/*

    File: DataProvider.c

Abstract: Implementation of the custom CGDataProvider

 Version: 1.1

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*/

#include "DataProvider.h"

size_t MyGetBytesAtOffset(void *info, void *buffer, off_t offset, size_t count);

void MyReleaseInfo(void * info);

static CGDataProviderDirectCallbacks callbacks = 

{

    0, // version

    NULL, // CGDataProviderGetBytePointerCallback

    NULL, // CGDataProviderReleaseBytePointerCallback

    &MyGetBytesAtOffset, // CGDataProviderGetBytesAtOffsetCallback

    &MyReleaseInfo // CGDataProviderReleaseInfoCallback

};

typedef struct

{

    // necessary for filling out the image data

    size_t width, height;

    off_t totalBytes;

    // Deference to UI - These allow us to provide and communicate with some form of UI.

    void *uiContext;

    DataProviderProgressCallback uiProgressCallback;

    DataProviderCancelCallback uiCancelCallback;

} DataProviderInfo;

// Simple inlines to make sure that we only call the callbacks if they were specified.

static inline void SafeProgressCallback(DataProviderInfo * data, float progress)

{

    if(data->uiProgressCallback != NULL)

        (data->uiProgressCallback)(data->uiContext, progress);

}

static inline bool SafeCancelCallback(DataProviderInfo *data)

{

    if(data->uiCancelCallback != NULL)

        return (data->uiCancelCallback)(data->uiContext);

    else

        return false;

}

// Callback to obtain bytes for the data provider.

// You must provide at least 1 byte or Quartz will cancel the request.

// You cannot provide more than count bytes at a time via this method

// (use the CGDataProviderGetBytePointerCallback instead to provide an entire block of data instead).

size_t MyGetBytesAtOffset(void * info, void * buffer, off_t offset, size_t count)

{

    DataProviderInfo * data = (DataProviderInfo *)info;

    size_t provided = count;

    // Deference to UI - check for cancel

    if(!SafeCancelCallback(data))

    {

        float num = (float)(offset + count);

        float denom = (float)(data->totalBytes);

        float percent = num / denom;

        // Determine where in the Image CG is asking for data from

        off_t rowbytes = (off_t)data->width * kBytesPerPixel;

        off_t y = offset / rowbytes, x = offset - y * rowbytes;

        size_t i;

        // This sample uses 32-bit pixels in XRGB format - you will want to update this loop

        // for whatever image format you choose to use.

        UInt8 *pixelData = (UInt8*)buffer;

        for(i = 0; i < count; ++x)

        {

            // This is just going to fill the image with a repeating pattern.

            // Nothing particularly special, but you would replace it with

            // whatever code would be required to fill in the image appropriately.

            // X

            pixelData[i++] = 0;

            // R

            pixelData[i++] = y & 255;

            // G

            pixelData[i++] = x & 255;

            // B

            pixelData[i++] = lrintf(percent * 255);

        }

        // Deference to UI - we're just signallying the controller

        SafeProgressCallback(data, percent * 100.0f);

    }

    else

    {

        // On cancel return 0 signaling that the Data Provider has no more data

        // which will in turn signal Image IO to fail trying to save the image

        provided = 0;

    }

    return provided;

}

void MyReleaseInfo(void * info)

{

    // info block was malloc()'d, so free() it.

    free(info);

}

CGDataProviderRef CreateDataProvider(size_t width, size_t height, void * context, DataProviderProgressCallback progressCallback, DataProviderCancelCallback cancelCallback)

{

    DataProviderInfo *info = (DataProviderInfo*)malloc(sizeof(DataProviderInfo));

    info->width = width;

    info->height = height;

    info->totalBytes = (off_t)width * (off_t)height * kBytesPerPixel;

    info->uiContext = context;

    info->uiProgressCallback = progressCallback;

    info->uiCancelCallback = cancelCallback;

    return CGDataProviderCreateDirect(info, info->totalBytes, &callbacks);

}