iface_bridge.cpp

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// Copyright (C) 2026 Douglas Quigg (dstroy0) <dquigg123@gmail.com>
// SPDX-License-Identifier: AGPL-3.0-or-later
 
#include "services/iface_bridge/iface_bridge.h"
 
#if DETWS_ENABLE_IFACE_BRIDGE
 
#include <string.h>
 
namespace
{
/// The one owned mutable: the address:port -> bus rule table.
struct BridgeCtx
{
    BridgeRule rules[DETWS_BRIDGE_MAX_RULES];
    uint8_t count;
};
BridgeCtx s_bridge;
} // namespace
 
void bridge_clear()
{
    for (uint8_t i = 0; i < DETWS_BRIDGE_MAX_RULES; i++)
        s_bridge.rules[i].used = false;
    s_bridge.count = 0;
}
 
bool bridge_add(const BridgeRule *rule)
{
    if (!rule)
        return false;
    if (bridge_find(rule->listen_port, rule->proto))
        return false; // a rule already binds this port+proto
    for (uint8_t i = 0; i < DETWS_BRIDGE_MAX_RULES; i++)
    {
        if (!s_bridge.rules[i].used)
        {
            s_bridge.rules[i] = *rule;
            s_bridge.rules[i].used = true;
            s_bridge.count++;
            return true;
        }
    }
    return false; // table full
}
 
bool bridge_map(const char *ip, uint16_t port, BridgeProto proto, const BridgeTarget *target)
{
    if (!target)
        return false;
    BridgeRule r;
    memset(&r, 0, sizeof(r));
    r.listen_ip.family = DetIpFamily::DET_IP_NONE; // "any interface" unless a valid address is given
    if (ip && ip[0] && !det_ip_parse(ip, &r.listen_ip))
        return false; // malformed bind address
    r.listen_port = port;
    r.proto = proto;
    r.target = *target;
    return bridge_add(&r);
}
 
const BridgeRule *bridge_find(uint16_t port, BridgeProto proto)
{
    for (uint8_t i = 0; i < DETWS_BRIDGE_MAX_RULES; i++)
        if (s_bridge.rules[i].used && s_bridge.rules[i].listen_port == port && s_bridge.rules[i].proto == proto)
            return &s_bridge.rules[i];
    return nullptr;
}
 
uint8_t bridge_count()
{
    return s_bridge.count;
}
 
size_t bridge_txn_parse(const uint8_t *buf, size_t len, uint16_t *write_len, uint16_t *read_len,
                        const uint8_t **write_data)
{
    if (!buf || len < (size_t)DETWS_BRIDGE_TXN_HDR)
        return 0;
    uint16_t wl = (uint16_t)(((uint16_t)buf[0] << 8) | buf[1]);
    uint16_t rl = (uint16_t)(((uint16_t)buf[2] << 8) | buf[3]);
    if (len < (size_t)DETWS_BRIDGE_TXN_HDR + wl)
        return 0; // the write payload has not fully arrived yet
    if (write_len)
        *write_len = wl;
    if (read_len)
        *read_len = rl;
    if (write_data)
        *write_data = buf + DETWS_BRIDGE_TXN_HDR;
    return (size_t)DETWS_BRIDGE_TXN_HDR + wl;
}
 
size_t bridge_txn_build(uint8_t *out, size_t cap, const uint8_t *write_data, uint16_t write_len, uint16_t read_len)
{
    size_t need = (size_t)DETWS_BRIDGE_TXN_HDR + write_len;
    if (!out || cap < need)
        return 0;
    out[0] = (uint8_t)(write_len >> 8);
    out[1] = (uint8_t)write_len;
    out[2] = (uint8_t)(read_len >> 8);
    out[3] = (uint8_t)read_len;
    if (write_len && write_data)
        memcpy(out + DETWS_BRIDGE_TXN_HDR, write_data, write_len);
    return need;
}
 
#endif // DETWS_ENABLE_IFACE_BRIDGE