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//
// Internal (Image) Reader class for the Fast Light Tool Kit (FLTK).
//
// Copyright 2020-2021 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
// file is missing or damaged, see the license at:
//
// https://www.fltk.org/COPYING.php
//
// Please see the following page on how to report bugs and issues:
//
// https://www.fltk.org/bugs.php
//
/*
This internal (undocumented) class reads data chunks from a file or from
memory in LSB-first byte order.
This class is used in Fl_GIF_Image and Fl_BMP_Image to avoid code
duplication and may be extended to be used in similar cases. Future
options might be to read data in MSB-first byte order or to add more
methods.
*/
#ifndef FL_IMAGE_READER_H
#define FL_IMAGE_READER_H
#include <stdio.h>
class Fl_Image_Reader
{
public:
// Create the reader.
Fl_Image_Reader() :
pIsFile(0), pIsData(0),
pFile(0L), pData(0L),
pStart(0L),
pEnd((const unsigned char *)(-1L)),
pName(0L),
pError(0)
{}
// Initialize the reader to access the file system, filename is copied
// and stored.
int open(const char *filename);
// Initialize the reader for memory access, name is copied and stored
int open(const char *imagename, const unsigned char *data, const long datasize = -1);
// Close and destroy the reader
~Fl_Image_Reader();
// Read a single byte from memory or a file
unsigned char read_byte();
// Read a 16-bit unsigned integer, LSB-first
unsigned short read_word();
// Read a 32-bit unsigned integer, LSB-first
unsigned int read_dword();
// Read a 32-bit signed integer, LSB-first
int read_long() {
return (int)read_dword();
}
// Move the current read position to a byte offset from the beginning
// of the file or the original start address in memory
void seek(unsigned int n);
// Get the current file or memory offset from the beginning
// of the file or the original start address in memory
long tell() const;
// Get the current EOF or error status of the file or data block
int error() const {
return pError;
}
// return the name or filename for this reader
const char *name() { return pName; }
// skip a given number of bytes
void skip(unsigned int n) { seek(tell() + n); }
private:
// open() sets this if we read from a file
char pIsFile;
// open() sets this if we read from memory
char pIsData;
// a pointer to the opened file
FILE *pFile;
// a pointer to the current byte in memory
const unsigned char *pData;
// a pointer to the start of the image data
const unsigned char *pStart;
// a pointer to the end of image data if reading from memory, otherwise undefined
// note: currently (const unsigned char *)(-1L) if end of memory is not available
// ... which means "unlimited"
const unsigned char *pEnd;
// a copy of the name associated with this reader
char *pName;
// a flag to store EOF or error status
int pError;
};
#endif // FL_IMAGE_READER_H
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