/*----------------------------------------------------------------------------
.BMP file dumper
Chris Giese	<ChrisGiese@SisAndHappy.com>
http://SisAndHappy.com/ChrisGiese/

This code is public domain (no copyright).
You can do whatever you want with it.

7 April 2018: initial release
----------------------------------------------------------------------------*/
#include <stdio.h>
#if 0
#include <stdint.h>
#else
typedef unsigned char	uint8_t;
typedef unsigned short	uint16_t;
typedef unsigned long	uint32_t;
#endif
/****************************************************************************/
static uint16_t read_le16(const void *buf0)
{
	const uint8_t *buf = buf0;
	uint16_t rv;

	rv = buf[1]; /* MSB */
	rv <<= 8;
	rv |= buf[0]; /* LSB */
	return rv;
}
/****************************************************************************/
static uint32_t read_le32(const void *buf0)
{
	const uint8_t *buf = buf0;
	uint32_t rv;

	rv = buf[3]; /* MSB */
	rv <<= 8;
	rv |= buf[2];
	rv <<= 8;
	rv |= buf[1];
	rv <<= 8;
	rv |= buf[0]; /* LSB */
	return rv;
}
/****************************************************************************/
int main(int arg_c, char *arg_v[])
{
	uint32_t file_len, raster_start, bih_len, compr, start, len;
	uint16_t depth;
/* 14-byte BITMAPFILEINFO header plus the first part of the 40-byte
(usually) BITMAPINFO header */
	uint8_t buf[34];
	FILE *f;
	int j;

	if(arg_c < 2)
	{
		printf("Displays information about .BMP files.\n");
		return 1;
	}
	for(j = 1; j < arg_c; j++)
	{
		if((f = fopen(arg_v[j], "rb")) == NULL)
		{
			printf("Error: can't open file '%s'\n", arg_v[j]);
			continue;
		}
		fseek(f, 0, SEEK_END);
		file_len = ftell(f);
		fseek(f, 0, SEEK_SET);
		if(fread(buf, 1, sizeof(buf), f) != sizeof(buf)
			|| buf[0] != 'B' || buf[1] != 'M')
		{
			printf("Error: file '%s' is not a .BMP file\n",
				arg_v[j]);
			fclose(f);
			continue;
		}
		printf("\n.BMP file '%s':\n", arg_v[j]);
		raster_start = read_le32(&buf[10]);
		bih_len = read_le32(&buf[14]);
		depth = read_le16(&buf[28]);
		compr = read_le32(&buf[30]);
		printf("%lu x %lu pixels, %u planes", read_le32(&buf[18]),
			read_le32(&buf[22]), read_le16(&buf[26]));
		printf(", %u bits per pixel, compression %lu",
			depth, compr);
		if(compr == 0)
			printf(" (uncompressed)\n");
		else if(compr == 1)
			printf(" (RLE8)\n");
		else if(compr == 2)
			printf(" (RLE4)\n");
		else if(compr == 3)
			printf(" (BITFIELDS)\n");
		else
			printf(" (?)\n");
/* extra space at the end of BITMAPINFOHEADER might be used for the
RGB masks... */
		if(compr == 3 && raster_start > 14 + bih_len)
/* ...or for something else; though I know not what:
		if(depth > 8 && raster_start > 14 + bih_len) */
		{
			fseek(f, 54, SEEK_SET);
			if(fread(buf, 1, 12, f) != 12)
			{
				printf("Error reading .BMP file '%s'\n",
					arg_v[j]);
				fclose(f);
				continue;
			}
			printf("RGB masks=%08lX:%08lX:%08lX\n",
				read_le32(&buf[0]), read_le32(&buf[4]),
				read_le32(&buf[8]));
		}
		fclose(f);
		printf("Offset Size     Description\n"
			"------ -------- -----------\n"
			"     0       14 BITMAPFILEHEADER\n"
			"    14 %8lu BITMAPINFOHEADER\n", bih_len);
		start = 14 + bih_len;
		if(depth <= 8 && raster_start > start)
		{
			len = raster_start - start;
			printf("%6lu %8lu palette\n", start, len);
		}
		printf("%6lu %8lu raster\n", raster_start,
			file_len - raster_start);
	}
	return 0;
}