FPGC6/BCC/BDOS/lib/stdlib.c

/*
* Standard library
* Contains basic functions, including timer and memory functions
*/

// uses math.c 

#define UART_TX_ADDR 0xC02723

// Timer I/O Addresses
#define TIMER1_VAL 0xC02739
#define TIMER1_CTRL 0xC0273A
#define TIMER2_VAL 0xC0273B
#define TIMER2_CTRL 0xC0273C
#define TIMER3_VAL 0xC0273D
#define TIMER3_CTRL 0xC0273E

word timer1Value = 0;
word timer2Value = 0;
word timer3Value = 0;

/*
* TODO:
* - Convert most of these functions to assembly
*/

/*
Copies n words from src to dest
*/
void memcpy(word* dest, word* src, word n)
{
    word i;
    for (i = 0; i < n; i++)
    {
        dest[i] = src[i];
    }
}

/*
Compares n words between a and b
Returns 1 if similar, 0 otherwise
*/
word memcmp(word* a, word* b, word n)
{
    word i;
    for (i = 0; i < n; i++)
    {
        if (a[i] != b[i])
        {
            return 0;
        }
    }

    return 1;
}


// Returns length of string
word strlen(char* str)
{
    word retval = 0;
    char chr = *str;            // first character of str

    while (chr != 0)            // continue until null value
    {
        retval += 1;
        str++;                  // go to next character address
        chr = *str;             // get character from address
    }

    return retval;
}


/*
Copies string from src to dest
Returns number of characters copied
*/
word strcpy(char* dest, char* src)
{
    // write to buffer
    word i = 0;
    while (src[i] != 0)
    {
        dest[i] = src[i];
        i++;
    }

    // terminate
    dest[i] = 0;

    return i;
}


/*
Appends string from src to dest
Returns number of characters appended
*/
word strcat(char* dest, char* src)
{
    // move to end of destination
    word endOfDest = 0;
    while (dest[endOfDest] != 0)
        endOfDest++;

    // copy to end of destination
    return strcpy(dest+endOfDest, src);
}


/*
Compares two strings a and b
Returns 0 if similar
 otherwise returns the difference in the first non-matching character
*/
word strcmp(char* s1, char* s2)
{
  while(*s1 && (*s1 == *s2))
  {
    s1++;
    s2++;
  }
  return *s1 - *s2;
}


/*
Recursive helper function for itoa
Eventually returns the number of digits in n
s is the output buffer
*/
word itoar(word n, char *s)
{
    word digit = MATH_modU(n, 10);
    word i = 0;

    n = MATH_divU(n,10);
    if ((unsigned int) n > 0)
        i += itoar(n, s);

    s[i++] = digit + '0';

    return i;
}


/*
Converts integer n to characters.
The characters are placed in the buffer s.
The buffer is terminated with a 0 value.
Uses recursion, division and mod to compute.
*/
void itoa(word n, char *s)
{
    // compute and fill the buffer
    word i = itoar(n, s);

    // end with terminator
    s[i] = 0;
} 





/*
Recursive helper function for itoa
Eventually returns the number of digits in n
s is the output buffer
*/
word itoahr(word n, char *s)
{
    word digit = MATH_modU(n, 16);
    word i = 0;

    n = MATH_divU(n,16);
    if ((unsigned int) n > 0)
        i += itoahr(n, s);

    char c;
    if (digit > 9)
    {
        c = digit + 'A' - 10;
    }
    else
    {
        c = digit + '0';
    }
    s[i++] = c;

    return i;
}


/*
Converts integer n to hex string characters.
The characters are placed in the buffer s.
A prefix of 0x is added.
The buffer is terminated with a 0 value.
Uses recursion, division and mod to compute.
*/
void itoah(word n, char *s)
{
    // add prefix
    s[0] = '0';
    s[1] = 'x';
    s+=2;

    // compute and fill the buffer
    word i = itoahr(n, s);

    // end with terminator
    s[i] = 0;
} 


/*
Converts string into int.
Assumes the string is valid.
*/
word strToInt(char* str)
{
    word retval = 0;
    word multiplier = 1;
    word i = 0;
    while (str[i] != 0)
    {
        i++;
    }
    if (i == 0)
        return 0;

    i--;

    while (i > 0)
    {
        // Return 0 if not a digit
        if (str[i] < '0' || str[i] > '9')
            return 0;
        
        word currentDigit = str[i] - '0';
        word toAdd = multiplier * currentDigit;
        retval += toAdd;
        multiplier = multiplier * 10;
        i--;
    }

    word currentDigit = str[i] - '0';
    word toAdd = multiplier * currentDigit;
    retval += toAdd;

    return retval;
}


/*
Prints a single char c by writing it to UART_TX_ADDR
*/
void uprintc(char c) 
{
    word *p = (word *)UART_TX_ADDR; // address of UART TX
    *p = (word)c;                   // write char over UART
}


/*
Sends each character from str over UART
by writing them to UART_TX_ADDR
until a 0 value is found.
Does not send a newline afterwards.
*/
void uprint(char* str) 
{
    word *p = (word *)UART_TX_ADDR; // address of UART TX
    char chr = *str;                // first character of str

    while (chr != 0)                // continue until null value
    {
        *p = (word)chr;             // write char over UART
        str++;                      // go to next character address
        chr = *str;                 // get character from address
    }
}


/*
Same as uprint(char* str),
except it sends a newline afterwards.
*/
void uprintln(char* str) 
{
    uprint(str);
    uprintc('\n');
}


/*
Prints decimal integer over UART
*/
void uprintDec(word i) 
{
    char buffer[20];
    itoa(i, buffer);
    uprint(buffer);
    uprintc('\n');
}

/*
Prints hex integer over UART
*/
void uprintHex(word i) 
{
    char buffer[16];
    itoah(i, buffer);
    uprint(buffer);
    uprintc('\n');
}


/*
Prints decimal integer over UART, with newline
*/
void uprintlnDec(word i) 
{
    char buffer[20];
    itoa(i, buffer);
    uprint(buffer);
    uprintc('\n');
}

/*
Prints hex integer over UART, with newline
*/
void uprintlnHex(word i) 
{
    char buffer[16];
    itoah(i, buffer);
    uprint(buffer);
    uprintc('\n');
}


// sleeps ms using timer1.
// blocking.
// requires int1() to set timer1Value to 1:
/*
    timer1Value = 1; // notify ending of timer1
*/
void delay(word ms)
{

    // clear result
    timer1Value = 0;

    // set timer
    word *p = (word *) TIMER1_VAL;
    *p = ms;
    // start timer
    word *q = (word *) TIMER1_CTRL;
    *q = 1;

    // wait until timer done
    while (timer1Value == 0);
}


// Returns interrupt ID by using the readintid asm instruction
word getIntID()
{
    word retval = 0;

    asm(
        "readintid r2    ;reads interrupt id to r2\n"
        "write -4 r14 r2 ;write to stack to return\n"
        );

    return retval;
}



// Converts char c to uppercase if possible
char toUpper(char c)
{
    if (c>96 && c<123) 
        c = c ^ 0x20;

    return c;
}


// Converts string str to uppercase if possible
void strToUpper(char* str) 
{
    char chr = *str;            // first character of str

    while (chr != 0)            // continue until null value
    {
        *str = toUpper(chr);    // uppercase char
        str++;                  // go to next character address
        chr = *str;             // get character from address
    }
}


/*
For debugging
Prints a hex dump of size 'len' for each word starting from 'addr'
Values are printed over UART
*/
void hexdump(char* addr, word len)
{
    char buf[16];
    word i;
    for (i = 0; i < len; i++)
    {
        // newline every 8 words
        if (i != 0 && MATH_modU(i, 8) == 0)
            uprintc('\n');
        itoah(addr[i], buf);
        uprint(buf);
        uprintc(' ');
    }
}