Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/vanetza/asn1/support/INTEGER_oer.c

@@ -0,0 +1,174 @@
+/*
+ * Copyright (c) 2017 Lev Walkin <vlm@lionet.info>.
+ * All rights reserved.
+ * Redistribution and modifications are permitted subject to BSD license.
+ */
+#include "asn_internal.h"
+#include "INTEGER.h"
+
+asn_dec_rval_t
+INTEGER_decode_oer(const asn_codec_ctx_t *opt_codec_ctx,
+                   const asn_TYPE_descriptor_t *td,
+                   const asn_oer_constraints_t *constraints, void **sptr,
+                   const void *ptr, size_t size) {
+    const asn_INTEGER_specifics_t *specs =
+        (const asn_INTEGER_specifics_t *)td->specifics;
+    asn_dec_rval_t rval = {RC_OK, 0};
+    INTEGER_t *st = (INTEGER_t *)*sptr;
+    struct asn_oer_constraint_number_s ct = {0, 0};
+    size_t req_bytes;
+
+    (void)opt_codec_ctx;
+    (void)specs;
+
+    if(!st) {
+        st = (INTEGER_t *)(*sptr = CALLOC(1, sizeof(*st)));
+        if(!st) ASN__DECODE_FAILED;
+    }
+
+    FREEMEM(st->buf);
+    st->buf = 0;
+    st->size = 0;
+
+    if(!constraints) constraints = td->encoding_constraints.oer_constraints;
+    if(constraints) ct = constraints->value;
+
+    if(ct.width) {
+        req_bytes = ct.width;
+    } else {
+        /* No lower bound and no upper bound, effectively */
+
+        ssize_t consumed = oer_fetch_length(ptr, size, &req_bytes);
+        if(consumed == 0) {
+            ASN__DECODE_STARVED;
+        } else if(consumed == -1) {
+            ASN__DECODE_FAILED;
+        }
+        rval.consumed += consumed;
+        ptr = (const char *)ptr + consumed;
+        size -= consumed;
+    }
+
+    if(req_bytes == 0 || req_bytes > size) {
+        ASN__DECODE_STARVED;
+    }
+
+    if(ct.positive) {
+        /* X.969 08/2015 10.2(a) */
+        unsigned msb;   /* Most significant bit */
+        size_t useful_size;
+
+        /* Check most significant bit */
+        msb = *(const uint8_t *)ptr >> 7; /* yields 0 or 1 */
+        useful_size = msb + req_bytes;
+        st->buf = (uint8_t *)MALLOC(useful_size + 1);
+        if(!st->buf) {
+            ASN__DECODE_FAILED;
+        }
+
+        /*
+         * Record a large unsigned in a way not to confuse it
+         * with signed value.
+         */
+        st->buf[0] = '\0';
+        memcpy(st->buf + msb, ptr, req_bytes);
+        st->buf[useful_size] = '\0';    /* Just in case, 0-terminate */
+        st->size = useful_size;
+
+        rval.consumed += req_bytes;
+        return rval;
+    } else {
+        /* X.969 08/2015 10.2(b) */
+        st->buf = (uint8_t *)MALLOC(req_bytes + 1);
+        if(!st->buf) {
+            ASN__DECODE_FAILED;
+        }
+
+        memcpy(st->buf, ptr, req_bytes);
+        st->buf[req_bytes] = '\0'; /* Just in case, 0-terminate */
+        st->size = req_bytes;
+
+        rval.consumed += req_bytes;
+        return rval;
+    }
+}
+
+/*
+ * Encode as Canonical OER.
+ */
+asn_enc_rval_t
+INTEGER_encode_oer(const asn_TYPE_descriptor_t *td,
+                   const asn_oer_constraints_t *constraints, const void *sptr,
+                   asn_app_consume_bytes_f *cb, void *app_key) {
+    const INTEGER_t *st = sptr;
+    asn_enc_rval_t er = {0,0,0};
+    struct asn_oer_constraint_number_s ct = {0, 0};
+    const uint8_t *buf;
+    const uint8_t *end;
+    size_t useful_bytes;
+    size_t req_bytes = 0;
+    int sign = 0;
+
+    if(!st || st->size == 0) ASN__ENCODE_FAILED;
+
+    if(!constraints) constraints = td->encoding_constraints.oer_constraints;
+    if(constraints) ct = constraints->value;
+
+    er.encoded = 0;
+
+    buf = st->buf;
+    end = buf + st->size;
+
+    sign = (buf && buf < end) ? buf[0] & 0x80 : 0;
+
+    /* Ignore 9 leading zeroes or ones */
+    if(ct.positive) {
+        if(sign) {
+            /* The value given is a signed value. Can't proceed. */
+            ASN__ENCODE_FAILED;
+        }
+        /* Remove leading zeros. */
+        for(; buf + 1 < end; buf++) {
+            if(buf[0] != 0x0) break;
+        }
+    } else {
+        for(; buf + 1 < end; buf++) {
+            if(buf[0] == 0x0 && (buf[1] & 0x80) == 0) {
+                continue;
+            } else if(buf[0] == 0xff && (buf[1] & 0x80) != 0) {
+                continue;
+            }
+            break;
+        }
+    }
+
+    useful_bytes = end - buf;
+    if(ct.width) {
+        req_bytes = ct.width;
+    } else {
+        ssize_t r = oer_serialize_length(useful_bytes, cb, app_key);
+        if(r < 0) {
+            ASN__ENCODE_FAILED;
+        }
+        er.encoded += r;
+        req_bytes = useful_bytes;
+    }
+
+    if(req_bytes < useful_bytes) {
+        ASN__ENCODE_FAILED;
+    }
+
+    er.encoded += req_bytes;
+
+    for(; req_bytes > useful_bytes; req_bytes--) {
+        if(cb(sign?"\xff":"\0", 1, app_key) < 0) {
+            ASN__ENCODE_FAILED;
+        }
+    }
+
+    if(cb(buf, useful_bytes, app_key) < 0) {
+        ASN__ENCODE_FAILED;
+    }
+
+    ASN__ENCODED_OK(er);
+}