.TH "asn1 parsing and datatype manipulation routines." 3 "30 Jun 2005" "Version 5.2.1.rc3" "net-snmp" \" -*- nroff -*- .ad l .nh .SH NAME asn1 parsing and datatype manipulation routines. \- .SS "Defines" .in +1c .ti -1c .RI "#define \fBNULL\fP 0" .br .in -1c .SS "Functions" .in +1c .ti -1c .RI "int \fBasn_check_packet\fP (u_char *pkt, size_t len)" .br .ti -1c .RI "u_char * \fBasn_parse_int\fP (u_char *data, size_t *datalength, u_char *type, long *intp, size_t intsize)" .br .ti -1c .RI "u_char * \fBasn_parse_unsigned_int\fP (u_char *data, size_t *datalength, u_char *type, u_long *intp, size_t intsize)" .br .ti -1c .RI "u_char * \fBasn_build_int\fP (u_char *data, size_t *datalength, u_char type, const long *intp, size_t intsize)" .br .ti -1c .RI "u_char * \fBasn_build_unsigned_int\fP (u_char *data, size_t *datalength, u_char type, const u_long *intp, size_t intsize)" .br .ti -1c .RI "u_char * \fBasn_parse_string\fP (u_char *data, size_t *datalength, u_char *type, u_char *string, size_t *strlength)" .br .ti -1c .RI "u_char * \fBasn_build_string\fP (u_char *data, size_t *datalength, u_char type, const u_char *string, size_t strlength)" .br .ti -1c .RI "u_char * \fBasn_parse_header\fP (u_char *data, size_t *datalength, u_char *type)" .br .ti -1c .RI "u_char * \fBasn_parse_sequence\fP (u_char *data, size_t *datalength, u_char *type, u_char expected_type, const char *estr)" .br .ti -1c .RI "u_char * \fBasn_build_header\fP (u_char *data, size_t *datalength, u_char type, size_t length)" .br .ti -1c .RI "u_char * \fBasn_build_sequence\fP (u_char *data, size_t *datalength, u_char type, size_t length)" .br .ti -1c .RI "u_char * \fBasn_parse_length\fP (u_char *data, u_long *length)" .br .ti -1c .RI "u_char * \fBasn_build_length\fP (u_char *data, size_t *datalength, size_t length)" .br .ti -1c .RI "u_char * \fBasn_parse_objid\fP (u_char *data, size_t *datalength, u_char *type, oid *objid, size_t *objidlength)" .br .ti -1c .RI "u_char * \fBasn_build_objid\fP (u_char *data, size_t *datalength, u_char type, oid *objid, size_t objidlength)" .br .ti -1c .RI "u_char * \fBasn_parse_null\fP (u_char *data, size_t *datalength, u_char *type)" .br .ti -1c .RI "u_char * \fBasn_build_null\fP (u_char *data, size_t *datalength, u_char type)" .br .ti -1c .RI "u_char * \fBasn_parse_bitstring\fP (u_char *data, size_t *datalength, u_char *type, u_char *string, size_t *strlength)" .br .ti -1c .RI "u_char * \fBasn_build_bitstring\fP (u_char *data, size_t *datalength, u_char type, const u_char *string, size_t strlength)" .br .ti -1c .RI "u_char * \fBasn_parse_unsigned_int64\fP (u_char *data, size_t *datalength, u_char *type, struct counter64 *cp, size_t countersize)" .br .ti -1c .RI "u_char * \fBasn_build_unsigned_int64\fP (u_char *data, size_t *datalength, u_char type, const struct counter64 *cp, size_t countersize)" .br .ti -1c .RI "int \fBasn_realloc\fP (u_char **pkt, size_t *pkt_len)" .br .in -1c .SH "Detailed Description" .PP Note on .PP Re-allocating reverse ASN.1 encoder functions. Synopsis: .PP .PP .nf u_char *buf = (u_char*)malloc(100); u_char type = (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER); size_t buf_len = 100, offset = 0; long data = 12345; int allow_realloc = 1; if (asn_realloc_rbuild_int(&buf, &buf_len, &offset, allow_realloc, type, &data, sizeof(long)) == 0) { error; } .fi .PP .PP NOTE WELL: after calling one of these functions with allow_realloc non-zero, buf might have moved, buf_len might have grown and offset will have increased by the size of the encoded data. You should **NEVER** do something like this: .PP .PP .nf u_char *buf = (u_char *)malloc(100), *ptr; u_char type = (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER); size_t buf_len = 100, offset = 0; long data1 = 1234, data2 = 5678; int rc = 0, allow_realloc = 1; rc = asn_realloc_rbuild_int(&buf, &buf_len, &offset, allow_realloc, type, &data1, sizeof(long)); ptr = buf[buf_len - offset]; / * points at encoding of data1 * / if (rc == 0) { error; } rc = asn_realloc_rbuild_int(&buf, &buf_len, &offset, allow_realloc, type, &data2, sizeof(long)); make use of ptr here; .fi .PP .PP ptr is **INVALID** at this point. In general, you should store the offset value and compute pointers when you need them: .PP .PP .nf u_char *buf = (u_char *)malloc(100), *ptr; u_char type = (ASN_UNIVERSAL | ASN_PRIMITIVE | ASN_INTEGER); size_t buf_len = 100, offset = 0, ptr_offset; long data1 = 1234, data2 = 5678; int rc = 0, allow_realloc = 1; rc = asn_realloc_rbuild_int(&buf, &buf_len, &offset, allow_realloc, type, &data1, sizeof(long)); ptr_offset = offset; if (rc == 0) { error; } rc = asn_realloc_rbuild_int(&buf, &buf_len, &offset, allow_realloc, type, &data2, sizeof(long)); ptr = buf + buf_len - ptr_offset make use of ptr here; .fi .PP .PP Here, you can see that ptr will be a valid pointer even if the block of memory has been moved, as it may well have been. Plenty of examples of usage all over \fBasn1.c\fP, \fBsnmp_api.c\fP, \fBsnmpusm.c\fP. .PP The other thing you should **NEVER** do is to pass a pointer to a buffer on the stack as the first argument when allow_realloc is non-zero, unless you really know what you are doing and your machine/compiler allows you to free non-heap memory. There are rumours that such things exist, but many consider them no more than the wild tales of a fool. .PP Of course, you can pass allow_realloc as zero, to indicate that you do not wish the packet buffer to be reallocated for some reason; perhaps because it is on the stack. This may be useful to emulate the functionality of the old API: .PP .PP .nf u_char my_static_buffer[100], *cp = NULL; size_t my_static_buffer_len = 100; float my_pi = (float)22/(float)7; cp = asn_rbuild_float(my_static_buffer, &my_static_buffer_len, ASN_OPAQUE_FLOAT, &my_pi, sizeof(float)); if (cp == NULL) { error; } .fi .PP .PP IS EQUIVALENT TO: .PP .PP .nf u_char my_static_buffer[100]; size_t my_static_buffer_len = 100, my_offset = 0; float my_pi = (float)22/(float)7; int rc = 0; rc = asn_realloc_rbuild_float(&my_static_buffer, &my_static_buffer_len, &my_offset, 0, ASN_OPAQUE_FLOAT, &my_pi, sizeof(float)); if (rc == 0) { error; } .fi .PP