asn1c: Full working example of ASN.1 in C/C++
The following project demonstrates a full working example of encoding and decoding ASN.1
structures using the asn1c
compiler of http://lionet.info/asn1c/
In this project we assumed that we have to encode a set of geometric elements, including:
- A rectangle that is composed by its height and its width
- A rectangular cuboid that it is composed by a rectangle and a depth parameter
- A list of rectangular cuboids that has no limit on how many elements to add to it
- A list of rectangular cuboids that must have at least one element and at most three
- We assume that all parameters should be positive integer values
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Following is our ASN.1
syntax to describe the above elements:
Geometry.asn1
GeometryModule DEFINITIONS ::= BEGIN Rectangle ::= SEQUENCE { height INTEGER (0..MAX), width INTEGER (0..MAX) } RectangularCuboid ::= SEQUENCE { depth INTEGER (0..MAX), rectangle Rectangle } UnlimitedRectangularCuboids ::= SEQUENCE OF RectangularCuboid LimitedRectangularCuboids ::= SEQUENCE SIZE(1..3) OF RectangularCuboid END
Inside the directory where our source is located, we created folder called geometryASN
.
From that folder we executed the following command to generate the c code that is needed for our C/C++
source code to operate:
asn1c -fcompound-names -gen-PER ../Geometry.asn1
Following is our C
source code that creates new ANS.1
elements, encodes them, decodes them and verifies that all limitations and constraints were met.
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main.cpp
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 | //From the folder geometryASN, to convert the ASN1 to c execute the following // asn1c -fcompound-names -gen-PER ../Geometry.asn1 #include <iostream> #include "geometryASN/Rectangle.h" #include "geometryASN/RectangularCuboid.h" #include "geometryASN/LimitedRectangularCuboids.h" #include "geometryASN/UnlimitedRectangularCuboids.h" bool validate_constraints(asn_TYPE_descriptor_t *type_descriptor, const void *struct_ptr) { char error_buffer[128]; size_t error_length = sizeof (error_buffer); const int return_value = asn_check_constraints(type_descriptor, struct_ptr, error_buffer, &error_length); if (return_value) { perror ( "asn_check_constraints() failed" ); } return (return_value == 0); } void *encode_and_decode_object(asn_TYPE_descriptor_t *type_descriptor, void *struct_ptr) { //First we validate that our object meets the expected constraints if (validate_constraints(type_descriptor, struct_ptr)) { void *buffer; asn_per_constraints_s *constraints = NULL; //Then, we encode the object to ASN.1 and assign the data to a buffer in memory const ssize_t ec = uper_encode_to_new_buffer(type_descriptor, constraints, struct_ptr, &buffer); if (ec == -1) { perror ( "uper_encode_to_new_buffer() failed" ); } else { //ASN.1 encoded object is not in the buffer variable and it is available for you to use. //Finally, since the encoding process went fine, we decode the data to verify with our own eyes that the process went smoothly void *decoded_object = 0; const asn_dec_rval_t rval = uper_decode(0, type_descriptor, &decoded_object, buffer, ( size_t ) ec, 0, 0); free (buffer); if (rval.code != RC_OK) { perror ( "uper_decode() failed" ); fprintf (stderr, "Broken encoding at byte %ld\n" , rval.consumed); } else { return decoded_object; } } } return NULL; } int main( int argc, char *argv[]) { //Scenario A: We test basic encoding and decoding on a Rectangle. { //First we create a rectangle and then we encode it Rectangle_t *rectangle = (Rectangle_t *) calloc (1, sizeof (Rectangle_t)); if (rectangle == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } rectangle->height = 10; rectangle->width = 150; Rectangle_t *decoded_rectangle = (Rectangle_t *) encode_and_decode_object(&asn_DEF_Rectangle, rectangle); if (decoded_rectangle != NULL) { if (rectangle->height != decoded_rectangle->height || rectangle->width != decoded_rectangle->width) { perror ( "uper_decode() failed. Wrong values found after decoding" ); ASN_STRUCT_FREE(asn_DEF_Rectangle, rectangle); ASN_STRUCT_FREE(asn_DEF_Rectangle, decoded_rectangle); exit (EXIT_FAILURE); } } ASN_STRUCT_FREE(asn_DEF_Rectangle, rectangle); ASN_STRUCT_FREE(asn_DEF_Rectangle, decoded_rectangle); } //Scenario B: We test basic encoding and decoding on a Rectangle. //We will provide a value that is out of the constraints area to force the test to fail. { //First we create a rectangle and then we encode it Rectangle_t *rectangle = (Rectangle_t *) calloc (1, sizeof (Rectangle_t)); if (rectangle == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } rectangle->height = -10; rectangle->width = 150; Rectangle_t *decoded_rectangle = (Rectangle_t *) encode_and_decode_object(&asn_DEF_Rectangle, rectangle); if (decoded_rectangle != NULL) { perror ( "This test should have failed due to the constaint on the range of the valid values." ); ASN_STRUCT_FREE(asn_DEF_Rectangle, rectangle); ASN_STRUCT_FREE(asn_DEF_Rectangle, decoded_rectangle); exit (EXIT_FAILURE); } ASN_STRUCT_FREE(asn_DEF_Rectangle, rectangle); } //Scenario C: We test basic encoding and decoding on a Rectangular Cuboid. { //First we create a rectangular cuboid and then we encode it RectangularCuboid_t *rectangular_cuboid = (RectangularCuboid_t *) calloc (1, sizeof (RectangularCuboid_t)); if (rectangular_cuboid == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } rectangular_cuboid->depth = 27; rectangular_cuboid->rectangle.height = 10; rectangular_cuboid->rectangle.width = 150; RectangularCuboid_t *decoded_rectangular_cuboid = (RectangularCuboid_t *) encode_and_decode_object( &asn_DEF_RectangularCuboid, rectangular_cuboid); if (decoded_rectangular_cuboid != NULL) { if (rectangular_cuboid->rectangle.height != decoded_rectangular_cuboid->rectangle.height || rectangular_cuboid->rectangle.width != decoded_rectangular_cuboid->rectangle.width || rectangular_cuboid->depth != decoded_rectangular_cuboid->depth) { perror ( "uper_decode() failed. Wrong values found after decoding" ); ASN_STRUCT_FREE(asn_DEF_RectangularCuboid, rectangular_cuboid); ASN_STRUCT_FREE(asn_DEF_RectangularCuboid, decoded_rectangular_cuboid); exit (EXIT_FAILURE); } } ASN_STRUCT_FREE(asn_DEF_RectangularCuboid, rectangular_cuboid); ASN_STRUCT_FREE(asn_DEF_RectangularCuboid, decoded_rectangular_cuboid); } //Scenario D: We will create an array of elements that has no limitation on its size. { UnlimitedRectangularCuboids_t *unlimited_rectangular_cuboids = (UnlimitedRectangularCuboids_t *) calloc (1, sizeof (UnlimitedRectangularCuboids_t)); if (unlimited_rectangular_cuboids == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } int i; for (i = 0; i < 10; i++) { RectangularCuboid_t *tmp_rectangular_cuboid = (RectangularCuboid_t *) calloc (1, sizeof (RectangularCuboid_t)); if (tmp_rectangular_cuboid == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } tmp_rectangular_cuboid->depth = i; tmp_rectangular_cuboid->rectangle.height = i * 11; tmp_rectangular_cuboid->rectangle.width = i * 101; const int result = asn_set_add(unlimited_rectangular_cuboids, tmp_rectangular_cuboid); if (result != 0) { perror ( "asn_set_add() failed" ); ASN_STRUCT_FREE(asn_DEF_UnlimitedRectangularCuboids, unlimited_rectangular_cuboids); exit (EXIT_FAILURE); } } UnlimitedRectangularCuboids_t *decoded_unlimited_rectangular_cuboids = (UnlimitedRectangularCuboids_t *) encode_and_decode_object( &asn_DEF_UnlimitedRectangularCuboids, unlimited_rectangular_cuboids); if (decoded_unlimited_rectangular_cuboids != NULL) { for (i = 0; i < decoded_unlimited_rectangular_cuboids->list.count; i++) { RectangularCuboid_t *tmp_rectangular_cuboid = decoded_unlimited_rectangular_cuboids->list.array[i]; if (tmp_rectangular_cuboid->rectangle.height != i * 11 || tmp_rectangular_cuboid->rectangle.width != i * 101 || tmp_rectangular_cuboid->depth != i) { perror ( "uper_decode() failed. Wrong values found after decoding" ); ASN_STRUCT_FREE(asn_DEF_UnlimitedRectangularCuboids, unlimited_rectangular_cuboids); ASN_STRUCT_FREE(asn_DEF_UnlimitedRectangularCuboids, decoded_unlimited_rectangular_cuboids); exit (EXIT_FAILURE); } } } ASN_STRUCT_FREE(asn_DEF_UnlimitedRectangularCuboids, unlimited_rectangular_cuboids); ASN_STRUCT_FREE(asn_DEF_UnlimitedRectangularCuboids, decoded_unlimited_rectangular_cuboids); } //Scenario E: We will create an array of elements that has a limitation on how many elements it can accept. //We will add more elements than expected and we expect the encoding to fail. { LimitedRectangularCuboids_t *limited_rectangular_cuboids = (LimitedRectangularCuboids_t *) calloc (1, sizeof (LimitedRectangularCuboids_t)); if (limited_rectangular_cuboids == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } int i; for (i = 0; i < 10; i++) { RectangularCuboid_t *tmp_rectangular_cuboid = (RectangularCuboid_t *) calloc (1, sizeof (RectangularCuboid_t)); if (tmp_rectangular_cuboid == NULL) { perror ( "calloc() failed" ); exit (EXIT_FAILURE); } tmp_rectangular_cuboid->depth = i; tmp_rectangular_cuboid->rectangle.height = i * 11; tmp_rectangular_cuboid->rectangle.width = i * 101; const int result = asn_set_add(limited_rectangular_cuboids, tmp_rectangular_cuboid); if (result != 0) { perror ( "asn_set_add() failed" ); ASN_STRUCT_FREE(asn_DEF_LimitedRectangularCuboids, limited_rectangular_cuboids); exit (EXIT_FAILURE); } } LimitedRectangularCuboids_t *decoded_limited_rectangular_cuboids = (LimitedRectangularCuboids_t *) encode_and_decode_object( &asn_DEF_LimitedRectangularCuboids, limited_rectangular_cuboids); if (decoded_limited_rectangular_cuboids != NULL) { perror ( "This test should have failed due to limitation on the size of the list." ); ASN_STRUCT_FREE(asn_DEF_LimitedRectangularCuboids, limited_rectangular_cuboids); ASN_STRUCT_FREE(asn_DEF_LimitedRectangularCuboids, decoded_limited_rectangular_cuboids); exit (EXIT_FAILURE); } ASN_STRUCT_FREE(asn_DEF_LimitedRectangularCuboids, limited_rectangular_cuboids); } printf ( "All tests were successful\n" ); return EXIT_SUCCESS; } |
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