stdlib.c

一个mips虚拟机非常好代码,使用C++来编写的,希望大家多学学,

/*

	strlen(s)
	isspace(c)
	putchar(c)
	puts(s)
	bcmp(s1, s2, n)
	bcopy(src, dst, n)
	--------------------------------------------------------------

	Simple implementations  of the corresponding  ISO C functions.
	putc() does  not print the  final newline, and  some functions
	use  ints instead  of  size_t, and  don't  return values  like
	they're supposed to. bcmp() and bcopy() comes from BSD.

*/

#include "termio.h"

unsigned long strlen(
    const char* s)
{
    int n = 0;
    for (; *s != '\0'; ++s)
	++n;
    return n;
}

int isspace(
    int c)
{
    return c == ' ' || c == '\t' || c == '\n' || c == '\r';
}

void putchar(
    int c)
{
#if 0
    *(volatile char *)(0xFFFFFFFFBF400008 ^ 7) = c;
#else
    while(!pzscc(OP_TXRDY, 0xFFFFFFFFBC800030, 0, 0));
    pzscc(OP_TX, 0xFFFFFFFFBC800032, 0, c);
#endif
}

void puts(
    const char* s)
{
    while (*s)
	putchar(*s++);
}

int bcmp(
    const void* src,
    const void* dst,
    int n)
{
    const char* p = src;
    const char* q = dst;

    while (n > 0) {
	if (*p != *q)
	    break;
	++p, ++q, --n;
    }
    return 0;
}

void bcopy(
    const void* src,
    void* dst,
    int n)
{
    if (((long)src & 3) == 0 && ((long)dst & 3) == 0 && (n & 3) == 0) {
	/* Fast aligned copy. */
	const int* p = src;
	int* q = dst;
	for (; n > 0; n -= 4)
	    *q++ = *p++;
    }
    else {
	/* Slow byte copy. */
	const char* p = src;
	char* q = dst;;
	for (; n > 0; --n)
	    *q++ = *p++;
    }
}

void put_hex(
    unsigned long x,
    int padding,
    int width,
    int nice,
    int hex_case)
{
    int flush_left;
    char buffer[sizeof(x) * 8 / 4 + 2];
    char* p = buffer;

    /* Align left if width is negative. */
    if (width >= 0)
	flush_left = 0;
    else {
	flush_left = 1;
	width = -width;
    }
    /* Generate the digits (least-signficant one first.) */
    do {
	int digit = x & 15;
	*p++ = digit + ((digit < 10) ? '0' : hex_case - 10);
    } while (x >>= 4);
    /* Print the 'nice' 0x. */
    if (nice) {
	*p++ = 'x' - 'a' + hex_case;
	*p++ = '0';
    }
    /* Adjust the width by the number of already-generated characters. */
    width -= (p - buffer);
    /* Print the left padding. */
    if (!flush_left) {
	for (; width > 0; --width)
	    putchar(padding);
    }
    /* Print the generated digits in a reversed order. */
    do {
	putchar(*--p);
    } while (p > buffer);
    /* Print the right padding. */
    for (; width > 0; --width)
	putchar(' ');
}