/*
 * misc.c
 * 
 * This is a collection of several routines from gzip-1.0.3 
 * adapted for Linux.
 *
 * malloc by Hannu Savolainen 1993 and Matthias Urlichs 1994
 * puts by Nick Holloway 1993
 */

#include "gzip.h"
#include "lzw.h"

#include <asm/segment.h>

/*
 * These are set up by the setup-routine at boot-time:
 */

struct screen_info {
	unsigned char  orig_x;
	unsigned char  orig_y;
	unsigned char  unused1[2];
	unsigned short orig_video_page;
	unsigned char  orig_video_mode;
	unsigned char  orig_video_cols;
	unsigned short orig_video_ega_ax;
	unsigned short orig_video_ega_bx;
	unsigned short orig_video_ega_cx;
	unsigned char  orig_video_lines;
};

/*
 * This is set up by the setup-routine at boot-time
 */
#define EXT_MEM_K (*(unsigned short *)0x90002)
#define DRIVE_INFO (*(struct drive_info *)0x90080)
#define SCREEN_INFO (*(struct screen_info *)0x90000)
#define RAMDISK_SIZE (*(unsigned short *)0x901F8)
#define ORIG_ROOT_DEV (*(unsigned short *)0x901FC)
#define AUX_DEVICE_INFO (*(unsigned char *)0x901FF)

#define EOF -1

DECLARE(uch, inbuf, INBUFSIZ);
DECLARE(uch, outbuf, OUTBUFSIZ+OUTBUF_EXTRA);
DECLARE(uch, window, WSIZE);

unsigned outcnt;
unsigned insize;
unsigned inptr;

extern char input_data[];
extern int input_len;

int input_ptr;

int method, exit_code, part_nb, last_member;
int test = 0;
int force = 0;
int verbose = 1;
long bytes_in, bytes_out;

char *output_data;
unsigned long output_ptr;

extern int end;
long free_mem_ptr = (long)&end;

int to_stdout = 0;
int hard_math = 0;

void (*work)(int inf, int outf);
void makecrc(void);

local int get_method(int);

char *vidmem = (char *)0xb8000;
int lines, cols;

static void puts(const char *);

void *malloc(int size)
{
	void *p;

	if (size <0) error("Malloc error\n");
	if (free_mem_ptr <= 0) error("Memory error\n");

   while(1) {
	free_mem_ptr = (free_mem_ptr + 3) & ~3;	/* Align */

	p = (void *)free_mem_ptr;
	free_mem_ptr += size;

	/*
  	 * The part of the compressed kernel which has already been expanded
	 * is no longer needed. Therefore we can reuse it for malloc.
	 * With bigger kernels, this is necessary.
	 */
          
	if (free_mem_ptr < (long)&end) {
		if (free_mem_ptr > (long)&input_data[input_ptr])
			error("\nOut of memory\n");

		return p;
	}
	if (free_mem_ptr < 0x90000)
	return p;
	puts("large kernel, low 1M tight...");
	free_mem_ptr = (long)input_data;
	}
}

void free(void *where)
{	/* Don't care */
}

static void scroll()
{
	int i;

	memcpy ( vidmem, vidmem + cols * 2, ( lines - 1 ) * cols * 2 );
	for ( i = ( lines - 1 ) * cols * 2; i < lines * cols * 2; i += 2 )
		vidmem[i] = ' ';
}

static void puts(const char *s)
{
	int x,y;
	char c;

	x = SCREEN_INFO.orig_x;
	y = SCREEN_INFO.orig_y;

	while ( ( c = *s++ ) != '\0' ) {
		if ( c == '\n' ) {
			x = 0;
			if ( ++y >= lines ) {
				scroll();
				y--;
			}
		} else {
			vidmem [ ( x + cols * y ) * 2 ] = c; 
			if ( ++x >= cols ) {
				x = 0;
				if ( ++y >= lines ) {
					scroll();
					y--;
				}
			}
		}
	}

	SCREEN_INFO.orig_x = x;
	SCREEN_INFO.orig_y = y;
}

__ptr_t memset(__ptr_t s, int c, size_t n)
{
	int i;
	char *ss = (char*)s;

	for (i=0;i<n;i++) ss[i] = c;
}

__ptr_t memcpy(__ptr_t __dest, __const __ptr_t __src,
			    size_t __n)
{
	int i;
	char *d = (char *)__dest, *s = (char *)__src;

	for (i=0;i<__n;i++) d[i] = s[i];
}

extern ulg crc_32_tab[];   /* crc table, defined below */

/* ===========================================================================
 * Run a set of bytes through the crc shift register.  If s is a NULL
 * pointer, then initialize the crc shift register contents instead.
 * Return the current crc in either case.
 */
ulg updcrc(s, n)
    uch *s;                 /* pointer to bytes to pump through */
    unsigned n;             /* number of bytes in s[] */
{
    register ulg c;         /* temporary variable */

    static ulg crc = (ulg)0xffffffffL; /* shift register contents */

    if (s == NULL) {
	c = 0xffffffffL;
    } else {
	c = crc;
	while (n--) {
	    c = crc_32_tab[((int)c ^ (*s++)) & 0xff] ^ (c >> 8);
	}
    }
    crc = c;
    return c ^ 0xffffffffL;       /* (instead of ~c for 64-bit machines) */
}

/* ===========================================================================
 * Clear input and output buffers
 */
void clear_bufs()
{
    outcnt = 0;
    insize = inptr = 0;
    bytes_in = bytes_out = 0L;
}

/* ===========================================================================
 * Fill the input buffer. This is called only when the buffer is empty
 * and at least one byte is really needed.
 */
int fill_inbuf()
{
    int len, i;

    /* Read as much as possible */
    insize = 0;
    do {
	len = INBUFSIZ-insize;
	if (len > (input_len-input_ptr+1)) len=input_len-input_ptr+1;
        if (len == 0 || len == EOF) break;

        for (i=0;i<len;i++) inbuf[insize+i] = input_data[input_ptr+i];
	insize += len;
	input_ptr += len;
    } while (insize < INBUFSIZ);

    if (insize == 0) {
	error("unable to fill buffer\n");
    }
    bytes_in += (ulg)insize;
    inptr = 1;
    return inbuf[0];
}

/* ===========================================================================
 * Write the output window window[0..outcnt-1] and update crc and bytes_out.
 * (Used for the decompressed data only.)
 */
void flush_window()
{
    if (outcnt == 0) return;
    updcrc(window, outcnt);

    memcpy(&output_data[output_ptr], (char *)window, outcnt);

    bytes_out += (ulg)outcnt;
    output_ptr += (ulg)outcnt;
    outcnt = 0;
}

/*
 * Code to compute the CRC-32 table. Borrowed from 
 * gzip-1.0.3/makecrc.c.
 */

ulg crc_32_tab[256];

void
makecrc(void)
{
/* Not copyrighted 1990 Mark Adler	*/

  unsigned long c;      /* crc shift register */
  unsigned long e;      /* polynomial exclusive-or pattern */
  int i;                /* counter for all possible eight bit values */
  int k;                /* byte being shifted into crc apparatus */

  /* terms of polynomial defining this crc (except x^32): */
  static int p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};

  /* Make exclusive-or pattern from polynomial */
  e = 0;
  for (i = 0; i < sizeof(p)/sizeof(int); i++)
    e |= 1L << (31 - p[i]);

  crc_32_tab[0] = 0;

  for (i = 1; i < 256; i++)
  {
    c = 0;
    for (k = i | 256; k != 1; k >>= 1)
    {
      c = c & 1 ? (c >> 1) ^ e : c >> 1;
      if (k & 1)
        c ^= e;
    }
    crc_32_tab[i] = c;
  }
}

void error(char *x)
{
	puts("\n\n");
	puts(x);
	puts("\n\n -- System halted");

	while(1);	/* Halt */
}

#define STACK_SIZE (4096)

long user_stack [STACK_SIZE];

struct {
	long * a;
	short b;
	} stack_start = { & user_stack [STACK_SIZE] , KERNEL_DS };

void decompress_kernel()
{
	if (SCREEN_INFO.orig_video_mode == 7)
		vidmem = (char *) 0xb0000;
	else
		vidmem = (char *) 0xb8000;

	lines = SCREEN_INFO.orig_video_lines;
	cols = SCREEN_INFO.orig_video_cols;

	if (EXT_MEM_K < 1024) error("<2M of mem\n");

	output_data = (char *)0x100000;	/* Points to 1M */
	output_ptr = 0;

	exit_code = 0;
	test = 0;
	input_ptr = 0;
	part_nb = 0;

	clear_bufs();
	makecrc();

	puts("Uncompressing Linux...");

	method = get_method(0);

	work(0, 0);

	puts("done.\n");

	puts("Now booting the kernel\n");
}

/* ========================================================================
 * Check the magic number of the input file and update ofname if an
 * original name was given and to_stdout is not set.
 * Return the compression method, -1 for error, -2 for warning.
 * Set inptr to the offset of the next byte to be processed.
 * This function may be called repeatedly for an input file consisting
 * of several contiguous gzip'ed members.
 * IN assertions: there is at least one remaining compressed member.
 *   If the member is a zip file, it must be the only one.
 */
local int get_method(in)
    int in;        /* input file descriptor */
{
    uch flags;
    char magic[2]; /* magic header */

    magic[0] = (char)get_byte();
    magic[1] = (char)get_byte();

    method = -1;                 /* unknown yet */
    part_nb++;                   /* number of parts in gzip file */
    last_member = 0;
    /* assume multiple members in gzip file except for record oriented I/O */

    if (memcmp(magic, GZIP_MAGIC, 2) == 0
        || memcmp(magic, OLD_GZIP_MAGIC, 2) == 0) {

	work = unzip;
	method = (int)get_byte();
	flags  = (uch)get_byte();
	if ((flags & ENCRYPTED) != 0)
	    error("Input is encrypted\n");
	if ((flags & CONTINUATION) != 0)
	       error("Multi part input\n");
	if ((flags & RESERVED) != 0) {
	    error("Input has invalid flags\n");
	    exit_code = ERROR;
	    if (force <= 1) return -1;
	}
	(ulg)get_byte();	/* Get timestamp */
	((ulg)get_byte()) << 8;
	((ulg)get_byte()) << 16;
	((ulg)get_byte()) << 24;

	(void)get_byte();  /* Ignore extra flags for the moment */
	(void)get_byte();  /* Ignore OS type for the moment */

	if ((flags & EXTRA_FIELD) != 0) {
	    unsigned len = (unsigned)get_byte();
	    len |= ((unsigned)get_byte())<<8;
	    while (len--) (void)get_byte();
	}

	/* Get original file name if it was truncated */
	if ((flags & ORIG_NAME) != 0) {
	    if (to_stdout || part_nb > 1) {
		/* Discard the old name */
		while (get_byte() != 0) /* null */ ;
	    } else {
	    } /* to_stdout */
	} /* orig_name */

	/* Discard file comment if any */
	if ((flags & COMMENT) != 0) {
	    while (get_byte() != 0) /* null */ ;
	}
    } else
	error("unknown compression method");
    return method;
}