#pragma once

// Guards for C++ usage
#ifdef __cplusplus
extern "C" {
#endif

#include <string.h>
#include <stdbool.h>

/* A sized buffer abstraction.
 * 
 * Functions that return int's will return 0 on success and nonzero otherwise.
 */

typedef struct sized_buf SizedBuf;

struct sized_buf 
{
        char *data;
        size_t size;
};

// Returns 0 if the given buffer has at least size bytes available
inline int sb_check(const SizedBuf sb, const size_t size) 
{
        return !(sb.size >= size);
}

// Moves the buffer size bytes forward, makes no checks
inline void sb_update(SizedBuf *const sb, const size_t size) 
{
        sb->data += size;
        sb->size -= size;
}

// Copies size bytes of data from the source to the buffer
inline int sb_copyin(SizedBuf *const sb, const char *const source, const size_t size) 
{
        int ret = sb_check(*sb, size);
        if (!ret) {
                memcpy(sb->data, source, size);
                sb_update(sb, size);
        }
        return ret;
}

// "Recasts" size bytes of memory and returns a pointer to said memory in out
inline int sb_recast(SizedBuf *const sb, const size_t size, const void **const out) 
{
        int ret = sb_check(*sb, size);
        if (!ret) {
                *out = sb->data;
                sb_update(sb, size);
        }
        return ret;
}

// "Recasts" size bytes of memory without actually consuming the buffer
inline int sb_peek(const SizedBuf sb, const size_t size, const void **const out) 
{
        *out = sb.data;
        return sb_check(sb, size);
}

// Returns a pointer just after the end of the sized buffer
inline char *sb_end(const SizedBuf sb) 
{
        return sb.data + sb.size;
}

inline bool sb_empty(const SizedBuf sb) 
{
        return sb.size == 0;
}

// End C++ guard
#ifdef __cplusplus
}
#endif