/*
 * rdtarga.c
 *
 * Copyright (C) 1991-1996, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README file.
 *
 * This file contains routines to read input images in Targa format.
 *
 * These routines may need modification for non-Unix environments or
 * specialized applications.  As they stand, they assume input from
 * an ordinary stdio stream.  They further assume that reading begins
 * at the start of the file; start_input may need work if the
 * user interface has already read some data (e.g., to determine that
 * the file is indeed Targa format).
 *
 * Based on code contributed by Lee Daniel Crocker.
 */

#include "cdjpeg.h"		/* Common decls for cjpeg/djpeg applications */

#ifdef TARGA_SUPPORTED


/* Macros to deal with unsigned chars as efficiently as compiler allows */

#ifdef HAVE_UNSIGNED_CHAR
typedef unsigned char U_CHAR;
#define UCH(x)	((int) (x))
#else /* !HAVE_UNSIGNED_CHAR */
#ifdef CHAR_IS_UNSIGNED
typedef char U_CHAR;
#define UCH(x)	((int) (x))
#else
typedef char U_CHAR;
#define UCH(x)	((int) (x) & 0xFF)
#endif
#endif /* HAVE_UNSIGNED_CHAR */


#define	ReadOK(file,buffer,len)	(JFREAD(file,buffer,len) == ((size_t) (len)))


/* Private version of data source object */

typedef struct _tga_source_struct * tga_source_ptr;

typedef struct _tga_source_struct {
  struct cjpeg_source_struct pub; /* public fields */

  j_compress_ptr cinfo;		/* back link saves passing separate parm */

  JSAMPARRAY colormap;		/* Targa colormap (converted to my format) */

  jvirt_sarray_ptr whole_image;	/* Needed if funny input row order */
  JDIMENSION current_row;	/* Current logical row number to read */

  /* Pointer to routine to extract next Targa pixel from input file */
  JMETHOD(void, read_pixel, (tga_source_ptr sinfo));

  /* Result of read_pixel is delivered here: */
  U_CHAR tga_pixel[4];

  int pixel_size;		/* Bytes per Targa pixel (1 to 4) */

  /* State info for reading RLE-coded pixels; both counts must be init to 0 */
  int block_count;		/* # of pixels remaining in RLE block */
  int dup_pixel_count;		/* # of times to duplicate previous pixel */

  /* This saves the correct pixel-row-expansion method for preload_image */
  JMETHOD(JDIMENSION, get_pixel_rows, (j_compress_ptr cinfo,
				       cjpeg_source_ptr sinfo));
} tga_source_struct;


/* For expanding 5-bit pixel values to 8-bit with best rounding */

static const UINT8 c5to8bits[32] = {
    0,   8,  16,  25,  33,  41,  49,  58,
   66,  74,  82,  90,  99, 107, 115, 123,
  132, 140, 148, 156, 165, 173, 181, 189,
  197, 206, 214, 222, 230, 239, 247, 255
};



LOCAL(int)
read_byte (tga_source_ptr sinfo)
/* Read next byte from Targa file */
{
  register FILE *infile = sinfo->pub.input_file;
  register int c;

  if ((c = getc(infile)) == EOF)
    ERREXIT(sinfo->cinfo, JERR_INPUT_EOF);
  return c;
}


LOCAL(void)
read_colormap (tga_source_ptr sinfo, int cmaplen, int mapentrysize)
/* Read the colormap from a Targa file */
{
  int i;

  /* Presently only handles 24-bit BGR format */
  if (mapentrysize != 24)
    ERREXIT(sinfo->cinfo, JERR_TGA_BADCMAP);

  for (i = 0; i < cmaplen; i++) {
    sinfo->colormap[2][i] = (JSAMPLE) read_byte(sinfo);
    sinfo->colormap[1][i] = (JSAMPLE) read_byte(sinfo);
    sinfo->colormap[0][i] = (JSAMPLE) read_byte(sinfo);
  }
}


/*
 * read_pixel methods: get a single pixel from Targa file into tga_pixel[]
 */

METHODDEF(void)
read_non_rle_pixel (tga_source_ptr sinfo)
/* Read one Targa pixel from the input file; no RLE expansion */
{
  register FILE *infile = sinfo->pub.input_file;
  register int i;

  for (i = 0; i < sinfo->pixel_size; i++) {
    sinfo->tga_pixel[i] = (U_CHAR) getc(infile);
  }
}


METHODDEF(void)
read_rle_pixel (tga_source_ptr sinfo)
/* Read one Targa pixel from the input file, expanding RLE data as needed */
{
  register FILE *infile = sinfo->pub.input_file;
  register int i;

  /* Duplicate previously read pixel? */
  if (sinfo->dup_pixel_count > 0) {
    sinfo->dup_pixel_count--;
    return;
  }

  /* Time to read RLE block header? */
  if (--sinfo->block_count < 0) { /* decrement pixels remaining in block */
    i = read_byte(sinfo);
    if (i & 0x80) {		/* Start of duplicate-pixel block? */
      sinfo->dup_pixel_count = i & 0x7F; /* number of dups after this one */
      sinfo->block_count = 0;	/* then read new block header */
    } else {
      sinfo->block_count = i & 0x7F; /* number of pixels after this one */
    }
  }

  /* Read next pixel */
  for (i = 0; i < sinfo->pixel_size; i++) {
    sinfo->tga_pixel[i] = (U_CHAR) getc(infile);
  }
}


/*
 * Read one row of pixels.
 *
 * We provide several different versions depending on input file format.
 */


METHODDEF(JDIMENSION)
get_8bit_gray_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 8-bit grayscale pixels */
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  register JSAMPROW ptr;
  register JDIMENSION col;
  
  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
    *ptr++ = (JSAMPLE) UCH(source->tga_pixel[0]);
  }
  return 1;
}

METHODDEF(JDIMENSION)
get_8bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 8-bit colormap indexes */
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  register int t;
  register JSAMPROW ptr;
  register JDIMENSION col;
  register JSAMPARRAY colormap = source->colormap;

  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
    t = UCH(source->tga_pixel[0]);
    *ptr++ = colormap[0][t];
    *ptr++ = colormap[1][t];
    *ptr++ = colormap[2][t];
  }
  return 1;
}

METHODDEF(JDIMENSION)
get_16bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 16-bit pixels */
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  register int t;
  register JSAMPROW ptr;
  register JDIMENSION col;
  
  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
    t = UCH(source->tga_pixel[0]);
    t += UCH(source->tga_pixel[1]) << 8;
    /* We expand 5 bit data to 8 bit sample width.
     * The format of the 16-bit (LSB first) input word is
     *     xRRRRRGGGGGBBBBB
     */
    ptr[2] = (JSAMPLE) c5to8bits[t & 0x1F];
    t >>= 5;
    ptr[1] = (JSAMPLE) c5to8bits[t & 0x1F];
    t >>= 5;
    ptr[0] = (JSAMPLE) c5to8bits[t & 0x1F];
    ptr += 3;
  }
  return 1;
}

METHODDEF(JDIMENSION)
get_24bit_row (j_compress_ptr cinfo, cjpeg_source_ptr sinfo)
/* This version is for reading 24-bit pixels */
{
  tga_source_ptr source = (tga_source_ptr) sinfo;
  register JSAMPROW ptr;
  register JDIMENSION col;
  
  ptr = source->pub.buffer[0];
  for (col = cinfo->image_width; col > 0; col--) {
    (*source->read_pixel) (source); /* Load next pixel into tga_pixel */
    *ptr++ = (JSAMPLE) UCH(source->tga_pixel[2]); /* change BGR to RGB order */
    *ptr++ = (JSAMPLE) UCH(source->tga_pixel[1]);
    *ptr++ = (JSAMPLE) UCH(source->tga_pixel[0]);