+++ /dev/null
-// Copyright © 2011 Moritz Hanke
-
-// Based on Lossless Data Compression. Blue Book. Issue 1. May 1997.
-// CCSDS 121.0-B-1
-//
-// http://public.ccsds.org/publications/bluebooks.aspx
-// http://public.ccsds.org/publications/archive/121x0b1c2.pdf
-
-// Compression Identification Packet (optinal)
-// The CIP is used to configure the decompressor in case no configuration
-// data is available.
-// It is comprised of the cip Primary Header (as described in "CCSDS Space
-// Packet Protocol Blue Book") and the Packet Data Field.
-
-enum cip_packet_type {
-
- TELEMETRY, // reporting
- TELECOMMAND, // requesting (makes no sense for compression)
-};
-
-enum cip_sequence_flag {
-
- CONTINUE = 0,
- FIRST = 1,
- LAST = 2,
- UNSEGMENTED = 3,
-};
-
-enum cip_compression_technique {
-
- NO = 0, // no compression is used
- LOSSLESS = 1, // lossless compression is used
-};
-
-enum cip_predictor_type {
-
- BYPASS_P = 0, // bypass predictor
- UNIT_DELAY_P = 1, // unit delay predictor
- APP_SPECIFIC_P = 7, // application-specific predictor
-};
-
-enum cip_mapper_type {
-
- STANDARD_M = 0, // standard prediction error mapper as described in the reference
- APP_SPECIFIC_M = 3, // application-specific mapper
-};
-
-enum cip_data_sense {
-
- TWOS_COMPLEMENT = 0, // two's complement
- POSITIVE = 1, // positive (mandatory if preprocessor is bypassed)
-};
-
-enum entropy_coder_option {
-
- OPTION_S = 1, // for resolution n <= 8
- OPTION_M = 2, // for resolution 8 < n <= 16
- OPTION_L = 3, // for resolution 16 < n <= 32
-};
-
-struct cip_header {
-
- //----------------------------
- // Packet Primary Header data
- //----------------------------
-
- char packet_version_number; // Packet Version Number
-
- // Packet Identification
- enum cip_packet_type type; // Packet Type
- char secondary_header_available; // Sequence Header Flag
- unsigned apid; // Application Process Identifier
-
- // Packet Sequence Control
- enum cip_sequence_flag sequence_flag; // Sequence Flags
- unsigned sequence_count; // Packet Sequence Count
- // in case of a TELECOMMAND type cip
- // data package this contains the
- // Packet Name
-
- unsigned data_length; // length of the Packet Data Field - 1 in byte
-};
-
-struct cip_preprocessor_configuration {
-
- char preprocessor_present; // Preprocessor Status (0 - absent, 1 - present)
-
- enum cip_predictor_type predictor_type; // Predictor type (undefined if preprocessor is absent)
-
- enum cip_mapper_type mapper_type; // Mapper type (undefined if preprocessor is absent)
-
- char block_size; // Block size (8, 16 or application specific)
-
- enum cip_data_sense data_sense;
-
- char resolution; // Input data sample resolution (1-32)
-};
-
-struct cip_entropy_coder_configuration {
-
- enum entropy_coder_option option; // Entropy Coder option
-
- unsigned num_cds_per_packet; // Number of coded data sets per packet
-};
-
-struct cip_source_data_field {
-
- unsigned grouping_data_length; // Grouping Data Length
-
- enum cip_compression_technique compression_technique; // Compression Technique Identification
-
- unsigned reference_sample_interval; // Reference Sample Interval
- // - in case a preprocessor is
- // used that requires a
- // reference sample
- // - in case of the zero-block
- // option it contains the
- // interval of input data sample
- // blocks
-
- struct cip_preprocessor_configuration preprocessor_config; // Preprocessor Configuration
-
- struct cip_entropy_coder_configuration entropy_coder_config; // Entropy Coder Configuration
-};
-
-struct cip {
-
- struct cip_header header; // Information from the Primary Header
- struct cip_source_data_field sdf; // Information on the data
-};
-
-void * decode_cip(void * buffer, struct cip * cip);
- // data: buffer starting with a cip
- // cip: in case cip is not NULL the configuration information
- // contained in the cip is written to it
- // returns a pointer to the compressed data without the cip
- // returns NULL in case an error occured while decoding
+++ /dev/null
-// Copyright © 2011 Moritz Hanke
-
-#include <stdlib.h>
-#include <stdio.h>
-#include <assert.h>
-
-#include "bit_macros.h"
-#include "cip.h"
-
-// decode Packet Primary Header
-void * decode_pph(void * buffer, struct cip * cip);
-
-// decode Secondary Header
-void * decode_sh(void * buffer, struct cip * cip);
-
-// decode Source Data Field
-void * decode_sdf(void * buffer, struct cip * cip);
-
-// decode Preprocessor Parameters
-void * decode_preprocessor(void * buffer, struct cip * cip);
-
-// decode Entopy Coder Parameters
-void * decode_entropy_coder(void * buffer, struct cip * cip);
-
-// decode Instrument Configuration
-void * decode_instrument_configuration(void * buffer, struct cip * cip);
-
-void * decode_cip(void * buffer, struct cip * cip) {
-
- void * pdf; // Packet Data Field
- void * sdf; // Source Data Field
- void * cds; // Coded data sets
-
- pdf = decode_pph(buffer, cip);
-
- if (cip->header.secondary_header_available)
- sdf = decode_sh(pdf, cip);
- else
- sdf = pdf;
-
- cds = decode_sdf(sdf, cip);
-
- if ((char*)cds > (char*)pdf + cip->header.data_length + 1) {
-
- fprintf(stderr, "Packet Data Field is bigger than specified in CIP Packet Primary Header\n");
- exit(EXIT_FAILURE);
- }
-
- return (char*)pdf + cip->header.data_length + 1;
-}
-
-// decode Primary Header
-void * decode_pph(void * buffer, struct cip * cip) {
-
- char * cip_buf = buffer;
-
- // Packet Version Number
-
- cip->header.packet_version_number = (cip_buf[0] >> 5) & B3 ;
-
- if (cip->header.packet_version_number != 0) {
-
- fprintf(stderr, "Undefined Packet Version Number\n");
- exit(EXIT_FAILURE);
- }
-
- // Packet Identification
- {
- // Packet Type
-
- cip->header.type = ((cip_buf[0] >> 4) & B1)?TELECOMMAND:TELEMETRY;
-
- // is a Secondary Header available
-
- cip->header.secondary_header_available = (cip_buf[0] >> 3) & B1;
-
- // Application Process Identifer
-
- cip->header.apid = ((unsigned)(cip_buf[0] & B3) << 8) | cip_buf[1];
- }
-
- // Packet Sequence Control
- {
- // Sequence Flags
-
- cip->header.sequence_flag = (cip_buf[2] >> 6) & B2;
-
- // Packet Sequence Count or Packet Name
-
- assert(sizeof(unsigned) > 2);
-
- cip->header.sequence_count = ((unsigned)(cip_buf[2] & B6) << 8) |
- cip_buf[3];
- }
-
- // Packet Data Length
-
- cip->header.data_length = ((unsigned)cip_buf[4] << 8) | cip_buf[5];
-
- return (char*)cip + 6; // the Packet Primary Header has a size of 48
- // bits
-}
-
-void * decode_sh(void * buffer, struct cip * cip) {
-
- // The Secondary Header contains information like time and position
- // or attitude of a spacecraft.
- // The handling of a Secondary Header is currently not implemented.
-
- fprintf(stderr, "Compression Identification Packet contains a Secondary Header\n");
- exit(EXIT_FAILURE);
-
- return buffer;
-}
-
-void * decode_sdf(void * buffer, struct cip * cip) {
-
- char * sdf = buffer;
-
- // Grouping Data Length (number of packets containing compressed data)
-
- cip->sdf.grouping_data_length = (((unsigned)(sdf[0] & B4) << 8) |
- sdf[1]) + 1;
-
- // check whether a compression is used for the current group
-
- if (sdf[2] > 1) {
-
- fprintf(stderr, "Undefined compression technique\n");
- exit(EXIT_FAILURE);
- }
-
- cip->sdf.compression_technique = sdf[2];
-
- // Reference Sample Interval
-
- cip->sdf.reference_sample_interval = sdf[3]+1;
-
-
- if (cip->sdf.compression_technique == LOSSLESS) {
-
- // decode Preprocessor Parameters
- sdf = decode_preprocessor(sdf, cip);
- }
-
- // decode Entropy Coder Parameters
- sdf = decode_entropy_coder(sdf, cip);
-
- // decode Instrument Configuration
- sdf = decode_instrument_configuration(sdf, cip);
-
- return sdf;
-}
-
-void * decode_preprocessor(void * buffer, struct cip * cip) {
-
- char * sdf = buffer;
-
- unsigned header;
-
- // check for correct header
- header = (sdf[0] >> 6) & B2;
- if (header != 0) {
-
- fprintf(stderr, "Wrong header for preprocessor field\n");
- exit(EXIT_FAILURE);
- }
-
- // get preprocessor presents
- cip->sdf.preprocessor_config.preprocessor_present = (sdf[0] >> 5) & B1;
-
- // if a preprocessor is present
- if (cip->sdf.preprocessor_config.preprocessor_present) {
-
- // Predictor type
- switch ((sdf[0] >> 2) & B3) {
-
- case (0):
- cip->sdf.preprocessor_config.predictor_type = BYPASS_P;
- break;
- case (1):
- cip->sdf.preprocessor_config.predictor_type = UNIT_DELAY_P;
- break;
- case (7):
- cip->sdf.preprocessor_config.predictor_type = APP_SPECIFIC_P;
- break;
- default:
- fprintf(stderr, "Invalid predictor type\n");
- exit(EXIT_FAILURE);
- };
-
- // Mapper type
- switch (sdf[0] & B2) {
-
- case (0):
- cip->sdf.preprocessor_config.mapper_type = STANDARD_M;
- break;
- case (3):
- cip->sdf.preprocessor_config.mapper_type = APP_SPECIFIC_M;
- break;
- default:
- fprintf(stderr, "Invalid mapper type\n");
- exit(EXIT_FAILURE);
- };
- }
-
- // Block size (J)
- switch ((sdf[1] >> 6) & B2) {
-
- case (0):
- cip->sdf.preprocessor_config.block_size = 8;
- break;
- case (1):
- cip->sdf.preprocessor_config.block_size = 16;
- break;
- case(3):
- fprintf(stderr, "Missing implementation for application-specific block size\n");
- exit(EXIT_FAILURE);
- default:
- fprintf(stderr, "Invalid block size\n");
- exit(EXIT_FAILURE);
- };
-
- // Data sense
- cip->sdf.preprocessor_config.data_sense = (sdf[1] >> 5) & 1;
-
- // check whether preprocessor presents and data sense match
- if (!cip->sdf.preprocessor_config.preprocessor_present &&
- cip->sdf.preprocessor_config.data_sense != POSITIVE) {
-
- fprintf(stderr, "If no preprocessor is present, the data sense has to be positive.\n");
- exit(EXIT_FAILURE);
- }
-
- // Input data sample resolution
- cip->sdf.preprocessor_config.resolution = (sdf[1] & B5) + 1;
-
- return (char*)buffer + 2; // the preprocessor field has a size of 2 byte
-}
-
-void * decode_entropy_coder(void * buffer, struct cip * cip) {
-
- char * sdf = buffer;
-
- unsigned header;
-
- // check for correct header
- header = (sdf[0] >> 6) & B2;
- if (header != 1) {
-
- fprintf(stderr, "Wrong header for entropy coder field\n");
- exit(EXIT_FAILURE);
- }
-
- // Entropy Coder option
- switch ((sdf[0] >> 4) & B2) {
-
- case (1):
- if (cip->sdf.preprocessor_config.resolution > 8) {
-
- fprintf(stderr, "Entropy coder option does not match input data sample resolution\n");
- exit(EXIT_FAILURE);
- }
- cip->sdf.entropy_coder_config.option = OPTION_S;
- break;
- case (2):
- if ((cip->sdf.preprocessor_config.resolution <= 8) ||
- (cip->sdf.preprocessor_config.resolution > 16)) {
-
- fprintf(stderr, "Entropy coder option does not match input data sample resolution\n");
- exit(EXIT_FAILURE);
- }
- cip->sdf.entropy_coder_config.option = OPTION_M;
- break;
- case (3):
- if ((cip->sdf.preprocessor_config.resolution <= 16) ||
- (cip->sdf.preprocessor_config.resolution > 32)) {
-
- fprintf(stderr, "Entropy coder option does not match input data sample resolution\n");
- exit(EXIT_FAILURE);
- }
- cip->sdf.entropy_coder_config.option = OPTION_L;
- break;
- default:
- fprintf(stderr, "Invalid entropy coder option\n");
- exit(EXIT_FAILURE);
- };
-
- assert(sizeof(unsigned) > 2);
-
- // Number of coded data sets per packet
- cip->sdf.entropy_coder_config.num_cds_per_packet =
- (((unsigned)(sdf[0] & B4) << 8) | sdf[1]) + 1;
-
- return (char*)buffer + 2; // entropy coder field has a size of 2 byte
-}
-
-void * decode_instrument_configuration(void * buffer, struct cip * cip) {
-
- // Instrument Configuration is mission specific.
- // This implementation assumes that there is no.
- // In an one is added later, the first 2 bits of buffer have to 10.
-
- return buffer;
-}
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