CNBuffer.h

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#ifndef CNBUFFER_H
#define CNBUFFER_H

#include <stdlib.h>
#include <string.h>

struct CNBuffer
{
    size_t              writePosition ;
    size_t              currentSize ;
    unsigned char *     context ;
} ;

static inline size_t
CNCalcSizeOfBuffer(size_t size)
{
    static const size_t     CNUnitSizeOfBuffer = 512 ;
    if(size > 0){
        size_t s0 = (size + CNUnitSizeOfBuffer - 1) / CNUnitSizeOfBuffer ;
        return s0 * CNUnitSizeOfBuffer ;
    } else {
        return CNUnitSizeOfBuffer ;
    }
}

static inline void
CNInitBuffer(struct CNBuffer * dst)
{
    dst->writePosition = 0 ;
    dst->currentSize = CNCalcSizeOfBuffer(0) ;
    dst->context = malloc(dst->currentSize) ;
}

static inline void
CNDestroyBuffer(struct CNBuffer * dst)
{
    free(dst->context) ;
}

static inline void
CNResetBuffer(struct CNBuffer * dst)
{
    dst->writePosition = 0 ;
}

static inline void *
CNDetachDataFromBuffer(struct CNBuffer * dst)
{
        void * result = realloc(dst->context, dst->currentSize) ;
        dst->writePosition = 0 ;
        dst->currentSize = 0 ;
        dst->context = NULL ;
        return result ;
}

static inline size_t
CNSizeOfBuffer(const struct CNBuffer * src)
{
    return src->writePosition ;
}

static inline const void *
CNContextOfBuffer(const struct CNBuffer * src)
{
    return src->context ;
}

static inline void
CNPutBytesToBuffer(struct CNBuffer * dst, size_t srcsize, const void * srcptr)
{
    size_t  writepos = dst->writePosition ;
    size_t  nextpos  = writepos + srcsize ;
    if(dst->currentSize < nextpos){
        size_t nextsize = CNCalcSizeOfBuffer(nextpos) ;
        dst->context = realloc(dst->context, nextsize) ;
        dst->currentSize = nextsize ;
    }
    unsigned char * dstptr = &(dst->context[writepos]) ;
    memcpy(dstptr, srcptr, srcsize) ;
    dst->writePosition = nextpos ;
}

#endif  /* CNBUFFER_H */