Source: ../../libxorp/tlv.hh

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// -*- c-basic-offset: 4; tab-width: 8; indent-tabs-mode: t -*-
// vim:set sts=4 ts=8:

// Copyright (c) 2001-2009 XORP, Inc.
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License, Version
// 2.1, June 1999 as published by the Free Software Foundation.
// Redistribution and/or modification of this program under the terms of
// any other version of the GNU Lesser General Public License is not
// permitted.
// 
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. For more details,
// see the GNU Lesser General Public License, Version 2.1, a copy of
// which can be found in the XORP LICENSE.lgpl file.
// 
// XORP, Inc, 2953 Bunker Hill Lane, Suite 204, Santa Clara, CA 95054, USA;
// http://xorp.net

// $XORP: xorp/libxorp/tlv.hh,v 1.10 2009/01/05 18:30:58 jtc Exp $

#ifndef __LIBXORP_TLV_HH__
#define __LIBXORP_TLV_HH__

/**
 * <Type,Length,Value>
 * Read and Write TLV records.
 */
class Tlv {
 public:
    Tlv() : _fp(0)
	{}

    /**
     * Open file for reading or writing.
     *
     * @param fname filename or '-' for stdin/stdout.
     * @param read true if the file is to be opened for reading, false
     * if opened for writing.
     *
     * @return true on success
     */
    bool open(string& fname, bool read) {
	if ("-" == fname) {
	    _fp = read ? stdin : stdout;
	} else {
	    _fp = fopen(fname.c_str(), read ? "r" : "w");
	}
	if (0 == _fp)
	    return false;

	return true;
    }

    /**
     * Read a TLV entry from the file.
     *
     * @return type of entry.
     * @return data read.
     *
     * @return true on success
     */
    bool read(uint32_t& type, vector<uint8_t>& data) {
	uint32_t n;
	if (1 != fread(&n, sizeof(n), 1, _fp))
	    return false;
	
	type = ntohl(n);

	if (1 != fread(&n, sizeof(n), 1, _fp))
	    return false;

	uint32_t len = ntohl(n);

	data.resize(len);
	if (len != fread(&data[0], 1, len, _fp))
	    return false;

	return true;
    }

    /**
     * Write a TLV entry to the file.
     *
     * @return type of entry.
     * @return data to be written.
     *
     * @return true on success
     */
    bool write(uint32_t type, vector<uint8_t>& data) {
	uint32_t n = htonl(type);
	if (1 != fwrite(&n, sizeof(n), 1, _fp))
	    return false;
	
	uint32_t len = data.size();
	n = htonl(len);

	if (1 != fwrite(&n, sizeof(n), 1, _fp))
	    return false;

	if (len != fwrite(&data[0], 1, len, _fp))
	    return false;

	return true;
    }

    /**
     * Close the TLV file.
     *
     * @return true on success
     */
    bool close() {
	if (0 == _fp) {
	    return false;
	}
	return 0 == fclose(_fp) ? true : false;
    }

    /*
     * Get a 32 bit unsigned int from the data array.
     *
     * @param data array containing the value.
     * @param offset in data to start reading.
     * @param u32 value read from array.
     *
     * @return true on success
     */
    bool get32(vector<uint8_t>& data, uint32_t offset, uint32_t& u32) {

	if (data.size() < offset + sizeof(u32))
	    return false;

	u32 = data[offset + 0];
	u32 <<= 8;
	u32 |= data[offset + 1];
	u32 <<= 8;
	u32 |= data[offset + 2];
	u32 <<= 8;
	u32 |= data[offset + 3];
	
	return true;
    }

    /*
     * Put a 32 bit unsigned int into the data array.
     *
     * @param data array into which to place the value.
     * @param offset in data to start writing.
     * @param u32 value to put into the array.
     *
     * @return true on success
     */
    bool put32(vector<uint8_t>& data, uint32_t offset, uint32_t u32) {

	if (data.size() < offset + sizeof(u32))
	    return false;

	data[offset + 0] = (u32 >> 24) & 0xff;
	data[offset + 1] = (u32 >> 16) & 0xff;
	data[offset + 2] = (u32 >> 8) & 0xff;
	data[offset + 3] = u32 & 0xff;

	return true;
    }

 private:
    FILE *_fp;
};

#endif // __LIBXORP_TLV_HH__