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/*
* section and descriptor parser
*
* Copyright (C) 2005 Kenneth Aafloy (kenneth@linuxtv.org)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
*/
#ifndef _UCSI_SECTION_H
#define _UCSI_SECTION_H 1
#ifdef __cplusplus
extern "C"
{
#endif
#include <libucsi/endianops.h>
#include <libucsi/descriptor.h>
#include <libucsi/crc32.h>
#include <stdint.h>
#include <string.h>
#define CRC_SIZE 4
/**
* Generic section header.
*/
struct section {
uint8_t table_id;
EBIT4(uint16_t syntax_indicator : 1; ,
uint16_t private_indicator : 1; , /* 2.4.4.10 */
uint16_t reserved : 2; ,
uint16_t length :12; );
} __ucsi_packed;
/**
* Generic extended section header structure.
*/
struct section_ext {
uint8_t table_id;
EBIT4(uint16_t syntax_indicator : 1; ,
uint16_t private_indicator : 1; , /* 2.4.4.10 */
uint16_t reserved : 2; ,
uint16_t length :12; );
uint16_t table_id_ext;
EBIT3(uint8_t reserved1 : 2; ,
uint8_t version_number : 5; ,
uint8_t current_next_indicator : 1; );
uint8_t section_number;
uint8_t last_section_number;
} __ucsi_packed;
/**
* Structure for keeping track of sections of a PSI table.
*/
struct psi_table_state {
uint8_t version_number;
uint16_t next_section_number;
uint8_t complete:1;
uint8_t new_table:1;
} __ucsi_packed;
/**
* Determine the total length of a section, including the header.
*
* @param section The parsed section structure.
* @return The length.
*/
static inline size_t section_length(struct section *section)
{
return section->length + sizeof(struct section);
}
/**
* Determine the total length of an extended section, including the header,
* but omitting the CRC.
*
* @param section The parsed section_ext structure.
* @return The length.
*/
static inline size_t section_ext_length(struct section_ext * section)
{
return section->length + sizeof(struct section) - CRC_SIZE;
}
/**
* Process a section structure in-place.
*
* @param buf Pointer to the data.
* @param len Length of data.
* @return Pointer to the section structure, or NULL if invalid.
*/
static inline struct section * section_codec(uint8_t * buf, size_t len)
{
struct section * ret = (struct section *)buf;
if (len < 3)
return NULL;
bswap16(buf+1);
if (len != ret->length + 3U)
return NULL;
return ret;
}
/**
* Some sections have a CRC even though they are not section_exts.
* This function is to allow checking of them.
*
* @param section Pointer to the processed section structure.
* @return Nonzero on error, or 0 if the CRC was correct.
*/
static inline int section_check_crc(struct section *section)
{
uint8_t * buf = (uint8_t *) section;
size_t len = section_length(section);
uint32_t crc;
/* the crc check has to be performed on the unswapped data */
bswap16(buf+1);
crc = crc32(CRC32_INIT, buf, len);
bswap16(buf+1);
/* the crc check includes the crc value,
* the result should therefore be zero.
*/
if (crc)
return -1;
return 0;
}
/**
* Decode an extended section structure.
*
* @param section Pointer to the processed section structure.
* @param check_crc If 1, the CRC of the section will also be checked.
* @return Pointer to the parsed section_ext structure, or NULL if invalid.
*/
static inline struct section_ext * section_ext_decode(struct section * section,
int check_crc)
{
if (section->syntax_indicator == 0)
return NULL;
if (check_crc) {
if (section_check_crc(section))
return NULL;
}
bswap16((uint8_t *)section + sizeof(struct section));
return (struct section_ext *)section;
}
/**
* Encode an extended section structure for transmission.
*
* @param section Pointer to the section_ext structure.
* @param update_crc If 1, the CRC of the section will also be updated.
* @return Pointer to the encoded section_ext structure, or NULL if invalid.
*/
static inline struct section_ext * section_ext_encode(struct section_ext* section,
int update_crc)
{
if (section->syntax_indicator == 0)
return NULL;
bswap16((uint8_t *)section + sizeof(struct section));
if (update_crc) {
uint8_t * buf = (uint8_t *) section;
int len = sizeof(struct section) + section->length;
uint32_t crc;
/* the crc has to be performed on the swapped data */
bswap16(buf+1);
crc = crc32(CRC32_INIT, buf, len-4);
bswap16(buf+1);
/* update the CRC */
*((uint32_t*) (buf+len-4)) = crc;
bswap32(buf+len-4);
}
return (struct section_ext *)section;
}
/**
* Reset a psi_table_state structure.
*
* @param tstate The structure to reset.
*/
static inline void psi_table_state_reset(struct psi_table_state *tstate)
{
tstate->version_number = 0xff;
}
/**
* Check if a supplied section_ext is something we want to process.
*
* @param section The parsed section_ext structure.
* @param tstate The state structure for this PSI table.
* @return 0=> not useful. nonzero => useful.
*/
static inline int section_ext_useful(struct section_ext *section, struct psi_table_state *tstate)
{
if ((section->version_number == tstate->version_number) && tstate->complete)
return 0;
if (section->version_number != tstate->version_number) {
if (section->section_number != 0)
return 0;
tstate->next_section_number = 0;
tstate->complete = 0;
tstate->version_number = section->version_number;
tstate->new_table = 1;
} else if (section->section_number == tstate->next_section_number) {
tstate->new_table = 0;
} else {
return 0;
}
tstate->next_section_number++;
if (section->last_section_number < tstate->next_section_number) {
tstate->complete = 1;
}
return 1;
}
#ifdef __cplusplus
}
#endif
#endif
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