/* This file is part of dvi2bitmap; see README for copyrights and licence */

#include <config.h>

#include <FileByteStream.h>

#include <iostream>
//#include <fcntl.h>
#include <sys/stat.h>
#include <unistd.h>
#ifdef HAVE_CSTD_INCLUDE
#include <cstdio>
#include <cerrno>
#include <cassert>
#include <cstring>		// for strerror
#else
#include <stdio.h>
#include <errno.h>
#include <assert.h>
#include <string.h>
#endif

using STD::cerr;
using STD::endl;


/**
 * Opens the requested file.  If preload is true, then open the file
 * and read it entire into memory (possibly helpful if the client will
 * be seeking a lot).  If the file can't be opened, then try adding
 * <code>tryext</code> to the end of it.
 *
 * <p>The file to be opened must be a seekable object -- that is, it
 * must be a regular file, rather than a named pipe or a socket.  The
 * constructor checks this, and throws an exception if this is not the
 * case. If you wish to open a named pipe, you can do so using {@link
 * InputByteStream#InputByteStream(string)}.
 *
 * @param filename the file to be opened
 * @param tryext a file extension, including any dot, which should be
 * added to the end of <code>filename</code> if that cannot be opened;
 * default <code>""</code> suppresses this
 * @param preload if true, then the file is read entirely into memory
 *
 * @throws InputByteStreamError if there is a problem opening the
 * file, including the discovery that it is not a seekable object
 */
FileByteStream::FileByteStream(string& filename,
			       string tryext,
			       bool preload)
    throw (InputByteStreamError)
{
    if (getVerbosity() > normal)
	cerr << "FileByteStream(name=" << filename
	     << ",ext=" << tryext
	     << ",preload=" << (preload?"yes":"no") << ")" << endl;
    int newfd = -1;
    try {
	newfd = openSourceSpec("<osfile>" + filename);
    } catch (InputByteStreamError& e) {
	newfd = -1;
    }
    if (newfd < 0) {
	newfd = openSourceSpec("<osfile>" + filename + tryext);
	// Let it throw the exception, this time
	// If it succeeds, modify the argument
	filename += tryext;
    }
    assert(newfd >= 0);

    // ermm, we should test for HAVE_SYS_STAT_H, here, but (a) are
    // there really any platforms which don't have stat?, and (b) we
    // need the filesize information, and I don't know how else to
    // get it.  Deal with this if we really do find such a wierd
    // platform.
#ifndef HAVE_SYS_STAT_H
#error "Come on -- you _must_ have stat(2)!"
#endif
    struct stat S;
    if (fstat (newfd, &S))
    {
	string errstr = STD::strerror (errno);
	throw InputByteStreamError ("Can't stat open file (" + errstr + ")");
    }
    filesize_ = S.st_size;

    bindToFileDescriptor(newfd,
			 filename,
			 (preload ? filesize_ : 0),
			 preload,
			 true);	// assert is seekable
}

FileByteStream::~FileByteStream()
{
    // nothing
}

/**
 * Sets the position of the file pointer.
 *
 * @param pos if positive, the offset from the beginning of the file;
 * if negative, the offset from the end of the file
 *
 * @throws InputByteStreamError if the offset is larger
 * than the size of the file
 */
void FileByteStream::seek(int pos)
    throw (InputByteStreamError)
{
    int fd = getFD();
    int offset = (pos >= 0 ? pos : filesize_ + pos);
    if (offset < 0 || offset > filesize_)
	throw InputByteStreamError("FileByteStream: seek out of bounds");

    if (fd < 0) {
	// preloaded
	bufferSeek(offset);
	// no need to reload buffer
    } else {
	if (lseek(fd, offset, SEEK_SET) < 0) {
	    string errmsg = STD::strerror(errno);
	    throw InputByteStreamError("Can't seek (" + errmsg + ")");
	}
	if (getVerbosity() > normal)
	    cerr << "FileByteStream::seek(" << pos << "=>" << offset
		 << ") ok" << endl;
	reloadBuffer();
    }
}