/* ----------------------------------------------------------------------------
 *         ATMEL Microcontroller Software Support 
 * ----------------------------------------------------------------------------
 * Copyright (c) 2008, Atmel Corporation
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the disclaimer below.
 *
 * Atmel's name may not be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * DISCLAIMER: THIS SOFTWARE IS PROVIDED BY ATMEL "AS IS" AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT ARE
 * DISCLAIMED. IN NO EVENT SHALL ATMEL BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
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 * ----------------------------------------------------------------------------
 */

//------------------------------------------------------------------------------
/// \unit
///
/// !Purpose
///
/// Implementation of several methods defined in string.h, for reducing the
/// memory footprint when using them (since the whole libc.o file gets included
/// even when using a single method).
///
/// !Usage
///
/// Add string.c to the list of files to compile for the project. This will
/// automatically replace standard libc methods by the custom ones.
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
//         Headers
//------------------------------------------------------------------------------

#include <string.h>

//------------------------------------------------------------------------------
//         Global Functions
//------------------------------------------------------------------------------

//------------------------------------------------------------------------------
/// Copies data from a source buffer into a destination buffer. The two buffers
/// must NOT overlap. Returns the destination buffer.
/// \param pDestination  Destination buffer.
/// \param pSource  Source buffer.
/// \param num  Number of bytes to copy.
//------------------------------------------------------------------------------
void * memcpy(void *pDestination, const void *pSource, size_t num)
{
	unsigned char *pByteDestination;
	unsigned char *pByteSource;
	unsigned int *pAlignedSource = (unsigned int *) pSource;
	unsigned int *pAlignedDestination = (unsigned int *) pDestination;

	// If num is more than 4 bytes, and both dest. and source are aligned,
	// then copy dwords
	if ((((unsigned int) pAlignedDestination & 0x3) == 0)
		&& (((unsigned int) pAlignedSource & 0x3) == 0)
		&& (num >= 4)) {

		while (num >= 4) {

			*pAlignedDestination++ = *pAlignedSource++;
			num -= 4;
		}
	}

	// Copy remaining bytes
	pByteDestination = (unsigned char *) pAlignedDestination;
	pByteSource = (unsigned char *) pAlignedSource;
	while (num--) {

		*pByteDestination++ = *pByteSource++;
	}

	return pDestination;
}

//------------------------------------------------------------------------------
/// Fills a memory region with the given value. Returns a pointer to the
/// memory region.
/// \param pBuffer  Pointer to the start of the memory region to fill
/// \param value    Value to fill the region with
/// \param num      Size to fill in bytes
//------------------------------------------------------------------------------
void * memset(void *pBuffer, int value, size_t num)
{
	unsigned char *pByteDestination;
	unsigned int  *pAlignedDestination = (unsigned int *) pBuffer;
	unsigned int  alignedValue = (value << 24) | (value << 16) | (value << 8) | value;

	// Set words if possible
	if ((((unsigned int) pAlignedDestination & 0x3) == 0) && (num >= 4)) {
		while (num >= 4) {
			*pAlignedDestination++ = alignedValue;
			num -= 4;
		}
	}
	// Set remaining bytes
	pByteDestination = (unsigned char *) pAlignedDestination;
	while (num--) {
		*pByteDestination++ = value;
	}
	return pBuffer;
}

//-----------------------------------------------------------------------------
/// Search a character in the given string.
/// Returns a pointer to the character location.
/// \param pString   Pointer to the start of the string to search.
/// \param character The character to find.
//-----------------------------------------------------------------------------
char * strchr(const char *pString, int character)
{
	char * p = (char *)pString;
	char   c = character & 0xFF;

	while(*p != c) {
		if (*p == 0) {
			return 0;
		}
		p++;
	}
	return p;
}

//-----------------------------------------------------------------------------
/// Return the length of a given string
/// \param pString Pointer to the start of the string.
//-----------------------------------------------------------------------------
size_t strlen(const char *pString)
{
	unsigned int length = 0;

	while(*pString++ != 0) {
		length++;
	}
	return length;
}


//-----------------------------------------------------------------------------
/// Search a character backword from the end of given string.
/// Returns a pointer to the character location.
/// \param pString   Pointer to the start of the string to search.
/// \param character The character to find.
//-----------------------------------------------------------------------------
char * strrchr(const char *pString, int character)
{
	char *p = 0;

	while(*pString != 0) {
		if (*pString++ == character) {
			p = (char*)pString;
		}
	}
	return p;
}

//-----------------------------------------------------------------------------
/// Copy from source string to destination string
/// Return a pointer to the destination string
/// \param pDestination Pointer to the destination string.
/// \param pSource      Pointer to the source string.
//-----------------------------------------------------------------------------
char * strcpy(char *pDestination, const char *pSource)
{
	char *pSaveDest = pDestination;

	for(; (*pDestination = *pSource) != 0; ++pSource, ++pDestination);
	return pSaveDest;
}

//-----------------------------------------------------------------------------
/// Compare the first specified bytes of 2 given strings
/// Return 0 if equals
/// Return >0 if 1st string > 2nd string
/// Return <0 if 1st string < 2nd string
/// \param pString1 Pointer to the start of the 1st string.
/// \param pString2 Pointer to the start of the 2nd string.
/// \param count    Number of bytes that should be compared.
//-----------------------------------------------------------------------------
int strncmp(const char *pString1, const char *pString2, size_t count)
{
	int r;

	while(count) {
		r = *pString1 - *pString2;
		if (r == 0) {
			if (*pString1 == 0) {
				break;
			}
			pString1++;
			pString2++;
			count--;
			continue;
		}
		return r;
	}
	return 0;
}

//-----------------------------------------------------------------------------
/// Copy the first number of bytes from source string to destination string
/// Return the pointer to the destination string.
/// \param pDestination Pointer to the start of destination string.
/// \param pSource      Pointer to the start of the source string.
/// \param count        Number of bytes that should be copied.
//-----------------------------------------------------------------------------
char * strncpy(char *pDestination, const char *pSource, size_t count)
{
	char *pSaveDest = pDestination;

	while (count) {
		*pDestination = *pSource;
		if (*pSource == 0) {
			break;
		}
		pDestination++;
		pSource++;
		count--;
	}
	return pSaveDest;
}