#include "JpegImage.h"


namespace Image {

const static JOCTET EOI_BUFFER[1] = { JPEG_EOI };

JpegImage::JpegImage()
{
}

void JpegImage::SetImageData(const std::string& data)
{
	DecompressImage(data.c_str(), data.size());
}

unsigned int JpegImage::Width() const
{
	return m_width;
}

unsigned int JpegImage::Height() const
{
	return m_height;
}

unsigned int JpegImage::StrideX() const
{
	return m_strideX;
}

unsigned int JpegImage::StrideY() const
{
	return m_strideY;
}

const std::vector<char>& JpegImage::Data() const
{
	return m_data;
}

void JpegImage::InitSource(j_decompress_ptr pCinfo)
{
}

boolean JpegImage::FillInputBuffer(j_decompress_ptr pCinfo)
{
	SourceMgrPtr pSrc = reinterpret_cast<SourceMgrPtr>(pCinfo->src);
	pSrc->pub.next_input_byte = EOI_BUFFER;
	pSrc->pub.bytes_in_buffer = 1;
	return TRUE;
}

void JpegImage::SkipInputData(j_decompress_ptr pCinfo, long numBytes)
{
	SourceMgrPtr pSrc = reinterpret_cast<SourceMgrPtr>(pCinfo->src);
	if (pSrc->pub.bytes_in_buffer < static_cast<size_t>(numBytes))
	{
		pSrc->pub.next_input_byte = EOI_BUFFER;
		pSrc->pub.bytes_in_buffer = 1;
	}
	else
	{
		pSrc->pub.next_input_byte += numBytes;
		pSrc->pub.bytes_in_buffer -= numBytes;
	}
}

void JpegImage::TermSource(j_decompress_ptr pCinfo)
{
}

void JpegImage::SetSourceMgr(j_decompress_ptr pCinfo, const char* pData, size_t len) const
{
	SourceMgrPtr pSrc;
	if (pCinfo->src == 0)
		pCinfo->src = (struct jpeg_source_mgr *)(*pCinfo->mem->alloc_small)(reinterpret_cast<j_common_ptr>(pCinfo), JPOOL_PERMANENT, sizeof(SourceMgr));

	pSrc = reinterpret_cast<SourceMgrPtr>(pCinfo->src);
	pSrc->pub.init_source = JpegImage::InitSource;
	pSrc->pub.fill_input_buffer = JpegImage::FillInputBuffer;
	pSrc->pub.skip_input_data = JpegImage::SkipInputData;
	pSrc->pub.resync_to_restart = jpeg_resync_to_restart;
	pSrc->pub.term_source = JpegImage::TermSource;

	pSrc->data = (const JOCTET *)pData;
	pSrc->len = len;
	pSrc->pub.bytes_in_buffer = len;
	pSrc->pub.next_input_byte = pSrc->data;
}

void JpegImage::DecompressImage(const char* pData, size_t len)
{
	struct jpeg_decompress_struct cinfo; 
	struct jpeg_error_mgr jerr;

	jerr.trace_level = 0;
	cinfo.err = jpeg_std_error(&jerr); 
	jpeg_create_decompress(&cinfo); 
	SetSourceMgr(&cinfo, pData, len);

	jpeg_read_header(&cinfo, TRUE);
	jpeg_start_decompress(&cinfo);

	m_width = cinfo.image_width;
	m_height = cinfo.image_height;
	m_strideX = cinfo.num_components;
	m_strideY = m_width * cinfo.num_components;

	m_data.resize(m_height * m_strideY);

	JSAMPROW scanlines[1];
	while (cinfo.output_scanline < cinfo.image_height)
	{
		scanlines[0] = reinterpret_cast<JSAMPROW>(&m_data[cinfo.output_scanline * m_strideY]);
		jpeg_read_scanlines(&cinfo, scanlines, 1);
	}

	jpeg_finish_decompress(&cinfo);
	jpeg_destroy_decompress(&cinfo); 
}

} // namespace Image