#include <postgres.h>

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

#include "stringBuffer.h"

#define DEFAULT_STR_LENGTH_PADDING 10
#define DEFAULT_PERCENT_SIZE_INCREASE 0.25

/*NOTE: buffer->length does NOT include the null!!! */




/*constructor for the string buffer */
STRBUFF * new_strBUFF(int size) {
	STRBUFF * buffer;
	buffer = (STRBUFF *)palloc(sizeof(STRBUFF));
	buffer->string = (char * )palloc(size);
	buffer->size = size;
	buffer->length = 0;
	return buffer;
}

/*destructor */
void delete_StrBUFF(STRBUFF* buffer) {
	pfree(buffer->string);
	pfree(buffer);
}

/*returns a CString contained in the buffer */
char* to_CString(STRBUFF* buffer) {
	char* resultStr;
	if(buffer->length == 0) {
		return NULL;
	}

	resultStr = (char * )palloc(buffer->length+1);
	memcpy(resultStr, buffer->string, buffer->length+1);
	return resultStr;
}

/*add a string to the buffer- calls catenate */
void add_str_simple(STRBUFF* buffer, char* str) {
	if(str == NULL) {
		return;
	}
	catenate(buffer, str, strlen(str));
}

/* 
 * Adds the new string to the existing string in the buffer allocates
 */
void catenate(STRBUFF *buffer, char* str, int strLength)
{
	/* not big enough to hold this + null termination */
	if  (buffer->size <= (buffer->length+strLength)  )
	{
		/*need to re-allocate the buffer so its bigger */
		char *old_buffer = buffer->string;
		int  new_size    = getSize(buffer->size, buffer->length, strLength);  /*new size (always big enough) */

		buffer->string = palloc(new_size);
		buffer->size = new_size;
		memcpy(buffer->string, old_buffer, buffer->length+1); /* copy old string (+1 = null term) */

			/* buff is exactly the same as it was, except it has a bigger string buffer */
		pfree(old_buffer);
	}

		/*add new info */
	memcpy(buffer->string + buffer->length, str, strLength);
	buffer->length += strLength;
	buffer->string[buffer->length] = 0;/* force null-terminated */
}


/*
 * get new buffer size
 *  new size =    <big enough to put in the requested info> +
 *      10 +                                 -- just a little constant
 *      25% * <current buffer size>          -- exponential growth
 */
int getSize(int buffer_size, int buffer_length, int strLength)
{
	/* extra space required in buffer */
	int needed_extra = strLength - (buffer_size-buffer_length);

	return buffer_size + needed_extra + DEFAULT_STR_LENGTH_PADDING + buffer_size*DEFAULT_PERCENT_SIZE_INCREASE;
}