tbuffer.c

这是一个非常规范的文档编辑器

//-----------------------------------------------------------
/*
File Name:	TBuffer.c
Comments:	This file contains the functions which
			implement all of the valid operations on the
			text_buffer type.
*/
//-----------------------------------------------------------



//-----------------------------------------------------------
//Include files

#include "string.h"
#include "assert.h"
#include "stdlib.h"
#include "TBuffer.h"

//End Include files
//------------------------------------------------------------



//------------------------------------------------------------
//prototypes

static text_buffer_error AllocateRows(text_buffer *tBuffer,
								int totalRows);

//End prototypes
//------------------------------------------------------------



//------------------------------------------------------------
/*
Function Name:	TextBufferInitialize
Parameters:
	In:			None
	Out:			tBuffer - Contains the address of the 
						text buffer to initialize.
	In/Out:		None
Return Values:	None.
Comments:		This function sets the text buffer into a
				known state. If this function is not called
				before the text_buffer is used, it is 
				likely that there will be a program error.
*/

void TextBufferInitialize(text_buffer *tBuffer)
{
	assert(tBuffer!=NULL);

	//Initialize the first row to zero.
	tBuffer->topLine = 0;
	tBuffer->allRows = NULL;
	tBuffer->totalRows = 0;
	tBuffer->errorStatus = TBE_NO_ERROR;
}

// TextBufferInitialize
//-------------------------------------------------------



//-------------------------------------------------------
/*
Function Name:	TextBufferSetRow
Parameters:
	In:			rowNumber - Specifies the index number of 
					the row to set.
				textString - Contains a string of 
					characters that will be copied into
					the specified row.
	Out:			None.
	In/Out:		tBuffer - Contains the address of the 
					text buffer that the text string
					will be copied into.
Return Values:	None.
Comments:		Use this function to copy a string of 
				characters into a row in the text buffer.

				If this function fails, it sets the text
				buffer's error status to 
				TBE_CANT_ALLOCATE_BUFFER,which indicates
				that there is not enough memory to copy
				the characters from the string into 
				the specified row.
*/


void TextBufferSetRow(text_buffer * tBuffer, 
					int rowNumber, 
					text_string textString)
{
	text_buffer_error errorStatus = TBE_NO_ERROR;

	assert(tBuffer!=NULL);
	assert(rowNumber >= 0);

	//If the row is in range...
	if (rowNumber < tBuffer->totalRows)
	{
		/*If the characters from the text string can't
		be copied to the specified row...*/
		if (TextStringSetFromTextString(
				tBuffer->allRows[rowNumber],
				textString) == TSE_CANT_ALLOCATE_STRING)
		{
			tBuffer->errorStatus = TBE_CANT_ALLOCATE_BUFFER;
		}
	}
	//Else there are not that many rows in the buffer...
	else
	{
		//Allocate memory for the new row.
		tBuffer->errorStatus = AllocateRows(tBuffer,rowNumber+1);

		//If the memory could be allocated...
		if (tBuffer->errorStatus==TBE_NO_ERROR)
		{
			/*If the characters from the text string can't
			be copied to the specified row...*/
			if (TextStringSetFromTextString(
				tBuffer->allRows[rowNumber],
				textString) == TSE_CANT_ALLOCATE_STRING)
			{
				tBuffer->errorStatus = TBE_CANT_ALLOCATE_BUFFER;
			}			
		}
	}
}

//End TextBufferSetRow
//---------------------------------------------------------------




//---------------------------------------------------------------
/*
Function Name:	TextBufferGetRow
Parameters:
	In:			rowNumber - Specifies the index number of 
					the row to get.
				tBuffer - Contains the address of the 
					text buffer that the text string
					will be retrieved from.
	Out:			textString - Upon return, will contain the 
				text_string in the specified row.
	In/Out:		None.
Return Values:	None.
Comments:		This function retrieves the text_string
				contained in the specified row number. It
				does not create an additional instance of 
				the string. Nor does it copy any characters.
*/

void TextBufferGetRow(const text_buffer * const tBuffer,
					int rowNumber,
					text_string *textString)
{
	assert((rowNumber >= 0) && (rowNumber < tBuffer->totalRows));
	assert(textString!=NULL);
	assert(tBuffer!=NULL);

	*textString = tBuffer->allRows[rowNumber];
}
//End TextBufferGetRow
//---------------------------------------------------------------



//---------------------------------------------------------
/* 
Function Name:	TextBufferScrollUp
Parameters:
	In:			linesToScroll - Contains the number of 
					lines to scroll up.
	Out:		None.
	In/Out:		tBuffer - Contains the address of the 
					buffer to be scrolled.
Return Values:	None.
Comments:		This function scrolls the buffer up by 
				the number of lines specified in the 
				linestoScroll parameter. Scrolling the
				buffer up means moving the displayable
				area toward the beginning of the buffer.
				This is done by setting the top row of 
				the buffer.

				If scrolling the buffer results in the 
				top row of the buffer taking on a value
				that is less than zero, the top row is
				set to zero. 
*/

void TextBufferScrollUp(text_buffer *tBuffer,
						int linesToScroll)
{
	assert(tBuffer!=NULL);
	assert(linesToScroll>0);
}