#include <stdlib.h>
#include "cbuffer.h"

/* public functions */
error_code	cbuffer_init(CBUFFER *buffer, u_long size);
void		cbuffer_destroy(CBUFFER *buffer);
error_code	cbuffer_extract(CBUFFER *buffer, char *items, u_long count);
error_code	cbuffer_peek(CBUFFER *buffer, char *items, u_long count);
error_code	cbuffer_insert(CBUFFER *buffer, const char *items, u_long count);
u_long		cbuffer_get_free(CBUFFER *buffer);
u_long 		cbuffer_get_used(CBUFFER *buffer);
u_long		cbuffer_get_size(CBUFFER *buffer);


/* private functions */

static void	reset(CBUFFER *buffer);
static void	increment(CBUFFER *buffer, u_long *index);

error_code	cbuffer_init(CBUFFER *buffer, unsigned long size)
{
   if (size == 0) {
		return SR_ERROR_INVALID_PARAM;
   }
   if (size == 0) {
      buffer->size = 0;
      buffer->buf = NULL;
      reset(buffer);
   } else {
      buffer->size = size;
      buffer->buf = (char *)malloc(size);
      reset(buffer);
   }

   return SR_SUCCESS;
}

void cbuffer_destroy(CBUFFER *buffer)
{
	if (buffer->buf)
	{
		free(buffer->buf);
		buffer->buf = NULL;
	}
}

error_code cbuffer_extract(CBUFFER *buffer, char *items, u_long count)
{
	u_long i;	
	
	for(i = 0; i < count; i++)
	{
		if (buffer->item_count > 0)
			buffer->item_count--;
		else
			return SR_ERROR_BUFFER_EMPTY;

		increment(buffer, &buffer->read_index);
		items[i] = buffer->buf[buffer->read_index];
	}
	return SR_SUCCESS;
}


error_code cbuffer_peek(CBUFFER *buffer, char *items, u_long count)
{
	u_long i;	
	u_long my_read_index = buffer->read_index;
	u_long my_item_count = buffer->item_count;

	for(i = 0; i < count; i++)
	{
		if (my_item_count > 0)
			my_item_count--;
		else
			return SR_ERROR_BUFFER_EMPTY;

		increment(buffer, &my_read_index);
		items[i] = buffer->buf[my_read_index];
	}
	return SR_SUCCESS;
}


error_code cbuffer_insert(CBUFFER *buffer, const char *items, u_long count)
{
	u_long i;	
	
	for(i = 0; i < count; i++)
	{
		if (buffer->item_count < cbuffer_get_size(buffer))
			buffer->item_count++;
		else
			return SR_ERROR_BUFFER_FULL;

		increment(buffer, &buffer->write_index);
		buffer->buf[buffer->write_index] = items[i];
	}

	return SR_SUCCESS;
}

u_long cbuffer_get_size(CBUFFER *buffer)
{
	return buffer->size;

}

u_long cbuffer_get_free(CBUFFER *buffer)
{
	return cbuffer_get_size(buffer) - cbuffer_get_used(buffer);
}

u_long cbuffer_get_used(CBUFFER *buffer)
{
	return buffer->item_count;
}


void increment(CBUFFER *buffer, u_long *index)
{
   (*index)++;
   if (*index >= cbuffer_get_size(buffer))
      *index = 0;
}

void reset(CBUFFER *buffer)
{
	buffer->read_index = buffer->write_index = cbuffer_get_size(buffer) - 1;
	buffer->item_count = 0;
}