solarxr_ipc_message.h

// Copyright 2025, rcelyte
// SPDX-License-Identifier: BSL-1.0
 
#pragma once
#include <endian.h>
#include <string.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
struct solarxr_ipc_message
{
        uint32_t length;
        uint8_t body[];
};
 
static inline struct solarxr_ipc_message *
solarxr_ipc_message_start(uint8_t head[const], const uint8_t *const end)
{
        if ((size_t)(end - head) < sizeof(struct solarxr_ipc_message)) {
                return NULL;
        }
 
        struct solarxr_ipc_message *const message = (struct solarxr_ipc_message *)head;
        message->length = 0;
        return message;
}
 
static inline bool
solarxr_ipc_message_write(struct solarxr_ipc_message *const message,
                          const uint8_t *const end,
                          const uint8_t data[const],
                          const uint32_t data_len)
{
        if (message == NULL) {
                return false;
        }
 
        if ((size_t)(end - message->body) < message->length ||
            (size_t)(end - &message->body[message->length]) < data_len) {
                message->length = UINT32_MAX;
                return false;
        }
 
        memcpy(&message->body[message->length], data, data_len);
        message->length += data_len;
        return true;
}
 
static inline uint32_t
solarxr_ipc_message_end(struct solarxr_ipc_message *const message, uint8_t **const end_out)
{
        if (message == NULL || message->length >= UINT32_MAX - sizeof(*message)) {
                return 0;
        }
 
        *end_out = &message->body[message->length];
        const uint32_t length = sizeof(*message) + message->length;
        message->length = htole32(length);
        return length;
}
 
static inline uint32_t
solarxr_ipc_message_write_single(uint8_t **const head,
                                 const uint8_t *const end,
                                 const uint8_t data[const],
                                 const uint32_t data_len)
{
        struct solarxr_ipc_message *const message = solarxr_ipc_message_start(*head, end);
        solarxr_ipc_message_write(message, end, data, data_len);
        return solarxr_ipc_message_end(message, head);
}
 
static inline uint32_t
solarxr_ipc_message_inline(uint8_t data[const], const uint32_t data_len)
{
        struct solarxr_ipc_message *const message = solarxr_ipc_message_start(data, &data[data_len]);
        if (message != NULL) {
                message->length = &data[data_len] - message->body;
        }
        return solarxr_ipc_message_end(message, &(uint8_t *){NULL});
}
 
#ifdef __cplusplus
}
#endif