ASN.1编解码：asn1c-ORAN-E2AP编解码示例
荣涛9月2日
整体代码：/rtoax/test/tree/master/ASN.1/asn1c/jt_sran/e2ap
1. 生成的可执行文件
前面文档中已经给出了该测试文件的帮助信息，这里再给出一遍
[rongtao@localhost e2ap]$ ./test -hUsage: ./test [options] <datafile> ...Where options are:-iber Input is in BER (Basic Encoding Rules) or DER-ioer Input is in OER (Octet Encoding Rules)-iper Input is in Unaligned PER (Packed Encoding Rules) (DEFAULT)-iaper Input is in Aligned PER (Packed Encoding Rules)-ixer Input is in XER (XML Encoding Rules)-oder Output as DER (Distinguished Encoding Rules)-ooer Output as Canonical OER (Octet Encoding Rules)-oper Output as Unaligned PER (Packed Encoding Rules)-oaper Output as Aligned PER (Packed Encoding Rules)-oxer Output as XER (XML Encoding Rules) (DEFAULT)-otext Output as plain semi-structured text-onull Verify (decode) input, but do not output-per-nopad Assume PER PDUs are not padded (-iper)-1 Decode only the first PDU in file-b <size> Set the i/o buffer size (default is 8192)-c Check ASN.1 constraints after decoding-d Enable debugging (-dd is even better)-n <num>Process files <num> times-s <size> Set the stack usage limit (default is 30000)
这个可执行文件是比较复杂的，具体怎么使用，后续文档中再做解释，本文先到这。
2. 编译测试例
需要注意一下几点：
使用e2ap-v01.00.00.asn
在CMakeLists.txt中添加宏
-DPDU=RICcontrolRequest
RICcontrolRequest在e2ap-v01.00.00.asn中的定义如下，为了更加清晰，这里我使用截图显示：
首先有个枚举值
下面的不知道啥意思
接着是RICcontrolRequest结构体
当我们采用asn1c对上述的asn编码进行编译后，就可以得到C语言代码。下面一一列举：
数据结构被编译为：
ProtocolIE_Container_1544P7_t是什么，继续找。在文件ProtocolIE-Container.h中有：
再看RICcontrolRequest_IEs结构，在文件ProtocolIE-Field.h中有：
上面这些数据结构，我们不需要做出修改，我理解，也不用对他理解的太透彻，我们只需要知道如何修改标志性字段即可。
3. 编写编解码C语言代码
为了测试我自己对ASN.1编解码，我选取上一章节中使用的数据结构RICcontrolRequest。先直接给出测试例总的API
/*** RICcontrolRequest 测试例代码** 作者 荣涛* 创建 8月29日**/#define TEST_RICcontrolRequest int test_RICcontrolRequest(){#ifdef TEST_RICcontrolRequestFUNC_CALL();gen_RICcontrolRequest();load_RICcontrolRequest();#endifreturn 0;}
使用宏TEST_RICcontrolRequest控制，接口gen_RICcontrolRequest会生成ASN.1编码文件，load_RICcontrolRequest会再次解析使用gen_RICcontrolRequest生成的文件，验证准确性。
这里，我梳理了我使用的asn1c库函数API，如下图：
起始，也不用做过多的解释，直接上代码吧，解析过程比较简单：
/*** 测试 RICcontrolRequest_t* ** 作者：荣涛* 创建时间：8月30日* * 修改日志* 8月30日 创建 xer 编解码* 8月31日 尝试添加 ber 编解码, * 9月1日 aper 编解码 完成* 9月2日 ber、der编解码*/#include <stdio.h>/* for stdout */#include <errno.h>/* for errno */#include <stdlib.h>/* for malloc() */#include <assert.h>/* for run-time control */#include "../RICcontrolRequest.h"/* Include MyTypes definition */#include "../ProtocolIE-Field.h"#include "my-test/my_test.h"#define XER_RICcontrolRequest "RICcontrolRequest.xer"#define APER_RICcontrolRequest "RICcontrolRequest.aper"#define OER_RICcontrolRequest "RICcontrolRequest.oer"#define DER_RICcontrolRequest "RICcontrolRequest.ber"#define NEW_XER_RICcontrolRequest "RICcontrolRequest-New.xer"#define NEW_APER_RICcontrolRequest "RICcontrolRequest-New.aper"#define NEW_OER_RICcontrolRequest "RICcontrolRequest-New.oer"#define NEW_DER_RICcontrolRequest "RICcontrolRequest-New.ber"static RICcontrolRequest_IEs_t *alloc_RICcontrolRequest_IEs(ProtocolIE_ID_t id, RICcontrolRequest_IEs__value_PR choice, void *value){RICcontrolRequest_IEs_t *v = calloc(1, sizeof(RICcontrolRequest_IEs_t));assert(v && "NULL pointer");/*** 我不懂协议，这块不知道应该怎么填写（荣涛 8月31日）*/v->id = id;// v->criticality = id;v->value.present = choice;switch(choice) {default:case RICcontrolRequest_IEs__value_PR_NOTHING:{printf("Nothing to do.\n");break;}case RICcontrolRequest_IEs__value_PR_RICrequestID:{RICrequestID_t *RICrequestID = (RICrequestID_t*)value;v->value.choice.RICrequestID.ricInstanceID = RICrequestID->ricInstanceID;v->value.choice.RICrequestID.ricRequestorID = RICrequestID->ricRequestorID;break;}case RICcontrolRequest_IEs__value_PR_RANfunctionID:{RANfunctionID_t *RANfunctionID = (RANfunctionID_t*)value;v->value.choice.RANfunctionID = *RANfunctionID;break;}case RICcontrolRequest_IEs__value_PR_RICcallProcessID:{RICcallProcessID_t *RICcallProcessID = (RICcallProcessID_t*)value;OCTET_STRING_fromBuf(&v->value.choice.RICcallProcessID, (char*)RICcallProcessID->buf, RICcallProcessID->size);break;}case RICcontrolRequest_IEs__value_PR_RICcontrolHeader:{RICcontrolHeader_t *RICcontrolHeader = (RICcontrolHeader_t*)value;OCTET_STRING_fromBuf(&v->value.choice.RICcontrolHeader, (char*)RICcontrolHeader->buf, RICcontrolHeader->size);break;}case RICcontrolRequest_IEs__value_PR_RICcontrolMessage:{RICcontrolMessage_t *RICcontrolMessage = (RICcontrolMessage_t*)value;OCTET_STRING_fromBuf(&v->value.choice.RICcontrolMessage, (char*)RICcontrolMessage->buf, RICcontrolMessage->size);break;}case RICcontrolRequest_IEs__value_PR_RICcontrolAckRequest:{RICcontrolAckRequest_t *RICcontrolAckRequest = (RICcontrolAckRequest_t*)value;v->value.choice.RICcontrolAckRequest = *RICcontrolAckRequest;break;}}return v;}static void fprintf_RICcontrolRequest(FILE* fp, RICcontrolRequest_t *RICcontrolRequest){xer_fprint(fp, &asn_DEF_RICcontrolRequest, RICcontrolRequest);fprintf(fp, "\n");}static void printf_RICcontrolRequest(RICcontrolRequest_t *RICcontrolRequest){fprintf_RICcontrolRequest(stdout, RICcontrolRequest);}static void save_RICcontrolRequest_xer(const char *filename, RICcontrolRequest_t *RICcontrolRequest){FILE *fp = fopen(filename, "w");fprintf_RICcontrolRequest(fp, RICcontrolRequest);fclose(fp);}static size_t encode_RICcontrolRequest_aper(RICcontrolRequest_t* pdu, void* buffer, size_t buf_size){asn_enc_rval_t encode_result;encode_result = aper_encode_to_buffer(&asn_DEF_RICcontrolRequest , NULL, pdu, buffer, buf_size);// ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest , pdu);if(encode_result.encoded == -1) {fprintf(stderr, "Cannot encode %s: %s\n", encode_result.failed_type->name, strerror(errno));return -1;} else {return encode_result.encoded;}}static size_t encode_RICcontrolRequest_oer(RICcontrolRequest_t* pdu, void* buffer, size_t buf_size){asn_enc_rval_t encode_result;encode_result = oer_encode_to_buffer(&asn_DEF_RICcontrolRequest , NULL, pdu, buffer, buf_size);// ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest , pdu);if(encode_result.encoded == -1) {fprintf(stderr, "Cannot encode %s: %s\n", encode_result.failed_type->name, strerror(errno));return -1;} else {return encode_result.encoded;}}static size_t encode_RICcontrolRequest_der(RICcontrolRequest_t* pdu, void* buffer, size_t buf_size){asn_enc_rval_t encode_result;encode_result = der_encode_to_buffer(&asn_DEF_RICcontrolRequest , pdu, buffer, buf_size);// ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest , pdu);if(encode_result.encoded == -1) {fprintf(stderr, "Cannot encode %s: %s\n", encode_result.failed_type->name, strerror(errno));return -1;} else {return encode_result.encoded;}}static void save_RICcontrolRequest_aper(const char *filename, RICcontrolRequest_t *RICcontrolRequest){char buffer[2048] = {0};size_t size = encode_RICcontrolRequest_aper(RICcontrolRequest, buffer, 2048);FILE *fp = fopen(filename, "w");fwrite(buffer, 1, size, fp);fclose(fp);}static void save_RICcontrolRequest_oer(const char *filename, RICcontrolRequest_t *RICcontrolRequest){char buffer[2048] = {0};size_t size = encode_RICcontrolRequest_oer(RICcontrolRequest, buffer, 2048);FILE *fp = fopen(filename, "w");fwrite(buffer, 1, size, fp);fclose(fp);}static void save_RICcontrolRequest_der(const char *filename, RICcontrolRequest_t *RICcontrolRequest){char buffer[2048] = {0};size_t size = encode_RICcontrolRequest_der(RICcontrolRequest, buffer, 2048);FILE *fp = fopen(filename, "w");fwrite(buffer, 1, size, fp);fclose(fp);}/*** 生成 RICcontrolRequest 结构体*/static int gen_RICcontrolRequest(){RICcontrolRequest_t *RICcontrolRequest;RICcontrolRequest = calloc(1, sizeof(RICcontrolRequest_t));assert(RICcontrolRequest);/* Assume infinite memory *//*** */RICrequestID_t RICrequestID = {RICrequestID.ricInstanceID = 12,RICrequestID.ricRequestorID = 13,};RICcontrolRequest_IEs_t *RICcontrolRequest_IE = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RICrequestID, RICcontrolRequest_IEs__value_PR_RICrequestID, &RICrequestID);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE);/*** */RANfunctionID_t RANfunctionID = 14;RICcontrolRequest_IEs_t *RICcontrolRequest_IE2 = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RANfunctionID, RICcontrolRequest_IEs__value_PR_RANfunctionID, &RANfunctionID);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE2);/*** */RICcallProcessID_t RICcallProcessID;RICcallProcessID.buf = malloc(1);OCTET_STRING_fromBuf(&RICcallProcessID, "RICcallProcessID", strlen("RICcallProcessID"));RICcontrolRequest_IEs_t *RICcontrolRequest_IE3 = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RICcallProcessID, RICcontrolRequest_IEs__value_PR_RICcallProcessID, &RICcallProcessID);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE3);/*** */RICcontrolHeader_t RICcontrolHeader;RICcontrolHeader.buf = malloc(1);OCTET_STRING_fromBuf(&RICcontrolHeader, "RICcontrolHeader", strlen("RICcontrolHeader"));RICcontrolRequest_IEs_t *RICcontrolRequest_IE4 = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RICcontrolHeader, RICcontrolRequest_IEs__value_PR_RICcontrolHeader, &RICcontrolHeader);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE4);/*** */RICcontrolMessage_t RICcontrolMessage;RICcontrolMessage.buf = malloc(1);OCTET_STRING_fromBuf(&RICcontrolMessage, "RICcontrolMessage", strlen("RICcontrolMessage"));RICcontrolRequest_IEs_t *RICcontrolRequest_IE5 = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RICcontrolMessage, RICcontrolRequest_IEs__value_PR_RICcontrolMessage, &RICcontrolMessage);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE5);/*** */RICcontrolAckRequest_t RICcontrolAckRequest = RICcontrolAckRequest_nAck;RICcontrolRequest_IEs_t *RICcontrolRequest_IE6 = alloc_RICcontrolRequest_IEs(ProtocolIE_ID_id_RICcontrolAckRequest,RICcontrolRequest_IEs__value_PR_RICcontrolAckRequest, &RICcontrolAckRequest);ASN_SEQUENCE_ADD(&RICcontrolRequest->protocolIEs.list, RICcontrolRequest_IE6);/*** 输出到屏幕*/printf("################ Original Struct ##################\n");printf_RICcontrolRequest(RICcontrolRequest);printf("##################################\n");/*** 将其保存为 多种 文件格式*/save_RICcontrolRequest_xer(XER_RICcontrolRequest, RICcontrolRequest);save_RICcontrolRequest_aper(APER_RICcontrolRequest, RICcontrolRequest);save_RICcontrolRequest_oer(OER_RICcontrolRequest, RICcontrolRequest);save_RICcontrolRequest_der(DER_RICcontrolRequest, RICcontrolRequest);return 0;}static int decode_RICcontrolRequest_xer(){FUNC_CALL();RICcontrolRequest_t *RICcontrolRequest = NULL;char buf[2048] = {0};int size;asn_dec_rval_t rval;FILE *fp = fopen(XER_RICcontrolRequest, "r");size = fread(buf, 1, sizeof buf, fp);if(size == 0 || size == sizeof buf) {PRINT_ERROR("%s: Too large input\n", XER_RICcontrolRequest);exit(1);}fclose(fp);rval = xer_decode(NULL, &asn_DEF_RICcontrolRequest, (void**)&RICcontrolRequest, buf, size);if(rval.code != RC_OK) {ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return -1;}// printf("################ Decode XER file ##################\n");// printf_RICcontrolRequest(RICcontrolRequest);// printf("##################################\n");save_RICcontrolRequest_xer(NEW_XER_RICcontrolRequest, RICcontrolRequest);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return 0;}static int decode_RICcontrolRequest_aper(){FUNC_CALL();RICcontrolRequest_t *RICcontrolRequest = NULL;char buf[2048] = {0};int size;FILE *fp = fopen(APER_RICcontrolRequest, "r");size = fread(buf, 1, sizeof buf, fp);if(size == 0 || size == sizeof buf) {fprintf(stderr, "%s: Too large input\n", APER_RICcontrolRequest);exit(1);}fclose(fp);asn_dec_rval_t decode_result;decode_result = aper_decode_complete(NULL, &asn_DEF_RICcontrolRequest, (void **)&RICcontrolRequest, buf, size);if(decode_result.code != RC_OK) {ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return -1;}// printf("################# Decode APER file #################\n");// printf_RICcontrolRequest(RICcontrolRequest);// printf("##################################\n");save_RICcontrolRequest_aper(NEW_APER_RICcontrolRequest, RICcontrolRequest);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return 0;}static int decode_RICcontrolRequest_oer(){FUNC_CALL();RICcontrolRequest_t *RICcontrolRequest = NULL;char buf[2048] = {0};int size;FILE *fp = fopen(OER_RICcontrolRequest, "r");size = fread(buf, 1, sizeof buf, fp);if(size == 0 || size == sizeof buf) {PRINT_ERROR("%s: Too large input\n", OER_RICcontrolRequest);exit(1);}fclose(fp);asn_dec_rval_t decode_result;// oer_decode_primitive(NULL, &asn_DEF_RICcontrolRequest, (void **)&RICcontrolRequest, buf, size);decode_result = oer_decode(NULL, &asn_DEF_RICcontrolRequest, (void **)&RICcontrolRequest, buf, size);if(decode_result.code != RC_OK) {PRINT_ERROR("error. size = %d, ret = %d\n", size, decode_result.code);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return -1;}// printf("################# Decode OER file #################\n");// printf_RICcontrolRequest(RICcontrolRequest);// printf("##################################\n");save_RICcontrolRequest_oer(NEW_OER_RICcontrolRequest, RICcontrolRequest);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return 0;}static int decode_RICcontrolRequest_der(){FUNC_CALL();RICcontrolRequest_t *RICcontrolRequest = NULL;char buf[2048] = {0};int size;FILE *fp = fopen(DER_RICcontrolRequest, "r");size = fread(buf, 1, sizeof buf, fp);if(size == 0 || size == sizeof buf) {fprintf(stderr, "%s: Too large input\n", DER_RICcontrolRequest);exit(1);}fclose(fp);asn_dec_rval_t decode_result;decode_result = ber_decode(NULL, &asn_DEF_RICcontrolRequest, (void **)&RICcontrolRequest, buf, size);if(decode_result.code != RC_OK) {printf("error. size = %d, ret = %d\n", size, decode_result.code);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return -1;}save_RICcontrolRequest_der(NEW_DER_RICcontrolRequest, RICcontrolRequest);ASN_STRUCT_FREE(asn_DEF_RICcontrolRequest, RICcontrolRequest);return 0;}static void load_RICcontrolRequest(){decode_RICcontrolRequest_xer();decode_RICcontrolRequest_aper();decode_RICcontrolRequest_oer();decode_RICcontrolRequest_der();}/*** RICcontrolRequest 测试例代码** 作者 荣涛* 创建 8月29日**/#define TEST_RICcontrolRequest int test_RICcontrolRequest(){#ifdef TEST_RICcontrolRequestFUNC_CALL();gen_RICcontrolRequest();load_RICcontrolRequest();#endifreturn 0;}
