/*
 * Written in 2009 by Lloyd Hilaiel
 *
 * License
 *
 * All the cruft you find here is public domain.  You don't have to credit
 * anyone to use this code, but my personal request is that you mention
 * Igor Pavlov for his hard, high quality work.
 */

/* XXX: clean this up, it's mostly lifted from pavel */

#include "lzma_header.h"

#include <string.h>
#include <assert.h>

#define ELZMA_LZMA_HEADER_SIZE 13
#define ELZMA_LZMA_PROPSBUF_SIZE 5

/****************
  Header parsing
 ****************/

#ifndef UINT64_MAX
#define UINT64_MAX ((unsigned long long)-1)
#endif

/* Parse the properties byte */
static char lzmadec_header_properties(unsigned char *pb, unsigned char *lp, unsigned char *lc,
									  const unsigned char c)
{
	/*	 pb, lp and lc are encoded into a single byte.  */
	if (c > (9 * 5 * 5))
		return -1;
	*pb = c / (9 * 5);	   /* 0 <= pb <= 4 */
	*lp = (c % (9 * 5)) / 9; /* 0 <= lp <= 4 */
	*lc = c % 9;			 /* 0 <= lc <= 8 */

	assert(*pb < 5 && *lp < 5 && *lc < 9);
	return 0;
}

/* Parse the dictionary size (4 bytes, little endian) */
static char lzmadec_header_dictionary(unsigned int *size, const unsigned char *buffer)
{
	unsigned int i;
	*size = 0;
	for (i = 0; i < 4; i++)
		*size += (unsigned int)(*buffer++) << (i * 8);
	/* The dictionary size is limited to 256 MiB (checked from
	 * LZMA SDK 4.30) */
	if (*size > (1 << 28))
		return -1;
	return 0;
}

/* Parse the uncompressed size field (8 bytes, little endian) */
static void lzmadec_header_uncompressed(unsigned long long *size, unsigned char *is_streamed,
										const unsigned char *buffer)
{
	unsigned int i;

	/* Streamed files have all 64 bits set in the size field.
	 * We don't know the uncompressed size beforehand. */
	*is_streamed = 1; /* Assume streamed. */
	*size = 0;
	for (i = 0; i < 8; i++)
	{
		*size += (unsigned long long)buffer[i] << (i * 8);
		if (buffer[i] != 255)
			*is_streamed = 0;
	}
	assert((*is_streamed == 1 && *size == UINT64_MAX) ||
		   (*is_streamed == 0 && *size < UINT64_MAX));
}

static void initLzmaHeader(struct elzma_file_header *hdr)
{
	memset((void *)hdr, 0, sizeof(struct elzma_file_header));
}

static int parseLzmaHeader(const unsigned char *hdrBuf, struct elzma_file_header *hdr)
{
	if (lzmadec_header_properties(&(hdr->pb), &(hdr->lp), &(hdr->lc), *hdrBuf) ||
		lzmadec_header_dictionary(&(hdr->dictSize), hdrBuf + 1))
	{
		return 1;
	}
	lzmadec_header_uncompressed(&(hdr->uncompressedSize), &(hdr->isStreamed), hdrBuf + 5);

	return 0;
}

static int serializeLzmaHeader(unsigned char *hdrBuf, const struct elzma_file_header *hdr)
{
	unsigned int i;

	memset((void *)hdrBuf, 0, ELZMA_LZMA_HEADER_SIZE);

	/* encode lc, pb, and lp */
	*hdrBuf++ = hdr->lc + (hdr->pb * 45) + (hdr->lp * 45 * 9);

	/* encode dictionary size */
	for (i = 0; i < 4; i++)
	{
		*(hdrBuf++) = (unsigned char)(hdr->dictSize >> (i * 8));
	}

	/* encode uncompressed size */
	for (i = 0; i < 8; i++)
	{
		if (hdr->isStreamed)
		{
			*(hdrBuf++) = 0xff;
		}
		else
		{
			*(hdrBuf++) = (unsigned char)(hdr->uncompressedSize >> (i * 8));
		}
	}

	return 0;
}

void initializeLZMAFormatHandler(struct elzma_format_handler *hand)
{
	hand->header_size = ELZMA_LZMA_HEADER_SIZE;
	hand->init_header = initLzmaHeader;
	hand->parse_header = parseLzmaHeader;
	hand->serialize_header = serializeLzmaHeader;
	hand->footer_size = 0;
	hand->serialize_footer = NULL;
}