/*******************************************************************************
* bmp2.c
*		Microsoft Windows bitmap (BMP) file functions.
*
* 1.0 04-13-92 drt.  First cut.
* 1.1 08-25-92 drt.  Renamed bmp_header members.
*
* Copyright (c)1992-94, David R. Tribble.
*/


/* includes */

#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "bmp.h"


/* Private variables */

static unsigned short	h_id = BMP_HDR_MAGIC;


/*******************************************************************************
* bmp_read_hdr
*		Read header from BMP file `fp'.
*
* Returns
*		Zero if successful, otherwise -1.
*/

int bmp_read_hdr(BMP_FILE *fp)
{
	long		pos;
	size_t		len;
	struct os2_bmp_header	os2;

	/* Check args */
	if (fp == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

	/* Read header struct from file */
	pos = ftell(fp->fp);
	len = fread(&fp->h, sizeof(fp->h), 1, fp->fp);
	if (len != 1)
		goto fail;

	/* Check for bad magic */
	if (fp->h.id != h_id)
		goto fail;

	/* Header was successfully read, check for OS/2 header */
	if (fp->h.infoSize == 12)
	{
		/* OS/2 BMP header */

		/* Back up file pointer and reread header */
		if (fseek(fp->fp, pos, SEEK_SET) != 0)
			goto fail;

		len = fread(&os2, sizeof(os2), 1, fp->fp);
		if (len != 1)
			goto fail;

		/* Fill in file's info with OS/2 header info */
		memset(&fp->h, 0, sizeof(fp->h));
		fp->flags =			BMP_FILE_F_OS2 | BMP_FILE_F_RGB3;
		fp->h.id =			os2.id;
		fp->h.filesize =	os2.filesize;
		fp->h.headersize =	os2.headersize;
		fp->h.infoSize =	os2.infoSize;
		fp->h.width =		os2.width;
		fp->h.depth =		os2.depth;
		fp->h.biPlanes =	os2.biPlanes;
		fp->h.bits =		os2.bits;
		fp->h.biClrUsed =	0;
		memcpy(fp->h.r, os2.r, sizeof(fp->h.r));
	}

	/* Adjust file info */
	switch (fp->h.bits)
	{
	case 1:
	case 2:
	case 4:
	case 8:
		fp->linesz = fp->h.width / (8/fp->h.bits);	/** nplanes? **/
		break;

	case 24:
		fp->linesz = fp->h.width * 24/8;			/** nplanes? **/
		break;
	}

	fp->linesz =	(fp->linesz + 4-1) / 4 * 4;		/* Nearest longword */
	fp->byteno =	0;
	fp->bitno =		0;
	fp->rep =		0;
	fp->pix =		0;
	fp->byte =		0;

	/* Read was successful */
	return 0;

fail:
	fseek(fp->fp, pos, SEEK_SET);
	return -1;
}


/*******************************************************************************
* bmp_write_hdr
*		Write header to BMP file `fp'.
*
* Returns
*		Zero if successful, otherwise -1.
*/

int bmp_write_hdr(BMP_FILE *fp)
{
	long	pos;
	size_t	len;

	/* Check args */
	if (fp == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

#if 1
	/* Fill in header members */
	fp->h.id =			BMP_HDR_MAGIC;
	fp->h.r[0] =		0;
	fp->h.r[1] =		0;
	fp->h.r[2] =		0;
	fp->h.r[3] =		0;
#if 0
	fp->h.infoSize =	40;
#endif

	/* Adjust file info */
	switch (fp->h.bits)
	{
	case 1:
	case 2:
	case 4:
	case 8:
		fp->linesz = fp->h.width / (8/fp->h.bits);	/** nplanes? **/
		break;

	case 24:
		fp->linesz = fp->h.width * 24/8;			/** nplanes? **/
		break;
	}

	fp->linesz =	(fp->linesz + 4-1) / 4 * 4;		/* Nearest longword */
	fp->byteno =	0;
	fp->bitno =		0;
	fp->rep =		0;
	fp->pix =		0;
	fp->byte =		0;
#endif

	/* Write header struct to file */
	pos = ftell(fp->fp);
	len = fwrite(&fp->h, sizeof(fp->h), 1, fp->fp);
	if (len != 1)
		goto fail;

	/* Read was successful */
	return 0;

fail:
	fseek(fp->fp, pos, SEEK_SET);
	return -1;
}


/*******************************************************************************
* bmp_read_rgbtab
*		Read RGB color palette table from BMP file `fp'.
*
* Returns
*		Number of colors in the palette if successful, otherwise -1.
*
* Notes
*		This function leaves the file positioned at the start of the pixel
*		data, whether or not the file contains a palette map.
*/

int bmp_read_rgbtab(BMP_FILE *fp, struct bmp_rgb tab[])
{
	long		pos;
	size_t		len, alen;
	int			i;

	/* Check args */
	if (fp == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

	if (tab == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

	/* Read color palette (if there is one) */
	if (fp->h.bits > 0  &&  fp->h.bits <= 8)
	{
		/* Save current file position */
		pos = ftell(fp->fp);

		/* Determine actual size of color palette */
		len = bmp_pow2[fp->h.bits];
		alen = (fp->h.biClrUsed > 0 ? fp->h.biClrUsed : len);
		fp->ncols = alen;

		/* Read palette */
		if (fp->flags & BMP_FILE_F_OS2)
		{
			struct os2_bmp_rgb	map3[0x100];

			/* Read OS/2 BMP <r,g,b> color map */
			memset(map3, 0x00, sizeof(map3));

			if (fread(map3, sizeof(map3[0]), alen, fp->fp) != alen)
			{
				/* Can't read palette */
				goto fail;
			}

			/* Convert OS/2 <r,g,b> colors into Windows <r,g,b,x> colors */
			for (i = 0;  i < alen  &&  i < 0x100;  i++)
			{
				tab[i].r = map3[i].r;
				tab[i].g = map3[i].g;
				tab[i].b = map3[i].b;
				tab[i].a = 0x00;
			}
		}
		else
		{
			/* Read BMP <r,g,b,x> color map */
			memset(tab, 0x00, sizeof(tab));

			if (fread(tab, sizeof(tab[0]), alen, fp->fp) != alen)
			{
				/* Can't read palette */
				goto fail;
			}
		}
	}
	else
	{
		/* There is no color palette */
		alen = 0;
		fp->ncols = alen;
	}

	/* Save current file position */
	pos = ftell(fp->fp);

	/* Seek to start of pixel data */
	if (fp->h.headersize > pos)
	{
		/* Seek to start of pixel data */
		if (fseek(fp->fp, fp->h.headersize, SEEK_SET) != 0)
		{
			/* Seek failed */
			goto fail;
		}
	}

	/* Read was successful */
	return alen;

fail:
	fseek(fp->fp, pos, SEEK_SET);
	return -1;
}


/*******************************************************************************
* bmp_write_rgbtab
*		Write RGB color palette table `tab' of `num' colors to BMP file `fp'.
*
* Returns
*		Number of colors written to the palette if successful, otherwise -1.
*
* Notes
*		This function leaves the file positioned at the start of the pixel
*		data, whether or not the file contains a palette map.
*/

int bmp_write_rgbtab(BMP_FILE *fp, const struct bmp_rgb tab[], unsigned num)
{
	long		pos;
	size_t		len;
	int			i;

	/* Check args */
	if (fp == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

	if (tab == NULL)
	{
		/* Invalid pointer */
		errno = EINVAL;
		return -1;
	}

	/* Write color palette */
	if (num > 0  &&  fp->h.bits > 0  &&  fp->h.bits <= 8)
	{
		/* Save current file position */
		pos = ftell(fp->fp);

		/* Determine actual size of color palette */
		len = bmp_pow2[fp->h.bits];
		fp->h.biClrUsed = (num != len ? num : 0);

		/* Write palette */
		if (fp->flags & BMP_FILE_F_OS2)
		{
			struct os2_bmp_rgb	map3[0x100];

			/* Convert Windows <r,g,b,x> colors into OS/2 <r,g,b> colors */
			memset(map3, 0x00, sizeof(map3));
			for (i = 0;  i < num  &&  i < 0x100;  i++)
			{
				map3[i].r = tab[i].r;
				map3[i].g = tab[i].g;
				map3[i].b = tab[i].b;
			}

			/* Write OS/2 BMP <r,g,b> color map */
			if (fwrite(map3, sizeof(map3[0]), num, fp->fp) != num)
			{
				/* Can't write palette */
				goto fail;
			}
		}
		else
		{
			/* Write BMP <r,g,b,x> color map */
			if (fwrite(tab, sizeof(tab[0]), num, fp->fp) != num)
			{
				/* Can't write palette */
				goto fail;
			}
		}
	}
	else
	{
		/* There is no color palette */
		num = 0;
	}

	/* Save current file position */
	pos = ftell(fp->fp);

	/* Seek to start of pixel data */
	if (fp->h.headersize > pos)
	{
		/* Seek to start of pixel data */
		if (fseek(fp->fp, fp->h.headersize, SEEK_SET) != 0)
		{
			/* Seek failed */
			goto fail;
		}
	}

	/* Write was successful */
	return num;

fail:
	fseek(fp->fp, pos, SEEK_SET);
	return -1;
}


/* End bmp2.c */