    url = CFURLCreateWithFileSystemPath (None, path, kCFURLPOSIXPathStyle, False)
    if url is None:
        print >>sys.stderr, "Couldn't create url!"
        return None
    # Create a Quartz data provider for the URL.
    dataConsumer = CGDataConsumerCreateWithURL(url)
    if dataConsumer is None:
        print >>sys.stderr, "Couldn't create data consumer!"
        return None
    
    return dataConsumer

def myCFDataConsumerPutBytes(data, buffer, count):
    # Append 'count' bytes from 'buffer' to the CFData 
    # object 'data'.
    CFDataAppendBytes(data, buffer, count)
    return count

# This only builds on Tiger and later.
def myCGDataConsumerCreateWithCFData(data):
    # If the CFData object passed in is None, this code returns
    # a None data consumer.
    if data is None:
        return None

    # Test to see if the Quartz version is available.

    # XXX: force the replacement code to be used:
    #if hasattr(Quartz, 'CGDataConsumerCreateWithCFData'):
    #    return CGDataConsumerCreateWithCFData(data)

    consumer = CGDataConsumerCreate(data, (
        myCFDataConsumerPutBytes, None))
    return consumer