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tinycstd.c
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tinycstd.c
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#include "tinycstd.h"
#include "console.h"
#include "diag.h"
#include "syscalls.h"
#include "compiler-utils.h"
#include <stdarg.h>
// Format string handling
typedef ssize_t (*put_handler)(const char* buffer, ssize_t len, void** context);
int handle_format_string(const char* format, va_list args, put_handler handler, void* context);
// Function required by libgcc for a freestanding environment
void* memmove(void* dest, const void* source, size_t num) {
uint8_t* dst = (uint8_t*) dest;
uint8_t* src = (uint8_t*) source;
while (num > 0) {
*(dst++) = *(src++);
num--;
}
return dest;
}
void* memcpy (void* destination, const void* source, size_t num) {
return memmove(destination, source, num);
}
void* memset(void* ptr, int value, size_t num) {
uint8_t* char_ptr = (uint8_t*) ptr;
while (num > 0) {
*char_ptr = (uint8_t) value;
char_ptr++;
num--;
}
return ptr;
}
int memcmp(const void* ptr1, const void* ptr2, size_t num) {
uint8_t* p1 = (uint8_t*) ptr1;
uint8_t* p2 = (uint8_t*) ptr2;
for (size_t i = 0; i < num; i++) {
if (p1[i] < p2[i])
return -1;
if (p1[i] > p2[i])
return 1;
}
return 0;
}
uint64_t strlen(const char* str) {
uint64_t len = 0;
while (str && *(str++))
++len;
return len;
}
ssize_t strncmp(const char* first, const char* second, size_t n) {
for (size_t i = 0; i < n; i++) {
if (first[i] < second[i])
return -1;
else if(first[i] > second[i])
return 1;
else if (first[i] == '\0') // implies second[i] == '\0'
break;
}
return 0;
}
const char* strchr(const char* str, int c) {
while (*str != '\0') {
if (*str == ((char) c))
return str;
str++;
}
if (c == '\0')
return str;
else
return NULL;
}
size_t strlcpy(char* dest, const char* src, size_t n) {
size_t copied = 0;
while (copied < (n - 1)) {
if (src[copied] == '\0')
break;
dest[copied] = src[copied];
copied++;
}
dest[copied] = '\0';
return copied;
}
char* itoa_ext(uintmax_t value, uint8_t base, uint8_t bits, bool sign);
int printf(const char* format, ...) {
va_list args;
va_start(args, format);
int result = va_printf(format, args);
va_end(args);
return result;
}
ssize_t sprintf_put(const char* str, ssize_t len, void** ctxt) {
strlcpy((*ctxt)+1, str, len+1); // len+1 due to \0
return len;
}
int sprintf(char* buf, const char* format, ...) {
va_list args;
va_start(args, format);
int ret = handle_format_string(format, args, sprintf_put, buf);
// No need for explicitly setting \0 at the end - strlcpy in sprintf_put already does the job
va_end(args);
return ret;
}
void puts(const char* s) {
console_puts(s, strlen(s));
}
void putc(char c) {
console_putc(c);
}
int dprintf(int fd, const char* format, ...) {
va_list args;
va_start(args, format);
int ret;
if (fd_is_stdio(fd))
ret = va_printf(format, args);
else
panic("dprintf called with non-stdio descriptor (no write support on files)");
va_end(args);
return ret;
}
ssize_t printf_puts(const char* str, ssize_t len, void** ctxt) {
UNUSED_VAR(ctxt);
return console_puts(str, len);
}
int va_printf(const char* format, va_list args) {
return handle_format_string(format, args, printf_puts, NULL);
}
// TODO: This function mingles signed and unsigned characters of various sizes (32bit and 64bit).
// As long as the format operation does not exceed 2147483647 characters
// (2^31 - 1 due to the sign bit), it should work.
// However, this is still unclean and must be handled correctly
int handle_format_string(const char* format, va_list args, put_handler handler, void* context) {
int written = 0;
size_t len;
ssize_t handled;
const char* fmt_pos;
while (1) {
fmt_pos = strchr(format, '%');
if (fmt_pos == NULL) {
// Found no format specifier - print rest and return
len = strlen(format);
handled = handler(format, len, &context);
return written + handled;
} else {
// Found format specifier - print everything before it and handle specifier
handled = handler(format, fmt_pos - format, &context);
written += handled;
format = fmt_pos + 1;
switch (*format) {
case '%':
handled = handler("%", 1, &context);
written += handled;
format++;
break;
case 'c': {
char c = va_arg(args, int); // char is "promoted" to int by variable args
handled = handler(&c, 1, &context);
written += handled;
format++;
break;
}
case 'd':
case 'i': {
int i = va_arg(args, int);
char* buf = itoa_ext(i, 10, sizeof(int) * 8, true);
len = strlen(buf);
handled = handler(buf, len, &context);
written += handled;
format++;
break;
}
case 'u': {
uintmax_t i = va_arg(args, uintmax_t);
char* buf = itoa_ext(i, 10, sizeof(uintmax_t) * 8, false);
len = strlen(buf);
handled = handler(buf, len, &context);
written += handled;
format++;
break;
}
case 'x':
case 'X': {
uintmax_t i = va_arg(args, uintmax_t);
char* buf = itoa_ext(i, 16, sizeof(uintmax_t) * 8, false);
len = strlen(buf);
handled = handler(buf, len, &context);
written += handled;
format++;
break;
}
case 'p': {
void* i = va_arg(args, void*);
char* buf = itoa_ext((uintmax_t)i, 16, sizeof(void*) * 8, false);
// Fill missing bytes with zeros
// One hex number is a nibble (4 bits) -> two represent one byte
size_t filldiff = (sizeof(void*) * 2) - strlen(buf);
while (filldiff != 0) {
handled = handler("0", 1, &context);
written += handled;
filldiff--;
}
len = strlen(buf);
handled = handler(buf, len, &context);
written += handled;
format++;
break;
}
case 's': {
const char* s = va_arg(args, const char*);
len = strlen(s);
handled = handler(s, len, &context);
written += handled;
format++;
break;
}
default:
handled = handler("%", 1, &context);
handled += handler(format, 1, &context);
written += handled;
format++;
break;
}
}
}
}
// TODO: Not thread-safe
char* itoa_ext(uintmax_t value, uint8_t base, uint8_t bits, bool sign) {
const char* conv = "0123456789ABCDEF";
static char buf[2 + sizeof(uintmax_t) * 8]; // maximum integer bits + minus sign + null
char* pos = buf + sizeof(buf) - 1;
bool negative = false;
// If sign bit is set, convert to positive number (two's complement)
if (sign && (value & (1 << (bits - 1)))) {
negative = true;
value = ~value + 1;
if (bits < sizeof(uintmax_t) * 8)
// Cut off irrelevant bits
value = value & ((1ULL << bits) - 1);
}
*pos = '\0';
if (value != 0)
while (value != 0) {
uint8_t rem = value % base;
pos--;
*pos = conv[rem];
value = value / base;
}
else {
pos--;
*pos = conv[0];
}
if (negative) {
pos--;
*pos = '-';
}
return pos;
}